Piles are important to develop any building and an engineer has to consider many aspects namely duration, cost and sustainability while pile foundation. In most cases, the piles are established on clay and it is necessary to know the settlement time to maintain sturdiness of the pillars. In this context, the study has discussed time-dependent settlements of piles in clayey soil. Different secondary data have been considered for this study.
In the first chapter, the topic has been thoroughly introduced and a detailed background has been provided. The importance of the study has been mentioned and certain aims and objectives have been mentioned. In the second chapter, different literatures have been reviewed and a conceptual framework has been developed. Different processes of pile installation and designing have been mentioned the purposes of pile testing have been discussed and pile load capacity has been defined. The gaps in the literature have been found out. In the third chapter, the methods of pile load testing have been discussed in detail and experimental procedures have been mentioned. The fourth chapter has analysed various thematic data to find the answers of the literature gaps. A thematic analysis has been performed in this chapter. In the fifth and last chapter, the study has linked the objectives with the findings and relevant recommendations have been provided along with the future scopes.
This paper analyses the importance of pile tests in data analysis, particularly with respect to results extracted from axial testing of piles, which is one of the common filed tests performed. There have been several papers and tests, which have been carried out, and there are several research papers analyzing such tests. As a result, the understanding of significance of pile tests in engineering practices leaves a whole space for further research. There is a major concern among engineers with regard to capacity of pile tests for conducting field test data-analysis and there is little practical evidence. This research shows that value of engineering can be achieved from elaboration of pile tests.
This research paper provides a background of pile test regarding its historical significance, followed by the problems in adopting pile test. Review of literatures and research of past scholars have also been conducted with regard to process of pile installation, and methods of pile design. Importance of load test program, method of shaft capacity prediction along with outcome and drawbacks of pile test have been taken note of in this research.
There has been existence of deep foundations since last few millennia although faster growth in piling was evident in 20th century. Today, pile testing is done in done in all forms of soil and rock formations that require 4m diameters and 150m depth. Since the prehistoric era, people have been looking for dwelling sights across rivers and lake that provided protection and ample of water (Byrne et al. 2015). For supporting such dwellings above the water level, timber piles were used. The base of the study lies in understanding the evolution of pile test in present scenario and the advanced piling technology that is being used in present scenario. In 1960s brought in a new technique of integrity testing of deep foundations, which are acoustic or intrusive, and intrusive integrity testing requires installing of access ducts at the time of casting (Byrne et al. 2015).
In any construction company, the major setback is the calculation, and in case of pile, testing, similar problems are encountered. There are probabilities of pile load-test failure, which implies that pile settlements are sometimes beyond the specified settlements. One of the failures includes the creep rupture that occurs due to loss of strength in the soil. Such failure leads to de-structuration process leading to changes in effective stresses in case of kinematic constraints. Creep rupture may lead to excessive pore water pressure leading to reduction in stresses. It may also lead to change in water content leading to strength transformation. The figure below shows the spaces where creep rupture will not occur.
There are number of reasons behind creep failure some of which can be recorded as long-term deformations, load and rate effects as well as un-drained creep behavior. These creep failures are followed by pile displacements in upward direction, leading to direct pile uploading.
Another major issue is deficiency of concrete materials that happens due to integrity problems of the piles affecting their capacity of bearing loads. The pile foundations transfer the loads to substrates with friction. This transmission of loads can be performed when there are no major problems in substructures such as cracks and voids. Such deficiencies might bring in challenges when there is weak structure supporting the top structure, leading to partial or full collapse of top structure. Integrity problems can be challenging and so is the inspection of such problems because these elements can be accessed at the time of visual inspection (Zdravković et al. 2015).
Most often, it is observed that during pile testing, the pile goes out of their original location due to the less alignment control of hammer due to the soil condition. As mentioned by Meyer et al. (2016), poor hammer control alignment on the pile creates obstruction during excavation and removal of the pitfalls from the ground. Moreover, it is found it may times, casing is not provided on the sides due to which the sides of the piles collapse in the loose and soft soil which often creates disturbance in collecting data during field test. In addition, another major issue found during pile testing process is inadequate strength of concrete, which can occur due to poor mixing of the concrete in laboratory. This issue requires to be solved in order to make the construction projects effective. Moreover, errors in determining water content and cement content is found in most of the pile construction projects of UK. As per the research, it is found that the construction industry of UK has lost £13 million due to issues present in collecting field data during pile foundation in last few years (Taylor, 2018). Only 1.1% of the projects are improved which has raised the pre-profit tax of about £10.2 million. By analysing this fact, it can be said that the construction requires to be done by determining the tension stresses among the piles. It is found that piles are damaged due to the soil boring in the soft layers.
(Source: Taylor, 2018)
Pile cap failure occurs in pile foundation, which decreases the shearing strength of soil and result in deformation of piles. Another issue arises during pile foundation, voids that are present in the soil are not checked properly due to which improper compaction of the concrete is done which creates a major challenge in construction process. Moreover, due to ineffective monitoring of the soil, the field results are not achieved effectively which presents a serious issue in gaining effective results. In case of pile load test, it is assumed that result of ultimate pile capacity is the appropriate design process. However, during the installation of pile, it is found that the soil which is associated behind, experience a major deformation which result in the excess pore water pressure which further reduces the pile bearing ability and shearing strength. Sometimes, the workers in the construction projects do not have the accurate estimations of the setups of pile, which increases the costs of piling and the affects the performance of pile construction such as highway projects and water construction projects (Ng and Ksaibati, 2018).
Most often, piles suffer from the certain damages in the test procedures due to the workloads. In this case, common issues occur are working load failure in the bored piles and mechanical augured piles. Weakened ground, insufficient coverage of concrete, using wrong boring techniques and using poor implementation of the placement of concrete creates challenges in field data tests (Taylor, 2018). Therefore, this area is of utter concern and needs to be explored further.
The aim of the study is to focus on the major influences of pile test for field data analysis. It tries to show the problems within the pile test process for construction industry.
H0: Time dependent settlements of piles can be predicted based on curve fitting of field test data.
H1: Time dependent settlements of piles cannot be predicted based on curve fitting of field test data.
The significance of this study lies in the fact that it has provided a detailed overview of procedure of piling test in field-test data analysis. This study identifies some real life problems faced by construction engineers, one of which is calculations of height and diameter of piles. In such case, a proper design approach should be governed while foundations should guarantee failure factors and not just load carrying ability. This research evaluates some effective mechanisms through which the problems of calculation and measurements can be done in a better way. The study shows some of the pile design methods that can be used for bringing out correct measurement in construction industry. It also gives an overview of several other methods of pile testing including pile installation, current pile design, shaft capacity prediction and load test programs.
provides an overview and historical background of pile testing and its evaluation,
providing a clear discussion of evolution of various technique of pile testing,
and the issues encountered here with respect to measurement and calculations. In this chapter, types of failures that
occur in the tests results of pile load have been presented which is helpful
for performing the further tests accurately. In addition, analysis of the cap
failure and crack load have been done which are the major issues arise in the
pile load tests. This chapter provides an overview of the objectives
and aims that the research would focus and prove in whole and the significance
of the topic is mentioned in this chapter.
Pile load test is a direct method for identifying an ultimate geotechnical capability of a pile for construction industry. Through this process, a bearing capacity of pile is determined for further usages. The present study has focused on the prediction of time settlements of the pile test in order to facilitate the field data-analysis methods. In that case, pile design methods have been evaluated along with methods of shaft capacity. Though the process is highly cost effective, the construction industry uses it before making an entire project, as it is a highly efficient process for pile test in construction. Pile test is mainly the load carrying capacity test which is used for analyze the load carrying capacity of bearing. This test is initially used in geotechnical investigation purpose. The present study focuses on several elements, process and other factors relating to the pile test.
The pile test is mainly used in the construction related work. Hence, it can be considered and an important test in order to check the load capacity of bearing. Moreover, this test further analyses the safe load carrying capacity and ultimate load carrying capacity of a bearing. Apart from that the procedure of pile installation, design of pile, method of pile design are also discussed further in this study. Through this process, the construction companies are being able to determine the overall the load carrying capacity of the buildings, bridges and others. In this study, it has been discuss the procedure of pile testing. Digital examination and visual examination are two of the important procedure of pile test. In the present study, the methods of pile testing, has been discussed. It includes Situ test, drain canalization, undrawn canalization and others. Moreover, cost reduction procedure of pile test has been discussed.
For enhancing the pile installation process, it is important to verify the ground condition as it affects highly on pile installation. However, the pile installation processes have been described in following sections:
At first, management of construction industry arranges a pile test program based on which pile compression loading can be determined. On the other hand, various instruments such as pile integrity test instrument, pile hole testing equipment, pile dynamic measurement and others are installed which help to measure the displacements of pile along with its different loads (Tomlinson and Woodward, 2015). For that reason, five to six hours are determined to record and monitor the entire processes. Apparently, fort pile installation, curve-fitting methods is also used in order to forecast the pile displacements at infinite time. It is a fact that before pile installation, creep behavior of clay soils are also recognized as it provides the settlement control within the pile in a systematic manner.
It is also estimated that the construction department depends on soil stratigraphy and other test details related pile based on which pile installation is possible. As they use Mercia Mudstone for construction related works, they differentiate the pile from superficial soils which assist them to identify the load transfer of Mercia Mudstone in a proper way. On the contrary, of the above-mentioned views, T12 Hoop Wires are also very important for pile installation process as it is tied with the main bar for making the pile reinforcement cage. TP1 is also used to measure the shaft resistance capacity due to which it is formed with voided base before pile installation.
TP2 is also instrumented before pile installation and finally, TP4 is instrumented before pile installation in order to recognize the sudden strong vibration within pile. After it, extensometers are also implemented to monitor the axial compression of a particular pile. Management of construction industry also accesses in-situ grade 50 normal weights concrete in order to form pile through an appropriate manner. For measuring pile head displacement, four major electrical displacement transducers are used in a proper way. Finally, pile TP6 is implemented for compression testing within a pile before its installation (Omer et al., 2003).
Pile installation is a process of downing the pile into the ground without removing any material, soil and other element (Nguyen et al. 2017). There are several of methods for pile installation. The process is as follows-
In case of dropping the weight initially a hammer is used, this is also known as drop hammer. There are mainly two type of hammer used in case of dropping the weight. One is single action hammer and the other is double action hammer (Weichhold et al. 2016). Those hammers are used by the help of hydraulic actions. The main element to control the hammer is compressed air. Primarily the hammer is raised up and after release the pressure the hammer strike on the pile head to deep down the pile.
In case of pile installation sometime water, jetting can be used. Moreover water jetting is applied when the piles is installed in the sandy gravel. Moreover, the application of water jetting has limited effects on firm.
Pile installation through vibratory process is one of the suitable processes for installing pile in sandy area. The vibratory hammer is mainly operated with the help of hydraulic power or electric power (Huang et al. 2016). There are several of parts of vibratory hammer. It includes eccentric mass with contra rotating which is attached with the pile head.
This method is mainly suitable for soft ground. The boring process is help to install the various diameters of piles in soil ground and it is a helpful process to easy penetration of piles into the ground.
The main benefit of this technique is by using a process the soil may gather the capacity of standing freely and openly without any support (Józefiak et al. 2015). This technique is usually use for enlarging the base of the bearing to increase the bearing load carrying capacity.
(Source: Caulk et al.2016)
Practically, ground tests are highly needed for mentioning the pile design methods along with thorough calculation. It is estimated that main three methods are used for current pile design, which are as follows:
As per the notations of (Murff and Hamilton, 1993), un-drained analysis is proper for designing a pile as it distributes a thorough load within the pile while forming it for construction sector. However, on the contrary of the above discussed view, (Phoon and Kulhway, 2005) commented that drained analysis is vastly necessary for pile design as it clears the strength parameters of soil in front of pile forming procedures. However, it can be said that in-situ analysis is also very important for determining the strength of soils before designing a pile in a concrete manner.
Through defining the applications of load, pile penetration is measured as well as plotted in a thorough manner. This test program analyzes the six Steel I Sections that are highly important for forming the reaction of beam for jacking based on which pile is created. Through this load program, large concrete blocks are also created which assist to support the ends of loading beams. Through the load test, major four hydraulic jacks are centralized depending on which pile head displacement is possible along with jacking system against reaction beam. From four to six loads are applied while testing the pile in a proper manner. However, loading is applied in time of decrements and increments of 1MN. As per the argument of the above quotation, it can be stated that load program generates the VW strain capacity, which is majorly applicable for testing pile in an appropriate way. It is also true that for testing piles, 72 VW Strain gauges are also installed which also helps to display the malfunction within construction sector (Omer et al., 2003).The load test program helps to provide valuable data to the construction sector based on which they measure the axial forces within pile in a thorough manner. For converting measured strains into axial forces, construction sector calibrated the pile based on the load test program from the initial steps (Omer et al., 2003). Pile load test is performed to prove the suitable adequacy of the pile soil system in order to create the design and installation of pile effectively. As stated by Caulk et al. (2016), proper planning of the pile testing is required for developing the design criteria in the construction field. Hence, planning of the test program starts with the analysis of final test data, type of testing performance and extension of testing requirements. In case of small projects, it has been observed that costs of pile tests becomes a serious concern where adequate data of subsoil and sound analysis based on the load test program can help in design criteria. The load test program is helpful for analysing the after affect of pile load tests during construction process.
Shaft-capacity prediction methods can be divided into four major categories that are as follows:
It is estimated that the shaft capacity is mainly depended on the strengths of soil due to which drained analysis is performed as a method of shaft capacity prediction as drained analysis helps to experiment soil in a proper way. As per as (Phoon and Kulhway, 2005), this analysis defines the pile installation process to pile loading stage in an appropriate manner. On the other hand, through this analysis, soil stresses as well as soil properties are justified based on which shaft capacity is predicted. It is also true that the analysis helps to incorporate the variations within earth pressure along with determining the depth. As per the analysis, construction sector measures soil thickness, average value of earth pressure, depth layer and other things in a proper way. Drain analysis is done when the soils flows slowly resulting in the excess of the pore pressure which dissipate because of permeability. Parameters of drained strength soils are found to be c’ and φ which are used during the drained analysis of the piles. This method is based on the suitable analysis of the pile load capacity. It is found that in drain analysis, skin resistance is considered which is represented as “q” and is calculated with the frictional factor that is μ (Nguyen et al. 2017).
Undrained analysis helps to determine the shaft resistance through an excellent manner based on which shaft capacity is predicted. It also helps to define the load application within a pile through which numerous variables can be discussed. Roughness of pile soil interface is recognized through the above-mentioned analysis. On the other hand, load is also analyzed based on soil condition through which the pile is also selected. As per the argument of the above-discussed view, it can be marked that this analysis helps to provide guidelines for piles in wear rocks through which shaft capacity is also assumed. Based on various pile diameters as well as rock strengths, this analysis is done which provides a clear vision regarding shaft capacity. Furthermore, the predicted shaft capacity and the measured shaft capacity are also compared through the un-drained analysis in a systematic way. In this case, the un-drained parameters such as Cu are used for un-drained analysis in pile foundation. Method such as unit skin friction is used in un-drained analysis of pile for measuring the shearing strength of the cohesive soils. As opined by Nguyen et al. (2017), un-drained analysis of pile mostly suited for calculating short-term load capacity of pile. Moreover, CPT method is used for employing soil parameters like un-drained shearing strength and friction angle, which are obtained from the core data for estimating the bearing capacity of the soil. It is found that un-drained loading mainly occurs in case of fine grained soil, which is loaded at high rate. Moreover, they are found to generate huge pressure as these kinds of soils are having low permeability.
Mixed analysis is a combination process of both drained and un-drained analysis. Depending on the analysis, construction department tests the soil and verifies the load test program in order to place the pile to its appropriate space. As discussed by Seidel and Masce (2015), function of depth within pile penetration is recognized only based on mixed analysis. On the other hand, it analyzes the bored piles after determining its plots. Through these ways, the analysis method helps to provide information regarding shaft capacity while installing pile for construction related works.
The above-mentioned method can be recognized as a forecasting method for shaft capacity prediction. This analysis method is a precast concrete process through which building components are manufactured. On the other hand, it helps to bring the components to the particular sites as per the instruction of construction management. It is true that the method has several challenges such as on-site industrialization for consultants, designers, contractors and other people. However, this method makes a proper correlation between design and components based on which pile creation process becomes easy. It is found that load-carrying capacity in case of in situ piles is used for the testing of pile loads. The angle of the shearing resistance in this method is reduced with 30 in account to loosening the nature of the sand. Finally, through its formwork systems, it helps to make the pile concretely in a systematic way.
However, from the above discussion, it is clear that the four methods are highly necessary for identifying the shaft capacity in an appropriate manner. As per the huge number of construction companies in Australia, it has been come out that they majorly use mixed analysis method for their business as it helps them to examine the soil type as well as helps to apply load application to verify pile in a proper way. It can also be said that shaft capacity prediction has more than 10 methods among which the above-mentioned four methods are highly needed for construction sector.
There are two main approaches to determine the pile capacity. It includes field approaches and theoretical approaches.
(Zhou et al. 2016)
This test is usually done in the construction area to determine the pile’s load carrying capacity primarily the pile is loaded to the aimed level and then estimate the load carrying capacity of piles. This approach is giving result that is more realistic. Apart from that, this process is huge time consuming and more cost effective (Nguyen et al. 2017).
This process is based on the calculation. Usually this process is done in the laboratory. Through this process load, carrying capacity is calculated by the help of the necessary formulas, which is need for determination of the result.
Pile load tests are generally categorised as stress tests and strain tests. As commented by Lai et al. (2018), stress tests in the pile construction is performed for maintaining the load tests and constant rate of the penetration tests during field data collection. On the other hand, strain tests are considered in pile load tests for underpinning the low strain integrity and high strain integrity of the soil. Moreover, these tests are mostly carried out for the mentioned reasons below:
Lateral capacity of the pile is determined in the pile test for analysing the axial loads and measuring the lateral capacity of the pile. On the contrary, Baykal et al. (2017) argued that lateral pile load test associated with complex process as it requires the lateral deflection criteria. Hence, using vertical tests on pile is the effective one, which can help in the mobilisation of the pressure associated with the soil. This tests aid in determining the degree of distribution of the reaction of the soils for measuring the stiffness and fixity of the end pile. Factor of safety (FOS) requires being determined for measuring the ultimate load capacity of pile to consider the safety. Pile load test is the considered in large construction projects in order to make the foundation strong and effective. Hence, main purpose of conducting pile load tests is to analyse the FOS and to accommodate the soil with effective strata that can help in reducing the uncertainties of the construction projects.
Accurate estimation for pile setup provided the required information about the pile. Most of the setup of pile tests is attributed with the dissipation of huge pore water pressures associated with the pile. It is found that phenomenon of the time dependence is required for improving the pile capacity. In every study, the authors have agreed that there is a requirement of increase of skin friction of pile along with time in order to increase the bearing capacity of pile. Decrease in the pile capacity with the time has been reported in some construction, which has affected in the toe resistance rather than the shaft resistance. In case of clay soil, it is found that dissipation rates of pile are induced and the pore water pressure is quite slow (Lai et al. 2018). However, in granular soil, the pile setup is mainly consisting of breakdown of the pile load and the ageing of this soil. Parameters such as loaded platform, dial gauge, test plate, pore fluid composition, dial gauge fixture and others are used for controlling the thixotropy of the clay soil. As evident by Kramer et al. (2015), shearing strength of the soil varies based on the nature of the soil for which it is important to consider the features of the soil for mitigating the challenges like hardening and other failures. The majority of the set-up of pile tests is associated with the non-linear dissipation mainly in case of clayey soil.
(Source: Kramer et al. 2015)
The piles forward the loads in two ways. Primarily Tip in compression and secondly the piles are share the load along the surface, which also known as skin friction.
Capacity of load carrying in cohesive soil
The formula to determine the capacity of load carrying is as follows:
Qu= maximum load capacity (KN)
Ap = Area of cross- section of tip of the pile (m^2)
Nc = Factor of bearing capacity. (It is a constant value which is 9)
α= Adhesion factor
ci = average cohesion (KN / m^2)
Asi = Area of surface of pile (m^2)
Qsafe = Qu / 2.5
Capacity of load carrying in cohesion less soil
The formula to determine the load carrying capacity of cohesion less soil is as follows:
Ap = area of cross section of base of the pile
D = pile shaft diameter
Y = Soil effective weight of the soil
Nγ / Nq = factor of bearing capacity
Φ = Internal friction angle at the tip of the pile
PD = Effective excessive pressure at tip of the pile (KN / m^2)
Ki = Earth pressure coefficient
δi = Friction between soil and piles
Asi = Area of surface of pile (m^2)
Qsafe = Qu / 2.5 (Kramer et al. 2015)
From the above discussion, it can be said that pile test is highly necessary for making proper buildings under construction industry. The pile head settlement is a major result of pile test. From the installation of pile TP4, pile head settlement is possible. With the help of TP3, load test results are found through which many relationships are grown that are load versus settlement, load versus time and others (Omer et al., 2003). Shaft capacity is also considered as a result of pile test based on which shaft resistance capabilities are also declared. On the other hand, pile TP5 shows the pile diameter and its resistance capacity in a systematic way. Plasticity theory is also useful for getting major effects on pile test. Typical plots as well as net settlement are also discussed based on the pile test results where peak value is responsible for entire determination. TP2 and TP6 analyze shaft settlement along with shaft load based on only the pile test procedure.
Piles TP3, TP4 and TP5 were loaded sufficiently to mobilize shaft resistance Pus, as indicated by the plots in Figure 7. TP3 showed a clear failure as per Terzaghi’s (1943) where the maximum load was reached. In this case it was appx 15MN (Omer et al., 2003).
The study has developed various approaches of pile test which have major drawbacks while using in construction sector. The main disadvantage of the undrained analysis is that it performs in long term basis. Therefore, construction sector fails to use it for any short term project. In addition to this, drained analysis does not provide proper pile test in time of making wall systems under construction in an appropriate way (Alzoubi et al. 2015). Finally, the pile test methods are huge cost effective due to which various construction companies cannot use its approaches for properly testing the piles and its capacities.
The entire study has few limitations, as the researcher has not discussed all the things within the study. It is estimated that the researcher has discussed the undrained, drained, mixed and other methods for pile or shaft capacity prediction. However, the undrained an
d drained approaches have not been analyzed within study in a proper manner. The major assisting theory of pile test is the Pile Integrity Test theory, which has not been evaluated within the study. Moreover, the researcher has mainly focused on pile test methods through which the challenges have not been discussed in an appropriate manner.
The study has discussed the analytical methods of pile test in order to provide field test data analysis. It has been found that the pile test has major four methods based on which construction sector has predicted capacities of shaft. It has also been found that the management of construction department has followed plasticity theory in order to bring clear vision regarding the approaches of the methods of shaft capacity prediction. Pile load test is usually using for test the load carrying capacity of the bearing. Based on the overall study in has been discussed the several process of piles installation, including jetting, boring, unerring, dipping and others. Moreover those processes are done to determine the ultimate load carrying ability of bridge, buildings and others. There are several of ways to analyze the load carrying capacity like visual examination, digital examination and others. Obtain the load carrying capacity there are two approaches like field approaches and theoretical approaches. Field approach is mainly done by survey of construction area and the other hand the theoretical approaches are done by the help of the data analysis in the laboratories. Moreover in this study the necessary formulas for determine the load capacity of bearing has been discussed.
Two different set of approach have been identified that would help in achieving the research objectives, Inductive research and deductive research. The deductive research takes into account the scientific studies that have been performed earlier on the subject which are researched and collected in order review the facts. These are later then supported with secondary study data. The scope and benefit of this is to allow more focused study on the topic.
The other approach is inductive in nature, which is usually more appropriate in behavior understanding topics where the information is generalized using secondary data analysis and then confirmed with support of primary data. The current dissertation/research uses deductive research approach; there are a number of well established case studies in this field particularly by (Omer et al., 2003) which provides information for pile load tests in various settings and conditions.
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This research methodology section has demonstrated the procedures which are incorporated in the current design of pile. Moreover, in order to develop a better insight of time dependent settlement of pile materials in the clay soil and understand the frictional behaviour of the piles over time, experimentation process and laboratory testing of soil have been understood from secondary study. The experimental program has been carried out for examining the nature of the curve obtained while performing field test on piles by several researchers. The strength of piles on clayey soil has been analysed so that the projects of highway construction are done effectively. Moreover, analysis of methods for examining the creep behaviour of soil has been done with the use of laboratory testing process.
The soil sample has been collected from the clayey soil and the data of secondary sources have been tested in the laboratory for obtaining results. Time interval among testing and pile driving has been analysed for understanding the nature of test loading. Thesis papers and articles are evaluated for collecting the relevant data about the test. As mentioned by Sheil and McCabe (2016), three different types of piles are used in pile load test such as timber, concrete and steel. This study has analysed the tests result based on the steel and concrete piles to analysis the time dependent factors affecting in obtaining field test data.
Tests have been done for understanding the time dependent nature of piles and compared the tests results of field data. In this study, drained and undrained approaches have been compared for analysing the pile load-test results on the clay soil. In addition to this, tests results of compression tests have been verified for determining the bearing pressure of piles. Spacing of the piles has been checked so that pile foundation can be done in a order manner. Process of loading arrangement has been designed for transferring the load safety during the pile tests. Full methods have been discussed about the testing procedures so that challenges with this test process can be understood. As opined by Byrne et al. (2015), pile load testing is done based on the theoretical and field approaches in order to understand the in-depth tests results. Theoretical approach has been used in this study for predicting the field test values that are obtained during the pile testing. Measurement of pile heads are done with levelling methods with the use of external datum. In this method, settlement measurement is done with the use of scale and deep datum points. Movement of pile heads has been noted for understanding the time dependent settlement curve of the test.
Equipments used for pile load testing are helpful for implementing tests result in the field data. For example, use of double pile hammer is used for demolishing rocks for extracting the piles. Static pile load testing is done with the load system and data acquisition system. This study has used static pile load testing for determining the capacity of piles in order to increase the FOS factor during construction. Equipment like strain rods has been used for deriving the field data at every interval as per the desirability of pile shaft.
(Source: Byrne et al. 2015)
Laboratory testing plays an important role in determining the practical implications of test values. Not destruction testing process in the laboratory has been performed for understanding the level of impact on drop hammer. Based on the comments of Bourne-Webb et al. (2016), tests results of laboratory is helpful in the achievement of the real values, which are further helpful for understanding its challenges and benefits in the construction industry. As per the analysis of pile testing process, this study has considered the implications of static pile load tests for measuring the bearing capacity of piles. These results are important for presenting the final design in construction. The ultimate limit state and determination of geotechnical capacity of bearing is obtained. In this case, load tests have been applied for predicting the relationships among the time settlement of pile and time required for the load-holding period. In addition to this, lab tests results from several field studies has helps in understanding the time settlement based on the nature of applied load in the clayey soil.
Bearing capacity of the piles has been analysed with the use of both theoretical and experimental procedure in this study. Here, the researcher has used theoretical procedure based on the scholarly journals for discussing the properties of soil and magnitude of stress, which directly affects the time settlement curve. This study has evaluated the shear and horizontal displacement curves based on the test results. Moreover, time interval among testing and pile driving has been checked based on the pile type and condition of subsoil. For example, it is found that sufficient time is required for effective curing in cohesive soil that is clay soil. With the analysis of testing procedure, the researcher is able to identify the real data, which is required for making the pile tests process strong.
different field researches and thesis, analysis of testing methods has been
evaluated for understanding the relationship curve with time settlement and
field data. Moreover, in this chapter, it is found that researcher has
collected field data from secondary sources and has compared those data for
analysing the nature of curve and distinct relationships in the pile load
tests. Primary data that are used in the field studies are compared to
understand the effectiveness of obtaining ideal data that can help in the
uplift of construction industry. Based on the assessment of testing methods and
theoretical procedure, the next chapter of thematic data analysis has been
conducted in order to make the effective.
This study intends to progress further with the aim of obtaining the research objectives. Moreover, this chapter of the study intends to fill up the gaps found in literature review section. Different secondary data namely journals and articles have been considered for this task. The study has developed six themes based on the identified blind spot in the literature review. In this section, a detailed method of drained and undrained pile foundation will be discussed. The existing challenges in these methods will be mentioned here. Furthermore, this chapter will render a detailed analysis of Pile Integrity test theory, which has been overlooked in the literature review section. This chapter will also mention the effectiveness of Leda Clay load testing process to evaluate whether found challenges can be addressed in this method. The main intention of this chapter is to enhance topic-based knowledge and find out the scope of recommendation in the existing pile foundation processes.
(Source: Zhou et al. 2018)
Zhou et al. (2018) has used undrained approach in pile foundation for understanding the behaviour of piles, which are driven, with the use of numerical methods and experimental as well as theoretical data. Numerical analysis has been performed in this study by the author for describing the nature of the expansion based on the instrumented pile located in the construction site. The most suitable equation that is helpful for understanding the relationship among the setup of pile and logarithm is mentioned below:
Q/Qo = I + A log(t/to) ——— (1)
In this equation, Q is the pile capacity and t is the time after the pile driving. Moreover, Qo is the capacity of pile at initial time and it is to be the setup factor. It is found that this factor varies depending upon the type of soil, type of pile and driving technique. Moreover, another researcher, Keawsawasvong and Ukritchon (2017) has used different equation for estimating the setup for pile. This approach is the un-drained approach, which is used for understanding the skin friction resistance of pile, which is given below:
Qs = Σ fs p ΔL ———– (2)
Where, p is the parameter of pile, L is the length of pile and fs is the unit frictional resistance among clay soil and skin of pile. Hence, for employing and understanding the effect of behaviour of pile at several stages of time, Fs can also be calculated as per the laboratory testing and time dependent analysis. Using this equation, the field data from the instrumented piles has been verified with the use of apparatus of direct shear.
Un-drained approach in pile foundation is used for analysing the overburden pressure generated during pile installation. As mentioned by Abyaneh et al. (2018), un-drained shear strength is calculated with the use of un-drained approach for reducing the pressure level on pile. The formula used for calculating the un-drained shearing strength is mentioned below:
Su = (qc – σν) / Nk ———- (3)
In above equation, σν represents the overburden pressure associated at different depth level and Nk is the cone factor, which is based on the plasticity index value. This helps in determining the nature of internal friction angle of soil, which is further helpful for understanding the effective pressure on pile. Yang et al. (2016) has conducted extensive study on depicting the behaviour of pile group in the field. As per his observation, it is found that pile group is consolidated in the sensitive clay more than the sandy soil. From this, it can be noted that order and time of pile driving among every couple of pile in a specific group can represent as an ideal parameter for the dissipation of pore water pressure. Moreover, it can be said that this setup by using un-drained shearing approach can be helpful for deriving a specific curve that suits most of the construction projects.
2.2 Theme 2: Challenges associated with pile test process and un-drained approach in the construction industry
Major cracks that are found in the soil are responsible for affecting the reliability and quality of the piles. It is found that cracks can be developed if the pile construction is not done in effective manner. Pile integrity needs to be developed for attaining informative data based on the nature of the cracks developed in the pile. On the other hand, Nie et al. (2016) discussed that similar to cracks, there are voids, which are present in the clayey soil that is liable in affecting the quality and consistency of the pile material. This issue associated with the soil is found to affect the load bearing capacity of the concrete piles. Moreover, this also reduces the cross-sectional area and dimension of concrete piles. Apart from this, it has been found that necking occurs on the concrete piles during the casting of shafting when it is constructed in soft clay. The sudden change in the cross-section results in the occurrence of necking and creates gap among the length of the pile. Test process such as sonic echo can be used for the evaluation of this serious issue. Selecting the type of pile and installing method is the most common problem during pile foundation. It is found that estimation of time settlement along with the differential settlement among adjacent foundations is another issue that requires to be mitigated for generating smooth construction. Most of the time, it is observed that workers are not able to develop an effective margin safety against the pile and the soil. The challenges that are associated with the use of un-drained approaches are mentioned below:
From the previous studies, it has been found that different set up for pile has been derived which can help in the construction of highway and other projects. As commented by Hamada et al. (2015), pile construction requires to be done based on the implications and theory of pile integrity test. The challenges associated with the pile testing needs to be verified. Borehole stability issues are largely found in the static pile load test. These pile construction problem and their side effects are to be measured for the prevention of pile deformation. The piling constructions are found to face major issues in the urban-environment can be noticed such as pile bore-retention in concrete-errors in basement excavation. Hence, it can be said that these issues which are discussed needs to be diminished for making the pile construction within the infinite time so that time settlement curve is ideally generated.
In case of undrained pile foundation, the clay sustains water and the water cannot escape the wet clay for a long period. Though founding piles on such clay takes less time and renders effective short-term stability, it cannot render much long-term stability. Drained loading method is used in pile foundation to achieve more long-term stability. In this case the wet clay is left for a longer period (a few months even a year) to let the water escape fully. After the clay becomes dry, the base becomes sturdier. Except for these criteria, drained loading technique is used to found piles in stiff and consolidated clays (Han et al. 2016). In the drained pile foundation method, the value of pile soil adhesion is zero. The load capacity formula for drained pile foundation as follows.
qs(z) = μσ’h= μ(z) * K(z) * σ’v(z) = β(z) * σ’v(z)
In this equation, qs are the unit skin resistance between a pile and soil around it. The unit skin resistance is calculated by multiplying friction factor and vertical effective stress. The friction factor μ is the amount of friction between soil and pile. Therefore, this amount depends on the material of both elements. On the other hand, the vertical effective stress depends upon the dimension and material of the pile itself (Kramer et al. 2015). The rest pressure coefficient is K and it depends on the installation mode, which is the method of installing the pile in the soil. The formula of K is as follows.
K0 = (1 – sinφ′) (OCR)^0.5 ≤ 3
Here, OCR is the ratio of over consolidation.
(Source: Influenced by Han et al. 2016)
From the above figure, it can be said that in case of drained approach of loading, the shear strength increases due to consolidation. As mentioned by Mo and Yu (2017), drained strength cannot be measured easily because unlike drained approach, unconfined test of compression cannot be applied in this approach. On the other hand, the methods used for determining the drained strengths like undrained triaxial tests and consolidated drained tests are more expensive than unconfined tests of compression. Moreover, these tests are not applicable in all pile foundation cases and thus, pose as a limitation. Furthermore, unlike the undrained pile loading approach, the drained approach requires another factor called drained stiffness index. This factor is necessary in order to find out the pore water stiffness. As mentioned by Józefiak et al. (2015), soil shear strength is another important factor in this approach and it is easier to calculate. However, this factor aids the purpose only if the soil experiences load from outside. Otherwise, the drained strength will be less than undrained strength of clay and the approach will not be an effective one. Therefore, in case the overburden pressure is less than effective stress = (Su−c′) / tan (ϕ′), drained approach cannot be applied with total assurance.
Thus, the challenges of drained approach in pile foundation are listed below.
In order to understand the relationship between settlement of piles and elapsed duration of load holding period, it is necessary to the method of pile load testing. The settlement equation for a pile is mentioned here.
S = Ss + Spp + Sps
Here, Ss is the elasticity level of the shaft of the pile and it depends on the manufacturing product and other external environmental factors namely barometric pressure and gravitational force. Spp is the amount of settlement resulted by the pile tip’s load transfer. Sps is the amount of settlement resulted by the pile shaft load transfer. The main objectives of pile load testing method are to calculate the efficiency of soil and pile and load distribution capacity of the same. The Geotechnical Engineering Bureau has standardised this load testing method and rationalised it as the method that renders continuous improvement opportunity in designing (Bolarinwa, 2018). Moreover, it is useful to find out the resistance level of soil and it is more reliable than other used methods. As the safety factor is an important parameter in pile foundation, pile load testing method is an effective and suitable process. However, like other testing methods namely static formulation and dynamic formulation, load-testing method is not free of error and contains certain limitations.
There are many equipments required for pile load testing, namely test beams, oil manometers, hydraulic jack, dead weight, bearing plates, steel reference beams and few others. The associated cost is not minimal. The load test set up is also time consuming and critical.
(Source: Bolarinwa, 2018, p.7)
In this figure, a pile test loading setup has been developed with a jack that reacts from a dead weight heavier than the planned load amount. The support lines are kept at an equal distance from the position of test pile. A hydraulic jack is placed on the steel plate, placed on the centre of the pile’s head. The beam is placed in such way that its top level is within 50 mm of its normal level. Thus, it can be inferred that the whole procedure is complex enough. In case the load testing method reveals that residual movement is elastic, then it can be said that quality of the piles is superior. As mentioned by Ng and Ksaibati (2018), a PDI coefficient is a reliable tool to evaluate the capacity of a pile. Moreover, the ingredient of pile plays a critical role in determining the elasticity level. On the other hand, as mentioned by Houlsby (2016), installation coefficient is an effective parameter to prestress the clay under the tip of the pile. Therefore the main challenges of this pile load testing method are the complexity and high cost. Furthermore, there are certain limitations of pile load testing.
As the name suggests, pile integration test is effective to detect the integration level of the piles. This test is suitable in cases of driven concrete piles, structural piles, timber piles, cast in place piles and steel pipes filled with cement. As mentioned by Cui et al. (2017), a hammer is used to detect the flaw in the pile by creating acoustic waves inside the pile.
(Source: Influenced by Cui et al. 2017)
As shown in the picture above, a hammer is user to create sound wave inside the concrete pillar. In case, the wave reflects back, then the pile can be said to be intact. Though, in cases of necking and bulging, this method may not be much effective as the acoustic wave does not move along the sides and thus cannot render much information about the defects occured in the pile’s side (Wu et al. 2015). The method is effective to find out whether or not the depth of the pile is affected. Thus, the major defect like cross-sectional cracks in piles can be easily identified with this method.
The most usefulness of pile integrity test is its time and cost effectiveness. The result is instantaneous as the sound wave moves fast within solid objects. Though it is effective to detect major flaws in piles, there are certain limitations.
The analysis until now has shown the limitations from the aspect of cost and time in the major cases. Except these constraints, safety is another aspect in pile foundation activities. In this context, this study intends to mention Leda Clay method, an effective method of load testing that is more sustainable from all three factors namely time, cost and safety. In this method, the first step is to acquire Leda clay (Afshin and Rayhani, 2015). Excavators are used to collect this material from ocean and the method must be done slowly to maintain environmental sustainability. It is mentionable that, this material is available majorly by the seaside of Ottawa. The densil\ty of this soil is 1.53 Mg/m^3 and initially, it contains 67 % moisture particle.
The percentage of pure clay is 40 % and the consolidation coefficient is 1.4 x 10^-4 cm^2/s. Undrained shear stress of Leda clay is 50 kPa (Zhu et al. 2016). Due to this high amount of shear strength, Leda clay renders better sturdiness when they are drained. Thus, the aspect of safety and durability can be aligned with this method. It has been found out that, using Leda Clay may result up to 230 % sturdiness of piles. Furthermore, the sensitivity of Leda Clay is more than other porous materials used for piles foundation. This feature helps in fracture detection in primary stage of foundation. Leda clay is often a better choice to work with open end pillars with greater efficiency. Thus, itr can be said that, Leda Clay method is an effective choice for testing pile load.
This chapter has developed a thematic analysis on the topic in order to fill in the literature gap. Six themes have been developed in this chapter, where the first theme has discussed undrained approach of pile foundation and it has been mentioned that, this method is used to calculate the overburden pressure of pile foundation. Moreover, this approach can be suitable for many construction projects where the soil is soft. The second theme has mentioned certain challenges in pile testing methods namely finding cracks in pile integrity method. The third theme has mentioned drained approach of pile foundation and has found out certain limitations namely high cost and duration. Moreover, in this method, solid shear strength cannot be found out effectively. In the fourth theme, pile load testing method has been mentioned and its limitation regarding cross sectional variation has been mentioned. The fifth theme has discussed the effectiveness of pile integrity test and its effectiveness to find major fractures inside a pile. The six and last theme has mentioned Leda Clay testing method which as effective to address the issues of time, cost and safety.
Based on the overall discussion made above in the research study, it has been analyzed that there are several factors, which are related to pile testing. Even, discussion has been made on the relative problems, remedies and others factors regarding the pile load test. Apart from that examination methods of soil creep behaviour, methods of curve fitting, load displacement time data plotting, effective load value calculation process for infinite time are also has been discussed in this research. Moreover, it has been found that the pile load test is time depending test. Base on the literature review section it has been found that pile load test is direct method of identifying the ultimate geotechnical load carrying capacity. There have been several of methods for pile installation like weight dropping, explosion, water jetting, boring, under rimming and others. Moreover, water jetting has limited application in pile installation. Water jetting is applicable when piles are installed in the sandy gravel area. Weight dropping is done with the help of the hammer. The hammer is mainly operated by the help of hydraulic action. Apart from that it has been found that the pile load test is initially used for determine the load carrying capacity of buildings, bridges and other structures.
There are two approaches for design the piles it includes field approaches and theoretical approaches. Field approaches helps to get values that are more realistic. Based on the methodology section it has been found that there are several of methods used for analyzed the pile load test. Primarily Leda clay method has been used for pile load test. Into the haphazard sample of lead clay, the different diameter of piles was driven to determine the load carrying capacity of clay. It has been found that 60 % of pile capacity increase after the twelve days of the initial pile installation. Apart from that visual examination, digital examination, drained pile foundation method, untrained pile foundation method and others has been also used for pile load test. Secondary data analysis methods have been used for pile load test. Based on the overall research several of themes have been chosen by the help of the newspaper article, journal and other sources. It includes pile integrity test theory, Leda clay method, pile foundation method and others. Based on the overall research paper it has been found that load test is the primary step for any construction work. Pile load test is one of the main loads testing process among other load test. Moreover, through the Pile test it is possible to determine the ultimate and safe load carrying capacity of any buildings, bridges and others
|Specific||To provide training on time management and resource management|
|Measurable||This can be measured by providing the training among the workers to develop their working skills. This will also ensure in making them more appetite to achieve their goals in time within a restricted resource.|
|Achievable||This can be achieved by providing training among the workers in a specific season. They can be considering 40 to 50 workers per session to provide the training to develop their working skill, time management and resources management.|
|Realistic||Completion of the training the feedback can gather from the workers to understand their problems. Moreover it can also helpful to develop the procedure of pile load test for determine the load carrying capacity.|
|Time bound||1 to 2 months|
|Specific||To incorporate the unconsolidated undrained (UU) test in order to determine the drained strength|
|Measurable||The drained strength cannot be measured by the help of the unconfined compression test. They can incorporate the unconsolidated undrained (uu) test in order to find out the drained strength.|
|Achievable||This new process can be achieved by represent the proposal to the management team of the construction work. This will further reduce the issues while determining the drained strength. Hence, the planning will be more accurate and have a more productive impact on the overall planning. This process further need to be made by hiring professionals and providing effective mode of training to the workers.|
|Realistic||Determination of drained strength in case of determines the load test unconfined compression test cannot be useful. In order to find out the drained strength the construction company can introduce the unconsolidated undrained (UU) test.|
|Time bound||1 month|
|Specific||To organize a meeting about the implementation of new plan like Leda clay process to ensure the process of pile load test|
|Measurable||This can be measured by implementation of Leda clay method to determine the pile load test. This also ensures the process of pile load test to find out the load carrying capacity.|
|Achievable||This new implementation can be achieved by the meeting among the managers of the construction work. Moreover professional can be required for implementation of those new plan.|
|Realistic||Completion of the installation of Leda clay process it can be necessary to gather feedback from the workers about the working of the new plan.|
|Time bound||1 to 2 months|
|Specific||To organize meeting to discuss the cost factor of the pile load test|
|Measurable||This can be measured by organizing a meeting among the engineers, managers of the construction company to find out the cost reduction process of the pile load test. This will further make the managers and the associates of the project to gather information about the ways they can handle the project without further costs.|
|Achievable||This can be achievable by implement some new plan like Leda clay method to reduce the cost of the pile load test. Moreover high quality machine can be installed for increase the efficiency of the work and also increase the machine life.|
|Realistic||High quality machine can be installing for increase the life of the machine as well as reduce the cost of the pile load testing process. Moreover high skill labour can be required to maintain those machines.|
|Time bound||1 month|
In the present research study the objective are developed based on the topic which relates with pile testing in a construction project. Moreover, the benefits as well as the drawbacks of this testing method have been analyzed in the above discussion.
To study the relationship between settlement of pile and time elapsed during a load-holding period
This objective has been analyzed and explained in the data analysis section whether the relationship between settlements of pile ands time elapsed during a load holding has been administered. Based on the overall discussion it has been found that time is directly proportional to settlement of pile.
To fit Function curves that can be used to predict or extrapolate settlement at infinite time
The above objective has been analyzed and explained in the outcomes of pile test of literature review section. Based on the overall discussion it has been found that the function curve can be use to predict the settlement at infinite time. Moreover, pile head settlement is possible with the help of TP4. Shaft capacity has been also undertaken for the pile load test.
To investigate how the applied load value affects the settlement at infinite time
The above objective has been analyzed and explained in the literature review section, process of pile installation. Curve fitting methods is used to determine the process of pile displacement at infinite time. In addition to this, the behaviour of pile installation has been also analyzed in this section. Based on the discussion it has been found that for pile-displacement measurement pile hole testing equipment, pile dynamic measurement and others are required.
The overall research is based on the pile
test canalization. Based on this research pile test is usually done to
determine the load carrying capacity of clay. Apart from that secondary data
analysis method has been used to determine the pile load test. In future
research primary data analysis methods can be made to determine the load
carrying capacity of clay through pile load test. The primary data analysis
methods survey of the construction area, taking Interview of the workers and
others. Moreover, there has been found some gaps while research on the pile
load test. The pile load test is more time consuming and huge cost effective.
In future studies it can be analyze the factor of reducing the cost and time of
the pile load test.
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