Sandy Soil Foundation Research Articles

Seismic Damage Analysis of Pile Foundation on Liquefiable Sandy Soil Foundation

Under the action of cyclic dynamic loads caused by earthquakes, the sandy soil foundation will liquefy, which may easily lead to damage to the pile foundation. For example, the soil liquefaction will cause pile foundation subsidence, the failure of the connection between pile cap and cap, and the beam drop caused by pile foundation moving sideways with soil. There are many influencing factors of foundation liquefaction, and the influence of many factors on foundation liquefaction is highly nonlinear. The author analyzes the liquefaction principle of sandy soil foundation and combines the seismic damage data of pile foundation with the experimental data of large-scale shaking table. Then this paper describes the damage and failure characteristics of pile foundation on liquefied sandy soil foundation.

Penetration Performance of Steel Cylinders in Sand Foundations

In order to study the effect of wall thickness on the penetration process of steel cylinders, we carried out physical tests and numerical simulations of the penetration process of steel cylinders with different wall thicknesses in sandy soil foundations, focusing on analyzing the penetration force and soil uplift during the penetration process of steel cylinders. The results show that the coupled Eulerian-Lagrangian (CEL) approach can be used to simulate the penetration process of steel cylinders. During the penetration of steel cylinders with different wall thicknesses, the relationship between the penetration force and penetration depth can be approximated by a quadratic function. The larger the wall thickness is, the larger the plug volume inside the steel cylinder during penetration. The research results can provide support for the design and construction of steel cylinders.

Non-contact model test and numerical simulation of plastic zone in sandy soil foundation

Reasonable determination of the ultimate bearing capacity of the foundation is of great significance in engineering applications. Based on the self-developed non-contact testing device for the plastic zone of shallow foundation, this paper carries out model test research on the plastic zone of sandy soil shallow foundation and analyzes the development law of plastic zone under the action of foundation load. The main advantages and functional characteristics of the foundation plastic zone test system are that it can realize the non-contact test of displacement deformation of soil, the dynamic development process of shear deformation, and the plastic zone of model foundation can be obtained intuitively. The development process, morphological boundary characteristics, and foundation failure mode of the plastic zone of the sand foundation are obtained. The plastic zone of the foundation starts from the edges of both sides of the bearing plate; with the increase of the load, the plastic zone gradually develops downward and approaches to the center line, and finally crosses through at the bottom until the local shear failure of the foundation occurs. The measured plastic zone is a symmetrical spindle shape with thin ends and a bulge in the middle; the sand on both sides of the bearing plate partially bulges, forming a “V” shaped shear failure zone, and the bottom of bearing plate forms a triangular compression zone, the foundation failure mode of sandy soil represents a typical punching shear failure mode. In order to study the distribution characteristics of the plastic zone range of foundation under different foundation loads and foundation widths, the Universal Distinct Element Code (UDEC) based on the discrete element method is used for numerical simulation research. By conducting parameterized numerical simulation test for the plastic zone of foundation and analyzing the results, with the changes in the foundation load and the foundation width, the variation law of (1) the depth of the plastic zone on the foundation bottom, (2) the width of the plastic zone on both sides of the foundation, (3) the ratio for the depth of plastic zone to the width of foundation, (4) the ratio for the width of plastic zone to the width of foundation and (5) the ratio for the width of plastic zone to the depth of plastic zone is obtained. The research has significant guiding significance for the study of the development law of plastic zone and foundation design.

Strength and Environmental Behaviours of Municipal Solid Waste Incineration Fly Ash for Cement-Stabilised Soil

Many sandy soil foundations need to be solidified during traffic construction in Guangxi, China. Because it has a similar chemical composition as cement, municipal solid waste incineration fly ash (MSWIFA) can strengthen sandy soil. However, the chloride ions and heavy metals in MSWIFA may have a negative influence on the solidification of sandy soil. Thus, FA resource use faces great challenges. This study evaluates the feasibility of using MSWIFA to solidify sandy soil. The acetic acid buffer solution method was used in the leaching test to simulate the weak acid groundwater environment in the Guangxi karst landform. The effects of the treatment methods (washing with ferrous sulphate solution, pre-treatment of organics via chelation, and adding sugarcane ash) on the strength and environmental characteristics of fly ash cement-stabilised soil (FACS) are discussed in detail. The results indicate that the FACS unconfined compressive strength (UCS) decreased by 24.82–46.64% when 5% cement was replaced with FA. Sugarcane ash effectively improved the strength of FACS by more than 10%. The leaching concentrations of Zn and Cu in the FACS meet the concentration limit set by GB 16889-2008. The leaching concentrations of Cr and Pb after washing with 6% ferrous sulphate solution were reduced by more than 30%. Meanwhile, the FACS strength developed faster. Organic chelating agents solidified most heavy metals.

Data-Driven Modeling of Peak Rotation and Tipping-Over Stability of Rocking Shallow Foundations Using Machine Learning Algorithms

The objective of this study is to develop data-driven predictive models for peak rotation and factor of safety for tipping-over failure of rocking shallow foundations during earthquake loading using multiple nonlinear machine learning (ML) algorithms and a supervised learning technique. Centrifuge and shaking table experimental results on rocking foundations have been used for the development of k-nearest neighbors regression (KNN), support vector regression (SVR), and random forest regression (RFR) models. The input features to ML models include critical contact area ratio of foundation; slenderness ratio and rocking coefficient of rocking system; peak ground acceleration and Arias intensity of earthquake motion; and a categorical binary feature that separates sandy soil foundations from clayey soil foundations. Based on repeated k-fold cross validation tests of models, we found that the overall average mean absolute percentage errors (MAPE) in predictions of all three nonlinear ML models varied between 0.46 and 0.60, outperforming a baseline multivariate linear regression ML model with corresponding MAPE of 0.68 to 0.75. The input feature importance analysis reveals that the peak rotation and tipping-over stability of rocking foundations are more sensitive to ground motion demand parameters than to rocking foundation capacity parameters or type of soil.

Spatial Distribution Characteristics of Microbial Mineralization in Saturated Sand Centrifuge Shaking Table Test.

Calcium carbonate induced by microorganisms can quickly fill and cement sand particles, thereby effectively reducing the potential for the liquefaction of sand. This process could represent a new green approach to the liquefaction treatment of saturated sand and has good prospects for application. However, owing to the diversity of microbial activities and the heterogenous spatiotemporal distribution of bacterial nutrient seepage in sandy soil foundations, the resultant complex distribution of calcium carbonate deposition in a sandy soil foundation can lead to differences in solidification strength and improvement effect. To understand the influence of earthquake action on the liquefaction resistance of saturated sand treated by microorganisms, and to evaluate the effect of microbial technology on sand liquefaction prevention under dynamic load, this study simulated the dynamic stress conditions of saturated sand under shear waves, using the world′s first centrifuge shaking table (R500B), which realizes horizontal and vertical two-way vibration. On the basis of spatial heterogeneity of microbial mineralization after centrifuge shaking table tests, the effect of microbial strengthening on liquefied sand was analyzed, and the spatial distribution of calcium carbonate mineralization was examined. The results showed that the distribution of microorganisms in the solidified soil exhibited obvious spatial heterogeneity with a significant edge effect. Although microbial mineralization effectively improved the liquefaction resistance of saturated sand, a sudden change in the process of calcium carbonate deposition altered the cementation of the sand with depth. Moreover, the curing strength had obvious complexity and uncertainty that directly affected the shear stiffness of the soil under dynamic load, and this constitutes one of the reasons for the degradation of shear stiffness of sand during liquefaction. The derived conclusions could be used as a reference for engineering applications of microbial treatment of a liquefiable sandy soil foundation.

Research on improvement of Terzaghi’s bearing capacity equation for coral sand foundation

The mechanical characteristics of coral reef sandy soil is significantly different from the sand and clay soils. Currently, Terzaghi's bearing capacity equation is still commonly applied to evaluate the bearing capacity of coral reef, while the calculation result is not consistent with the actual condition. Based on a port project in east Africa, plate loading test of the coral reef sandy soil has been conducted and the P-S curves are obtained, and the bearing capacity values obtained from the plate loading test results are compared with the calculated results based on the Terzaghi’s bearing capacity equation. According to multiple linear regression and the optimal regression equation selected by the significance test, the modified Terzaghi foundation equation of bearing capacity in coral reef sandy soil area is proposed, and the modified Terzaghi foundation equation has important reference value for the calculating of the bearing capacity of the coral reef sandy soil foundations.

Model test study on horizontal bearing behavior of pile under existing vertical load

For the pile foundation subjected to both horizontal and vertical loads, the horizontal and vertical bearing capacities are often calculated separately according to existing methods, and the influence of the vertical loads on the horizontal bearing capacity of the pile is not considered. Several model tests were carried out for the horizontal loaded pile to study the horizontal bearing behavior of pile under the action of existing vertical load in sandy foundation. In order to avoid imposing additional constraints on the pile top under vertical loads, the self-designed test loading device was developed for vertical loading, and the thin film pressure sensor was used to accurately measure the horizontal soil resistance. The test results show that: in sandy soil foundation, vertical loads applied in advance reduces the horizontal displacement and bending moment of horizontal loaded pile in some segments. The maximum value of horizontal soil resistance first increases and then decreases with the increase of existing vertical load. The horizontal bearing behavior of the small-diameter preformed pile can be improved by the vertical load in sandy soil foundation when the horizontal displacement is small.

Multivariate adaptive regression splines model for reinforced soil foundations

In this study, a multivariate adaptive regression splines (MARS) model has been developed to predict the settlement of shallow reinforced sandy soil foundations (RSSFs). The potential of the MARS model is validated comparatively with four other robust artificial intelligence/machine learning regression models, namely extreme learning machines (ELM), support vector regression (SVR), Gaussian process regression (GPR), and stochastic gradient boosting trees (SGBT). The pertinent data retrieved from previously published well-established scientific studies have been used to calibrate and validate the data-driven intelligent machine learning models. The predictive strength of all the modelling tools mentioned above were assessed via several statistical indices. Moreover, the predictive ability and reliability of the developed models were also corroborated with ranking criteria and external validation analysis. The results as obtained have shown that the MARS modelling technique attains the superior veracity in predicting the settlement of reinforced foundations.

Shaking Table Tests and Numerical Analysis on the Seismic Response of Karst-Crossing Socketed Piles in Dry Sandy Soil Foundation

The foundation piles in karst areas have different mechanical properties from those in other areas. Targeting a critical highway bridge in a karst area, this paper designs two kinds of foundation pile models: friction pile, and KCSP, based on theories on dynamic tests. Then, shaking table tests were carried out to ascertain the features of pile strain distribution of KCSP under earthquakes. During the tests, a large laminar suspended shear box was adopted to mimic the boundary effect of soil. In addition, numerical simulations were conducted to disclose the effects of karst cave on pile strain. The test results indicate that: the peak strain of KCSP increased with the peak acceleration; For both KCSP and friction pile, the peak strain decreased first and then increased along the depth; The presence of karst cave can adversely affect the seismic response of foundation pile; The taller the karst cave, the larger the peak strain of the pile; the peak strain of KCSP was larger at the two ends, and smaller in the middle. The numerical analysis shows that: the peak strain of foundation pile in karst cave increased significantly with cave height; The peak strain of the pile passing through multiple caves was similar to that of the pile passing through only one cave, under the same cave height; But the multi-cave scenario differed from the single-cave scenario in peak strain distribution. The research results provide new insights into the seismic design of pile foundation of bridges in karst areas.

An extreme learning machine model for geosynthetic-reinforced sandy soil foundations

In the past, several experimental and theoretical studies have been carried out to evaluate the ultimate bearing capacity (UBC) of geosynthetic-reinforced sandy soil foundations (GRSSFs). The experimental studies consist of model footing load tests which are expensive and time consuming whereas the results obtained by theoretical expressions often lack consistency. In the study reported in this paper, a cost-effective, extreme learning machine (ELM) model was used for the first time to obtain a more realistic prediction of the UBC of a GRSSF. A large dataset consisting of actual field and laboratory measurements of UBC was used to develop and validate the model. Its predictive performance was then compared against robust machine learning regression models and traditional theoretical methods. The study shows that the proposed model is useful and attains an adequate level of accuracy in predicting the UBC of GRSSFs when compared with other data-driven models and some traditional methods. The research also shows that the ELM technique is a realistic and reliable approach that could be employed in geotechnical engineering intelligent systems for the prediction of multivariate non-linear problems.

Vertical bearing capacity of a pile-liquefiable sandy soil foundation under horizontal seismic force.

In this study, research on a pile group system was conducted using shaking table tests under four working conditions: a natural foundation and pile-spacing conditions of 3D, 3.5D, and 4D (D is the diameter of the pile). The time histories of the excess pore pressure ratio and settlement were analyzed. It was determined that pile foundations improved the anti-liquefaction performance of the soil, and the effect was much greater when the pile spacing was 3D. In addition, the settlement dynamic amplification factor (SDAF) was proposed and calculated at different vibration times. The result was fitted with a linear relationship, and the correlation coefficient was relatively high. During the aseismic design of the pile foundation bearing capacity, the SDAF was multiplied by the static load, and the results showed that in the dynamic design of the pile foundation, the dynamic problem can be transformed into a static analysis, which can provide a reference for the design of the vertical bearing capacity of pile foundations under seismic force.

Research of a new method of sealing of sandy soil foundations

The paper presents the results of the author's research aimed at finding new methods of vibrodynamic sealing of sandy soils foundation by using the energy of water flow. The data of water flow parameters providing the given speed of its movement without the significant carryover of sand particles based on the theoretical studies, as well as the laboratory studies of sandy soil dumping into a water flow (with an average horizontal velocity of about 10-15 cm/s) on a specially designed hydraulic tray are described in the paper.

Loose Sand Particles Cemented by Chem/Bio-BaHPO4 Powder

Bacillus subtilis was selected as the suitable microorganism, which could produce alkaline phosphatase and constantly hydrolyzed phosphate monoester in the mixture solution of bacteria with substrate, and then the PO 4 3- was obtained. Bio-phosphate cement was prepared by alkaline earth element (Ba) ions reacting with PO 4 3- in the mixture solution. Structure, size and thermal properties of the bio-phosphate cement were characterized by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis. The average crystallite sizes of chem-BaHPO4 and bio-BaHPO4 corresponded to 11.99 and 24.13 μm, respectively. Chem-BaHPO4 and bio-BaHPO4 were then adopted to bind loose sand particles. The results indicated that loose sand particles can be well cemented by the bio-BaHPO4 powder into a bio-sandstone with a certain mechanical properties, and the average compressive strength of the bio-sandstones can be up to 0.83 MPa when the curing time was 14 d. Along with the method in future studies, there will be multiple new opportunities for engineering applications, for instance, the treatment of sandy soil foundation, remediation of heavy metals in contaminated soil, and so on.

Potential uses and cementing mechanism of bio-carbonate cement and bio-phosphate cement

Bio-cement, based on microbial-induced mineralization, can consolidate the loose particles and be applied to foundation reinforcement, dust control, desert settlement, repair cementitious materials crack, and other fields. In the paper, two kinds of bio-cement, such as bio-carbonate cement and bio-phosphate cement, were discussed as novel binders. The calcium carbonate (calcite), induced precipitation via Sporosarcina pasteurii, could cement between loose sandy soil particles. A series of sand-cemented experiments were conducted to confirm the cemented properties, and a numerical model based on the distribution of the concentration of Sporosarcina pasteurii was established to further analyze bio-grouting process. The evolution law of microstructure was revealed by X-ray computed tomography (X-CT) technique. The atomic binding energy of C-O bond in calcium carbonate, Si-O bond and Si in sand analysis showed that microbial-induced calcium carbonate interacted with surface of loose sand particles formed the intermolecular hydrogen bond. The other kind of bacteria (Bacillus subtilis) could hydrolyze organic phosphate monoester and released PO43-, which could react with different metal cations formed bio-phosphate minerals. The bio-phosphate cement can be used as treatment of sandy soil foundation, functional materials, remediation of heavy metals in contaminated soil, and so on.

Effect of number of layers on coir geotextile reinforced sand under cyclic loading

The present investigation is on the behavior of coir geotextile-reinforced sandy soil foundations and to study the effect of different parameters contributing to their performance using laboratory model tests. The parameters investigated in this study included top layer spacing, number of reinforcement layers and vertical spacing between layers. The effect of coir geotextile reinforcement on the vertical stress distribution in the sand and the strain distribution along the reinforcement were also investigated. The test results established the potential benefit of using coir geotextile-reinforced sand foundations. The test results also showed that the reinforcement configuration/layout has a significant effect on the behavior of reinforced sand foundation. With two or more layers of reinforcement, the settlement can be reduced at all footing pressure levels. The inclusion of reinforcement can redistribute the applied footing load to a more uniform pattern, hence reducing the stress concentration, which will result reduced settlement.

Numerical modeling of pile penetration in silica sands considering the effect of grain breakage

Current numerical platforms rarely consider the effect of grain breakage in the design of sandy soil foundations. This paper presents an enhanced platform for large deformation analyses which considers the effect of grain breakage during pile penetration in silica sand. For this purpose, a model based on critical state theory has been developed within the framework of multisurface plasticity to account in the same constitutive platform the effect of stress dilatancy and particle fragmentation. Furthermore, to implement the underlying constitutive equations into a finite element code, a stress integration scheme has been adopted by extending a cutting plane algorithm to the model with multiple yielding mechanisms. A laboratory model test and a series of centrifuge tests of pile penetration are simulated to verify the performance of the selected constitutive approach in terms of pile resistance and grain breakage distribution, with the parameters of sand calibrated through a set of drained triaxial compression tests from low to very high confining pressure. Some extra features of the enhanced platform are also discussed, such as: i) the effect of sand crushability on pile resistance and ii) the nonlinear relation of pile resistance to sand density. The proposed findings demonstrate the capability of this numerical platform to proper design of pile foundation in sandy soils and highlight the interplay between stress dilatancy and grain breakage mechanisms during pile penetration processes.

Cyclic response of single-layer coir-mat-reinforced sand

The present experimental investigation is conducted to study the cyclic response of coir-mat-reinforced sandy soil foundations and the effect of different parameters contributing to their performance using laboratory model tests. The parameters investigated in this study included various positions of reinforcement layer. The test results established the potential benefit of using coir-mat-reinforced sand foundations. The test results also showed that the reinforcement configuration/layout has a significant effect on the behaviour of reinforced sand foundation. With a layer of reinforcement, the settlement can be reduced. The inclusion of reinforcement can redistribute the applied footing load to a more uniform pattern, hence reducing the settlement.

Model Tests of Foundation Bearing Capacity of Sandy Soil and Pile Foundation Bearing Capacity

Using self―made model device, researchers studied the characteristics of foundation settlement of sandy soil and pile foundation load―bearing in sandy soil. Through weight loading, researchers analyzed the phenomenon of foundation settlement. Then, researchers embedded friction piles in sand, so as to analyzed pile foundation bearing capacity. The methods and results of the research can provide guidance for teaching of Soil mechanics and foundation engineering.

Theoretical investigation of interaction between a rectangular plate and fractional viscoelastic foundation

The interaction between plates and foundations is a typical problem encountered in geotechnical engineering. The long-term plate performance is highly dependent on the rheological characteristics of ground soil. Compared with conventional linear rheology, the fractional calculus-based theory is a more powerful mathematical tool that can address this issue. This paper proposes a fractional Merchant model (FMM) to investigate the time-dependent behavior of a simply supported rectangular plate on viscoelastic foundation. The correspondence principle involving Laplace transforms was employed to derive the closed-form solutions of plate response under uniformly distributed load. The plate deflection, bending moment, and foundation reaction calculated using the FMM were compared with the results obtained from the analogous elastic model (EM) and the standard Merchant model (SMM). It is shown that the upper and lower bound solutions of the FMM can be determined using the EM. In addition, a parametric study was performed to examine the influences of the model parameters on the time-dependent behavior of the plate–foundation interaction problem. The results indicate that a small fractional differential order corresponds to a plate resting on a sandy soil foundation, while the fractional differential order value should be increased for a clayey soil foundation. The long-term performance of a foundation plate can be accurately simulated by varying the values of the fractional differential order and the viscosity coefficient. The observations from this study reveal that the proposed fractional model has the capability to capture the variation of plate deflection over many decades of time.