Experimental Study on the Effect of Fine-Grained Soil Content on the Freezing Strength of Aeolian Sand-Cement Interface

In cold regions,understanding the freezing strength of the interface between soil and structure is crucial for designing frost-resistant foundations.To investigate how the content of cement powder in aeolian sand affects this strength,we conducted direct shear tests under various conditions such as different fine-grained soil content,normal stress,and initial moisture content of the soil.By analyzing parameters like soil properties,and volume of ice content,and using the Mohr-Coulomb strength theory to define interface strength,we aimed to indirectly measure the cementation strength of the interface.Our findings revealed that as the particle content increased,the interface stress-strain curves became noticeably stiffer.We also observed a positive linear relationship between freezing strength and silt content,while the initial moisture content of the soil did not significantly impact the strengthening effect of fine-grained soil on freezing strength.Moreover,we discovered that as the powder content increased,the force binding the ice to the interface decreased,while the friction angle at the interface increased.However,the cohesion force at the interface remained relatively unchanged.Overall,our analysis suggests that the increase in freezing strength due to fine-grained soil content is primarily due to the heightened friction between aeolian sand and the interface.

Effects of cement-enhanced soil on the ultimate lateral resistance of composite pile in clayey soil

The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral resistance has not been fully investigated.In this paper,the ultimate lateral resistance of the composite pile was studied by finite element limit analysis(FELA)and theoretical upper-bound analysis.The results of FELA and theoretical analysis revealed three failure modes of laterally loaded composite piles.The effects of the enhanced soil thickness,strength,and pile-enhanced soil interface characteristics on the ultimate lateral resistance were studied.The results show that increasing the enhanced soil thickness leads to a significant improvement on ultimate lateral resistance factor(N P),and there is a critical thickness beyond which the thickness no longer affects the N P.Increasing the enhanced soil strength induced 6.2%-232.6%increase of N P.However,no noticeable impact was detected when the enhanced soil strength was eight times higher than that of the natural soil.The maximum increment of N P is only 30.5%caused by the increase of interface adhesion factor(a).An empirical model was developed to calculate the N P of the composite pile,and the results show excellent agreement with the analytical results.

Longitudinal vibration characteristics of a tapered pipe pile considering the vertical support of surrounding soil and construction disturbance

This research is concentrated on the longitudinal vibration of a tapered pipe pile considering the vertical support of the surrounding soil and construction disturbance.First,the pile-soil system is partitioned into finite segments in the vertical direction and the Voigt model is applied to simulate the vertical support of the surrounding soil acting on the pile segment.The surrounding soil is divided into finite ring-shaped zones in the radial direction to consider the construction disturbance.Then,the shear complex stiffness at the pile-soil interface is derived by solving the dynamic equilibrium equation for the soil from the outermost to innermost zone.The displacement impedance at the top of an arbitrary pile segment is obtained by solving the dynamic equilibrium equation for the pile and is combined with the vertical support of the surrounding soil to derive the displacement impedance at the bottom of the upper adjacent segment.Further,the displacement impedance at the pile head is obtained based on the impedance function transfer technique.Finally,the reliability of the proposed solution is verified,followed by a sensitivity analysis concerning the coupling effect of the pile parameters,construction disturbance and the vertical support of the surrounding soil on the displacement impedance of the pile.

Performance evaluation of laterite soil embankment stabilized with bottom ash,coir fiber,and lime

In tropical regions,heavy rainfall induces erosion and shallow landslides on road embankments.Cement-based stabilization methods,common in these regions,contribute to climate change due to their high carbon footprint.This study explored the potential application of coir fiber-reinforced laterite soil-bottom ash mixtures as embankment materials in the tropics.The objective is to enhance engineered embankment slopes'erosion resistance and stability while offering reuse options for industrial byproducts.This study examined various mix designs for unconfined compressive strength(UCS)and permeability,utilizing 30%bottom ash(BA)and 1%coir fiber(CF)with varying sizes ranging from 10 to 40 mm,6%lime,and laterite soil(LS),followed by microstructural analyses.The results demonstrate that the compressive strength increases as the CF length increases to 25 mm.In contrast,permeability increases continuously with increasing CF length.Lime-treated mixtures exhibit superior short-and long-term strength and reduce permeability owing to the formation of cementitious materials,as confirmed by microstructural analyses.A lab-scale slope box was constructed to evaluate the surface erosion of the stabilized laterite soil embankment.Based on the rainfall simulation results,the LS-BA-CF mixtures show better resistance to erosion and deformation compared to untreated LS,especially when lime is added to the top layer.This study provides insights into a sustainable and cost-effective approach for slope stabilization using BA and CF,offering a promising solution for tropical regions susceptible to surface erosion and landslides.

Digital mapping of soil physical and mechanical properties using machine learning at the watershed scale

Knowledge about the spatial distribution of the soil physical and mechanical properties is crucial for soil management,water yield,and sustainability at the watershed scale;however,the lack of soil data hinders the application of this tool,thus urging the need to estimate soil properties and consequently,to perform the spatial distribution.This research attempted to examine the proficiency of three machine learning methods(RF:Random Forest;Cubist:Regression Tree;and SVM:Support Vector Machine)to predict soil physical and mechanical properties,saturated hydraulic conductivity(Ks),Cohesion measured by fall-cone at the saturated(Psat)and dry(Pdry)states,hardness index(HI)and dry shear strength(SS)by integrating environmental variables and soil features in the Zayandeh-Rood dam watershed,central Iran.To determine the best combination of input variables,three scenarios were examined as follows:scenarioⅠ,terrain attributes derivative from a digital elevation model(DEM)+remotely sensed data;scenarioⅡ,covariates of scenarioⅠ+selected climatic data and some thematic maps;scenarioⅢ,covariates in scenarioⅡ+intrinsic soil properties(Clay,Silt,Sand,bulk density(BD),soil organic matter(SOM),calcium carbonate equivalent(CCE),mean weight diameter(MWD)and geometric weight diameter(GWD)).The results showed that for Ks,Psat Pdry and SS,the best performance was found by the RF model in the third scenario,with R2=0.53,0.32,0.31 and 0.41,respectively,while for soil hardness index(HI),Cubist model in the third scenario with R2=0.25 showed the highest performance.For predicting Ks and Psat,soil characteristics(i.e.clay and soil SOM and BD),and land use were the most important variables.For predicting Pdry,HI,and SS,some topographical characteristics(Valley depth,catchment area,mltiresolution of ridge top flatness index),and some soil characteristics(i.e.clay,SOM and MWD)were the most important input variables.The results of this research present moderate accuracy,however,the methodology employed provides quick and costeffective information serving as the scientific basis for decision-making goals.

Strength Model of Soda Residue Soil Considering Consolidation Stress and Structural Influence

Soda residue(SR)is a type of industrial waste produced in the soda process with the ammonia-soda method.Applying SR to backfilling solves the land occupation and environmental pollution problems in coastal areas and saves material costs for foundation engineering.The strength characteristics of soda residue soil(SRS)under different consolidation conditions are the key points to be solved in the engineering application of SRS.Triaxial compression tests were performed on the undisturbed SRS of Tianjin Port.The shear properties of SRS under different consolidation conditions were then discussed.Meanwhile,a structural strength model(SSM)based on Mohr-Coulomb theory was proposed.SSM reflects the influence of soil structure on undrained strength(Cu)and divides the Cu into the following two parts:friction strength(C_(uf))and original structural strength(C_(u0)).C_(uf)characterizes the magnitude of friction between soil particles,which is related to the consolidation stress.Meanwhile,C_(u0)represents the structural effect on soil strength,which is related to the soil deposition and consolidation processes.SSM was validated by the test data of undisturbed soils.Results reveal that the undisturbed soil generally had a certain C_(u0).Therefore,the SRS strength model was established by combining the experimental law of SRS with SSM.Error analysis shows that the SRS strength model can effectively predict the Cu of undisturbed SRS in Tianjin Port under different consolidation conditions.

Thermal integrity profiling of cast-in-situ piles in sand using fiber-optic distributed temperature sensing

Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature profiles of cast-in-situ piles, enabling the detection of structural defects or anomalies at the early stage of construction. However, using this integrity testing method to evaluate potential defects in cast-in-situ piles requires a comprehensive understanding of the mechanism of hydration heat transfer from piles to surrounding soils. In this study, small-scale model tests were conducted in laboratory to investigate the performance of TIP in detecting pile integrity. Fiber-optic distributed temperature sensing (DTS) technology was used to monitor detailed temperature variations along model piles in sand. Additionally, sensors were installed in sand to measure water content and matric suction. An interpretation method against available DTS-based thermal profiles was proposed to reveal the potential defective regions. It shows that the temperature difference between normal and defective piles is more obvious in wet sand. In addition, there is a critical zone of water migration in sand due to the water absorption behavior of cement and temperature transfer-induced water migration in the early-age concrete setting. These findings could provide important insight into the improvement of the TIP testing method for field applications.

A Simplified Method for Estimating the Initial Stiffness of Monopile-Soil Interaction Under Lateral Loads in Offshore Wind Turbine Systems

The interface mechanical behavior of a monopile is an important component of the overall offshore wind turbine structure design.Understanding the soil-structure interaction,particularly the initial soil-structure stiffness,has a significant impact on the study of natural frequency and dynamic response of the monopile.In this paper,a simplified method for estimating the interface mechanical behavior of monopiles under initial lateral loads is proposed.Depending on the principle of minimum potential energy and virtual work theory,the functions of soil reaction components at the interface of monopiles are derived;MATLAB programming has been used to simplify the functions of the initial stiffness by fitting a large number of examples;then the functions are validated against the field test data and FDM results.This method can modify the modulus of the subgrade reaction in the p-y curve method for the monopile-supported offshore wind turbine system.

Influence of Salt-Lime Stabilization on Soil Strength for Construction on Soft Clay

Construction on soft soil is one of the most challenging situations faced by geotechnical engineers. The heterogeneous and complex nature of soil, especially those containing organic clay, often makes it impossible for the construction specification to be addressed properly. Generally, clay exhibits low strength, high compressibility, and strength reduction when subjected to mechanical disturbance. This means that construction on clay soil is vulnerable to bearing capacity failure induced by low inherent shear strength. All these properties can be improved by the effective stabilization of soil. This study analyzed the effectiveness of incorporating salt-lime mixtures at various dosages in improving the strength increment of the soil. The results indicate that among different combinations of salt and lime, the best performance in terms of strength increase was achieved by adding 10% NaCl with 3% lime in the soil. The outcome of this study focuses on enhancing the ultimate strength of soil and its implementation in the field of foundation engineering.

Study on Optimization of Design Parameters for Precast Pipe Pile Treatment of Soft Soil Subgrade on the Jianghan Plain

The soft soil in the Jianghan Plain is characterized by a high water content, liquid limit, sensitivity, porosity ratio, and organic matter content and low strength and is commonly known as “five highs and one low” soft soil. Thus, the construction of expressways in this area is likely to cause subgrade settlement. The manuscript investigated the influence of the design parameters of precast pipe piles on the soft ground treatment in the Jianghan Plain based on the case of the soft soil subgrade project of the Xiaogan south section of the Wuhan city ring expressway, China. Midas GTS NX 2019 finite element software was used to analyse the settlement pattern of the subgrade under the variations in pile length, pile spacing and pile diameter. The results show that precast pipe piles are effective in reducing the settlement of soft soil subgrades with a high compressibility and water content;the soft foundation settlement decreases with increasing pile length and pile diameter and decreasing pile spacing. As the pile tip is embedded in the bearing stratum, the settlement of the soft foundation is greatly affected by the variations in pile length and pile spacing while slightly influenced by the variation in pile diameter;in combination with the curve fitting obtained from the real-time monitoring data, the analysis concludes that the soft foundation treatment plan with a pile length of 15 m, pile spacing of 1.2 m to 1.5 m and pile diameter of 0.6 m can better contain the soft soil subgrade settlement in this section.

Influence of the roots of mixed-planting species on the shear strength of saline loess soil

In order to improve our knowledge of the mechanical effect of the roots of mixed-plantings on soil reinforcement and slope protection,the influence of roots of a mixed-planting with four herb species(Medicago sativa L.,Elymus nutans Griseb.,Puccinellia distanx(L.),and Poa pratensis L.)and one shrub species(Caragana korshinskii Kom.)were investigated on the shear strength characteristics of saline loess soil.The root distribution characteristics were assessed via a survey when the plants grew for one year.The effects of the root biomass density,the root mass ratio(RMR)of the fine roots to the coarse roots,the moisture content,and the salt content on the shear strength index of the rooted soil were analyzed via a triaxial compression test,and the mechanism of these effects was discussed.The results indicate that the biomass density decreased linearly with increasing depth.The RMR initially decreased with depth and then increased,exhibiting in a quadratic relationship.The cohesion of the rooted soil increased linearly as the biomass density increased.The cohesion of the rooted soil initially increased with increasing RMR and salt content,and then it decreased.The turning point of the cohesion occurred when the RMR was 0.6 and the salt content was 1.18%.The internal friction angle of the rooted soil initially increased with biomass density and then decreased,and the turning point of the internal friction angle occurred when the biomass density was 0.015 g/cm3.The relationships between the internal friction angle of the rooted soil and the RMR and salt content were exponential incremental and linear subtractive relationship,respectively.Both the cohesion and the internal friction angle of the rooted soil linearly decreased with increasing moisture content.

Centrifuge experiment on the penetration test for evaluating undrained strength of deep-sea surface soils

Rapid advances in deep-sea mining engineering have created an urgent need for the accurate evaluation of the undrained strength of marine soils,especially surface soils.Significant achievements have been made using full-flow penetration penetrometers to evaluate marine soil strength in the deep penetration;however,a method considering the effect of ambient water on the surface penetration needs to be established urgently.In this study,penetrometers with multiple probes were developed and used to conduct centrifuge experiments on South China Sea soil and kaolin clay.First,the forces on the probes throughout the penetration process were systematically analyzed and quantified.Second,the spatial influence zone was determined by capturing the resistance changes and sample crack development,and the penetration depth for a sample to reach a stable failure mode was given.Third,the vane shear strength was used to invert the penetration resistance factor of the ball and determine the range of the penetration resistance factor values.Furthermore,a methodology to determine the penetration resistance factors for surface marine soils was established.Finally,the effect of the water cavity above various probes in the surface penetration was used to formulate an internal mechanism for variations in the penetration resistance factor.

Revisiting the Bjerrum's correction factor:Use of the liquidity index for assessing the effect of soil plasticity on undrained shear strength

The undrained shear strength （su） of fine-grained soils that can be measured in situ and in laboratory isone of the key geotechnical parameters. The unconfined compression test （UCT） is widely used in laboratoryto measure this parameter due to its simplicity; however, it is severely affected by sampledisturbance. The vane shear test （VST） technique that is less sensitive to sample disturbance involves acorrection factor against the soil plasticity, commonly known as the Bjerrum＇s correction factor, m. Thisstudy aims to reevaluate the Bjerrum＇s correction factor in consideration of a different approach and arelatively new method of testing. Atterberg limits test, miniature VST, and reverse extrusion test （RET）were conducted on 120 remolded samples. The effect of soil plasticity on undrained shear strength wasexamined using the liquidity index instead of Bjerrum＇s correction factor. In comparison with the resultobatined using the Bjerrum＇s correction factor, the undrained shear strength was better representedwhen su values were correlated with the liquidity index. The results were validated by the RET, whichwas proven to take into account soil plasticity with a reliable degree of accuracy. This study also showsthat the RET has strong promise as a new tool for testing undrained shear strength of fine-grained soils.

Cyclic Lateral Responses of Monopiles Considering the Influence of Pile−Soil Relative Stiffness in Sand

The existing studies have primarily focused on the effect of cyclic load characteristics(namely,cyclic load ratio and amplitude ratio)on cyclic lateral response of monopiles in sand,with little attention paid to the effect of pile−soil relative stiffness(K_(R)).This paper presents a series of 1-g cyclic tests aimed at improving understanding of the cyclic lateral responses of monopiles under different pile−soil systems.These systems are arranged by two model piles with different stiffness,including four different slenderness ratios(pile embedded length,L,normalized by diameter,D)under medium dense sand.The K_(R)-values are calculated by a previously proposed method considering the real soil stress level.The test results show that the lateral accumulation displacement increases significantly with the increment of the K_(R)-value,while the cyclic secant stiffness performs inversely.The maximum pile bending moment increases with the cycle number for the rigid pile−soil system,but shows a decreasing trend in the flexible system.For an uppermost concern,an empirical model is proposed to predict the accumulated displacement of arbitrary pile−soil systems by combining the results from this study with those from previous experimental investigations.The validity of the proposed model is demonstrated by 1-g and centrifuge tests.

A theoretical analysis of vertical dynamic response of large-diameter pipe piles in layered soil

Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was derived by Laplace transformation method.The responses in time domain were obtained by inverse Fourier transformation.The results of the analytical solution proposed agree well with the solutions in homogenous soil.The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched.The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil.The smaller the shear modulus,the larger the amplitude of velocity admittance.The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil.The displacements of the piles with the same damping coefficients of the outer soil have less difference.Moreover,the effects of the distribution of soil layers are analyzed.The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer.A larger damping coefficient of the upper layer results in a smaller velocity admittance.The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.

New method of designing anti-slide piles——the strength reduction FEM

At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.

Study on the shear strength of deep reconstituted soils

Based on analytical methods of strength studies for deep soils, direct shear tests were carried out to investigate the shear strength of deep reconstituted soils at different initial dry densities and amounts of water.The results indicate that the shear strength of deep reconstituted soils for identical amounts of water below the plastic limit is enhanced with increasing dry density and but reduced sharply at the critical density, the point at which coarse particles break down.Moreover, the shear strength for identical dry density decreases with additional amounts of water and the rate of degradation is the greatest at the critical density.This is because the friction resistance between coarse particles reduces with increasing amounts of water higher than the plastic limit.In order to obtain reliable strength of deep reconstituted soils, suitable dry densities and amounts of water are necessary.

Determination Method for Shear Strength Parameters of Rock-Soil Mixtures Using Close-Range Photogrammetry and 3-D Limit Equilibrium Theory

Using a combination of close-range photogrammetry and three-dimensional(3-D) limit equilibrium theory, a determination method for the shear strength parameters of rock-soil mixture is presented. A close-range photogrammetry method is used for measurement of the 3-D terrain of the experimental target. Auto CAD Lisp and EXCEL VBA are used to perform 3-D limit equilibrium analysis of the stability of sliding mass and perform backanalysis of shear strength parameters. The presented method was used to determine the shear strength parameters of rock-soil mixtures at the Liyuan Hydropower Station. The 3-D terrain of sliding surface could be measured notably well using of closerange photogrammetry. The computed results reveal that the cohesion and friction angle of rock-soil mixtures were 3.15 k Pa and 29.88o for test A, respectively, and 4.43 k Pa and 28.30o for test B, respectively, within the range of shear strength parameters, as determined by field and laboratory tests. The computation of shear strength parameters is influenced by the mesh grid number, especially the cohesion of the rock-soil mixture. The application of close-range photogrammetry can reduce the siteworks and improve the computational efficiency and accuracy.

Transport of Phenol in BS-12 Modified Lou Soil in the Column Experiment: Effect of Concentrations, pH and Ionic Strength

Lou soil was modified by amphoteric surfactant in column experiment which was conducted. This study attempts to explore the transport of phenol to unmodified and modified soil and inquire into the effect of concentrations, pH, and ionic strength on phenol migration in the soil column. The parameters and breakthrough curves (BTCs) of transport were fitted by using the CXTFIT (version 2.1) model. The result of Cl?’s BTCs for non-reactive by determining the equilibrium model (EM) showed the retardation factor which was smaller than 1. The result of phenol’s BTCs by determining non-equilibrium model (NEM) was shown that the R-value increased while modification ratio increased, and the R was in order of CK (1.337) < 50BS-12 (4.085) < 100BS-12 (7.048). The lower to higher concentration of phenol didn’t affect to CK and 100BS-12 was able to block higher concentration. The effect of pH on transport to CK and 100BS-12 didn’t react and the average pore water velocity was decreased at pH = 4. The decreasing ionic strength of phenol migration on CK and 100BS-12 had effect and the average pore water velocity and retardation factor also decreased. The residual retention in soil was in order of CK < 50BS-12 < 100BS-12, and 100BS-12 could hold the amount of phenol than CK 7.21 times. Thus, amphoteric modified lou soil definitely blocks phenol migration and controls groundwater pollution.

Corrigendum to “Optimizing the evolution of strength for lime-stabilized rammed soil” [J Rock Mech Geotech Eng 11(2019)882-891]

The authors regret that in the paper of Baldovino et al.(2019),published in Journal of Rock Mechanics and Geotechnical Engineering(JRMGE),Eq.(2)must be corrected.Eq.(2)in the original paper describes a formula to calculate the unconfined compressive strength(q_u).But Authors wrote it as if it were the formula for calculating the split tensile strength(qt).To amend this error,Eq.(1)and Eq.(2)are the correct expressions for q_u and q_t measurements,respectively.