Pile Diameter Research Articles

Experimental Study of Axially Loaded Pile Group Near a Sloping Ground

Understanding the axial loading response of pile group located near the crest of the slope is of practical value to structural design. In this paper, a large-scale test setup (1.8 m × 0.90 m × 0.90 m) has been developed to investigate the response of pile group (2 × 2) located near the crest of the slope under axial loading. This paper presents a series of physical modelling tests performed to investigate the effects of slope angles, distance of the pile group from the slope crest, embedment length of the pile group and pile diameter on the axial loading response of pile groups. The results show that the response of pile group located near the crest of the slope approaches to the level ground condition with increasing edge distance from slope crest. In addition, the horizontal displacement of pile group towards the slope face increases with decreasing distance of pile group from the slope crest or embedded length of piles or with increasing slope angle. Furthermore, increasing pile diameter results in a low increase in the horizontal displacement for edge distances less than 3 dp (dp = pile diameter). However, the horizontal displacement is almost independent of pile diameter at edge distances greater than 3 dp. Higher embedded length results in the response of pile group approaches to the response of pile group located on the level ground at a shorter edge distance from the slope crest.

Experimental Analysis of Vertical Deformation and Bearing Characteristics of Bridge Piles in High and Steep Slopes

More and more rigid frame bridges with high piers and large spans are built in the high and steep slope areas of deep valleys in southwest China. The slow deformation of the slope in the geological sense often causes the problems of piles, which in turn causes damage of the upper bridges. The vertical bearing characteristics of bridge piles in slope still need to be conducted because of the peculiarity of slope topography. The vertical deformation and bearing characteristics of piles in the slope area were experimentally studied by considering different influencing factors and the fitting formula for the ultimate bearing capacity of the piles under vertical load is obtained. The results show that the vertical deformation and ultimate bearing capacity (defined by vertical limit settlement deformation of 0.013 times the pile diameter) of the pile are closely related to its position in the slope. The pile in the middle of the slope has the lowest vertical ultimate bearing capacity. Moreover, the side frictional resistance transfer depth of the pile in continuous slope is greater than that of the pile in unilateral slope. Additionally, the slope angle has a significant influence on the vertical bearing performance of piles. The delayed settlement of the pile top decreases approximately 40% at most and the vertical ultimate bearing capacity of the pile increases 48.6% at most as the slope angle decreases by 15°. Meanwhile, the side friction resistance of the pile increases with the decrease of slope angle. The bending moment applied to the pile top reduces the vertical ultimate bearing capacity of the pile and increases the axial force of the pile body. The results can provide data support for pile design and instability judgment with similar geological conditions.

A laboratory study of wave-induced local scour at an emergent pile breakwater

A pile breakwater is a row of closely-spaced piles, placed in a side-by-side arrangement, to dissipate wave energy and prevent coastal erosion. It is important to understand the local scour at a pile breakwater for its foundation design. This paper reports a set of wave-flume tests on the local scour around the piles in regular waves. A laser scanner was used to measure the change in the three-dimensional bed elevation. Five values of Keulegan–Carpenter number were examined in this study. Scour holes near the pile breakwater were developed due to the oscillatory jet flow through the gaps between adjacent piles, and sand ripples were observed on both sides of the structure. The migration of the sand ripples was either onshore or offshore, depending on the wave conditions. The maximum scour-hole depth had an exponential growth with the duration of wave attack, and the equilibrium depth was found to be deeper than that for a standalone pile. Both the scour-hole depth and length were found to be scaled by the pile diameter. The ripple length and steepness were in general agreement with recent empirical formulas in the literature in spite of the presence of a pile breakwater.

Numerical Study on Lateral Response of Offshore Monopile in Sand under Local Scouring Conditions

Currently, p-y models have been broadly adopted for estimating the lateral bearing capacity of large-diameter monopiles in offshore engineering. However, the existing p-y curves cannot reflect the effect of pile diameter D on the lateral response of monopiles under local scouring conditions. In order to extend the existing p-y model to a large-diameter pile, a well-calibrated three-dimensional pile-soil model performed by ABAQUS is used to study the effect of the pile diameter D on the ultimate soil resistance P and the initial stiffness k of the Lin’s p-y model. Based on the numerical simulation results, two diameter-related parameters A and B, which represent the relationships between the ultimate soil resistance and the initial stiffness obtained by the numerical model and the Lin’s p-y model, respectively, are proposed and introduced into the Lin’s p-y model to present a modified p-y model. The comparison results show that the proposed modified p-y model is capable of providing a better estimation of the lateral response of large-diameter monopiles than the existing p-y model under a scouring condition.

Lateral response of pile due to combined load under free and fixed conditions

Pile foundations are used to support both vertical and horizontal loads in many geotechnical projects, such as coastal and offshore engineering. In this project, the Finite Difference Method is proposed to solve the differential equation governing the lateral and axial pile response. Initially, the behaviour of the pile subjected to lateral load will be analysed. The effect of various parameters like pile head fixity, the cohesion of surrounding soil, pile diameter, and length of the pile on lateral pile response will be analysed. Finally with these conditions, the deflections profile of the pile subjected to both lateral and axial load is investigated. By using python code we can easily find out the increase in diameter of pile, cohesion of surrounding soil effect on pile head and effect of increase in combined load will be studied. The above stated parameters will be studied for combined loading also under the free and fixed head conditions.

Assessment of Lateral Load Capacity of Single Pile at Bettiah Site: A Parametric Study

Pile foundations are widely used and accepted approach to transfer superstructure load to a deeper and stronger stratum. This work has been focused on the assessment of the effect of different parameters associated with piles such as pile diameter, pile length, grade of concrete and pile head condition (i.e., free or fixed) on the lateral load capacity. To evaluate the lateral load capacity considering the aforementioned parameters ‘IS Code’ and ‘Matlock and Reese’ methodologies have been utilized. The soil exploration data has been collected from ten different boreholes near to the railway bridge at Bettiah site, Bihar. The results of lateral pile load at different boreholes reflects that the lateral load capacity of pile significantly increased with the increase of pile diameters and grades of concrete. The lateral load capacity of pile was increased approximately by 13%, from both IS Code and Matlock and Reese methods, when the grade of concrete was increased from M25 to M40. It was also found that the condition of pile head also plays a major role in lateral load capacity. The lateral load capacity of pile obtained from IS code method under fixed head condition was found to be higher as compared to free head condition. It has also been observed that the lower values of ultimate lateral load capacity for fixed head and lower values for free head condition was obtained by IS Code as compared to Matlock and Reese method.

Scour depth development at piles of different height under the action of cyclic (tidal) flow

The impact of cyclic (tidal) flow on scour at cylindrical monopiles in the live-bed regime has been examined on the basis of results from mobile sand bed flume experiments. Four tests were conducted with four 0.114 m diameter piles of differing stickup height placed across the 4 m wide test section of the Fast Flow Facility. The tidal tests Tide01, Tide02 and Tide03 had the same peak current speed in forward and reverse direction with different cycle periods to examine the role of cycle length on scour. The period in Tide01 was approximately halved in Tide02 and doubled in Tide03. A unidirectional test Uni01 was run for comparative purposes. The results have shown how the cycle length adopted in testing has a key controlling effect on the scour achieved in a fixed number of cycles. The scour data measured on two sides of the piles at 1 Hz are plotted both in time-series format and pairwise to illustrate the cyclic nature of the scour development and recycling of sediment within the scour hole. The effective work method of Link et al. (2016) provides a good correlation for the dimensionless scour depth. The cyclic behaviour of the scour difference across the pile diameter has been analysed in terms of a basal slope and the magnitude of the scour depth, akin to geotechnical testing of monopile response to cyclic loads. Comparison with field measurements of scour shows that the cyclic tests can achieve non-dimensional scour depths found in the field. A progressive reduction in the slope angle is demonstrated for increasing number of cycles but further investigation of the different angle observed in field and laboratory is required. Finally the effect of pile stickup height is evaluated using both published and the current data, and a modified value of the Sumer and Fredsøe coefficient is proposed for undirectional and tidal scour. • Experimental analysis of tidal (cyclic) flow impact on scour development at piles. • Updated coefficient in prediction equation for scour at truncated piles in unidirectional and tidal currents. • Presentation of results in terms of cyclic behaviour of scour magnitude and basal slope in the scour pit.

Enhancement of Open-Ended Pipe Pile Embedded in Sand Using Steel Collar

The open-ended pipe piles are among the piles that are employed the most frequently because of their advantages, including their ease of transport and resistance to driving stress. It is further distinguished by the fact that the soil column formed inside the pile increases the pile capacity. Numerous ideas have been presented forth in the literature to enhance the performance of these piles. In this study, it is suggested that a steel collar be used at its lowest end to enhance the performance of the pile. Ten experimental tests for piles embedded in loose sand soil were carried out to determine the impact of the collar diameter and length concerning the pile diameter and length. Three diameters, 1.5D, 2D, and 3D, and three length ratios: 10, 20, and 30% were employed. The use of a steel collar improves the load capacity of the pile and reduces settlement, according to the data, although the collar with a diameter of 1.5D and a length of 10% had little effect. According to the study, using a collar with a diameter of 2D and a length of 20% is enough to double pile capacity and prevent the overlapping effect of stress bulbs between neighboring piles. As a result, using such a method minimizes the cost of constructing the foundations because of the reduction in the number of piles required.

Finding reserves of bearing capacity of bored piles

In recent years, due to population growth plans and accelerated economic development, high-rise buildings have become increasingly common in many cities and megapolises around the world. Due to the development of engineering construction, the type and technology of pile footing, which form the basis of such buildings, as well as the control of both single piles and a group of piles, have been significantly improved. At the same time, today the task of adequate assessment of the pile load capacity and justification of effective methods of revealing the reserves of its increase is actualized, because the manufacturing technology is constantly developing, in addition, often the functional purpose of the building itself, the type and intensity of the loads acting on it change. In view of the above, the purpose of the article is to investigate modern scientific- methodological approaches to search for reserves of bored pile load capacity. In order to carry out the study, the article used numerical methods for analyzing the stress-strain state of piles and means of the software package "Plaxis 3D Faundation". In the course of empirical experiments, it was found that the most acceptable results in the load testing of bored piles are given by the Shen method. Besides, the comparison of the results of static probing and static tests with theoretical calculations allowed to reveal the reserves of the actual pile load capacity, and also to determine on what parameters of its installation and characteristics the difference in load capacity depends more: the soil sciences in the pile base, pile diameter, pile length. Theoretical significance of the obtained results lies in the development of methodology for identifying reserves to increase the load capacity of bored piles. Conclusions have practical value that can be used in the process of laying the foundation of high-rise buildings to optimize the number and geometry of pile placement taking into account the reserve of their bearing capacity.

Evaluation of the Bearing Capacity of the Board Pile in Collapsible Soil using A Laboratory Model

The pile’s ultimate capacity or failure load must be computed by some criteria using load-settlement curve data gathered during the pile load test. Many scholars have proposed several approaches for evaluating the pile’s ultimate capacity in the past. This study compared different failure criteria to predict the ultimate load capacity for piles with two different lengths-to-diameter ratios embedded in gypseous soil with gypsum content of 60% under soaked and unsoaked conditions. Two types of piles were used. Floating pile and end-bearing pile. Davisson, Brinch Hansen’s 80 percent, Chin-Kondner, Mazurkiewicz’s, and Brinch Hansen’s 90 methods that were used in this study predict a higher value of the ultimate pile capacity, whereas the Decourt Extrapolation method gave fluctuated value. Fuller and Hoy’s, Butler and Hoy’s methods give far away value from realistic. On the other hand, Shen’s, ASTM, Terzaghi, and DeBeer’s methods predicted an acceptable and realistic value. The failure criterion of (15%D) where (D) is pile diameter according to(ASTM D-1143) was adopted in this type of soil.

Analysis of different elevation buildings with heights of 4, 8, 12, 16, 20, and 24 floors on friction piles

Foundation is one of the most important parts of the structure. The design and selection of foundations must be carried out properly to strengthen the structure. Different elevation buildings require more careful foundation design than other structures. The bearing capacity and settlement of the soil acting on the pile foundation will be very important to be taken into consideration in the construction of different elevation buildings, because the different elevation buildings have different heights, so the placement of the foundation depths is also different. There is load data to be used, load data will vary according to the elevation of the building. The difference on structure elevation is four-storey buildings until it reaches 24 storey building. Each floor has a height of three meters. The foundation analyzed by using bored pile. The soil data is from Central Jakarta. The foundation will be analyzed under the following condition. The foundation will be placed at the same pile diameters which is one meter and uses different dephts. In this study, the bearing capacity and soil settlement analysis was carried out using bored piles on the conditions described before. The result of this research will provide information about bearing capacity and settlement that occurs on different elevation building if the foundation uses a friction piles. This research concludes that the use of friction piles in ineffective.

Analysis of the behaviour of the floating pipe pile foundation on soft soil

Planning the foundation according to the characteristics of the soil is the most important thing before starting construction. In recent studies, the use of PVC pipe pile foundations has been introduced. These foundations, called floating foundations, offer a lighter and more economical solution for simple buildings on soft soils. The study involved variations in pipe diameters of consistent lengths. In laboratoryscale axial loading tests, the behaviour of pipe stacks against load drop is observed. The bearing capacity of pipe piles is evaluated through a static loading test, with one end of the pipe pile hermetically sealed and aspirated in an alternating pile in a glass box filled with soft soil with a content of 98%. The results of this test are then analyzed with the Chin Method Interpretation to determine the carrying capacity and behaviour of pipe piles against soft soil, The results of the analysis show that the diameter of the pipe piles has a significant effect on the bearing capacity of the foundation. Although the results are promising, further research is still needed, especially in the development of foundation construction suitable for multi-storey buildings in areas with soft soil or peat

水平力を受ける中詰めコンクリート二重鋼管杭の変形特性とその算定法

Loading tests and numerical analyses using the finite element method were carried out to clarify the deformation characteristics of a concrete-filled double steel pipe pile subjected to a horizontal load. The diameter and length of the concrete-filled double steel pipe pile were about two times and ten times the inner pipe diameter, respectively. The results indicated that the steel pipe and concrete behaved as a single unit from the pile head to the central part of the concrete-filled double steel pipe pile. On the other hand, this unity was lost in the length range of 3 to 4 times the diameter of the inner steel pipe from the bottom end of the concrete-filled double steel pipe pile. This is due to slippage at the boundary between the steel pipe and the concrete, and local compressive deformation of the concrete. We attempted to simply calculate the deformation of this pile when subjected to a horizontal load by constructing a beam spring model that combines the interface springs between the steel pipe and concrete and Timoshenko beams. The applicability of this calculation method was verified by comparing the results with those of loading tests.

Model and field tests of drilled displacement system piles

Drilled Displacement System (DDS) and Continuous Flight Auger (CFA) piles are two popular techniques used for building pile foundations that offer advantages over traditional pile systems, including improved load-carrying capacity, reduced installation time, and less spoil generation. This article presents laboratory-scaled model tests conducted on model piles installed using the Drilled Displacement System (DDS) and Continuous Flight Auger (CFA) technologies on a test tank setup filled with soil. Model piles considering a scaling factor of 1/20 with a diameter of 20 mm and a length of 300 mm were adopted for the study. Static loading is applied to the model piles and the corresponding displacements are measured during each loading phase. The results of the analysis were compared for load-settlement curves and ultimate bearing capacity estimates for both DDS and CFA piles. Based on the study, the DDS piles were observed to perform well in terms of load-carrying capacity compared to the CFA piles. Further, full-scale field tests under static load conditions were carried out on DDS-drilled piles of diameter 400 mm and length 6 m. The load-settlement response from the field test shows good agreement with the model tests. Overall, the results of the study provide valuable insights into the behavior and performance of DDS piles that can be used to optimize their design and installation in different soil types.

Numerical study on pile group efficiency for piles embedded in cohesive and cohesionless soils

This paper aims to study the efficiency of pile groups with various numbers of piles and pile spacing. Axial loading tests on pile groups and also single piles were simulated using a three-dimensional finite element program to obtain the load-settlement curve and the ultimate bearing capacity of the piles which was later used to estimate the pile group efficiency. In this study, the piles were embedded in cohesive and cohesionless soils. The stress-strain responses of the soils and the concrete pile and pile cap were simulated using the Mohr-Coulomb and the linear elastic models, respectively. The numerical-based pile group efficiencies were then compared to those computed using the published formulas. To verify the findings, a series of parametric studies on pile groups embedded in stratified soil was performed where the parameters of the soils were derived based on a back analysis on a case study of a single pile axial loading test in South Jakarta. The results show that the axial pile group efficiency in cohesive soil would be less than or equal to one, whereas in cohesionless soil would be more than or equal to one, especially at pile spacing more than three times the pile diameter. Meanwhile, similar results as found in cohesionless soil were obtained for the stratified soil case.

Experimental Analysis of the Behaviour of Piled Raft Foundations in Loose Sand

This paper presents the experimental analysis that was conducted on small-scale 1g physical models of piled raft foundation structures with a group of 2 × 2 piles in loose sand. The purpose of the piles was to reduce the settlement of the raft. The test program included twelve experiments, three of which were conducted on a raft alone and nine on piled rafts at pile distances of 3d, 4d, and 5d and pile lengths of 10d, 20d, and 40d, where d is pile diameter. The test results show that the current conventional approach to design of piled raft foundations, at a high safety load factor in piles that assume to take the whole external applied load, is very conservative. Instead, it is more economical to apply a low bearing capacity factor for piles as settlement reducers and maximize use of raft bearing capacity to carry part of the external load.

A case study on the bearing characteristics of a bottom uplift pile in a layered foundation

The bottom uplift pile, which has been applied in practical projects, has the following advantages: the pile body is not easy to crack, good bearing characteristics, and small displacement of the pile top. Based on the bearing capacity test of foundation piles in the third stage expansion project of Lanzhou Zhongchuan International Airport, the upper part pile of the self-balancing test method was used to simulate the bottom uplift pile, and the anchor piles in the anchor pile method were regarded as normal uplift piles. The bearing characteristics of the bottom uplift pile in a layered foundation were studied by comparing these two kinds of piles. The results show that under the same displacement of the pile top, the ultimate uplift bearing capacity of the bottom uplift pile can be more than twice that of the normal uplift pile because of the fully exerted frictional resistance of the soil at the bottom of the pile, the Poisson effect of the pile body and the avoidance of the influence of pile body deformation on the pile top displacement. The maximum axial force of the bottom uplift pile appears at the bottom of the pile and gradually decreases from the bottom to the top, which is opposite to that of the normal uplift pile. The properties and thickness of the soil layers around the pile have a great influence on the distribution curves of the frictional resistance along the pile length of the two kinds of uplift piles. With changing soil layer conditions, the distribution curve may be a "parabola", a "straight line" or a "double line". The soil property plays a decisive role in the frictional resistance, which may cause softening. The influence of the pile diameter on the ultimate uplift bearing capacity is greater than that of the pile length, while the elastic modulus of the pile has little influence.

A small-strain soil constitutive model for initial stiffness evaluation of laterally loaded piles in drained marine sand

Three-Dimensional Finite-Element Method (3-D FEM) analyses were performed to investigate the initial stiffness of the laterally loaded piles in drained marine sand. A small-strain soil constitutive model developed based on Menq model was implemented in the 3-D FEM model to simulate the response of laterally-loaded piles in the sand over a range of small displacements. The model incorporated how the shear modulus for sand increased with the mean effective stress and decreased non-linearly with the increasing shear strain. The procedure of calibrating the model was proposed based on fitting the measurements from both laboratory tests and in-situ site investigation This soil constitutive model was implemented within a 3-D FEM analysis using an isotropic material with strain-induced anisotropy behavior in order to simulate the response of laterally-loaded piles under monotonic loading. A comparison of model predictions with laboratory and field test results indicated that this model had the promise to simulate the non-linear relationship between lateral load and pile-head deflection for mudline deflections ranging from less than 0.25-percent of the pile diameter.

Optimizing the thermal performance of energy piles using response surface methodology

Energy piles have been recently utilized as ground heat exchangers in ground source heat pump systems to improve the energy efficiency in the heating, ventilation and air conditioning (HVAC) systems for residential and commercial buildings. On top of the structural role of energy piles to transfer the mechanical loads of buildings to the ground, they are used to dissipate heat energy into the soil to reduce the consumption of energy and hence lower greenhouse gas emissions. In this study, eight factors affecting the thermal conductance of the energy piles are investigated to maximize the thermal performance of energy piles. These eight factors are the number of U-tubes, pile diameter, tube diameter, tube thickness, pile thermal conductivity, tube thermal conductivity, soil thermal conductivity, and velocity of circulated water in U-tubes. The significance of these factors is statistically evaluated, and the optimal values of the significant factors are obtained using response surface methodology. The results reveal that tube thickness, water velocity, and soil conductivity have an insignificant impact on thermal conductance of the energy piles, while other factors have a significant effect. This research may lay a foundation for future research in optimizing the thermal performance of energy piles and promoting their applications in practice.

Design of an Energy Pile Based on CPT Data Using Soft Computing Techniques

The present study focused on the design of geothermal energy piles based on cone penetration test (CPT) data, which was obtained from the Perniö test site in Finland. The geothermal piles are heat-capacity systems that provide both a supply of energy and structural support to civil engineering structures. In geotechnical engineering, it is necessary to provide an efficient, reliable, and precise method for calculating the group capacity of the energy piles. In this research, the first aim is to determine the most significant variables required to calculate the energy pile capacity, i.e., the pile length (L), pile diameter (D), average cone resistance (qc0), minimum cone resistance (qc1), average of minimum cone resistance (qc2), cone resistance (qc), Young’s modulus (E), coefficient of thermal expansion (αc), and temperature change (ΔT). The values of qc0, qc1, qc2, qc, and E are then employed as model inputs in soft computing algorithms, which includes random forest (RF), the support vector machine (SVM), the gradient boosting machine (GBM), and extreme gradient boosting (XGB) in order to predict the pile group capacity. The developed soft computing models were then evaluated by using several statistical criteria, and the lowest system error with the best performance was attained by the GBM technique. The performance parameters, such as the coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), mean biased error (MBE), median absolute deviation (MAD), weighted mean absolute percentage error (WMAPE), expanded uncertainty (U95), global performance indicator (GPI), Theil’s inequality index (TIC), and the index of agreement (IA) values of the testing data for the GBM models are 0.80, 0.10, 0.08, −0.01, 0.06, 0.21, 0.28, −0.00, 0.11, and 0.94, respectively, demonstrating the strength and capacity of this soft computing algorithm in evaluating the pile’s group capacity for the energy pile. Rank analysis, error matrix, Taylor’s diagram, and the reliability index have all been developed to compare the proposed model’s accuracy. The results of this research also show that the GBM model developed is better at estimating the group capacity of energy piles than the other soft computing models.