Settlement Of Pile Foundation Research Articles

Settlement of a Pile Foundation Considering Linear and Rheological Properties of Soils

Despite numerous studies of single piles and practical experience with their application, methods for calculating settlements of pile foundations remain limited. The existing objective need for specialized methods of pile foundation settlement calculation that take into account the rheological properties of the base soils is becoming more and more important, especially in the construction of unique objects in complex ground conditions. When predicting the stress–strain state of the pile–raft-surrounding soil mass system, it is allowed to consider not the entire pile foundation as a whole, but only a part of it—the computational cell. In the present work, we have solved the problems of determining the strains of the computational cell consisting of the pile, the raft and the surrounding soil according to the column pile scheme and hanging pile scheme, on the basis of the Kelvin–Voigt rheological model, which is a model of a viscoelastic body consisting of parallel connected elements: Hooke’s elastic spring and Newtonian fluid. According to our results, we obtained graphs of the dependence of strains of the computational cell on time at different pile spacing and different values of coefficients of viscosity of the surrounding soil, and a formula for calculating the reduced modulus of deformation of the pile. The results of the present study can significantly improve the accuracy of calculations during construction on clayey soils with pronounced rheological properties and, as a result, increase the reliability of pile structures in general.

ИССЛЕДОВАНИЕ НЕСУЩЕЙ СПОСОБНОСТИ СВАЙ НА ОСНОВЕ ЭМПИРИЧЕСКИХ ДАННЫХ, ДИНАМИЧЕСКИХ ИСПЫТАНИЙ И ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Axial bearing capacity is an important factor in designing of foundation. It must be able to carry the load of upper structure without any significant deformation due to important role in pile design. A part from empirical and numerical methods, axial pile bearing capacity can be predicted by pile driving analyzer test that use wave equation analysis during the test. Prediction of the axial bearing capacity and its distribution can be achieved by combining wave equation analysis with dynamic pile monitoring. This paper compares the axial capacity of pile obtained from PDA records with predicted axial capacities obtained using empirical, numerical, and interpretation of static load test method. The empirical method used NSPT data from bore testing that conduct in site, finite element method that uses in this study is Plaxis 8.6. Both of them was compared with PDA test result of axial bearing capacity. There is a difference value of the calculation results of axial pile bearing capacity and foundation settlement. Comparing with PDA, from empirical method has smallest deviation for axial bearing capacity which equal to -268.45 kN with percentage -6.05%, smallest settlement equal to 0,0044 m. Plaxis result shows that distinction between Qult result equal to -11.00 kN with percentage -0.24% and settlement of foundation equal to 0,005 m. From interpretation of static loading test method smallest deviation for Qult which equal to -40,00 kN, with percentage -0,90%, and smallest settlement equal to 0,0055 m. So, from all method the smallest deviation for Qult and PDA result is used finite element method. This is due to many data parameters has been inputted and analyzed in the Plaxis program, so the results of calculation analysis are more detailed and closer to the situation in the research site. Differences in axial bearing capacity can be caused by the test was carried out which depends on the accuracy of operator and parameters that used in the calculations.

Numerical Study of Piled Raft Foundation in Non-Homogeneous Soil Using Finite Element Method

This paper analyzes a piled-raft foundation on non-homogeneous soils with variable layer depth percentages. The present work aims to perform a three-dimensional finite element analysis of a piled-raft foundation subjected to vertical load using the PLAXIS 3D software. Parametric analysis was carried out to determine the effect of soil type and initial layer thickness. The parametric study showed that increasing the relative density from 30 % to 80 % of the upper sand layer and the thickness of the first layer has led to an increase in the ultimate load and a decrease in the settlement of piled raft foundations for the cases of sand over weak soil. In clay over weak soil, the ultimate load of the piled raft foundation was increased, and the settlement decreased by increasing the clay cohesion of the upper layer from 20 kPa to 70 kPa. It was observed that the load shared by the raft was very effective when using dense sand in the upper layer. In the case of dense sand over stiff clay, the percent of load carried by the raft is (30-40) %. Although, for the case of stiff clay over soft clay, the load percentage was almost constant (16-20) %. While for other issues, the sharing load of raft foundation was close and had the same behavior, the load carried by raft is between (8-12) %.

A new type of bridge structure reinforcement effect evaluation algorithm based on time series

A supplement method based on reusing the original bridge structure is suggested to expedite construction and reduce costs. Furthermore, theoretical analysis of the single pile bearing capacity is conducted, primarily involving the calculation of the bridge pile foundation settlement, horizontal resistance and axial bearing capacity. At the same time, considering that the time series data generated in the actual process often have characteristics of imbalance between classes, a cost-sensitive hybrid network model is also constructed. Its significance is the analysis of bridge reinforcement performance data. The experimental results show that compared with the cross-entropy loss function, the introduction of a cost-sensitive loss function can significantly improve the monitoring accuracy of abnormal data sets. The ACC– score, G-means and F-measures are higher than those of the specific cross-entropy loss function. The permissible bearing capacity of muddy clay determined using a network model complies with engineering standards in the evaluation of bridge reinforcement performance. As a result, the reliability of this form of reinforcement is improved.

Settlement of combined piled raft foundation of a nuclear power plant in non-liquefiable and liquefiable soils

The settlement analysis of a nuclear power plant (NPP) resting on the combined pile raft foundation (CPRF) under static and seismic loads is very important. However, it has not yet been reported in the literature as most NPPs are founded on raft foundation rather than on CPRF. In this paper, the settlement has been examined in detail. The geometrical nonlinearity at the interface of raft-soil and pile-soil is considered using the coulomb friction. The piles are rigidly connected to the raft. The nonlinear behaviour of the soil in the non-liquefiable soil is modelled using elasto-plastic Drucker Prager cap model and CycLiq model for the liquefiable soil. For this, user defined material (UDM) is implemented in the FLAC3D material library. Thus, a complete 3D finite difference model of an NPP considering raft-pile-soil-structure interaction (RPSSI) for nonlinear settlement analysis is developed. After successful validation of the present CPRF, numerical model with the literature, it has been used for further study under real earthquake acceleration–time history. Next, CPRF with NPP structure is studied under static loading, which is further extended for the nonlinear time domain settlement analysis. The effects of variation in various parameters i.e., spacing between piles, cohesion, friction angle, and Poisson's ratio of soil on the settlement, are examined and found to be significant. The dominant frequency of the earthquake significantly affects the response of the CPRF. It was inferred that the interface nonlinearity has greater significance in the liquefiable soil as compared to the non-liquefiable soil. Higher differential settlement in the liquefiable soil is attributed to the reduction in the stiffness of the soil. The findings of this study could be useful to frame the general guidelines for the economical design of NPP-CPRF systems.

Study on the Impact of a Metro Depot Cover Structure on the Existing Metro Structure and Additional Settlement of Tracks

The superstructure of the metro depot is not only convenient for traffic but also solves the land-use problem. However, the construction of the superstructure comes after the metro depot has been put into normal operation. The foundation of the depot is bound to produce secondary settlement. Based on the calculation method of the friction-end bearing pile of Mindlin’s solution in the specification, the superstructure construction project above the Beijing Guogongzhuang metro depot is taken as the basis. Under certain conditions, the settlement of the pile foundation under the action of secondary load and the influence on the track structure are calculated. Moreover, the finite element analysis software ANSYS 18.0 is used to establish the analysis model of the construction of the superstructure of the applied depot. The results show that the influence of the pile foundation settlement produces a certain additional influence on the surrounding tracks, and the maximum value locates at the center of the bearing platform and gradually decreases outward. Under the conditions of informative construction, uniform loading of the structure and control of the construction process, local bias loads and uneven settlements are avoided. The impact of the construction on the track can be effectively controlled, and the impact on the structure can be kept within the allowable limits. By comparing this instance with a number of similar superstructure projects in Beijing, this study shows that the overall risk of this type of project can be controlled and can provide a technical reference for similar superstructure projects on top of a metro depot construction in the future.

Analysis of Settlement of Group Pile Foundation in Linear Viscoelastic Soil

The settlement of a group pile foundation is the result of elastic-plastic settlement of the pile and rheological settlement of the soil. Unfortunately, most research only considers elasto-plasticity settlement of piles or rheological settlement of soils. Classical theories like the Poynting-Thompson model only provide some prediction for the elasto-plasticity behavior of pile groups, which cannot satisfactorily reflect the total settlement characteristics of pile group foundation. In the current paper, we presented a method to study settlement behaviors of pile group foundation in linear viscoelastic soil based on the pile-pile interaction factors, the calculated equation of settlement of single piles and pile groups under vertical loads that are derived, the influence law of pile end resistance, pile spacing, slenderness ratio, elastic modulus ratio, and Poisson ratio on pile end load ratio, and the interaction factors that have been presented. Finally, some typical predictive examples have been presented for a 2 × 2, 3 × 3 group pile showing settlement from a field test. It is found that the pile-pile interaction factors increase with the increase of the pile-soil elastic modulus ratio and length-to-diameter ratio but decrease with the increase of the ratio of distance to diameter, and the ratio of distance to diameter has little effect on the interaction factor when pile spacing is more than 10 d (d is the diameter of the pile). The error between the field test results and computed data is 14.9%, the settlement calculated by the present method shows good agreement with the reported results, and the correlativity coefficients R2 are greater than 0.9223, which signifies that the present method is suitable for the theoretical calculation and prediction of the composite foundation settlement of linear viscoelastic soil when piles are used to strengthen the foundation. The method would provide a unique view to quantitative prediction of the settlement characteristic of group pile foundation.

A novel short pile foundation system bonded to highly cemented layers for settlement control

While design methods of deep foundations are mainly developed for homogenous soil deposits, the presence of highly cemented layers could lead to underestimation of resistance and overestimation of settlement of pile foundations. This study presents a novel approach using competent caliche layers bonded to the top and bottom of a continuous flight auger (CFA) pile as a new composite foundation system named caliche stiffened pile (CSP). The key objective is to optimize the required pile length in a cost-effective approach without ameliorating soil properties. Settlements of the CSP foundation for a high-rise building were monitored and full-scale tests were conducted to measure piles’ capacity. Finite element back analyses were performed to avoid adverse effect of sample disturbance in settlement calculations. A back calculation of a test fill embankment was performed to determine soil stiffness parameters by simulating an unscheduled imposed load to the structure. Impacts of the CSP on controlling the settlement of pile foundation and optimizing the required pile length are investigated using finite element analysis and a parametric study. The proposed CSP foundation can reduce the CFA pile settlement significantly in the presence of caliche layers with thickness equal or greater than a pile diameter at CFA pile head and toe, where the CSP is located.

Performance of a Subgrade-Embankment-Seawall System Reinforced by Drainage PCC Piles and Ordinary Piles Subjected to Lateral Spreading

Coral sand is widely distributed in coastal areas and used as a soil foundation in an increasing number of projects. Historical records show that the liquefaction and lateral spreading of coral sand foundations occurred many times during earthquakes, resulting in serious geological and engineering disasters. Based on a rigid drainage pile, a PCC pile (Large Diameter Pipe Pile by using Cast-in-place Concrete) and drainage body are innovatively combined into a new drainage PCC pile, to reduce the harm caused by liquefaction and lateral spreading of the coral sand foundation. In this study, the seismic response of the subgrade-embankment-seawall system on the coral sand liquefaction site was simulated using a shaking table. The excess pore water pressure ratio, acceleration, average foundation settlement, seawall displacement, embankment deformation, and pile body bending moment of the ordinary pile foundation and new drainage PCC pile foundation under seismic loads of PGA peak ground acceleration = 0.05 g , PGA = 0.1 g , and PGA = 0.2 g on the coral sand site were analyzed and compared. Compared with ordinary pile foundations, the excess pore water pressure ratio, pile bending moment, seawall displacement, foundation settlement, and embankment deformation of the new drainage PCC pile foundation were markedly reduced, while acceleration increased, which showed that the new drainage PCC pile had a positive anti-liquefaction effect on the coral sand foundation.

Deviation rectification of a high-rise building with piled raft foundation: a case study

Deviation rectification of a high-rise building with a piled raft foundation was successfully carried out by vertically digging holes. Through site investigation and finite-element analyses of pile foundation settlement, the building tilt was attributed to shortening of the pile length, large post-construction settlement and cancellation of the setting of the post-cast strip of concrete between the main building and the skirt of an underground garage. A comprehensive rectification scheme was conducted, including drilling settlement-resisting micropiles on the side with a greater subsidence, cutting off the raft between the main building and the garage, vertically digging holes and disturbing soil on the side with less subsidence. When the rectified inclination reached the proposed value, the foundation was strengthened by the micropiles for settlement reduction and bearing capacity enhancement. During construction, close monitoring was carried out to guide dynamically the soil extraction operation and monitor building settlement. By analysing the monitoring data over time, the effectiveness of soil extraction for building rectification was verified, and the rectification mechanism of high-rise buildings supported on piled raft foundations was clarified. Finally, the rectification scheme was evaluated and discussed.

Calculation of surface settlement and pile foundation deformation caused by shield machine tunnelling along curve section

The shield machine tunnelling along the curve section causes more disturbance to the surrounding environment than the straight section. Pile foundation is the most commonly used foundation form in high-rise buildings, and high-rise buildings have extremely high requirements for controlling non-uniform deformation. Therefore, it is necessary to study the surface settlement and the deformation law of pile foundations caused by shield machine tunnelling along the curve section. Considering the shield machine tunnelling factors along the curve section and the coupling effect of piles and soil, the analytical calculation formula of the ground settlement and the pile foundation deformation caused by the shield machine tunnelling along the curve section is deduced. According to the actual project situation, a finite difference model (FDM) is constructed, and the correctness of the FDM and analytical prediction formula is verified by comparing the on-site monitoring data. The research shows that the error among the FDM results, the analytical prediction results, and the on-site monitoring data are small, and the surface settlement and pile foundation deformation meet the construction control standards. The friction resistance of the shield shell, the integrative gap at the shield tail (IGST), and the over-cutting gap (OG) are the main factors leading to the surface settlement. However, the shield shell friction and OG are the main reasons leading to the inner settlement of the curve section being more prominent than the outer side. The difference in the pile foundation settlement on both sides of the curve section is slight, the maximum settlement difference rate is 1.8%, and the maximum horizontal deformation rate of the pile foundation on the inner and outer sides is 9.2%, which shows that the horizontal deformation of the pile foundation is more sensitive to the asymmetrically distributed construction factors.

Safety Assessment of Tunnel Shield Construction for Existing Adjacent Bridges

Disturbances to the surrounding soil layer from a tunnel shield passing under a viaduct can cause uneven pile foundation settlement, negatively affecting the structure’s normal functionality. Therefore, its safety must be evaluated before tunneling. In this study, a numerical model is developed on Midas to simulate the differential settlement of pile foundations under a viaduct during the entire construction tunneling process. The evaluation basis is derived by verifying the various bearing capacities of the viaduct. The results indicate that when the shield excavation face is 12 m from the pile foundation axis, vertical displacement begins to appear and increases gradually as the excavation face approaches the pile foundation. The bearing capacity of the girder support and midspan section is lower than the section resistance and meets the specifications. In the anti-cracking calculation, when the bearing differential settlement is 5 mm, there is no tensile stress in the normal section of the main beam, and the tensile stress of the oblique section meets the specifications. Furthermore, in situations when the pressure must be verified, tthe calculation results meet the specifications. Based on this evaluation criteria, it is ultimately determined that the viaduct can be used normally after shield construction. This safety assessment method can serve as a reference for similar construction projects.

A simplified settlement prediction method for piled rafts in clay

A method for the estimation of the non-linear, time-dependent settlement of piled raft foundations (PRFs) embedded in saturated clayey soils subjected to uniformly distributed load under the single-drainage condition was developed. A total of 20 different rectangular PRFs resting on four different types of normally consolidated to moderately overconsolidated clays (overconsolidation ratios of 1, 2 and 5) were analysed to quantify their short- and long-term settlements. Rigorous three-dimensional, elasto-plastic finite-element (FE) analyses were performed with the critical-state-based modified Cam Clay soil constitutive model. Biot's coupled consolidation theory was used to model the time-dependent dissipation of excess pore pressure under the single-drainage condition. The FE analysis results were used to investigate systematically the influence of time and various soil and PRF parameters on the settlement responses of piled rafts. Fitted equations correlating PRF settlements and the degree of consolidation with various influencing parameters were developed. The proposed equations predicted the immediate and primary consolidation settlements and the degree of consolidation with reasonable accuracy and can be used in initial design stages.

Method for Calculating the Settlement of Circular Pile Foundations of a Reservoir

Method for Calculating the Settlement of Circular Pile Foundations of a Reservoir

Model Test Study on Bearing Capacity of Nonuniformly Arranged Pile Groups

The uniform arrangement of pile groups widely used in practice often causes obvious differential settlement of pile foundations. To decrease differential settlement of pile groups, individual piles nonuniformly arranged can be adopted. This paper presents a model test study on the bearing capacity of pile foundations under different pile arrangements. A versatile full-automatic loading system and data acquisition and analysis systems of the model test were developed. Using the model test setup, the response of a single pile subjected to axial load was clarified, and the reinforcing effect between an axially loaded pile and a load-free pile was then analyzed. Furthermore, model tests were carried out to assess the behavior of the pile groups composed of individual piles with variable length and diameter. For practical purposes, some suggestions on the nonuniformly arranged individual piles within pile groups were given to decrease differential settlement among each individual pile and make maximum use of the bearing capacity of each individual pile.

An experimental evaluation of helical piles as a liquefaction-induced building settlement mitigation measure

This study evaluates the application of helical piles to reduce liquefaction-induced foundation settlement and investigates their seismic performance in liquefiable grounds. Two large-scale shake table test series, one without mitigation and one using helical piles, were conducted using the shake table facility at the University of California, San Diego. Each model was extensively instrumented and subjected to two consistently applied shaking sequences. The experimental results indicated reduced excess pore-water pressure generation around the helical pile group, attributed mainly to the densification around the piles during installation. The foundation supported on helical piles underwent almost no foundation differential settlement and tilt. The post-shaking liquefaction-induced settlement mechanisms did not affect the helical pile foundation settlement. Although this study introduced helical piles as a reliable and highly efficient measure to mitigate liquefaction-induced foundation tilt and settlement, the proper design and application of helical piles still need thorough investigation due to possible amplified superstructure response.

Numerical Simulation of Pile Settlement under Large Diameter Submarine Shield Tunnel

In view of the domestic first large diameter shield close Marine environment down wear large bridge project, Shenzhen high-speed along the river shield tunnel under wear before the Shenzhen Sea bridge as the background, the numerical simulation method, in view of the large diameter submarine shield under the bridge pile foundation, through different ways and methods on influence of settlement of pile foundation. The calculation results show that the additional bending moment of the bridge pile is small, the maximum settlement of the bridge pile is within the range of the control standard value, and the maximum horizontal displacement of the bridge pile is within the range of the control standard value, so the bridge will not be damaged. It can be seen that the construction of submarine shield tunnel has a certain degree of influence on the cross-sea bridge, but after applying engineering measures, the impact on the bridge can be effectively reduced to ensure the safety of high-speed railway bridge. The research results can provide reference for the construction design of the type of engineering.

Response of Piles Group embedded in Sandy Soil with Cavities to Seismic Loading

This research is looking at the impact of cavities on the group pile foundation settlement subjected to seismic loads in the dry sandy soil of dry unit weight 16 kN/m3. The finite element software (Plaxis 3D 2020) was used to represent the way of behaving of gypseous soil under the group of piles with cavity formation. The study included the presence of a single cavity, the group of cavities, and different diameters of the cavity in different locations. The horizontal distance from the centerline of the cavity to the centerline of the pile or group of piles is defined as (X), and the vertical distance from the bottom of the pile to the cavity centerline is defined as (Y). The variations in cavity locations, numbers, and diameters were all studied. The results showed that the impact of the earthquake (El Centro) of the settlement of pile group with cavity increased the settlement when the cavity was located near the edge of piles and that when the diameter of the cavity increased, the settlement has been increased for the same vertical distance of the cavity below the group piles and under the influence of the earthquake. The effect of cavity diminishes at a horizontal distance a cavity at horizontal depth (X = 4D).

Pile Foundation Design and Analysis of Teaching Building in A High School

The foundation design should adhere to the principles of adapting measures to local conditions, using local materials, protecting the environment and saving resources. Based on the geotechnical engineering survey data, the design should be carried out by comprehensively considering the factors such as structure type, material situation and construction conditions. The pile foundation design is adopted in this project. includes the determination of pile end bearing layer and pile length, the determination of vertical bearing capacity of single pile, the calculation of pile number and pile layout form, the checking calculation of pile foundation bearing capacity and settlement, the design and checking calculation of pile body structure, the design and checking calculation of pile cap. Until all requirements of the specification are met.

PEMETAAN PENURUNAN ELASTIS FONDASI TIANG BERDASARKAN DATA SONDIR KOTA PEKANBARU

Pekanbaru City has developed quite rapidly. Therefore, local governments are aware of the high demand for multi-story building construction, so that buildings built with more than two floors are required to conduct a land subsidence test. The load of a structure will be transmitted by the foundation to the ground, where the soil is expected to be able to support the load. The soil subsidence test is obtained from the sondir test data or also called the Dutch Cone Penetration Test (DCPT) which is used to determine the profile into the soil continuously with the value of cone tip resistance and blanket resistance (Wafi et al., 2013).The purpose of this study is to analyze the calculation of the settlement of a single pile foundation based on the foundation bearing capacity data from the sondir data obtained from the Riau University Laboratory using the elastic settlement method. The research stages carried out are reviewing theories related to piles, then collecting data including data on the carrying capacity of the foundation and sondir data. The final stage is conducting calculation analysis. The results of this study obtained a map of the elastic settlement of the pile foundation at a depth of 6 meters, 12 meters and 18 meters.