Soil Strength Parameters Research Articles

A new calculation method for the response of active-passive bridge piles considering pile-soil interface friction

The pile foundation of bridges under unregulated surcharge loads experiences a complex force pattern, which is subject to active loads and passive loads. In this paper, a more comprehensive calculation method for the response of active-passive piles was proposed, which considered the effect of pile-soil interface friction and soil stress states on the passive loads. First, the Ito theory was improved by adopting the adhesion c a and external friction angle φ a to characterize the pile-soil interface friction. Then, the soil around the pile in elastic, elastoplastic, and plastic flow states was considered to calculate the variation of the passive load. Finally, a nonlinear p-y curve was introduced to establish the calculation model of active-passive piles, and the finite difference program CPAPP was prepared for the solution. The results show that the pile response calculated by CPAPP is consistent with the field measurement, indicating that the proposed calculation method has high accuracy. When the soil is in an elastic state, the pile-soil interface friction does not affect the passive load. When the soil is in a plastic state, the passive load is closely related to soil strength parameters and pile-soil interface friction parameters.

Deterministic and Probabilistic Assessment of Failure Mechanisms in Geosynthetic-Reinforced Embankments

Geosynthetic-reinforced embankments are subject to two primary failure mechanisms: bond failure and rupture. Bond failure occurs when the critical slip surface extends beyond the reinforced zone, while rupture occurs when the slip surface intersects the reinforcement. For a specified factor of safety and reinforcement length, there exists a minimum tensile strength of the reinforcement required to ensure bond failure only. Increasing the tensile strength beyond this minimum does not alter the failure mechanism or the factor of safety. Conversely, extending the reinforcement length while keeping the tensile strength below this critical value may lead to rupture failure at the same factor of safety. This study utilizes Monte Carlo simulation to perform a probabilistic stability analysis of these failure mechanisms in embankments with varying soil types and slope angles. The analysis evaluates safety margins in terms of the factor of safety and probability of failure. Furthermore, this study investigates the impact of cross-correlation between soil strength parameters, demonstrating that realistic values of the correlation coefficient can reduce the probability of failure for both failure mechanisms.

Shear strength parameters identification of loess interface based on borehole micro static cone penetration system

BackgroundLoess is prone to large deformation and flow slide due to natural and artificial interfaces inside. The strength of these interfaces controls the mechanical properties of loess. Obtaining their mechanical parameters through in-situ testing is essential for evaluating the mechanical stability in loess engineering with interfaces.MethodsBy developing a borehole micro static cone penetration system and creating various types of loess with interfaces, extensive borehole penetration model tests were conducted to observe changes in cone tip resistance during penetration. The response surface method was used to analyze the impact of various test conditions on the calculated resistance. A three-dimensional surface fitting method was employed to establish the relationship between penetration parameters and shear strength parameters, which was validated through in-situ testing.ResultsThe developed borehole micro static cone penetration system achieves overall miniaturization while providing significant penetration power and ensuring an effective penetration distance. Cone tip resistance development during penetration can be divided into three stages: initial, rapid increase, and slow increase. The transition times between these stages vary for different soils. Calculated resistance is positively correlated with dry density and normal stress and negatively correlated with water content. A quadratic positive correlation was established between calculated resistance and shear strength parameters during penetration. In composite soils, the interaction between water content and normal stress is strong. Compared to intact soil samples, the shear strength parameters of composite soils are more prominently influenced by water content.ConclusionA system for testing interface mechanical parameters was innovatively developed, fulfilling the need to obtain interface shear strength parameters for deep soil. This study can provide support for ensuring the long-term stability of the loess slope or subgrade with interfaces.

Hybrid soil strength prediction model for geotechnical ground investigation using convolutional neural network and ensemble learning

Abstract A hybrid model of soil strength prediction from the image data and feature data of soil was proposed, which is aimed at providing an efficient solution in geotechnical ground investigation by leveraging the power of AI. In this model, CNN purely with the encoder was used to establish the relationship between image data and strength parameters of soil, while ensemble learning stacked of three base learners, i.e., KNN, LASSO, and LSVM, was applied to the feature data. Then, the CNN part and the ensemble learning part were integrated into the loss function. Results show that the convergence of the hybrid model was slower than that of the ensemble learner. However, with the aid of soil image which has more features of soil in essence, the predicted soil strengths by the hybrid model better matched with the actual ones, compared with the ensemble learner and base learners. This hybrid model offers an effective framework of multi-modal data fusion for geotechnical engineering, by leveraging the synergy of the high-dimensional feature extraction capabilities of CNN and the generalization abilities of ensemble learning.

Bio-Electrokinetic Improvement of Deltaic Soil

In addressing problematic soils, geotechnical engineers employ two key strategies: compatibility and improvement. This study focuses on soft and CL deltaic sediments, and seeks to enhance cementation by investigating microbially-induced calcium carbonate precipitation (MICP). Sporosarcina pasteurii bacteria, together with a cementation solution (urea and calcium-containing salt), were electrokinetically injected into deltaic clay soil from the Telar River in Iran. The initial samples, with a dry unit weight (γd) of 12.75 kN/m³, underwent injections in two modes: simultaneous injection of the bacterial and cementation solutions and individual injection in a sequential order. Unconfined compression strength tests and laboratory vane shear tests were conducted to assess changes in soil strength parameters, while a consolidation test was performed to investigate alterations in soil settlement parameters. A comparative analysis with an electroosmosis control sample revealed a remarkable increase in compressive strength and undrained shear strength for MICP bio-electrokinetic improvement. Moreover, the consolidation test demonstrated that the compression index (Cc) and recompression index (Cr) exhibited a more pronounced decline in the simultaneous injection than individual injection. This highlights the dual impact of the bio-electrokinetic method, namely the enhancement of shear strength and the mitigation of settlement in deltaic clay soil. The calcium carbonate content was measured for the samples, and the results indicated a higher degree of participation for the samples subjected to simultaneous injection. Microstructure analyses were conducted on samples, and calcite and vaterite were observed in bio-cemented samples.

Face stability assessment of a longitudinally inclined tunnel considering pore water pressure

AbstractThe face stability analysis of a longitudinally inclined shield tunnel using an analytical approach in water‐rich areas is still a research gap. To solve this face stability problem, a numerical simulation based on the FLAC3D is first conducted to calculate the seepage field behind the inclined tunnel face. An improved rotational failure mechanism is developed to make it possible to investigate the face stability of inclined tunnels using analytical approaches. In the framework of the kinematic approach of limit analysis, the limit support pressures and corresponding failure surfaces of the inclined tunnel face are determined to analyze the face stability issue. The interpolation tool (griddata) in MATLAB is adopted to involve the obtained numerical values of pore water pressures into the analysis of the stability issue. The analytical solutions obtained from the proposed method are validated by comparisons with existing results from published literatures and numerical results. For a quick estimation of the inclined tunnel face stability in water‐rich areas, a series of design charts are then presented for various soil strength parameters, water tables, and inclined angles. Finally, an application of the proposed method to a practical tunneling case is provided, which further illustrates the effectiveness of the proposed method.

Modification in Strength Parameter (CBR) of Sub-Grade Soil with Addition of Fly Ash

The determination of the California Bearing Ratio value of soil is tiresome, uneconomical, and time-consuming in the laboratory. Therefore, there is a required automation system to determine the California Bearing Ratio value of soil. Machine learning algorithms are being used for automation systems. In this paper, Artificial Neural Network has been proposed for the prediction of the California Bearing Ratio value of soil. Ash percentage, Liquid Limit, Plastic_Limit, Plasticity index, Shrinkage Limit, MDD and OMC parameters of soil affect the value of the California Bearing Ratio. In the laboratory, the training dataset has generated using these parameters of soil. The proposed classifier has been trained and tested using the training and testing dataset. Experimental results show that the proposed Artificial Neural Network is very accurate to predict California Bearing Ratio values of soil. It is also observed that the linear regression algorithm is very easy and useful to determine the value of the California Bearing ratio depending on seven attributes of soil. The rules generated by J48 and PART can be used to determine the California Bearing ratio. These models are very useful for civil engineers and civil constructors as a California Bearing ratio prediction automation system.

Experimental study on the effect of waste plastic powder and marble powder on the swelling behavior and strength parameters of a clay soil

This research aims to provide insights into how the combination of waste plastic powder and marble powder affects the geotechnical properties of clay soil. The findings from this study can have practical implications for construction, foundation design, and environmental sustainability, as the reuse of waste materials can potentially improve soil properties and reduce environmental impacts. In this context, we executed a series of experiments involving samples that were fortified with varying proportions of plastic powder (0%, 1.5%, 2%, 2.5%, and 3%) and stabilized using marble powder at concentrations of 3%, 4.5%, 6%, and 7.5 %. The findings indicate a gradual decrease in liquid limits, swell potentials, and swelling pressure as the proportions of waste plastic powder and marble powder increase. The stress-strain curves obtained from the unconfined compressive strength (UCS) tests revealed that the incorporation of waste plastic powder into marble-stabilized soil led to an increase in UCS. These results emphasize the positive impact of waste plastic powder in enhancing the mechanical properties of the specimens. This research aims to provide insights into how the combination of waste plastic powder and marble powder affects the geotechnical properties of clay soil.

Interpretation of the data of modern methods of field soil research

This study examines modern in-situ testing methods for soils; it investigates the impact of interpreting these methods on the calculated strength and deformation parameters of soils and compares them with tabulated values according to the DSTU (Standard of Ukraine). In today's world, there is an urgent need for accurate and prompt soil investigations, which are crucial for design and construction. Although laboratory methods are reliable, they often require significant time and resources. The advantage of in-situ methods lies in the fact that testing is performed directly in the soil mass, meaning that the results are not influenced by the transportation and preparation of samples. Conducting tests directly in the soil massif allows for the acquisition of information about soil characteristics and their classification, providing data on soil stratification. This publication reviews modern methods of in-situ soil investigations, specifically CPTu (Cone Penetration Test) and DMT (Dilatometer Test) [1, 2]. These methods are widely used in Europe, while in Ukraine, they are relatively new and are just beginning to gain popularity. Therefore, it is relevant to compare these methods with the tabulated values provided in Ukrainian reference guides. The deformation and stress values were compared using three calculation models based on CPTu, DMT, and DSTU data. A comparative analysis of the foundation slab deformations was conducted using models with elastic and elastic-plastic model. For this purpose, a foundation slab was designed, and a finite element model of the building was developed, examining the foundation on a soil massif with inclined stratification, using both elastic and elastic-plastic soil models.

Biopolymers in geotechnical engineering for soil improvement

AbstractSeveral biopolymer applications in geotechnical engineering have been adopted in recent years, notably dust control, soil strengthening, and erosion control. Although biopolymer soil treatment approaches can assure engineering efficiency while satisfying environmental protection standards, this technology requires more validation regarding site adaptability, durability, and economic feasibility. The influence of biopolymers on soil behavior is discussed within geotechnical engineering applications and practices, including soil consistency limits, strength and deformation parameters, hydraulic conductivity, soil-water properties, and erosion prevention.Laboratory studies were performed to confirm the behavior of the treated soil, including Atterberg limits, proctor, and direct shear tests utilizing two types of biopolymers: guar gum and xanthan gum.

Evaluating of 14H-Piles’ Load Capacity in Cohesionless Soils for Edward’s Project Using ?-Method and Finite Element Method

Abstract: This paper presents a comprehensive study on evaluating the load capacity of 14H-piles in cohesionless soils for Edward's infrastructure project[1]. The project, overseen by the Federal Highway Administration (FHWA) and the Colorado Department of Transportation (CDOT), focuses on bridge replacements in Edwards, Colorado, with an emphasis on foundation improvements using driven pile foundations[2]. The research utilizes Finite Element Analysis (FEA) and the β-method to assess the total bearing capacity of 14H-piles in sandy soil conditions[3]. Field exploration, including Standard Penetration Tests (SPT), is conducted to determine soil parameters, followed by calibration of soil strength parameters. The study involves modelling the piles using the Soil-Structure Interaction 3-D program (SSI3D) and comparing the total bearing capacity obtained from FEA with nominal capacities calculated by the β-method. Additionally, the paper discusses load resistance and factor design, as well as the importance of static load testing for validation[4]. The results highlight the efficacy of FEA in predicting pile behaviour and provide valuable insights for foundation design in similar geological settings.

The Use of Plastic Bottle Fibers in the Geotechnical Improvement of Tropical Soils from the Municipality of Viçosa - Brazil

Motivated by the environmental issues generated by the accumulation of waste from discarded plastic bottles and recognizing the utility of plastic properties in engineering, this research aimed to evaluate the application of plastic bottle fibers in the geotechnical improvement of tropical soils. In this context, the influence of quantity, roughness, and width of plastic bottle fibers on the shear strength parameters of soil- fiber mixtures, of two tropical residual soils, was analyzed. The fibers used in this study are made of Polyethylene Terephthalate (PET), generated from soft drink bottles, and added to the soil in different widths, textures, and contents. Results of the direct shear test showed higher shear strength for all soil-fiber systems compared to fiber-free mixtures. Additionally, the findings indicated that the systems with rough fibers presented better performances for clayey soil, whereas those with smooth fibers obtained better behavior for sandy soil. The cohesion results highlighted the better performance of mixtures with 0.5% fibers when compared to mixtures with 1% fibers. The enhancement of mechanical properties obtained in the studied soil-fiber systems demonstrates the potential application of these composites in geotechnical works.

INVESTIGATING SHEAR STRENGTH CHARACTERISTICS OF COHESIVE SOILS: STATISTICAL ANALYSIS IN KPK, PAKISTAN

It is crucial to determine the shear strength parameters (Cohesion (C) and Angle of internal friction (Φ) ) in order to encounter soil stability issues such as slope stability, bearing capacity and lateral earth pressure on retaining structures. The shear strength of cohesive soils is an essential parameter in Geotechnical Engineering design and construction. In Khyber Pakhtunkhwa (KPK), Pakistan, the soil is predominantly cohesive. it is essential to evaluate these parameters accurately to ensure safety and stability in civil engineering structures. In this research an effort has been made to evaluate statistically shear strength parameters of cohesive soils in KPK Pakistan. Engineers and construction experts can use the study's findings to influence judgments about the design and building of structures in the area. It highlights the importance of conducting proper soil testing and analysis before designing and constructing any engineering structure in the region. The study was conducted by collecting soil samples from different locations in KPK including Peshawar, Charsadda, Bannu, Swabi, Nowshera, Swat, Abbottabad, Haripur, Lakki Marwat, Tribal Areas, DI Khan, Mardan, and Kohat. The results of the statistical analysis indicate that the Cohesion(C) and Angle of Internal Friction (Φ) in KPK vary significantly across different locations, they are also presented in map of KPK showing values of Cohesion and Angle of Internal Friction using QGIS software. The average values of Cohesion (C) range from 12-47 kPa while mean values of Angle of Internal Friction (Φ) range from 16.2 – 41.1 degrees. The Standard Deviation & Coefficient of Variation was relatively high, indicating significant variation within each location.

Experimental study on the dynamic strength characteristics of combined heavy metals contaminated soil with nZVI treatment

Nanoscale zero-valent iron (nZVI), a high-performance nanomaterial, can treat heavy metal contaminants and is extensively employed for in-situ treatment of groundwater and contaminated subsoil. However, there are few studies that indicate trends in the dynamic strength parameters of nZVI-treated soils to assess site safety. In this study, three heavy metal contaminants, Zn(II), Pb(II), and Ni(II), were selected to contaminate virgin soil. The heavy-metal-contaminated soil was treated with nZVI at two concentrations (a low dose and high dose of 0.5% and 2%, respectively) of the soil's dry mass. Analyses of particle size distribution revealed a consistent shift towards larger particles upon nZVI treatment, and the percentage of sand gradually increased. Heavy metal contamination decreased the liquid and plastic limits of the virgin soil, while those of the treated soil increased with nZVI content. The dynamic triaxial results showed significantly lower maximum dynamic shear modulus for MS, MS-LdN, and MS-HdN than for NS. The damping ratios of all samples showed an S-shaped trend. Thus, nZVI has the potential to create cemented structures and immobilize heavy metals. However, its effectiveness is significantly modulated by the initial water content of the soil. While the application of nZVI proves beneficial in immobilizing heavy metal contaminants, careful consideration is imperative under dynamic loading conditions.

Studying the Impact of Soil Stabilization Techniques on Rigid Pavement Joints Across Various Axle Loads

Rigid pavement slabs are erected on a prepared subgrade or foundation layer, providing a hard and continuous surface. Transverse joints made of dowel bars connect them, and longitudinal joints made of tie bars join them longitudinally. This study is an investigation of the impact of soil strength and concrete parameters on the effectiveness of dowel bars in rigid pavements. Moreover, three parameters were examined; California Bearing Ratio (CBR), concrete compressive strength and slab thickness. The analysis was conducted using the Ever FE program and focused on several axle configurations applied to the joint. The results indicate inverse association between the pavement slab thickness and the concrete strength, under the assumption of consistent soil strength. Moreover, an assortment of reduced shear forces on the dowel bars is seen when the soil strength values increase. It indicates that soil strength has a greater impact on the shear load of dowel bars compared to the qualities of concrete. Additionally, the type of axles used and the magnitude of soil strength were shown to have a significant effect on the shear load.

Impact of Vetiver Plantation on Unsaturated Soil Behavior and Stability of Highway Slope

Due to cyclic wetting and drying, the hydro-mechanical behavior of unsaturated soil is impacted significantly. In order to assess the soil strength parameters, knowing the unsaturated behavior is important. Soil moisture content is an important parameter that can define the shear strength of the soil. Most of the highway slopes of Mississippi are built on highly expansive clay. During summer, the evaporation of moisture in the soil leads to shrinkage and the formation of desiccation cracks, while during rainfall, the soil swells due to the infiltration of water. In addition to this, the rainwater gets trapped in these cracks and creates perched conditions, leading to the increased moisture content and reduced shear strength of slope soil. The increased precipitation due to climate change is causing failure conditions on many highway slopes of Mississippi. Vetiver, a perennial grass, can be a transformative solution to reduce the highway slope failure challenges of highly plastic clay. The grass has deep and fibrous roots, which provide additional shear strength to the soil. The root can uptake a significant amount of water from the soil, keeping the moisture balance of the slope. The objective of the current study is to assess the changes in moisture contents of a highway slope in Mississippi after the Vetiver plantation. Monitoring equipment, such as rain gauges and moisture sensors, were installed to monitor the rainfall of the area and the moisture content of the soil. The data showed that the moisture content conditions were improved with the aging of the grass. The light detection and ranging (LiDAR) analysis was performed to validate the field data obtained from different sensors, and it was found that there was no significant slope movement after the Vetiver plantation. The study proves the performance of the Vetiver grass in improving the unsaturated soil behavior and stability of highway slopes built on highly expansive clay.

Effects of Bio-enzyme on the strength properties of soil

Engineers regularly attribute the complexity of constructing parts on or by soils, those do not have sufficient strength to sustain the loads required leading them either all over construction or in the study life of the structure. The more areas of India shows of CH (Inorganic Clay of High Plasticity) clay soil characterized by more small portion, lower shear strength and lesser bearing capability. The unfortunate engineering performances of these soils has enforced Engineers to instrument charge competent and eco-friendly processes for increasing the engineering properties of these soils. As the conservative soil stabilizers like gravel, sand, etc. Are declining and suitable expensive day by day at an extremely quick rate, it becomes necessary to emerge for possible ecological stabilizers as their substitute. In current scenario the various Bio-enzymes have emerged as lesser cost stabilizers for soil stabilization. Bio-enzyme is a common, harmless, non-flammable, noncorrosive liquid enzyme formulation fermented from vegetable forms that creates the engineering behavior of soil, generates more soil compaction densities and more stability. One such Bio-enzyme, Terrazyme, has been applied in the current occupation to study its consequence on Atterberg Limits, Unconfined Compressive strength, and shear strength parameters of a CH soil. It has been confirmed that Terrazyme purifications of CH soil outcome in main development in Unconfined Compressive strength and Shear Strength parameters separately from Index characteristics. The entire characteristics are reliant on remedial time also. There is a specific best concentration for each characteristic in concern and it ranges from 0.2 ​ml/kg and 0.4 ​ml/kg of soil. Although, the more plastic clay soil is get to be addition responsive to Terrazyme purifications.

Improving Strength by Increased Compaction of Gypsum—Enriched Soil under Long-Term Soaking Conditions

This study investigated the effect of compaction effort and soaking time on the shear strength properties of fine-grained gypsum-containing soils. The objective was to demonstrate that increasing compaction effort increases soil strength, specifically cohesion and the angle of shear strength, when subjected to soaking in freshwater. Unconsolidated undrained triaxial tests were carried out on CBR soil samples with different soaking times. The results showed a transition from brittle to ductile failure behaviour as the soaking time increased. Mohr–Coulomb failure envelopes showed reduced cohesion and angle of shear strength with increasing soak time. Regression models were developed to establish correlations between soaked and unsoaked strength parameters. Strong relationships were found between soil strength properties, compaction effort and soaking time. Empirical equations were proposed to estimate the cohesion and angle of shear strength from compaction effort and soaking time. This study highlighted the importance of considering gypsum-rich soils in civil engineering design. Gypsum dissolution during wetting significantly affected soil strength parameters. The regression models and empirical equations provide engineers with tools to assess the influence of compaction effort and soaking time on soil strength, thus aiding decision making when designing structures on gypsum-rich soils.

Study on the CPTu inversion methods for strength and consolidation parameters of gassy soil with different gas contents

Gassy clay deposits are widely distributed in marine sediments. Clarifying the influence patterns of the trapped gas phase on the mechanical properties of gassy clay is of significant importance. Establishing an in-situ strength parameter and consolidation coefficient inversion method based on CPTu is crucial for gassy clay characterization. In this study, gassy clay was prepared using the zeolite method. The variations of strength and consolidation parameters of gassy clay concerning gas content were obtained based on laboratory triaxial and one-dimensional tests. It was observed that the trapped gas phase enhances the undrained shear strength and hinders drainage. Specifically, gassy clay with a gas content of 3.5 % exhibited an 18 % increase in undrained shear strength compared to saturated clay and a 50 % reduction in consolidation coefficient. In addition, laboratory calibration chamber tests were conducted to investigate the cone penetration test (CPTu) in gassy clay with varying gas contents and penetration rates. The drainage effect during the CPTu penetration process in gassy clay was discussed. The reasons behind the variations in static cone penetration parameters under undrained conditions for normally consolidated gassy clay were analyzed by combining the results of triaxial tests and one-dimensional consolidation experiments. A proposed formula for the cone factor Nkt was also provided under undrained penetration conditions. The accuracy of conventional methods for estimating the consolidation coefficient of gassy clay was verified, the basic properties of the gassy clay used in the indoor experiment are similar to those of the seabed gassy silt at the project site, and the environmental conditions are similar to those at locations with low initial pore pressure, such as mudflat or shallow sea bed, thereby offering a reference for in-situ testing of strength parameters and consolidation coefficients in gassy clay seabed.

Study on the mechanical characteristics of sand pebble surrounding rock considering the disturbance effect of tunnel excavation

When conducting tunnel construction in sandy gravel strata, disturbance to the sandy gravel soil is inevitable, resulting in alterations to the properties of the surrounding rock. This paper investigates the relationship between the relative density (Dr) and shear strength parameters under different disturbance states through the implementation of indoor triaxial tests. Utilizing Dr as a disturbance parameter, a unified disturbance function that reflects the weakening and strengthening of sandy gravel soil is proposed. Furthermore, a revised constitutive model based on this unified disturbance function is established for the first time. The study results indicated that the results calculated by traditional models, which do not take into account disturbance effects, deviate from the experimental results by more than 20%. However, the error rate of the results computed by the modified model can be reduced to within 8%. The new model establishes a dynamic relationship between relative compactness and shear strength parameters of sand and pebble soils, which can take into account both the effects of negative and positive perturbations. The results can more accurately characterise the strength and deformation properties of the surrounding rock under the influence of construction disturbances in sand and pebble ground tunnels.