Strength Of Clay Research Articles

Numerical analysis of downward progressive landslides in long natural slopes with sensitive clay

Landslides occurring in sensitive clay often result in widespread destruction, posing a significant risk to human lives and property due to the substantial decrease in undrained shear strength during deformation. Assessing the consequences of these landslides is challenging and necessitates robust numerical methods to comprehensively investigate their failure mechanisms. While studies have extensively explored upward progressive landslides in sensitive clays, understanding downward progressive cases remains limited. In this study, we utilised the nodal integration-based particle finite element method (N-PFEM) with a nonlinear strain-softening model to analyse downward progressive landslides in sensitive clay on elongated slopes, induced by surcharge loads near the crest. We focused on elucidating the underlying failure mechanisms and evaluating the effects of different soil parameters and strain-softening characteristics. The simulation results revealed the typical pattern for downward landslides, which typically start with a localised failure in proximity to the surcharge loads, followed by a combination of different types of failure mechanisms, including single flow slides, translational progressive landslides, progressive flow slides, and spread failures. Additionally, inclined shear bands occur within spread failures, often adopting distinctive ploughing patterns characterised by triangular shapes. The sensitive clay thickness at the base, the clay strength gradient, the sensitivity, and the softening rate significantly influence the failure mechanisms and the extent of diffused displacement. Remarkably, some of these effects mirror those observed in upward progressive landslides, underscoring the interconnectedness of these phenomena. This study contributes valuable insights into the complex dynamics of sensitive clay landslides, shedding light on the intricate interplay of factors governing their behaviour and progression.

Reinforcement of soft clay using industrial residue-based soil stabilizer and recycled fine aggregate: A comprehensive investigation

This study aims to assess the effectiveness of an industrial residue-based soil stabilizer (GDP) and recycled fine aggregate (RFA) in enhancing the properties of soft clay. The GDP is composed of ground granulated blast furnace slag (GGBS), desulfurized gypsum (DG), and Portland cement (PC). The optimal formula for GDP and the appropriate amount of RFA needed to reinforce the soft clay were determined through unconfined compressive strength (UCS) testing. The microscopic characteristics and reinforcement mechanism of the GDP-RFA-reinforced soft clay were then analyzed using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetry (TG), and scanning electron microscopy (SEM) techniques. The effectiveness of utilizing GDP and RFA as reinforcement additives in soft clay ground was also validated through field testing. The experiments showed that using GDP instead of cement significantly increased the strength of soft clay, with the optimal mass ratio of GGBS, DG, and PC in GDP being 6:1:3. The strength of the GDP-reinforced sample initially increased and then decreased as the RFA content increased, reaching its peak at a RFA content of 30 %. The formation of C-S-H and C-A-H gels, along with AFt crystals, in the GDP-RFA-reinforced sample greatly enhanced its mechanical properties. RFA helped to form more hydrated products and provide effective mechanical support, but excessive RFA could lead to large pores in the matrix. The use of GDP and RFA in reinforcing soft clay ground significantly improved its specific penetration resistance, bearing capacity, and compressive modulus. A significant linear correlation was found between the compressive modulus of reinforced clay and its specific penetration resistance or UCS. As a result, an empirical model has been developed to predict the compressive modulus of reinforced clay based on this correlation.

INFLUENCE OF CRUSHED BRICK COLUMNS ON GEOTECHNICAL PROPERTIES OF EXPANSIVE SOIL

Utilization of crushed brick which is a common industrial material that is potentially wasted during the construction process in ground improvement can relieve its detrimental effects on the environment thereby reducing the waste disposal challenges. Hence, this study proposes its utilization as reinforcement to the soft clay soil. The tests mainly focused on the particle size distribution (PSD), specific gravity, Atterberg limit, proctor analysis as well as the shear strength parameters from Unconfined Compression Test (UCT). Coherently, the vibro-replacement method was deployed within a small-scale laboratory approach as a prediction model for the construction of a group of crushed brick columns. The column design was mainly classified into partially penetrated columns which have 60 mm and 80 mm height, and fully penetrated columns with 100 mm height. The mass of crushed brick used was approximately 1.07% - 4.56% of its total mass of specimen which produces the shear strength improvement rate from 11.00% - 18.55%. From the obtained results, the use of fully penetrated 100 mm diameter columns enhanced the undrained shear strength of kaolin clay to the maximum value, 26.20kPa or 18.55% as compared to the control sample with no reinforcement, which reduced the soil settlement and promoted the use of sustainable material in ground improvement.

Enzyme-induced Carbonate Precipitation (EICP) Combined with Lignin to Improve the Unconfined Compression Strength (USC) of Shanghai Clay

In order to improve the mechanical properties of high moisture content and low strength of clay particles in Shanghai, the effects of different lignin content on the unconfined compressive strength of EICP-lignin-cured clay were studied by using the method of lignin combined with EICP technology to strengthen the clay by lignin combined with EICP technology. The experimental results showed that EICP-lignin could enhance the unconfined compressive strength of Shanghai clay. With the increase of lignin content, the unconfined compressive strength of clay first increased and then decreased, and there was an optimal content value. The optimal lignin content is 8%.

Influence of consolidation on undrained capacity of two interfering footings on heterogeneous clays

The effect of consolidation on the undrained capacity of two interfering footings has not been investigated previously in a systematic manner, although this is particularly interest for offshore foundations, where consolidation will occur as a result of working load or preload. This paper presents results of a numerical investigation into the consolidated undrained bearing capacity of two interfering footings resting on heterogeneous clays. Finite difference code FLAC with the modified Cam Clay soil model is applied to couple the effect of consolidation and strength gain of clay beneath the footings. The results are expressed in dimensionless form of the gain in capacity, accounting for the coupling effects of the spacing between two footings, the magnitude and duration of applied preloads, and the clay strength heterogeneity. A design approach based on the data-fitting equations of the obtained solutions is proposed, and the failure mechanisms of the two adjacent footings after consolidation are also discussed.

Triaxial Test and Discrete Element Numerical Simulation of Geogrid-Reinforced Clay Soil

Indoor triaxial tests on geogrid-reinforced clay elucidate the macroscopic changes in soil strength indices post-reinforcement, yet the underlying mechanisms of strength enhancement require further investigation. By conducting indoor triaxial tests and establishing a corresponding discrete element numerical model, we can delve into the fine-scale mechanisms of geogrid-reinforced soil. This includes analyzing changes in fine-scale parameters such as porosity, the coordination number, and contact stress between soil particles. The findings suggest that an increase in the number of geogrid reinforcement layers leads to a more pronounced improvement in peak strength and cohesion, albeit with minimal impact on the internal friction angle of the specimens. Furthermore, analysis of the triaxial test curves of reinforced soils indicates that the stress–strain relationship adheres to the Duncan–Chang model. Parameters derived from this model have been validated against experimental data, confirming their accuracy. The discrete element model was used to analyze the variations in fine-scale parameters such as porosity and coordination number. It revealed that reinforcement reduces the fluctuation amplitude of porosity and significantly increases the number of particle contacts, resulting in a denser soil structure. Further analysis of the change in contact stress between particles in the discrete element model revealed that the contact force between particles increased significantly after reinforcement and that the reinforcement played a role in restraining the soil particles and dispersing the reinforcement stress, which explains the increase in the strength of the mesh-reinforced clays from another perspective. This further elucidates the strength enhancement mechanism in geogrid-reinforced clay, offering a new perspective on the mechanical behavior and strength development of such materials.

Hydraulic conductivity of cement and fly ash stabilised clay mixes – Application to soil mixing techniques for seepage barrier construction

In-situ ground improvement techniques, namely, deep soil mixing, jet grouting, cutter soil mixing, and mass stabilisation are often utilized to improve the strength of soft grounds, and construct seepage barriers. Due to economic and environmental concerns, there is a global shift towards using industrial wastes such as fly ash (FA) from conventional binders such as ordinary Portland cement and lime. There is a plethora of literature on unconfined compressive strength (UCS) of cement-treated clays, and clays treated with fly ash-cement mixes with alkali activator (FCAA) binders. However, much remains unclear about the hydraulic conductivity of the FCAA-treated clays as low permeable hydraulic barrier systems. In this paper, the hydraulic conductivities of cement-treated and FCAA-treated clays are studied both quantitatively and qualitatively for different binder-content, FA:cement ratios, curing periods, and effective confining stress. The hydraulic conductivity of treated clay is measured by performing a series of accelerated permeability tests using a custom-fabricated triaxial system. The trends obtained from the measured hydraulic conductivity values are explained from the observations of X-ray diffraction analysis and scanning electron microscopy analysis. Results showed that the values of hydraulic conductivity for cement-treated clay were mostly higher than those of untreated clay. On the contrary, the hydraulic conductivities for the FCAA clay mixes were comparable to, or even lower than those for the untreated clay. The hydraulic conductivity reduced with the increase in effective confining stress; the influence of effective confining stress, however, became less substantial for 28 days curing period and higher cement-content (40 and 50 %). The relationships between the hydraulic conductivity, UCS, and water-binder (w/b) ratios were also determined for both cement-treated and FCAA-treated clays. The exponential function was found suitable to express the relationship between hydraulic conductivity and UCS of treated clays. In contrast, a strong logarithmic relationship was obtained for measured values of hydraulic conductivity and adopted w/b ratios. The results shall serve as a guide to adopting suitable binder-content or target UCS for achieving design hydraulic conductivity in ground improvement projects that involve cement and/or FCAA-treatment of clays.

Effectiveness of lime kiln dust on swelling of subgrade expansive soil

BackgroundThe structure of flexible or rigid pavement built on expansive subgrade soil that has a volumetric change is vulnerable to many problems that might cause failure. Pavement and construction became more durable and economical by enhancing the quality of subgrade expansive soil. Solid waste recycling has become very popular recently as a means of attaining sustainable waste management, so using lime kiln dust (LKD), which is a by-product of quick lime production, to treat expansive soil in pavement subgrades. This research describes the effect of LKD on the chemical composition, strength, and swelling of high and low-plastic clay that were extracted from two sites. The minimum LKD required for treating expansive soils was determined by using the Eades and Grim pH test. From tests, it was found that the addition of LKD increased the shrinkage limit by a range (250–500)% and decreased the plasticity and swelling potential by between (50 and 100)% of expansive subgrade soils. The strength according to CBR, increased approximately by 150% for CL soil and 800% for CH soil.ResultsThe optimal percentage of LKD for CH soil is 6%, and for CL soil, it is 2%. The plastic limit increased by 50% for CH soil at 6% LKD. On the other hand, CL soil became non-plastic at 4% LKD. With an increase in the percentage of LKD, it led an the increase in the shrinkage limit by 500% in CH soil and 250% in CL soil. The free swell decreased by 50% in CH soil and 100% in CL soil. The swelling pressure decreased by 50% for two expansive soils. CBR increased by 800% in CH soil and by 150% in CL soil.ConclusionThis work found that the addition of LKD improves the physical, chemical, and mechanical properties of expansive subgrade soil.

Multi-scale analysis of carbon mineralization in lime-treated soils considering soil mineralogy

Mineral carbonation is emerging as a reliable CO2 capture technology that can mitigate climate change. In lime-treated clayey soils, mineral carbonation occurs through the carbonation of free lime and cementitious products derived from pozzolanic reactions. The kinetics of the reactions in lime-treated clayey soils are variable and depend primarily on soil mineralogy. The present study demonstrates the role of soil mineralogy in CO2 capture and the subsequent changes caused by carbon mineralization in terms of the unconfined compressive strength (UCS) of lime-treated soils during their service life. Three clayey soils (kaolin, bentonite, and silty clay) with different mineralogical characteristics were treated with 4% lime content, and the samples were cured in a controlled environment for 7 d, 90 d, 180 d, and 365 d. After the specified curing periods, the samples were exposed to CO2 in a carbonation cell for 7 d. The non-carbonated samples purged with N2 gas were used as a benchmark to compare the mechanical, chemical-mineralogical, and microstructure changes caused by carbonation reactions. Experimental investigations indicated that exposure to CO2 resulted in an average increase of 10% in the UCS of lime-treated bentonite, whereas the strength of lime-treated kaolin and silty clay was reduced by an average of 35%. The chemical and microstructural analyses revealed that the precipitated carbonates effectively filled the macropores of the treated bentonite, compared to the inadequate cementation caused by pozzolanic reactions, resulting in strength enhancement. In contrast, strength loss in lime-treated kaolin and silty clay was attributed to the carbonation of cementitious phases and partly to the tensile stress induced by carbonate precipitation. In terms of carbon mineralization prospects, lime-treated kaolin exhibited maximum carbonation due to the higher availability of unreacted lime. The results suggest that, in addition to the increase in compressive strength, adequate calcium-bearing phases and macropores determine the efficiency of carbon mineralization in lime-treated clayey soils.

Shear Strength of Soft Soil Reinforced with Singular Bottom Ash Column

Structures construct on soft clays are often affected by stability and settlement problems due to high compressibility, low shear strength and low permeability of soft clay which will lead to bearing capacity failure and excessive settlement. The soft clay samples had the dimensions of 50 mm diameter and 100 mm in height. The bottom ash column had two (2) different area replacement ratios which were 4% and 9% (10 mm and 15 mm diameters respectively) with the bottom ash column penetration ratio of 0.3, 0.7 and 1.0. The results of the unconfined compression test show that there is an improvement in shear strength of soft kaolin clay when reinforced with bottom ash column. For samples with area replacement ratio 4%, the results show the increment of 25%, 37.5% and 50% at height penetrating ratio of 0.3, 0.7 and 1.0, respectively in shear strength. Meanwhile, for samples of 9% area replacement ratio, the shear strength of the soft kaolin clay increased about 14.29, 28.57 and 57.14%, respectively. It can be concluded that by reinforcing the soft clay using singular bottom ash column, the shear strength of the soils increases and become more significant as the area replacement ratios and the column penetration ratios increase.

Strength of Kaolinitic Clay Soil Stabilized with Lime and Palm Oil Fuel Ash

The use of palm oil fuel ash (POFA) mixed with lime as a catalyst in soil stabilization can significantly improve the stability of problematic soils and improve their engineering properties. Problematic soils can obstruct the construction process due to its low strength and low bearing capacity. In this study, various laboratory tests were carried out to determine the engineering properties of the soil’s mixture which includes Atterberg limit, particle size distribution, compaction, and unconfined compression test. 4%, 8% and 12% POFA were mixed with 6% hydrated lime to stabilized the kaolinitic clay soil at different curing days (1, 7, 14, and 30 days). Compared to untreated kaolin, the addition of POFA plus lime resulted in higher undrained shear strength. The maximum undrained shear strength (USS) is 32.68kN/m2, which was obtained on the 30th day of curing with the optimal mixture of stabilized kaolin which is kaolin mixed 6% of lime and 12% of POFA. The unconfined compressive strength increased by 185.04% compared to the unconfined compressive strength of untreated kaolinitic clay with a value of 65.36 kN/m2. This proves that kaolin stabilized with lime and POFA can increase the strength parameters of clay, thus reducing construction costs for soil stabilization and reducing environmental issues.

Undrained shear strength of artificially flocculated clays

The flocculation and sedimentation of suspended clay particles in marine environments are an important process to form natural marine clays. In this study, the process of flocculation and sedimentation is simulated using appropriate flocculating agents in the laboratory. A series of laboratory sedimentation tests are carried out on various floc samples prepared with different concentrations of flocculating agents, and the size and density of flocs are measured and are found to serve as good parameters to characterise the development of flocculation. Multiple series of undrained triaxial compression tests under normal consolidation, as well as under over-consolidation, are then carried out on a slightly flocculated sample and a largely flocculated sample, as well as an ordinary remoulded sample. The values of the undrained shear strength of the flocculated samples are compared with those of the ordinary remoulded sample. The largely flocculated sample exhibits a higher undrained shear strength under normal consolidation as well as under over-consolidation. A comparison with past studies on natural marine clays also indicates that the highly variable values of the undrained shear strength of marine clays can be attributed to the different levels of development of flocculated structures in clays.

IMPROVING THE ENGINEERING PROPERTIES OF CLAYEY SOIL USING SILICA FUME AND SISAL FIBER

Building on soft soils continues to be a challenge for civil engineers in the modern world, despite the rapid development of infrastructure projects and advancements in construction technology. They exhibit a large volumetric change upon contact with water, which is the cause of their limited bearing capacity. Various stabilization strategies can be used to handle the soft clay's shear strength issue. In this experiment, sisal fibers and silica fumes were added in different amounts to the clay soil in order to determine the ideal moisture content and strength parameters for reaching the maximum dry density of the soil. By adjusting the amount of sisal fiber for each amount of silica fume, the Unconfined Compressive Strength (UCS) test has been used to examine the strength of both natural clay and clay modified with silica fume (6%, 12%, 18%) and sisal fibers (0.5%, 1.0%, 1.5%) separately, as well as the combination of all the materials. Using a small compaction device, standard proctor test was used to determine the ideal moisture content and maximum dry density. According to the test results, the maximum dry density falls with increasing silica fume content likewise, the maximum dry density increases with increasing sisal fiber content. The addition of 12% silica fume and 2.0% sisal fiber to the clay sample results in a maximum strength when taking the strength parameter into account. Key Words: Compaction test, CBR, UCS, Silica fume, Sisal Fiber

Optimizing the compressive strength of low-grade hydrous clay and copper slag‐based sustainable ternary blended geopolymer mortar

Ternary blended geopolymers represent a new class of sustainable binders with improved properties when compared to mono and binary blended geopolymers under ambient conditions. The study focuses on low grade industrial waste materials; locally sourced hydrous clay (HC) waste and copper slag (CS), to create novel Ternary Blended Geopolymer Mortars (TBGM). The addition of CS had a positive effect on strength development. The incorporation of 40 % CS as fine aggregate replacement, improved the proportion of HC in precursors from 10 % to 30 %. The design parameters considered were sodium silicate to sodium hydroxide solution ratio (SS/SH) at (2,2.5,3), the alkaline solution (AL) to binder (B) material ratio (AL/B) at (0.35,0.4,0.45), and the molarity of the sodium hydroxide solution (M) at (8,10,12) respectively. Box Behnken Design (BBD) with response surface methodology (RSM) was used to reduce the number of trial experiments to 15 from a total of 27 and, to statistically optimize and evaluate the interactions of SS/SH, AL/B, and M on the performance of TBGM. The compressive strength of 72 N/mm2 at the SS/SH, M and AL/B as 2.5, 12 and 0.4, respectively, was in good agreement with the experimental result of 78 N/mm2 at similar proportions. From the diagnostics and response plots of RSM, it can be inferred that the molarity of NaOH and AL/B and its combined interaction had more critical influence on the compressive strength of TBGM compared to SS to SH ratio. The microstructural and durability investigation further validated the optimization studies, as the optimum mortar specimen exhibited a denser microstructure with reduced shrinkage and sorptivity values.

Increasing Unconfined Compressive Strength of Soft Clay Stabilized with Coir Fiber and Bagasse Ash Mix

Increasing coir fiber and bagasse ash waste can cause environmental degradation. Utilization of this waste in construction work is still rarely done. Coir fiber is a natural material with the highest coefficient of friction and tensile strength. Bagasse ash has a high silica content and is suitable for use as pozzolan. Soil stabilization with a combination of both is expected to improve the geotechnical properties of soft soil. This research aims to analyze the unconfined compressive strength (UCS) and secant modulus of soft clay stabilized with coir fiber-bagasse ash mix. Coir fiber as much as 0.75% and ash with varying contents: 0%, 2%, 4%, 6%, 8%, and 10% of the total weight of the mixture. The specimens were cured for 28 days. UCS tests were conducted according to ASTM D2166-16 with the axial stress and strain relationship curve results to determine the UCS and secant modulus. The results showed that the UCS value and secant modulus value increased along with increasing bagasse ash content. The maximum value was achieved at 8% ash variation with a UCS value of 472.45 kPa (an increase of 382% from a soil-coir fiber mix) and a secant modulus value of 21.94 MPa (an increase of 571% from a mixture of soil and coir fiber). The research results show that this mixed soil is classified as hard soil, which can withstand high loads. It is hoped that the results of this research can become a reference for stabilizing soft soil in the field.

Comparison of soil improvement techniques on the development of efficient consolidation response

A comprehensive experimental program including two distinct series of consolidation tests was performed on clay specimens prepared at different dry weight proportions including 0%, 1%, 2.5%, 5%, 7.5%, 10% polypropylene fiber or lime by weight mixed with clayey soil. Fiber inclusion into clay resulted in enhancement of compressive strength characteristics, improvement of hydraulic properties that is an advantage for modification of stability and durability properties of clayey soil under loads. Similarly, the higher hydraulic conductivity of clay resulted that will shorthen duration of consolidation settlement, hence, eventually influence completion of plastic consolidation deformation favorably for soft clays. Lime-treatment on clay specimens showed that the compressibility properties are improved such that the strength of clay against loading enhances, exhibits less consolidation deformation under load owing to increase in lime content. On the other hand, clay becomes highly impermeable, displays substantially larger water-resistant properties because of increased lime mass proportion (i.e. time-extension) in clayey soil that results in prolongation of expulsion of excess porewater pressure from clay due to load application, relevant induced stresses. Fiber-inclusion resulted in exhibiting logarithmic decrement with a mild rate of decline while lime-treatment led to exponential reduction with a sharp rate of drop for compression index (Cc), compressibility coefficient (αv), volume compressibility coefficient (mv). Further, fiber-inclusion stimulated exponential and quadratical increment whereas lime-treatment induced exponential decrement for coefficient of consolidation (cv), hydraulic conductivity (k), respectively. As a result, the Cc, αv, mv enhanced on the order of within 10 at average of 80% to 90% with a minimum of 70% by value for both fiber-reinforcement and lime-stabilization soil-stabilization techniques. The cv, k improved on the order of within 10 at average of 75% to 85% by value for fiber-reinforcement whereas dis-improved on the order of within 10 at average of 70% to 80% by value for lime-stabilization.

Experimental investigation on the physical and mechanical properties of silty clay enhanced by microencapsulated phase change materials

Microencapsulated phase change materials (mPCM) can absorb or release heat by transforming their core phase. This study investigated the effect of mPCM on the thermal and mechanical properties of silty clay in seasonally frozen strata. It analyzed and researched the thermal and mechanical properties of silty clay blended with different contents (2%, 4%, and 6%) of mPCM, as well as its changing rules, using the DSC thermal cycling test, the specific heat capacity test, the freeze-thaw (F-T) cycling test, the no-limit compressive strength test, and the microscope observation test. In addition, this study utilized hyperspectral equipment to assess the applicability of improved silty clay soils in practical engineering on seasonally frozen ground. The results show that mPCM has no supercooling phenomenon and has stable and reversible transformation characteristics, which improves the thermal stability of silt. The specific heat capacity of silt increased with the increase of mPCM dosage. The unconfined compressive strength of silty clay increased to 162.5 kPa at 2% dosage, which was 16.8% higher than that of silty clay, while the unconfined compressive strength of silty clay at 6% dosage decreased to 119.1 kPa, which was 14.4% lower than that of silty clay after freeze-thaw cycles. Adding mPCM reduces the microscopic damage to the pore structure of silty clay soils caused by the freeze-thaw process and mitigates the macroscopic attenuation of their mechanical strength. The mPCM can effectively reduce the solar radiation reflectivity of silty clay, thus providing long-term utility for winter projects.

LOAD VERSUS SETTLEMENT BEHAVIOR OF SOFT CLAY REINFORCED WITH CEMENT STABILIZED RECYCLED ASPHALT PAVEMENT-LATERITIC SOIL COLUMN

In this paper, the performance of cement stabilized recycled asphalt pavement (RAP)-Lateritic column inclusion in soft clay was investigated via a physical model. The load-settlement response and bearing capacity of the composite ground was studied at various cement contents (0%, 1% and 3%) and at 30% RAP replacement ratio. The soft clay was consolidated in the PVC mold in a diameter of 150 mm and 300 mm high while the stabilized RAP-lateritic soil column with a diameter of 50 mm was used as a column at the center of the soft clay. The results showed that the bearing capacity of the composite ground significantly increased with the increased shear strength of column. The purposed bearing capacity equation derived from the unconfined compressive strength of column and undrained shear strength of soft clay was found to predict the bearing capacity of the composite ground satisfactorily.

Roles of corn starch and gellan gum in changing of unconfined compressive strength of Shanghai alluvial clay

Abstract This article aims to study the effects of corn starch and gellan gum (gellan glue) on the unconfined compressive strength of alluvial soft clay in Shanghai. Firstly, starch and gellan gum were evenly mixed into Shanghai cohesive soil in a certain proportion, and soil samples were prepared according to the optimal water content. Secondly, the unconfined compressive strength test was carried out according to the content of corn starch, gellan glue, and curing time. The strength characteristics of Shanghai soft clay under various test conditions were studied. Finally, the software for statistics and drawing was used to perform regression analysis and drawing on the experimental data. The results showed that in the unconfined compressive strength test, when the curing time was 28 days, the starch content was 3% mixed with 0.5% gellan gum, the unconfined compressive strength of the sample was the highest, and generally, it seems that the strength keep increasing with curing time.

The effect of shear rate and overconsolidation ratios on undrained clay–suction caisson interface behaviors

The interface resistance during installation is crucial for the stability and safety of suction caisson in offshore geotechnical engineering, which is strongly affected by the penetration rate and soil–structure interface mechanical properties. This research conducts a series of clay–structure interface shear tests using modified direct simple shear device to fully study the mechanical behavior of clay–suction caisson interface. The effect of shear rate, over consolidation ratios (OCRs), interface boundary conditions, stress levels, and interface roughness were considered. Results show that as the OCR increases, the strength of both the clay and interface increase but show distinct patterns under constant volume (CV) and constant normal load (CNL) boundary condition. It was found that the interface strength is positively related to interface roughness and shear rate impact both the clay and corresponding interface strength. Under CNL conditions, the strength of normally consolidated (NC) clay decreases with rising shear rate, while the over consolidated (OC) clay demonstrate a opposite trend. In contrast, the effect of shear rate on interface behavior gets complicated owing to the combination of roughness, stress levels, and OCRs. Under CV conditions, the shear strength of clay and interface exhibits a logarithmic growth relationship with shear rates. The result of this work can provide a basis for interface resistance evaluation for suction caisson installation in clay.