Settlement Of Composite Foundation Research Articles

Composite Foundation Settlement Prediction Based on LSTM–Transformer Model for CFG

Roadbed construction typically employs layered and staged filling, characterized by a periodic feature of ‘layered filling—filling interval’. The load and settlement histories established during staged construction offer crucial insights into long-term deformation under filling loads. However, models often rely solely on post-construction settlement data, neglecting the rich filling data. To accurately predict composite foundation ground (CFG) settlement, an LSTM–Transformer deep learning model is used. Five factors from the ‘fill height–time–foundation settlement’ curve are extracted as input variables. The first-layer LSTM model’s gate units capture long-term dependencies, while the second-layer Transformer model’s self-attention mechanism focuses on key features, efficiently and accurately predicting ground settlement. The model is trained and analyzed based on the newly constructed Changsha–Zhuzhou–Xiangtan intercity railway section CSLLXZQ-1, which has a CFG pile composite foundation. The research shows that the proposed LSTM–Transformer model for the settlement prediction of composite foundations has an average absolute error, mean absolute percentage error, and root mean square error of 0.224, 0.563%, and 0.274, respectively. Compared to SVM, LSTM, and Transformer neural network models, it demonstrates higher prediction accuracy, indicating better reliability and practicality. This can provide a new approach and method for the settlement prediction of newly constructed CFG composite foundations.

Settlement Behavior of Composite Foundation with Deep Mixed Piles Supporting Highway Subgrades in Water-Rich Flood Plains

The settlement behavior of composite foundations plays an important role in the serviceability and stability of the subgrade or other infrastructures supporting the foundation. However, in water-rich flood plains, due to the complexity of the soft soil properties, the settlement behavior has not been well understood. The objective of this study is to investigate the effects of various key factors on the settlement behavior of composite foundations with deep mixed piles supporting highway subgrade in water-rich flood plains. The investigated subgrade is in operation, and the vehicle load is taken into account. The G347AH Project is considered in this study. Several typical models for predicting composite foundation settlements are discussed. By performing three-dimensional finite difference analysis, a comparison is made between the settlement behavior of the natural foundation and the composite foundation with deep mixed piles. Based on the single factor sensitivity analysis and the multi-factor orthogonal experimental design, the effects of pile length, pile diameter, pile spacing, pile elasticity modulus, cushion elasticity modulus, and cushion thickness on the composite foundation settlement are captured. It is found that among these factors, the degree of influence of pile length is superior. The composite foundation settlements predicted by the models agree well with the field-monitoring data, with the error being about 8.42% and 6.38%, respectively, at two monitoring sections. The research conducted in this paper can effectively reduce the probability of various settlement-related disasters occurring on highway subgrades in water-rich flood plains. Moreover, the research has important theoretical guidance for design optimization in terms of settlement control of highway subgrades in soft soil areas.

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.

Settlement Characteristics of Split Grouting Pile Composite Foundation in Loess Areas

Loess foundations often affect the stability of superstructures due to their insufficient bearing capacities; thus, reinforcement measures are crucial for mitigating the uneven settlement of foundations. This study aims to investigate the settlement characteristics of composite foundations for loess foundations reinforced by splitting grouting piles. First, split grouting tests were carried out on loess foundations. After the test piles reached the design strength, static load tests and geotechnical tests were carried out to obtain the Q-s curves of the test piles. The pile-forming mechanism was analyzed via excavations at an on-site test pile. Furthermore, the traditional settlement calculation method of composite foundations was used to calculate the settlement of split grouting pile composite foundations, and the results were compared with field test results to explore a suitable settlement calculation method of split grouting pile composite foundations. Finally, the numerical model of split grouting pile composite foundations was established according to the pile forming mechanism, and the settlement deformation characteristics of single pile and pile group composite foundations were analyzed. The relative errors of the composite modulus method and the stress correction method for calculating the settlement of the composite foundations were 6.4% and 32.8%, respectively, and the composite modulus method was closer to the test values. The calculated curves of the numerical model were in good agreement with the measured curves and relevant literature research results, demonstrating the rationality of the modeling method; the findings of this study provide theoretical guidance for designing loess foundation splitting grouting reinforcement and for predicting settlement during later construction periods.

Bearing Capacity Characteristics and Differential Settlement of Composite Foundation with Column-Hammered and Thrusted-Expanded Piles

The foundation bearing-capacity characteristics and differential settlement have become the vital issues of high-speed rail study. Because of the collapsibility around loess foundations, the bearing characteristics as well as differential settlement are significantly different from other soil foundations. At present, there are many studies on other types of soil foundations, while the bearing capacity characteristics and differential settlements of the column-hammered and thrusted-expanded pile (CHTEP) composite foundation in the collapsible loess area are rarely involved. Therefore, based on the current codes, field tests and finite-element method (FEM), the variation in the differential settlement and bearing capacity characteristics of composite foundations with CHTEP is studied in collapsible loess areas. This paper mainly obtains the changing law of pile body stress, pile–soil stress ratio, pile side-friction resistance, differential settlement about the pile, and the soil between the piles of the composite foundation with CHTEP during different construction conditions. The result also shows the bearing capacity and settlement about composite foundation with CHTEP is up to code. This paper can provide some important rule to the design or construction about composite foundations with CHTEP at collapsible loess areas or other similar cases.

Pile-Soil Stress Ratio and Settlement of Composite Foundation Bidirectionally Reinforced by Piles and Geosynthetics under Embankment Load

The settlement calculation of composite foundation bidirectionally reinforced by piles and geosynthetics is always a difficult problem. The key to its accuracy lies in the determination of pile-soil stress ratio. Based on the theory of double parameters of the elastic foundation plate, the horizontal geosynthetics of composite foundation are regarded as the elastic thin plate, and the vertical piles and surrounding soil are regarded as a series of springs with different stiffness. The deflection equation of horizontal geosynthetics considering its bending and pulling action is obtained according to the static equilibrium conditions. The equation is solved by using Bessel function of complex variable, and the corresponding deflection function of horizontal geosynthetics is deduced. Then, the calculation formula of pile-soil stress ratio and settlement of composite foundation is derived by considering the deformation coordination of pile and soil. The results of engineering case analysis show that the theoretical calculation results are in good agreement with the measured values, which indicates that the proposed method is feasible and the calculation accuracy is good. Finally, the influence of composite modulus of horizontal geosynthetics, tensile force of geosynthetics, and pile-soil stiffness ratio on pile-soil stress ratio and settlement is further analyzed. The results show that the pile-soil stress ratio increases with the increase of the composite modulus of the horizontal geosynthetics, the tensile force of geosynthetics, and the pile-soil stiffness ratio, and the settlement decreases with the increase of the composite modulus of the horizontal geosynthetics, the tensile force of geosynthetics, and the pile-soil stiffness ratio. When the flexural stiffness of the horizontal geosynthetics is small, the influence of the tensile action of the geosynthetics on the pile-soil stress ratio and settlement of the composite foundation cannot be ignored.

A Three-Section-Settlement Calculation Method for Composite Foundation Reinforced by Geogrid-Encased Stone Columns

The analysis of the bearing characteristics and deformation mechanism of composite foundation reinforced with geogrid-encased stone columns is presented in order to obtain its settlement calculation method. The settlement of composite foundation is divided into three sections which are the reinforced section, unreinforced section, and underlying stratum. Based on Hooke’s law of space problem and the thoughts of the layer-wise summation method, the relative slip displacement between pile and soil of reinforced section without plastic zone is analyzed. The settlement of reinforced section is calculated by the layered iteration method based on the pile element model. The compatibility of vertical and radial deformations of unreinforced section is analyzed based on the pile-soil element model. The settlement of underlying stratum is still calculated by the layer-wise summation method. Finally, two engineering examples are analyzed and the results show that the settlement calculated by the presented method is close to the measured one. The method overcomes the defect that the calculated results by the other existing methods are more dangerous and it is more feasible and can be applied in engineering practice.

Behavior characteristics of geosynthetic-encased stone column under cyclic loading

As a new type of soft ground treatment technology, the geosynthetic-encased stone column (GESC) has been extensively used in engineering of roads and highways. In order to investigate the bearing mechanism of GESCs under cyclic loading, a series of experiments and numerical simulations were carried out using the proportional model. This paper described these changes in settlement and pile-soil stress ratio with emphasis on the ratio of length to diameter and the strength of wrapping material. Under the background of model test, a GESC reinforced composite foundation was simulated by the particle flow method. The reliability of the numerical simulation results was verified by the test results. The results demonstrate that GESC can effectively reduce the settlement of composite foundation. As the ratio of length to diameter and the strength of the wrapping material increase, this reduction is more significant. The GESC can effectively decrease the soil stress in composite foundation. The simulation results show the behavior of load transfer and expansion in GESC reinforced composite foundation. The displacement vector of soil particles in composite foundation shows that the failure mode of soil is shear failure. As the number of cycles increases, the range of failure surface expands.

Experimental Investigation of Geosynthetic-Reinforced Pile-Supported Composite Foundations under Cyclic Loading

A series of model tests were conducted in this study to investigate the deformation characteristics of geosynthetic-reinforced pile-supported (GRPS) composite foundations under cyclic loading. The effects of the applied load, the number of geogrid layers, and types of piles on the performance of the GRPS composite foundation were studied through 1g physical models of composite foundation with well-planned instrumentation. Furthermore, a numerical fitting method was used to assess the relationship between the foundation settlement and the number of load cycles. The results show that with the increase in the magnitude of cyclic load and the number of load cycles, the settlement of GRPS composite foundations and the strain of the pile and geogrid increased accordingly. Adding rigid piles and increasing the number of geogrid layers both could reduce the settlement of GRPS composite foundations, while adding rigid piles was more effective. The relationship between the foundation settlement and the number of load cycles can be expressed by an exponential regression function. The pile strain varied from place to place that the strain of the upper part of the pile was greater than that of the lower part. The geogrid showed a significant impact on the load transfer mechanism of the composite foundation as the geogrid closer to piles endured larger strain. It is critical to consider the variation of the pile strain and the geogrid strain under cyclic loading in the geotechnical practice of composite foundation. The model test results also suggest that the use of GRPS system can effectively reduce the composite foundation settlement. This paper can provide useful references for developing the theoretical framework and design guides for GRPS composite foundations under cyclic loading.

Numerical analysis of bearing characteristics of composite foundation with variable diameter rigid pile

Variable diameter rigid pile composite foundation are proposed for the multi-layer foundation. The bearing characteristics of composite foundation with variable diameter rigid pile under vertical load are numerically calculated and analysed. The research content of this paper focuses on the variation law of load and settlement of composite foundation, pile axial force, pile lateral friction resistance and distribution law of soil internal force between piles under different diameter ratios etc. The results showed that Variable diameter of rigid pile composite foundation can effectively improve bearing capacity and control settlement and reduce the stress level of soil; negative skin friction section at the top of pile decreases with variable diameter ratio D/d increases, Zero skin friction section in diameter produced and increases with variable diameter ratio D/d increases; Optimal diameter ratio of pile in the variable diameter rigid pile composite foundation should be at about 1.75.

Research on Influencing Factors of Composite Foundation Settlement with Capped Pipe Piles Based on Centrifugal Model Test

In order to study the influence of design factors of capped pipe pile composite foundation on differential settlement of expressways, using a geotechnical centrifugal model test platform, a centrifugal model of widen roadbed has been constructed. The effects of pile length, pile spacing, pile cap and cushion thickness on differential settlement were analyzed through comparative experiments. The test results show that increasing the pile length, pile cap size and cushion thickness can effectively control the differential settlement between old and new embankments. The research results can provide a theoretical basis for the design of composite foundations with capped pipe piles.

Analysis of Deformation Characteristics of Long-Short Pile Composite Foundation in Salt Lake Area, Iran

To study the settlement and deformation characteristics of a long-short pile composite foundation and its influencing factors, the indoor centrifuge model test and numerical simulations were performed under the actual working conditions to treat the saline soft soil foundation in the Soltan salt lake area of Iran. Firstly, the settlement of a long-short pile composite foundation and the law of pile-soil stress ratio development with time were studied using a centrifuge model test. In addition, FLAC3D was used to simulate the test conditions, and it has been observed that the numerical and experimental results were in good agreement. Based on the numerical model, the effects of the replacement rate of long and short piles, cushion modulus, and pile length on the settlement of the composite foundation and the stress ratio of long and short piles were analyzed. The results show that the long-short pile composite foundation can effectively control settlement. Compared to the untreated foundation, the total settlement of a long-short pile composite foundation was reduced by 67%, and the postconstruction settlement was reduced by 47.7%. Compared to the final settlement of the composite foundation obtained using the centrifuge model test, the error range of the numerical simulation results was between 2.4% and 8%. The influence of pile spacing on the settlement and stress characteristics of a long-short pile composite foundation is greater than that attributable to the arrangement of the piles. Under this geological condition, it is reasonable to choose a pile spacing of 4d∼5d. When the long pile reaches the bearing stratum, the length of the short pile should not exceed 0.6 times the length of the long pile. The setting cushion not only reduces uneven settlement of the composite foundation but also improves the joint bearing capacity of the pile and the soil between the piles.

Test study on the load transfer behavior of the composite foundation of pipe-pile with cap & holes

As the vertical reinforcement of composite foundation, the concrete pipe pile is suitable for the treatment of deep soft foundation engineering. In order to explore the working characteristics of the composite foundation of pipe-pile with cap & holes, the model tests have been carried out between the composite foundation of pipe-pile with cap & non-hole and the composite foundation of pipe-pile with cap & holes, which are three arrangements of holes. The working properties of settlement deformation, load transfer and the pile-soil stress ratio of the composite foundation of all piles have been analyzed. The test results show that: (1) the total settlement of composite foundation of pipe pile with cap & holes is smaller than that of the composite foundation of pipe pile with cap & non-holes, and its settlement curve is relatively gentle.(2)The pile axial force and the pile-soil stress ratio of the composite foundation of pipe-pile with holes is slightly less than that of pipe-pile. (3)The pile side frictional resistance and the soil pressure between two pile caps of the pipe-pile with holes is greater than the pipe-pile with cap & non-holes composite foundation.

Simple Method to Predict Settlement of Composite Foundation under Embankment

Simple Method to Predict Settlement of Composite Foundation under Embankment

Study on the Law of Cement-Soil Mixing Pile Composite Foundation Settlement in Ancient Tower Translocation Project

Longxi Tower translocation project is the first case of high-rise ancient tower structure translocation on soft soil foundation in China. Foundation treatment protocol and building materials are essential to control soft soil foundation settlement. Depending on Longxi Tower translocation project, firstly this thesis analyzed and confirmed control factors that impact foundation settlement and deformation; then combing with project experience, it selected cement soil mixing pile composite foundation method to treat soft soil foundation; and finally it confirmed the optimal solution to treat cement soil mixing pile composite foundation through analyzing the settlement law of cement soil mixing pile composite foundation. The analysis indicated that cement soil mixing pile composite foundation settlement are obviously impacted by translocation speed and retention time; foundation settlement and deformation level increase as translocation speed decreases and retention time increases; in the case that foundation settlement difference is not beyond 1/1000 of half the distance of track beams at the bottom of building, a treatment solution was made by analyzing how cement soil mixing pile settlement changes as translocation speed, retention time and other factors. The result showed that this treatment solution saved 42% of project cost more than the previous design solution. The research result of this thesis could be taken as a reference for the future similar projects.

Settlement Analysis of Saturated Tailings Dam Treated by CFG Pile Composite Foundation

Cement fly ash gravel (CFG) pile composite foundation is an effective and economic foundation treatment approach, which is significant to building foundation, subgrade construction, and so forth. The present paper aims at investigating the settlement behaviors of saturated tailings dam soft ground under CFG pile composite foundation treatment, in which FEM and laboratory model test were utilized. The proposed findings demonstrate that CFG pile treatment is effective in reinforcing saturated tailings dam and loading has little influence on settlement of soil between piles. The variation of soil between piles settlement in FEM has a good agreement with the laboratory model test. Additionally, the cushion deformation modulus has a small effect on the composite foundation settlement, although the cushion thickness will generate certain influence on the settlement distribution of the composite foundation.

Deterioration of Soil-Cement Piles in a Saltwater Region and Its Influence on the Settlement of Composite Foundations

AbstractSoil-cement mixed piles are widely used to improve soft subsoil. But in regions with high-salinity groundwater, the soil-cement is susceptible to deterioration. At present, however, the design code for soil-cement pile composite foundations does not consider the deterioration effect of soil-cement. The saltwater region in the Yellow River Delta of China is used as a case study. Based on early strength tests of soil-cement, a practical prediction method for the lifecycle bearing capacity of soil-cement piles is put forward, and the influence of deterioration on the settlement of composite foundations is studied using model tests and numerical simulation. The prediction method of pile bearing capacity considers the progressive deterioration of soil-cement, and it shows that the deterioration of soil-cement has a great influence on bearing capacity of mixed piles with an increase in age, and the loss ratio of bearing capacity quickly reduces with a decrease in pile diameter. The deterioration also in...

Prediction of Composite Foundation Settlement Based on Multi-Variable Gray Model

In this paper, based on the principle of gray theory, MGM(1,n) multi-variable settlement prediction model was established. Combined with specific examples of projects, settlement of rigid pile composite foundation was predicted, and the prediction results are compared with both prediction results of GM(1,1) gray model which is currently comparatively mature and the settlement observation results. The study shows that it is effective to use MGM(1,n) multivariate gray model to predict composite foundation settlement.

Centrifuge Model Study of High Strength Piles Composite Foundation Settlement & Instability under Embankment in Different Kind Soils by Different Pile Spacing

A series of centrifuge model tests has been conduced to examine the behavior of high strength piles composite foundation stability under railway embankment in silt or clay or sand different kind of soils. The high strength composite foundation has a symmetrical plan layout consisting of 3×4, 4×6, and 5×8 piles with a center-to-center spacing of 6 or 4 or 3 times pile width. The piles are under the same height of railway embankment, with the same length, and on the same lying soil layer. The high strength composite foundation stability test results are expressed in terms of soils kinds-pile displacement response of the composite foundation, embankment load experienced by soil between piles and piles in the composite foundation, and bending moment profile along individual pile. It is established that the high strength composite foundation stability efficiency reduces significantly with decreasing of the strength of soil between piles in composite foundation. The tests reveal the shadowing effect phenomenon in which the marginal piles experienced larger laterally and bending moment than that of the central piles. The shadowing effect is most significant for the lead row piles and considerably less significant for subsequent rows of middle piles. The approach adopted by many researchers of taking the average performance of piles in the same row is found to be inappropriate for the middle rows, of piles for composite foundation as the outer piles in the row carrying significantly more laterally load and experience considerably higher bending moment than those of the inner piles.

Piled Raft Structure Finite Element Analysis of Composite Foundation Settlement in Da XI Passenger Dedicated Line

Composite foundation settlement of piled raft structure in Da Xi passenger dedicated line is analyzed by the large finite element software MIDAS/GTS and established calculation model of foundation treatment. The problem of pile-soil contact is highlighted in the trail and analyzes the settlement nephogram and pile-soil stress nephogram. On this basis the foundation settlement factors was analyzed systematically that focus on the elastic modulus of pile, pile spacing, pile diameter and pile length in foundation treatment, especially for the characteristics parameters of contact element. Result shows that increasing the pile modulus, pile diameter, pile length and decreasing the pile spacing is all conducive to reducing settlement. The best advice is got that the pile diameter should be not more than 0.5m, pile length not more than 27m and the pile spacing be around 2m.