Performance of composite foundations with different load transfer platforms and substratum stiffness over silty clay

The semi-rigid pile-supported composite foundation is widely used in highway projects due to its effectiveness in increasing the bearing capacity and stability of foundations.It is crucial to understand the stress distribution across the embankment width and the behaviour of unreinforced foundations.Thus,five centrifuge tests were conducted to examine the bearing and deformation behaviours of NPRS(Non-Connected Piled Raft Systems)and GRPS(GeosyntheticReinforced Pile-Supported systems)with varying substratum stiffness,then a comparative analysis was conducted on embankment settlement,pressures underneath the embankments,and axial forces along the piles.The results indicated that greater substratum stiffness correlates with reduced settlement and deformation at various depths.Deformation occurring 5 meters from the embankment toe includes settlement in NPRS and upward movement in GRPS.The potential sliding surface is primarily located within the embankment in NPRS,whereas it may extend through both the embankment and foundation in GRPS.The pile-soil stress ratio and efficiency in NPRS are higher than in GRPS across the embankment.The axial force borne by end-bearing piles is significantly greater than that by floating piles.As the buried depth increases,the axial force in GRPS initially rises then declines,whereas in NPRS,it remains relatively constant within a certain range before decreasing.This study aids in assessing the applicability of composite foundations in complex railway environments and provides a reference for procedural measures under similar conditions.

Experimental study on seismic reinforcement of bridge foundation on silty clay landslide with inclined interlayer

A shaking table test for a bridge foundation reinforced by anti-slide piles on a silty clay landslide model with an inclined interlayer was performed.The deformation characteristics of the bridge foundation piles and anti-slide piles were analyzed in different loading conditions.The dynamic response law of a silty clay landslide with an inclined interlayer was summarized.The spacing between the rear anti-slide piles and bridge foundation should be reasonably controlled according to the seismic fortification requirements,to avoid the two peaks in the forced deformation of the bridge foundation piles.The“blocking effect”of the bridge foundation piles reduced the deformation of the forward anti-slide piles.The stress-strain response of silty clay was intensified as the vibration wave field appeared on the slope.Since the vibration intensified,the thrust distribution of the landslide underwent a process of shifting from triangle to inverted trapezoid,the difference in the acceleration response between the bearing platform and silty clay landslide tended to decrease,and the spectrum amplitude near the natural vibration frequency increased.The rear anti-slide piles were able to slow down the shear deformation of the soil in front of the piles and avoid excessive acceleration response of the bridge foundation piles.

Effects of transient temperature gradient on frost heave of saturated silty clay in an open system

Frost heave in seasonally frozen regions is a one-dimensional process that could severely damage infrastructure subgrades.Stress state,temperature and water migration are important factors for frost heave.This work investigated the effects of soil temperature and volumetric water content on the transient frost heave ratio during the freezing of saturated silty clay in an open system and analyzed the relationships between the transient frost heave ratio and freezing rate and between temperature gradient and frost heave rate.The results show that the frost heave ratio,frost heave rate,and freezing rate are positively correlated with the temperature gradient since the temperature gradient drives the water migration during freezing,indicating the transient temperature gradient could be used to evaluate the frost heave of saturated silty clay.The transient freezing rate and transient frost heave ratio are logarithmically related to the transient frost heave ratio and transient temperature gradient,respectively.The effects of transient temperature gradient on frost heave are the principal mechanism responsible for different frost heave characteristics and uneven frost heave along a subgrade of the same soil type.

Experimental study on mechanical properties of basalt fiber-reinforced silty clay

Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering.Basalt fiber is a new kind of environment-friendly and highperformance soil reinforcement material,and the mechanical properties of basalt fiber-reinforced soil have become a hot research topic.In this paper,we conducted monotonic triaxial and cyclic triaxial tests,and analyzed the influence of the fiber content,moisture content,and confining pressure on the shear characteristics,dynamic modulus,and damping ratio of basalt fiber-reinforced silty clay.The results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its cohesion.We find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%(optimum moisture content).Similarly,we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%.The dynamic modulus is positively correlated with the confining pressure.However,the change in the damping ratio with fiber content,moisture content,and confining pressure is opposite to that of the dynamic modulus.It can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%.After our experiments,we used scanning electron microscope(SEM)to observe the microstructure of specimens with different fiber contents,and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.

Eco friendly adsorbents for removal of phenol from aqueous solution employing nanoparticle zero-valent iron synthesized from modified green tea bio-waste and supported on silty clay

The present research investigated a novel route for the synthesis of nanoparticle zero-valent iron(NZVI)utilizing an aqueous extract of green tea waste as a reductant with ferric chloride.Also,the supported nanoparticle zerovalent iron was synthesized using natural silty clay as a support material(SC-NZVI).The NZVI and SC-NZVI were characterized by infrared spectroscopy(FTIR),scanning electron microscope(SEM),X-ray diffraction(XRD),Brunauer–Emmett–Teller(BET),and zeta potential(ζ).The interpretation of the results demonstrated that the polyphenol and other antioxidants in green tea waste can be used as reduction and capping agents in NZVI synthesis,with silty clay an adequate support.Additionally,the experiments were carried out to explore phenol adsorption by NZVI and SC-NZVI.To determine the optimum conditions,the impact of diverse experimental factors(i.e.,initial pH,adsorbent dose,temperature,and concentration of phenol)was studied.Langmuir,Freundlich,and Tempkin isotherms were used as representatives of adsorption equilibrium.The obtained results indicated that the adsorption processes for both NZVI and SC-NZVI well fitted by the Freundlich isotherm model.The appropriateness of pseudofirstorder and pseudosecondorder kinetics was investigated.The experimental kinetics data were good explained by the second-order model.The thermodynamic parameters(ΔH0,ΔS0,andΔG0)for NZVI and SC-NZVI were determined.The maximum removal rates of phenol at optimum conditions,when adsorbed onto NZVI and SC-NZVI,were found to be 94.8%and 90.1%,respectively.

Studies on batch adsorptive removal of cadmium and nickel from synthetic waste water using silty clay originated from Balochistan-Pakistan

The potentials of silty clay(SC),acquired from Chaman,Balochistan,were investigated as adsorbent for Ni(Ⅱ)and Cd(Ⅱ)removal from contaminated media.The influence of different operating factors like dose,pH,temperature,and time of contact was explored,and optimum values were noted under batch adsorption method.Isothermal study was conducted with varying concentrations of solutions on optimized conditions and different adsorption models i.e.,Langmuir,Freundlich,Temkin and Dubinin-Radushkevich(D-R)isotherm,which were employed to interpret the process.The isothermal data of both Ni(Ⅱ)and Cd(Ⅱ)were well fitted to Langmuir isotherm suggesting the formation of monolayer of metal ions on silty clay.The values of adsorption capacity noted for Ni(Ⅱ)and Cd(Ⅱ)were 3.603 mg·g^-1 and 5.480 mg·g^-1,respectively.Kinetic studies affirmed that pseudo second order(PSO)kinetics was being obeyed by the removal of Ni(Ⅱ)and Cd(Ⅱ).Thermodynamic variables like free energy change(ΔG°),enthalpy change(ΔH°)and entropy change(ΔS°)were calculated.The negative value ofΔG°and the positive values ofΔH°andΔS°unfolded that the removal process of both metal ions of by SC was spontaneous,endothermic and feasible.

Lateral displacement of silty clay under cement-fly ash-gravel pile-supported embankments: Analytical consideration and field evidence

Based on back analysis of lateral displacements measured in situ by using the analytical solution, a useful method for estimating stress concentration ratio of geosynthetic-reinforced and pile-supported(GRPS) embankments was proposed. In order to validate the proposed method, a full-scale high-speed railway embankment(HSRE) with four instrumented subsections over medium compressibility silty clay was constructed in three stages. The soil profile, construction procedure and monitoring of settlements and lateral displacements of the four test sections were described. The field deformation analysis results show that 1) the combined reinforcement of CFG piles and geosynthetic layer perform well in terms of reducing lateral displacements; 2) the development of lateral displacements lags behind the increase of fill load, which can be attributed to the vertical load transfer mechanism of the pile foundation; and 3) pile length has a dominant effect on the stress distribution proportion between piles and surrounding soils. The comparison between predicted and experimental results suggests that the proposed analytical solution and the back analysis-based method are capable of reasonably estimating the lateral deformation and the stress concentration ratio, respectively, if the appropriate soil elastic modulus is chosen.

Microstructural insight into permeability and water retention property of compacted binary silty clay

The durability of silty clay embankments is partially controlled by the moisture migration, which depends on soil hydraulic properties. This paper presents an experimental study of hydraulic properties of compacted binary silty clay. Specimens with different mixing ratios and dry densities were prepared. Scanning electron microscopy and mercury intrusion porosimetry were used to characterise the microstructure of silty clay. Thereafter, falling-head permeability tests and water retention tests were conducted to study the permeability and water retention property, respectively. The results demonstrate that clay particles are dispersed and show preferred arrangements after compaction when the clay content is 100%. As the clay content decreases, the arrangement of clay particles is gradually disturbed because of the existence of silt particles, causing the formation of large pores around silt particles. When the dry density increases, the pores around silt particles significantly decrease. Moreover, the permeability of silty clay decreases but the water retention capacity increases with increasing clay content and dry density. This is because the silty clay with larger clay content and dry density has fewer large pores, which greatly restrains the flow of water. Both the permeability and water retention property of silty clay can be predicted from pore size distribution parameters.

Simulation of Silty Clay Compressibility Parameters Based on Improved BP Neural Network Using Bayesian Regularization

Soil compressibility parameters are important indicators in the geotechnical field and are affected by various factors such as natural conditions and human interference.When the sample size is too large,conventional methods require massive human and financial resources.In order to reasonably simulate the compressibility parameters of the sample,this paper firstly adopts the correlation analysis to select seven influencing factors.Each of the factors has a high correlation with compressibility parameters.Meanwhile,the proportion of the weights of the seven factors in the Bayesian neural network is analyzed based on Garson theory.Secondly,an output model of the compressibility parameters of BR-BP silty clay is established based on Bayesian regularized BP neural network.Finally,the model is used to simulate the measured compressibility parameters.The output results are compared with the measured values and the output results of the traditional LM-BP neural network.The results show that the model is more stable and has stronger nonlinear fitting ability.The output of the model is basically consistent with the actual value.Compared with the traditional LMBP neural network model,its data sensitivity is enhanced,and the accuracy of the output result is significantly improved,the average value of the relative error of the compression coefficient is reduced from 15.54%to 6.15%,and the average value of the relative error of the compression modulus is reduced from 6.07%to 4.62%.The results provide a new technical method for obtaining the compressibility parameters of silty clay in this area,showing good theoretical significance and practical value.

Geotechnical Characterization of Silty Clay Reinforcedwith Jute Cloth as Waster Product

Soil reinforcement is a recent and special field of soil improvement.It covers a range of techniques,which consists of placing inclusions in soil.The most conferences devoted partly or totally the behavior of foundation on reinforced subgrade without regarding the basic characteristics of the reinforced soil.So,the paper presents an experimental investigation into the mechanical and compressibility properties of the reinforced silty clay samples by jute cloth at intermediate depth.The effects of the reinforcement on shear stress and shear failure were studied;also,the presence of the reinforcement on behavior of consolidation process was distinctly described.The laboratory tests were supported by the finite element analysis to identify only the consolidation process and explained the effect of the reinforcement on the effective vertical stress and pore water pressure.The results indicated that the presence of such reinforcement has a considerable effect in increasing the shear strength of the reinforced samples and decreasing the compressibility especially decreasing the soil movement also,relieving both the effective and pore water pressure.

Statistical Analysis of the Dynamic Parameters of Silty Clay in the Beijing Area

Soil dynamic parameters,including dynamic shear modulus ratio and damping ratio,have important effects on the results of layered soil earthquake response. In this paper,the mean parameter values of silty clay in different depths are obtained after statistical analysis of the experimental soil dynamic data from 20 recent site seismic safety evaluation reports in the Beijing area. Furthermore,based on two typical engineering sites,the influence of four different soil dynamic parameters,the statistic mean values,experimental values, values recommended by Yuan Xiaoming,and the values recommended in the code for seismic safety evaluation of engineering sites( DB001-94) are analyzed. The result shows that mean statistical values are applicable to seismic safety evaluation work in the Beijing area,especially for some inter-layered silty clays whose undisturbed soil samples are hard to obtain.

Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

In this study,model tests were conducted to investigate the bearing capacities of tripod caisson foundations subjected to eccentric lateral loads in silty clay.Lateral load–rotation curves of five eccentric-shaped tripod suction foundations were plotted to analyze the bearing capacities at different loading angles.It was observed that the loading angle significantly influenced the bearing capacity of the foundations,particularly for eccentric tripod caisson foundations.Compared with eccentric tripod caisson foundations,the traditional tripod foundation has a relatively high ultimate lateral capacity at the omnidirectional loading angle.By analyzing the displacement of the caissons,a formula for the rotational center of the tripod caisson foundation subjected to an eccentric lateral load was derived.The depth of the rotation center was 0.68–0.92 times the height of the caisson when the bearing capacity reached the limit.Under the undrained condition,suction was generated under the lid of the“up-lift”caisson,which helps resist lateral forces from the wind and waves.

Thermomechanical properties of an energy micro pile-raft foundation in silty clay

Micro steel pipe pile was used for existing foundation reinforcement and renovation.An energy micro pile-raft foundation equipped with heat exchange tube was constructed in silty clay.The diameter and the length of the energy micro pile are 160 mm and 13.0 m,respectively.A series of in situ thermal performance tests were carried out by controlling cycle heating,in which the inlet and outlet water temperatures,flow rate,and thermomechanical properties of the energy micro pile were measured.Combined with a numerical simulation method,the thermomechanical stresses and displacement of the raft were also analyzed and discussed.The energy micro pile-raft foundation was also analyzed for different combinations of energy piles and nonenergy piles in the group.Results show that the micro pile-raft foundation can provide sufficient heat exchange compared with other types of ground heat exchangers.Differential settlement at both the pile top and tip were observed for the groups that contained both energy piles and nonenergy piles.

Synthesis of zinc oxide nanoparticles reinforced clay and their applications for removal of Pb(II)ions from aqueous media

The aim of the study was to synthesize zinc oxide nanoparticles(ZnONPs)composite with clay by a novel route and then to explore the capability of composite of ZnONPs and silty clay(SC)as adsorbents for Pb(II)eradication from aqueous media by batch adsorption method.The effect of different operating factors like temperature,pH,dose and time of contact on the adsorption process were studied to optimize the conditions.Langmuir,Freundlich,Dubinin-Radushkevich(DR)and Temkin isotherms were applied for the interpretation of the process.The R^(2)and q values obtained from Langmuir model suggested that the process is best interpreted by this model.The values of adsorption capacity(qm)noted were 12.43 mg·g^(-1) and 14.54 mg·g^(-1)on SC and ZnONPsSC respectively.The kinetic studies exposed that pseudo second order(PSO)kinetics is followed by the processes suggesting that more than one steps are involved to control the rate of reactions.Various thermodynamic variables such as change in free energy(AGe),change in enthalpy(AH9)and change in entropy(ASe)were calculated.Thermodynamic data suggested that Pb(II)adsorption on SC and ZnONPsSC are spontaneous,endothermic and feasible processes.