Cohesive Soils Research Articles

INNOVATIVE EXPERIMENTAL TESTING PROGRAM OF DIRECT SHEAR TEST IN SOIL MECHANICS

The research work aims at analyzing for the first time the data set obtained on cohesive soil samples following the publication of the Romanian Invention Patent RO 134239. The standard test method for the direct shear test provides the shear strength parameter – internal friction angle in consolidated drained condition - of either undisturbed or remolded soil samples forcing the shear plane at the midsection of the sample in the horizontal direction. The samples are provided in parallelepipedal shape (6 cm x 6 cm x 2 cm) and the displacement rate in horizontal direction is 0.1 mm/min. The new equipment patented in Romania changes the direction of shearing, from horizontal to vertical, and the soil samples are of cubic shape (6 cm x 6 cm x 6 cm). The experimental program involves testing both the parallelepipedal and cubic samples using the same motorized mechanism, with simultaneous readings from their respective micro-comparators. The UU test is performed without allowing consolidation and shearing at 1.0 mm/min. For the CD test, samples are consolidated under vertical loads for 24 hours before shearing at 0.1 mm/min. The shear stresses for cubic samples were higher than those for parallelepipedal samples, with residual stresses reflecting this trend. For cubic samples, both the peak and residual shear stresses trend lines indicated higher cohesion (c) and lower internal friction angle (𝜙) for UU tests and CD tests in contrast to parallelepipedal samples in both testing conditions. The innovative testing program allows for variability in shear strength parameters along the soil failure surface in both natural and compacted soil structures. This differentiation divides the soil condition into drained and undrained states at the initiation, emergence points, and the point of maximum depth along the failure surface. This approach is significant for accurately assessing soil shear resistance and potential failure mechanisms. The study's findings suggest a nuanced approach to parameter selection for slope stability analysis, ensuring accurate representation of both cohesion and internal friction in stability models.

Numerical Simulation Analysis of Dock Bank Slopes’ Soil–Water Interface Recognition and Monitoring Device Models Based on Heat Transfer Principles

The erosion and sedimentation of bank slopes are important factors affecting the safety of wharf operations. The essence of bank slope monitoring is to identify the water–soil interface. This paper proposes a model for soil-and-water interface identification and monitoring equipment buried on the bank slope of the wharf, based on the difference in thermodynamic heat transfer between water and soil media, and presents the results of multi-condition numerical simulation. The comparison between numerical simulation results and indoor experimental results shows that the overall patterns are consistent, with an error of less than 11.4%, which is lower than the deviation between theoretical calculation results and indoor experiments. Based on the accuracy of the numerical calculation results, the temperature rise and propagation characteristics of linear heat sources made of iron and PVC in eight types of cohesive soils and six types of non-cohesive soils were studied. The results indicate that there are significant differences in the temperature distribution of linear heat sources made of iron and PVC in both water and soil media. The monitoring equipment model based on the difference in heat transfer between water and soil can be applied in practical engineering. This provides a foundation for the design and application of subsequent monitoring equipment.

Kinematic bearing capacity analysis of strip footings on reinforced soils using discretisation technique

The kinematic discretisation technique of upper bound limit analysis is adopted in this study to evaluate the limit load of a strip footing located on the soils reinforced with different geosynthetic layers. The reinforcement is assumed to withstand the tension but not bending moment. The failure model of the reinforced foundation soil is generated using the discretisation method, a ‘point by point’ technique. Two failure modes of the reinforcement, the tensile rupture and sliding, are considered in the analysis. This article proposed the formulas for the first time to evaluate the effect of soil friction angle φ on the ultimate bearing capacity and on the failure mechanism of foundation. The calculation results are given considering different reinforcement layers, which describe the impact of different reinforcement depth and length on the ultimate bearing capacity. The optimum positions of different reinforcement layers and the optimum reinforcement length are obtained. The bearing capacity ratios are also presented in figures combing impact of reinforcement depths, soil cohesion and friction angle. The present method was verified by the results reported in literature. The present method can provide a reference for the footing design on the reinforced soils.

Hybrid XGB model for predicting unconfined compressive strength of solid waste-cement-stabilized cohesive soil

The utilization of cement has been found to have negative environmental impacts. In order to reduce the quantity of cement used and improve the mechanical properties of solid waste-cement-stabilized cohesive soil, the incorporation of solid waste as additives has been investigated. Unconfined compressive strength is a crucial parameter in geotechnical engineering. However, existing empirical formulas have limited accuracy and applicability when it comes to the unconfined compressive strength of solid waste-cement-stabilized cohesive soil. The machine learning model can be used to provide accurate and comprehensive predictions by considering the nonlinear relationships between independent and dependent variables. This study aims to propose a machine learning model tuned by optimization algorithms with high generalization performance in accurately predicting the unconfined compressive strength. Firstly, a database containing 474 specimens was developed. Secondly, eight machine learning models were established, composed five single models and three hybrid models, to train and test the database. Six performance indicators were employed to evaluate the generalization ability of these models. Finally, the optimal model was selected for analysis of the importance of the feature variables using shapley additive explanations, which were compared with those of the existing empirical model. The research findings indicated that, the extreme gradient boosting model tuned with tree-structured parzen estimators exhibited the highest predictive accuracy and generalization ability. The curing age, cement content, plastic limit, and water content were identified as the most critical factors influencing the unconfined compressive strength. Among the chemical components in solid waste, the aluminum oxide content and silicon dioxide content were found to significantly influence the unconfined compressive strength, while the impact of calcium oxide content was relatively minor. Furthermore, the optimal solid waste content was found to be around 10 %. This study made a significant contribution to the effective utilization of waste resources in the context of sustainable construction practices.

Correlation between cone resistance with standard penetration value for predicting consistency of cohesive soil in Eastern India

Correlation between cone resistance with standard penetration value for predicting consistency of cohesive soil in Eastern India

Study on Soil Stabilization and Slope Protection Effects of Different Plants on Fully Weathered Granite Backfill Slopes

The slope erosion in the distribution area of completely weathered granite is often relatively severe, causing serious ecological damage and property loss. Ecological restoration is the most effective means of soil erosion control. Taking completely weathered granite backfill soil as the research object, two types of slope protection plants, Vetiver grass and Pennisetum hydridum, were selected. We analyzed these two herbaceous plants’ soil reinforcement and slope protection effects through artificial planting experiments, indoor simulated rainfall experiments, and direct shear tests. The test results showed that the runoff and sediment production rates of the two herbaceous plant slopes were significantly lower than those of the bare slope, with the order of bare slope > Vetiver grass slope > Pennisetum hydridum slope. Compared with the bare slope, the cumulative sediment production of the Vetiver grass slope at 60 min decreased by 56.73–60.09%, and the Pennisetum hydridum slope decreased by 75.97–78.45%. The indoor direct shear test results showed that soil cohesion decreases with increasing water content. As the root content of Vetiver grass roots increases, soil cohesion first increases and then decreases, reaching a maximum value when the root content is 1.44%. As the root content of Pennisetum hydridum increases, soil cohesion increases. The internal friction angle increases slightly with increasing water content, while the root content does not significantly affect the internal friction angle. Therefore, the shear strength of soil decreases when the water content increases. The shear strength of the Vetiver grass root-soil composite reaches a peak at a root content of 1.44%, while the shear strength of the giant king grass root-soil composite increases as the root content increases. At the same root content, the shear strength of the Vetiver grass root-soil composite is slightly higher than that of giant king grass. The reinforcement effect of roots on shallow soil is better than on deep soil. Both herbaceous plants have an excellent soil-fixing and slope-protecting impact on the fully weathered granite backfill slope. Pennisetum hydridum’s soil and water conservation effect is significantly better than that of the Vetiver grass. In contrast, Vetiver grass roots slightly outperform Pennisetum hydridum in enhancing the shear strength of the soil. The research results can provide a theoretical basis for the vegetation slope protection treatment of fully weathered granite backfill slopes.

Effect of Iron Nanoparticles Prepared from Onion Extract on Cucumber Plant Growth and Production

In recent years, it has been shown that the use of chemical fertilizers negatively affects the environment and public health. Nano fertilizer have been discovered and used, and one of their many advantages is the speed and ease of obtaining them from various plant sources, which are cheap and currently available it's friendly for environment. The field experiment was carried out in the spring season of 2021 in a mixture of salty clay (cohesive soil) for the purpose of studying the effect of spraying synthetic nanoparticles used from iron oxide particles with onion plant extract at concentrations of 100, 200 and 300 parts per million on the growth and yield of cucumber (Cucumis melo var. flexuosus). The prepared nanoparticles were identified by the following assays: UV-visible spectrophotometry, XRD, FTIR, TEM, SEM and AFM. The results showed a significant effect of using Nano pesticides, especially with high concentration, in increasing average plant height, plant dry weight, leaf area and total plant yield. It was concluded from this study that the positive effect of Nano-fertilizer prepared with onion extract on plant growth, which led to an increase in cucumber productivity and the quality of its fruits, from that there is the possibility of using it as an alternative to conditional mineral fertilizers, after conducting several studies on the safety of using these plants treated with Nano-fertilizers for humans.

Numerical study on Slurry-induced Fracturing Pressure of Cohesive Soil

The stability of the tunnel face during the slurry shield tunnelling is controlled by the slurry pressure in the slurry chamber, and excessive slurry pressure will cause fracturing on excavation face. In order to prevent the occurrence of slurry fracturing, it is necessary to conduct a detailed study on the slurry support pressure when the slurry fracturing occurs. In this study, the hydraulic fracturing experiment of cohesive soil samples was carried out by the self-developed hydraulic fracturing device, and the improved XFEM was used to simulate the experiment process. The influence of various factors on the fracturing pressure was analyzed, and the accuracy of the numerical simulation method was also verified. In addition, the calculation method of fracturing pressure of soft cohesive soil is obtained by fitting the influence of each factor. The results show that the improved XFEM can accurately simulate the shear failure of soft cohesive soil. The fracturing pressure increases linearly with the increase in the circumferential pressure, indicating that a higher overburden of the tunnel can help resist the initial fracturing induced by shield tunneling. The fracturing pressure increases with an increase in the unconfined compressive strength as well as the slurry viscosity. Based on the regression analysis of the numerical results, an empirical approach was proposed for estimating the slurry-induced fracturing of soil.

Effects of electrokinetic stabilization combined with addition of calcium ions on soil shear strength characteristics in the hilly granitic region of southern China

Enhancing soil shear strength is of great importance in preventing soil collapse and erosion in the hilly granitic region of southern China. However, limited studies have been conducted on improving soil shear strength in collapsing gullies. Electrokinetic stabilization (EKS) involves applying an electrical current through a soil mass to promote the migration of chemicals from injection points, thereby altering the chemical composition of the treated soil to improve its physical properties. In this study, the effects of calcium chloride (CaCl 2 ) addition and EKS techniques on the soil shear characteristics (shear strength, and its two components: cohesion and internal friction angle) of three different soil layers in collapsing gullies were investigated. The results showed that the EKS techniques significantly increased the migration of calcium ions from the anode to the cathode region of the power supply device used in the soils. Using EKS process alone did not increase or even decrease the soil shear strength, but combining EKS with CaCl 2 injection (Ca-EKS) increased the soil shear strength, and this increase was mainly due to the increasing the soil cohesion. The soil cohesion after Ca-EKS treatment increased on average by 49.84%, 83.11%, and 100.36% compared with the soil without treatments (CK) for the red soil, sandy soil, and detritus, respectively. However, soil amended by sole CaCl 2 addition, Water-EKS or Ca-EKS all can not increase soil internal friction angles compared with the CK. These results demonstrated that the application of Ca-EKS can be applied to improve the soil shear strength and stability of gully walls in hilly granitic regions.

Specific ion effects on the soil shear strength and clay surface properties of collapsing wall in Benggang.

Benggangs are a special type of soil erosion in the hilly granite regions of the tropical and subtropical areas of Southern China. They cause severe soil and water loss, which can severely deteriorate soil quality and threat to the local ecological environment. Soils (red soil, sandy soil and detritus soil) were collected from collapsing wall of a typical Benggang in Changting County of Fujian Province, and their physicochemical and mineralogical properties were analyzed. Five different monovalent cations were used to saturate the soil samples to examine the specific ion effects on the shear strength and clay surface properties. Red soil had a higher clay content, plastic limit, liquid limit and shear strength than sandy soil and detritus soil. The studied soils mainly consisted of kaolinite, hydroxy-interlayer vermiculite, illite and gibbsite clay minerals. The soils saturated with K+, NH4 +and Cs+ had greater cohesion than the Li+- and Na+-saturated soils, e.g., the cohesion of the red soil saturated with Li+, K+, NH4 + and Cs+ cations were 1.05, 1.23, 1.45 and 1.20 times larger than that of the Na+-saturated soil, respectively. While the internal friction angle was slightly different, which indicated that different monovalent cations affected the shear strength differently. K+-, NH4 +- and Cs+-saturated clay particles had higher zeta potentials and thinner shear plane thicknesses than Li+- and Na+-saturated clay particles and showed strong specific ion effects on the clay surface properties. The changes in clay surface properties strongly affected the soil mechanical properties. Soils saturated with K+, NH4 + and Cs+ could increase the shear strength, and then increase the stability of the collapsing wall, thus might decrease the erosion intensity of Benggang. The results provide a scientific basis for the interpretation of and practical treatment of Benggang.

Enhancement of soil ecological remediation using a hydrogel material constructed by freeze–thaw driving force

Composite polymer materials as soil improvers are developed to enhance soil cohesion and aggregate stability. However, the improved soil still struggles to overcome the reduction in strength caused by day-to-day freeze–thaw (FT) cycle in the plateau area with large temperature difference. In this study, the natural power of FT cycle was used to drive the crosslinking of poly (vinyl alcohol) (PVA) and sodium alginate (SA) to form the interpenetrating networks of PVA-SA hydrogel. Then, this hydrogel was applied to stabilize the soil. The characterizations by FTIR, TGA, SEM and XRD indicated that the PVA-SA hydrogel had a porous, multi-channel and multi-chamber structure. Under the action of FT driving force, a series of studies including physical, chemical, water retention, direct shear, permeability, and aggregate stability were carried out on the soil with hydrogel applied. Compared to the control group, the data indicated that the cohesion of soil is significantly improved to 80 kPa. And the saturated hydraulic conductivity of the soil was reduced to 1/45 of the pre-modification rate, which had a positive impact on the water retention of the soil. What’s more, the results revealed that the PVA-SA hydrogel had effects on the aggregate stability, the submerged soil with added PVA-SA hydrogel still had no sign of disintegration and its mass percentage was greater than 99 % after 70 days. In a word, this composite material can effectively improve the cohesion and aggregate stability of the soil with the help of natural driving forces, which is potential to be used as remediation material for the plant layer in ecological restoration process.

Bank erosion under the impacts of fluvial erosion, frost heaving/freeze-thaw process of rivers in seasonal frozen regions

Bank erosion is a key feature of channel evolution in alluvial rivers, and will occur under the combined effect of hydraulic erosion and frost heave/freeze-thaw process of rivers in seasonal frozen regions. However, most research on bank erosion modeling has seldom considered the impact of the frost heave/freeze-thaw process. Therefore, the variation in the mechanical characteristics of riverbank soil under the freeze-thaw cycle was investigated firstly in the current research and then used in the modeling of bank erosion processes at typical sections of the Songhua River. Additionally, a sensitivity analysis of riverbank stability was conducted using orthogonal experiments. The results indicate that after 7 freeze-thaw cycles, the soil cohesion and internal friction angle of bank soil decreased by about 10%–47 % and 9%–19 %, respectively. Unlike lowland rivers, bank erosion of rivers in seasonal frozen regions is more likely to occur during the rising water period. The frost heaving/freeze-thaw process will make the bank stability safety coefficient Fs more quickly decrease to the unstable critical value. As compared with the case without considering the frost heaving/freeze-thaw process, the mass failure occurred in advance when the frost heaving/freeze-thaw process was considered, and the calculated bank erosion volume was increased by 11%–51 %, agreeing better with the measured value. The sensitivity ranking of the four influencing factors on riverbank stability under freezing-thawing conditions is as follows: river stage > groundwater level > cohesion > internal friction angle. The current study can provide a reference for research on bank erosion and channel evolution of rivers in seasonal frozen regions.

Analytical solution of overlying pressure for shallowly buried underwater box tunnel: A case study of box jacking in Suzhou, China

Accurately predicting the overlying pressure is crucial for determining an appropriate cover depth of underwater box tunnels to avoid the uplifting failure. Based on the project of box jacking crossing the Beijing-Hangzhou Grand Canal in Suzhou, the characteristics of overlying pressure variation during tunneling are investigated. The monitoring results reveal that the fluctuation of overlying pressure is weakened during the rapid tunneling process. A modified analytical model for vertical earth pressure is conceived, in which the active and passive limit states for multi-layered soils are both considered. The probable range of overlying pressure obtained by the proposed model is suitable to cover the actual values. The anti-floating behavior of underwater box tunnels for two different working conditions is discussed by calculating the minimum cover depth. Using the calibrated analytical models, a parametric study is conducted to explore the influence of injection pressure, hardened slurry unit weight, soil internal friction angle, soil cohesion, and tunnel geometry. It is found that the injection pressure during the construction process is crucial for determining the necessary cover depth, and the change of box tunnel height makes it easier to trigger the variation of minimum cover depth.

A 3D SPH framework for simulating landslide dam breaches by coupling erosion and side slope failure

Depicting the co-occurrence of erosion and side slope failure during landslide dam breaches using numerical models remains a challenge. In this study, a 3D Smoothed Particle Hydrodynamics (SPH) framework is proposed by coupling the erosion and side slope failure processes. Erosion downcutting is depicted by calculating the washed-away materials due to shear forces exerted by overtopping flow, while side slope failure is simulated using the Drucker-Prager model. In the computation domain, the destabilized slope soil particles are identified, then set to deform like fluid, and subsequently mixed with the flow. The proposed model achieves a refined 3D simulation of breach channel morphology evolution. According to the driving factors, the breaching process can be divided into two stages: the erosion-dominated breach deepening stage, and the simultaneous deepening and widening stage driven by both erosion and side slope failure. Dam erodibility affects the rate of breaching, while soil cohesion influences the breach channel evolution. As soil erosion rate increases, peak discharge increases following a power function, while peak timing decreases according to a power function. As soil cohesion increases, side slope failure slows, resulting in steeper slopes and more pronounced “headcut” erosion, which shifts the slope failure mode from sliding to collapsing.

Amelioration of fat clay treated with CNS and cohesionless soils

The present study evaluates the amelioration of fat clay by blending it with cohesive non-swelling soil (CNS) and cohesionless silty sandy soil (Kassu). The fat clay sample with a liquid limit (LL) of 50 and a plasticity index (PI) of 26 was collected from Narowal, while CNS and Kassu samples were procured from Lahore's outskirts. Geotechnical tests on the virgin soil indicated its unsuitability for construction. Laboratory tests, including modified Proctor compaction, unconfined compression, California bearing ratio (CBR), and one-dimensional consolidation, were performed on samples blended with 0–35% CNS or Kassu in 5% intervals. The LL and PI of fat clay decreased significantly with the addition of 35% CNS (LL: 50–32%, PI: 24 to 13) and Kassu (LL: 50–29%, PI: 24–12). The CBR value increased from 4 to 7%, making the blended soil suitable for subgrade use. Unconfined compression tests showed a strength increase from 102 to 185 kPa with 35% CNS and up to 140 kPa with 25% Kassu. Compaction tests revealed improved maximum dry unit weight and reduced optimum moisture content. Swell potential decreased from 4 to 1.2 and 0.26% with CNS and Kassu additions. Regression models predict swell pressure and ultimate swell potential. The study concludes that blending fat clay with CNS and Kassu significantly improves its geotechnical properties, with CNS being more effective in controlling swell characteristics.

Numerical prediction of ground-borne vibrations due to continuous vibratory driving of circular closed-ended piles

Various types of pile driving work may induce high-intensity ground-borne vibrations. Predicting vibration intensity before adopting mitigation measures is vital for minimizing the impact of vibration on nearby structures and occupants. Vibratory pile driving is a commonly applied foundation construction method. However, numerical simulation models for ground vibrations during a complete process of vibratory driving have rarely been studied. This study introduces an axisymmetric finite element model that utilizes the arbitrary Lagrangian-Eulerian technique to simulate the continuous vibratory driving of a circular closed-ended pile penetrating from the ground surface to a target depth. The model validity was confirmed by assessing the calculated ground vibrations against the findings documented in earlier research. The results showed that the critical penetration depth of piles, at which the maximum peak particle velocity (PPV) occurs, varied with the radial distance and depth of points of interest, contradicting a common preconception. Moreover, the maximum PPV did not always occur on the ground surface across all radial distances. Parametric analysis revealed that an increase in the soil cohesion strength, pile diameter, or soil-pile friction, or a decrease in the driving frequency or soil damping ratio would increase ground vibrations due to vibratory pile driving.

Predicting Micropile Group Capacity in Soft Cohesive Soil by Artificial Neural Network

Predicting Micropile Group Capacity in Soft Cohesive Soil by Artificial Neural Network

RETRACTED: Relationships among fall cone flow index and consistency identifiers of fine-grained soils with emphasis on toughness limit

It is well known that plasticity characteristics are one of the most important factors controlling the engineering behavior of fine-grained soils. In this regard, Atterberg limits are used for evaluation of plasticity and strength behavior of soils. Of all the plasticity identifiers, fall cone flow index, which is the slope of the flow curve is a descriptor of plasticity and undrained shear strength characteristics of cohesive soils. On the other hand, toughness limit is also efficient in prediction of many index properties of soils including plasticity characteristics, compression index as well as residual friction angle. This study is an attempt to establish relationships among fall cone flow index and consistency identifiers of fine-grained soils. Emphasis is given on toughness limit, which is believed to be a practical and efficient approach in assessment of fall cone flow index. Regression-based equations establishing relationships between fall cone flow index, plasticity index, plasticity ratio, toughness limit and liquid limit were presented. Besides, the efficiency of artificial neural networks in prediction of toughness limit and fall cone flow index was investigated. It should be noted that established relationships using regression equations are based on regional data, which come up with coefficient of determination (R2) values ranging between 0.706 and 0.978. On the other hand, ANN models were used to model global data, R2 values were obtained to be between 0.586-0.972 and 0.522-0.889 for training and testing phases, respectively. Relationships concerning local and global data were presented, along with analysis of effectiveness of application of relationships established for analysis of global data.

Mechanical and hydraulic characteristics of unvegetated or vegetated loess soils amended with xanthan gum

With the development of western and central China, the increasing construction of transportation infrastructures (e.g., roads, railways, etc.) has been producing a large number of man-made slopes in loess regions. Biopolymer as an eco-friendly stabilizing material, has a great potential to amend soils for the purpose of ground improvement and slope stabilization, with its application in vegetated soils particularly at the initial growing stage to support vegetation growth as well as offer reinforcement to unprotected soils being reported recently. In the current study, the contribution of xanthan gum (XG) to both mechanical and hydraulic behaviors of the unvegetated and vegetated loess soils subjected to climatic wetting–drying cycles under the impacts of degree of compaction and biopolymer content are explored, whilst the effectiveness of the two XG-based soil reinforcing methods (with and without vegetation) are compared. Results indicate that XG treatment improved the water-retention capacity of loess soils to an extent that even the degradation of water retention upon initial wetting–drying cycles could be mitigated particularly at higher degrees of compaction. The strengthened shear resistance of loess soils was observed, mainly attributed to the increased soil cohesion, whilst the friction angle remained almost constant. The unvegetated loess soils basically had an increased cohesion proportional to the XG content up to 1.00% of the dry soil mass, whilst the vegetated soils had the highest soil cohesion at a fixed XG content of 0.50% which corresponded to the mostly promoted vegetation growth. Although a dense soil structure inhibited the seed germination and growth of sprouts and roots, it contributed to the overall shear strength of the vegetated soils similar to its effect on the unvegetated soils. XG amendment outperformed planting vegetation at enhancing soil shear strength at a degree of compaction of 95% (comparable to those adopted for design of highway subgrade), whilst providing XG in combination with vegetation was able to result in a more sizable strength increment over the summation of gains in strength by utilizing XG and vegetation separately, suggesting the considerable potential of XG in assisting vegetated soils for ecological slope stabilization. The results obtained from the current research support the broader usage of biopolymers (either used alone or in combination with vegetation) as reliable geotechnical engineering materials in practical implementations.

Experimental study on the effect of freeze–thaw cycles to the cohesion and moisture content of geogrid reinforced silty clay

The freezing and thawing cycle is one of the primary causes of damage and instability to buildings in seasonal frost regions. During this process, the mechanical properties of soil are affected, leading to settlement, cracking, or deformation of infrastructure. Mitigating or reducing the occurrence of building frost damage in seasonal frost regions has become an important subject of study. Freeze–thaw (F–T) action will influence the distribution of moisture inside the reinforced soil and change the strength of thawing soil, which is closely related to the main influencing factors, such as initial moisture content, compaction degree, reinforced spacing, number of freeze–thaw cycles (FTC), freezing temperature, and effective vertical stress. Cohesion is an important index to determine the shear strength of clay, which is important to analyze the change in cohesion after F–T. Meanwhile, cohesion is closely related to soil moisture content. This study conducted orthogonal experiments on these primary influencing factors (6 factors at 5 levels) through FTC tests, triaxial tests, and moisture content tests to determine the undrained cohesion and moisture content of the clay after FTC, thereby establishing the influence of reinforcement on soil strength under freeze–thaw conditions. Based on the experimental results, SPSS software was used to fit the regression equations of undrained cohesion and moisture content expressed by the main influencing factors at different heights of the clay. Optimization options for the main influencing factors were obtained with Matlab software when the highest undrained cohesion values 6.8, 10.6, 8.9 kPa and lowest moisture content values 24.0%, 24.3%, 26.2% appeared in upper, middle and lower parts of the testing clay structure respectively, in conditions of − 15 °C freezing temperature and 5 times FTC. And determined the optimal combinations of moisture content, reinforcement spacing, compaction density, and vertical load at different heights. Decreasing reinforced spacing in silty clay was beneficial for liquid underwater seepage after F–T. The redistribution of internal moisture in the soil sample strengthened its undrained cohesion, thereby increasing the soil's shear strength. Comparing reinforcement conditions at different locations, it was found that when there were 3 layers of reinforcement with a spacing of 150 mm between them, this spacing was optimal. It played a significant role in improving the soil's shear strength and enhancing its bearing capacity. For reinforced clay itself, the order of the main factors influencing the undrained cohesion of soil after F–T, from high to low, was initial moisture content, reinforced spacing, and compaction degree.