Soft Clay Research Articles

Sensitivity Analysis of Different Hydrothermal Characteristics in the Variable Thermodynamic Processes of Soft Clay Rock

Sensitivity Analysis of Different Hydrothermal Characteristics in the Variable Thermodynamic Processes of Soft Clay Rock

Vertical bearing capacity of HSCM pile groups in marine soft clay

Vertical bearing capacity of HSCM pile groups in marine soft clay

Prediction of bearing capacity of geogrid-reinforced sand over stone columns in soft clay

It is a challenge to estimate the ultimate bearing capacity (qrs) of a geogrid-reinforced sandy bed on vertical stone columns in soft clay due to their complex geometry and uncertain parameters. Predicting qrs can be costly and challenging, so creating an accurate prediction model is important for real-world applications. The research aims to use ensemble techniques like K Nearest Neighbors (KNN), Random Forest (RF), and Extreme Gradient Boosting (XGBoost) to develop a model for estimating the bearing capacity of geogrid-reinforced stone columns (GRBS) on a sandy bed with vertical stone columns in soft clay. A dataset of 245 experimental observations is used to train the models. The present study highlights the potential use of the XGBoost model as a useful tool that can assist in predicting the bearing capacity. The results of the study reveal that this model has performed well in predicting the bearing capacity with high correlation coefficients of 0.9947. Furthermore; a SHAP dependency analysis was conducted to ascertain the significance of each parameter.

Database for Deep Excavations in Soft Clay with Focus on Groundwater Drainage and Installation Effects

Database for Deep Excavations in Soft Clay with Focus on Groundwater Drainage and Installation Effects

Synergetic Effects of Alkaline and Sulfate-Based Waste Binders on Undrained Triaxial Behavior of Cement-Admixed Soft Clay

Synergetic Effects of Alkaline and Sulfate-Based Waste Binders on Undrained Triaxial Behavior of Cement-Admixed Soft Clay

Shaking Table Test and Numerical Modeling of Seismic Behavior of Rectangular Tunnel Structures Embedded in Soft Clay

In this paper, a series of 1-g shaking table model tests were carried out to investigate the seismic behavior of a relatively stiff rectangular tunnel structure installed in soft clay bed, accounting for different ground motions with varying peak accelerations. Using a validated numerical analysis procedure, a suite of three-dimensional (3D) finite element (FE) analyses was performed to systematically study the factors of tunnel burial depth, seismic intensity, flexural rigidity of the middle column and tunnel wall thickness on the seismic response of rectangular tunnel structures installed in clayey ground. It was found that, with the increasing burial depth, the seismic response of rectangular tunnel structure became more intense due to the increased inertial force arising from the overlying clay; in terms of improving the seismic performance of tunnel structure, increasing tunnel wall thickness seemed more effective than increasing flexural rigidity of the middle column. Furthermore, it was found that the existing simplified approaches generally tended to overestimate the earthquake-induced racking distortions of rectangular tunnels installed in clayey ground. A new semi-empirical relationship was derived for better correlating the racking ratio with flexibility ratio for rectangular tunnels embedded in soft clays, which could provide a useful reference for the seismic design and risk assessment of similar clay-tunnel systems.

Salinity and oven-drying effects on the plasticity of a marine soft clay

Considering the extensive use of plasticity-based correlations in geotechnical practice to estimate soil parameters, this paper evaluates the influence of pore fluid salinity and soil drying on the plasticity of Ballina clay, an estuarine soft clay from northern New South Wales (Australia). A comprehensive experimental study, which includes controlled leaching/salinisation paths applied to natural (remoulded) as well as oven-dried clay, prior to the estimation of the Atterberg limits, is presented. Plasticity tests are complemented with chemical analysis of the pore fluid carried out to evaluate the processes involved in the leaching/salinisation mechanisms for remoulded and oven-dried clay. A strong dependency of liquid limit on pore fluid salinity and oven-drying is observed in Ballina clay. Leaching modifies the soil fabric from an initially saline–sodic flocculated towards a normal flocculated arrangement. The experimental results show that changes in soil plasticity upon leaching are largely reversible upon salinisation paths. Oven-drying promotes the stacking of clay minerals (aggregation), which in turn reduces the water absorption capacity of the clay. The consequences of neglecting both salinity and drying effects in practice when adopting well-established relationships between mechanical parameters and soil plasticity are also briefly discussed.

Database Analysis of Long-Term Settlement Behavior of Pile Foundations in Shanghai Soft Coastal Clays

A database of 195 field records of long-term settlement of high-rise buildings in Shanghai soft coastal clays is presented. The collected field records are divided into two categories based on pile type, i.e., bored pile and precast pile. Based on the settlement recorders collected, the long-term settlement behavior and settlement duration of the pile foundations in soft coastal clays are investigated. The statistical results show that the pile foundation in Shanghai soft coastal clays can be divided into three kinds of site conditions by considering the pile length and variation of long-term deformation behavior. Prediction models based on the power function are proposed to calculate the normalized final settlement for both bored pile and precast pile foundations. Based on the statistical results, the average normalized final settlement (settlement per floor), average settlement ratio (final settlement to the settlement when the superstructure is completed), and average settlement duration in the three site conditions for both bored pile and precast pile foundations are given. Additionally, an exponential settlement prediction model that can accurately forecast the entire settlement and post-construction settlement characteristics of buildings in Shanghai’s soft soil area is proposed. These statistical results can be referred to the preliminary foundation design works, which contribute to the quick evaluation of the possible settlement range, settlement ratio, and settlement duration of the proposed building constructed in the soft coastal clay area in Shanghai.

A 3-D modelling of monopile behaviour under laterally applied loading

Deploying higher-capacity offshore wind turbines to meet the growing energy demand poses a significant challenge in designing their foundations. Monopiles currently constitute 80% of the foundation installations for these turbines. This study utilizes a nonlinear three-dimensional (3D) finite element model to explore the behavior of monopiles underpinning a five megawatt wind turbine under horizontal loads. The findings reveal that the performance of monopiles is influenced by the strength of the soil and the ratio of pile depth of embedment to diameter (L/D). Examination of flexural bending profiles at/close to failure loads demonstrates the flexible behavior of monopiles, even with a low L/D ratio. The L/D ratio exhibits varying degrees of impact on the normalized ultimate lateral capacity of monopiles, with a notable effect observed in soft clays, resulting in an increase of up to five times for L/D ratios ranging from 3.33 to 13.33. Stiff clays show comparatively lesser effects. Under serviceability loading, an increase in the L/D ratio leads to a 3–6% rise in the maximum flexural moment of monopiles, while the maximum shear force experiences a decrease of 20–30%. Furthermore, a significant reduction, up to five-fold, in the maximum tower tip displacements and rotations at the mudline is observed with an increasing L/D ratio. However, this reduction is more pronounced for higher foundation rigidity.

Enhancing the Strength of Soft Clay Using Date Seed Ash

Enhancing the Strength of Soft Clay Using Date Seed Ash

Scaled model tests on pile types influencing the stability of stiffened deep mixed pile-supported embankment over soft clay

Scaled model tests on pile types influencing the stability of stiffened deep mixed pile-supported embankment over soft clay

The Evaluation of Effect of Jet Grout Columns to the Settlements in Soils with Numerical Methods

Increasing population bring together the need for construction on weak soils. At this point, soil improvement methods gain importance in which the problematic properties of soils aimed to enhance. Among these, jet grout columns are widely applied method and have advantages such as increasing the bearing capacity, reducing settlements and the risk of liquefaction. In this paper, jet grout columns utilized to reduce settlements in weak soil layers and the effect of several parameters on settlement examined. The analyzes, performed with Plaxis 2D and Plaxis 3D. The jet grouts are modeled with both single columns and composite region by changing jet grout length, diameter and spacing. To assess the soft clay effect, columns were socketed into different clay layers. The results proved that improvement with jet grout reduces the settlements, but the change in diameter, length and spacing affects the results at different rates. Through 3D analysis, up to 22% reductions in settlements obtained in case where the longest columns were assigned at the lowest spacings. The most effective factor was found as spacing rather than diameter. The increase in diameter after a certain value led to lower the performance due to the group effect. In case of the composite region, 3D and 2D analyzes converge very much, so it would be practical to perform 2D analysis for the composites. However, the ones modelled with single columns predicted more settlement and remained on the safe side. Additionally, jet grout columns performed better than in weak soils.

Sedimentation characteristics of surficial sediments in Baiyun Canyon area, Northern South China Sea

The Baiyun Canyon area on the Northern Slope of the South China Sea is a potential hotspot for oil and gas resource development, but the sediment characteristics and sedimentary environment in this region present challenges for offshore engineering. This study comprehensively analyzed the physical, and mechanical properties of sediments in the area using geophysical exploration, engineering geological investigation, fixed-point sampling and hydrological observation. The engineering geological characteristics and sedimentary environment of surface sediments in the Baiyun Canyon area were studied, and the relationship between physical and mechanical properties and sedimentary environment was explored. The study revealed that the sediments in this area consist mainly of organic soft clay with high water content, low density, high pore ratio, high liquid limit, high plasticity and low strength. The physical and mechanical properties of the sediments vary, with the mechanical properties exhibiting higher variability than the physical properties. The research findings offer a scientific basis for understanding the seabed soil properties for designing submarine engineering structures in the deep waters of the northern South China Sea. This study holds significant theoretical and practical implications for oil and gas exploration and offshore engineering construction.

Effect of Electrode Positioning on Electrokinetic Remediation of Contaminated Soft Clay with Surface Electrolyte.

Soft clay contamination is an increasingly global issue with significant implications for land development and human health. Electrokinetic remediation (EKR) has demonstrated significant potential for cleaning contaminated soils. It is crucial to develop efficient processes that minimize environmental impact and reduce costs. A series of citric acid (CA)-enhanced EKR tests were conducted using a novel experimental setup, with the electrolyte positioned above the soil surface, to examine the impact of four different electrode arrangements on the effectiveness of EKR. The position of the electrode end had a significant impact on the migration of ions in the anolyte and catholyte, which in turn affected the volume reduction in the anolyte, the magnitude of the current, and the migration of heavy metals. The electrode arrangement mode c (electrodes suspended in the electrolytes) can enhance the migration of the anolyte and reduce the drainage of the soil, making it an effective measure for improving the removal rate of heavy metals. After the heavy metal remediation is complete, the bearing capacity of the soil should be increased. Changing the electrode arrangement to mode d (anode suspended in the anolyte, a very small part of the cathode inserted into the soil) is an effective measure for reducing the soil water content and improving soil strength.

Experimental study on the thixotropic strength of the marine soft clay from the Yangtze River estuary

Soft clay in the offshore area of the Yangtze River estuary has been investigated considering its basic physical properties. Forty-five unconfined compressive strength tests were conducted on the remolded marine soft clay to investigate the impacts of curing time T, water content w, plasticity index IP, and clay particle content ρc on the thixotropic static shear strength ratio As of the marine soft clay from the Yangtze River estuary. Results show that the stress–strain curves were primarily strain hardening and strain softening curve types. Unconfined compressive strength qu increased with an increase in T. All specimens with different basic physical properties were capable of thixotropic strength recovery. When T = 0–28 days, As increased rapidly, while for T > 28 days, As of most specimens increased slightly or tended to stabilize. The impacts of w, IP and ρc on As do not follow a consistent pattern, but there is a strong correlation between As and w/wL (wL is the liquid-limit water content). For w/wL < 0.75, As increased with increasing w/wL, whereas for w/wL ≥0.75, As decreased with increasing w/wL. We proposed a simple and widely applicable power function prediction model for the As of the soft clay from the Yangtze River estuary.

Effect of torsional shear stress on the deformation characteristics of clay under traffic load

The soft clay under the road ground will suffer cyclic torsional shear stress encountered traffic load in addition to axial stress, which will cause further deformation of clay. To investigate the effect of torsional shear stress on the cumulative axial strain of clay, a series of undrained tests under cardioid stress path were performed on K0 consolidated undisturbed samples by using a hollow cylinder apparatus (HCA). The effect of vertical cyclic stress ratio (VCSR) and shear stress ratio (η) on the deformation and degradation characteristics of clay was investigated. The results indicate that there is inconsistency between the strain path and stress path. The increase in η further accelerates the accumulation of axial strain, which resulted from the degradation of clay induced by torsional shear stress. Considering the VCSR and η, a calculation method of degradation index was developed. Furthermore, a cumulative axial strain prediction model of clay under the cardioid stress path was established considering the degradation. This model addresses the limitation of traditional prediction models by considering the impact of torsional shear stress on cumulative axial strain.

Numerical analysis of a deep and oversized group excavation: A case study

Group excavations are composed of several individual excavations adjacent to each other with simultaneous or successive construction sequences (CS), which are distinctive from individual excavation in terms of the performance of excavation. In this study, a hyper-scale 3D finite element model was established to investigate the deformation behavior of a diaphragm wall system retaining a deep and oversized group excavation (DOGE) in Shanghai soft clay deposits. The numerical model simulated the practical construction stages and sequences, and it was verified by a series of comparisons with field measurements. Based on the numerical model, the spatial effect of the performance of DOGE in the process of excavation stages was investigated in this study, which cannot be addressed by limited field measurements. Furthermore, the effects of partition walls and CS on the deformation control were discussed to provide practical suggestions for oversized and deep excavations. The results indicate that the employment of bi-partition walls to divide the oversized excavation into several small pits and mono-partition walls and cross walls to further divide the pits near the metro lines into smaller ones, was proved to have significant effectiveness in controlling the wall deflection and protecting the adjacent metro line. For the partition wall, the magnitude and direction of the wall deflection primarily depended on the initial excavation, while the influence of subsequent excavation activities proved insignificant. Thus, it should be noted that the effect of the initial excavation should be especially concentrated. The findings can help optimize similar DOGE engineering.

Stability and Deformation Analysis of Embankment on Soft Clay

Soft clay generally poses a problem for civil engineers due to its high compressibility and low shear strength. Structures built on soft soil are subjected to excessive settlement and the settlement is attributed to the consolidation process. A large percentage of the settlement is accredited to a consolidation process that could persist for a long period, depending on the ability of the soil to dispel excess pore water. Prediction of the settlement of embankment is important for the design of the highway, to prevent excessive post-construction settlement which can lead to failure. Construction on soft clays has become more important and common in urban areas In this study, the time-settlement behavior of an embankment on soft clay predicted using analytical methods is compared with those predicted by Geo studio SIGMA/W software. Thus the magnitudes of final settlement using Terzaghi theory differ from the magnitudes of final settlement computed from SIGMA/W software by approximately ±10% difference. The differences could be due to the assumption properties such as Young’s modulus (E) and Poisson’s ratio (ν) in the SIGMA/W Geo studio, and the coefficient of compressibility considered in the analytical method. Moreover, this study presented the results of the stability analysis of the embankment on soft clay, and the performances of the barrier were analyzed. The limit equilibrium method (LEM) using Geo studio SLOPE/W software and hand calculations were used to calculate the factor of safety. The results showed that the calculated factors of safety obtained from Fellenius, Bishop, Janbu, and Morgenstern-Price methods using both ways are very similar, with an approximate difference of only ±10%.

Large-Scale Direct Shear Tests on Soft Clay Treated with Reinforced Lime Columns

Large-Scale Direct Shear Tests on Soft Clay Treated with Reinforced Lime Columns

Reliability of dynamically-embedded anchors in soft clay

Reliability of dynamically-embedded anchors in soft clay