Shear Strength Research Articles

Correlations for undrained shear strength of fine-grained soils with SPT-values: literature review and uncertainty analysis

ABSTRACT Despite significant advances in laboratory testing in recent decades, geotechnical designs that incorporate data from in-situ testing remain predominant worldwide. One of the most commonly employed techniques for correlating soil mechanical properties is the standard penetration test. However, while this test provides valuable information for identifying soil strata and offering general descriptions of soil characteristics, its correlation with shear strength parameters has several limitations that are often overlooked. In this article, we aim to i) present a critical literature review concerning the applicability of correlations between the undrained shear strength of fine-grained soils and standard penetration test data; ii) estimate the uncertainties associated with the adoption of these empirical correlations, which are frequently disregarded in engineering practice; iii) present simulation results from typical slope stability analyses, taking into account the uncertainties associated with the estimation of the undrained shear strength. The findings of our study suggest that geotechnical engineers should exercise caution when using such simplified equations, as they often lead to underestimations or overestimations of the stability of geotechnical structures.

Optimizing number, locations, and types of ground investigations for slope stability assessment with value of information analysis

ABSTRACT This study examines the application of Value of Information (VOI) analysis to identify the optimal number, types, and locations of ground investigations for slope safety assessment. VOI analysis integrates a probabilistic slope stability model with uncertain shear strength of clay, a detailed ground investigation model, and a utility function to assess the benefits of reducing uncertainties in soil properties by conducting ground investigations. This study extends earlier VOI approaches for optimising ground investigations by examining not only the optimal number and locations, but also the types of ground investigations. The optimal ground investigations are determined among several common ground investigation methods for estimating undrained shear strength of clay including cone penetration, traxial, uniaxial compression, and vane shear tests. A comprehensive ground investigation model is implemented to realistically evaluate the costs for each of the investigations methods. This was complemented by a detailed assessment of the quality of the investigation methods by accounting for the measurement and transformation errors. The optimal number, locations and types of ground investigations were examined for a range of parameters that can affect outcomes of VOI analyses including the level of prior knowledge on uncertain soil properties, spatial similarity of soil properties, and consequences of slope failures.

Nanochitin-Fortified Polyphenol Complexes for Dry and Wet Adhesion.

Synthetic adhesives commonly used in shipbuilding, plumbing, and various industrial and household applications pose environmental and health concerns due to chemical leaching and other issues. In this work, we present a sustainable alternative using chitin nanofibers (ChNF) to enhance the networking and surface binding of biomolecules. We investigate aqueous-based formulations composed of tannic acid (TA), poly(vinyl alcohol) (PVA), and chitin nanofibers, which form robust adhesive complexes. These are driven by multiple interactions involving phenolic and hydroxyl groups, which are present at high densities and contribute to exceptional adhesion upon drying. Unlike most two-component structural adhesives, the ChNF-based adhesives introduced here do not rely on organic solvents and demonstrate versatility across surfaces with contrasting topologies and surface energies, including stainless steel, polypropylene, wood, and others. With an ultimate shear strength reaching up to 20 MPa, these adhesives rival commercially available structural adhesives commonly used for bonding metals, wood, and glass. The addition of chitin nanofibers enhances adhesion by up to 400%, depending on the PVA-to-TA ratio. Furthermore, these adhesives exhibit long-term structural integrity under wet conditions, showing no signs of swelling or degradation. To elucidate the mechanisms underlying adhesion in both wet and dry states, we conducted comprehensive analyses, including morphological, mechanical, rheological, spectroscopic, thermal, and surface characterizations. The findings highlight the potential of ChNF-based adhesives as a viable and sustainable alternative for diverse industrial applications.

Molecular dynamics simulation study of the mechanical properties of silane coupling agent‐enhanced glass fiber/epoxy resin interfaces

AbstractThe molecular dynamics of epoxy resin were modeled using an automated crosslinking program, and the resulting epoxy resin model underwent performance analysis and validation, confirming its validity. Then, using the model of epoxy resin as a foundation, interface models for glass fiber/epoxy resin modified with the silane coupling agents KH550, KH570, and KH792 were constructed. Tensile and shear simulations were conducted on these modified interface models, and the effects of varying grafting densities and temperature on their properties were investigated. The results indicate that following interface modification, the shear strength is significantly improved and increases with grafting density. The three silane coupling agents are ranked according to their effectiveness in increasing shear strength as follows: KH550 > KH792 > KH570. The tensile strength of the interface improves only at the appropriate grafting density, while the tensile strength is reduced when the grafting density becomes excessive. Moreover, the tensile and shear strengths of the modified interface are observed to decrease progressively with rising temperatures.Highlights Molecular dynamics modeling of epoxy resin was conducted and verified. The mechanical properties of the modified interface were analyzed. The failure mechanisms of the modified interface were examined. The temperature impact on the glass fiber/epoxy resin interface was analyzed. The results provide insights into the application of high‐performance composites.

A parametric study on the effect of pilot hole diameter on the mechanical and microstructural properties of AA6061-AA7075 friction stir spot welding

This study investigates the impact of pilot holes and welding parameters, including pilot hole size, rotational speed, and dwell time on the mechanical and microstructural properties of dissimilar (7075-6061) aluminum joints using friction stir spot welding. Mechanical properties were assessed using shear and hardness tests, while microstructural analysis involved optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX). The Taguchi approach determined optimal process parameters. Pilot hole size guidelines in welding were introduced, called pilot hole to keyhole (PTK) ratio. Results show that a specimen with a 4 mm pilot hole, 800 rpm rotational speed, and 5-s dwell time achieved a maximum ultimate shear strength (USS) of 89.29 MPa, closely matching the Taguchi-calculated value of 81 MPa with a 9% error. The HAZ has the lowest hardness, averaging at 76.3 ± 2 HV, while the SZ shows intermediate hardness, averaging at 83.8 ± 3 HV. Analysis of variance (ANOVA) results indicate that pilot hole size is the most significant factor, contributing 97%. Specimens with a 4 mm pilot hole size (0.7 PTK) ratio demonstrated the highest shear strength due to superior material mixing compared to those with 5 mm (0.8 PTK) ratio and 6 mm (1 PTK) ratio pilot hole’ size. SEM identified two distinct areas on the joint surface, and EDX confirmed AA7075 as the predominant joining material. These findings suggest pilot hole size affects the material’s mechanical and microstructural properties.

Decoupling of Bonding Strength and Water Retention in Aqueous Wood Adhesive Inspired by Plant Cell.

Aqueous wood adhesives with both water retention and strong bonding strength are essential for wood industrial applications. However, the enhanced water retention of adhesive often suffers from low water resistance and bonding strength due to its increased hydrophilicity. Inspired by the water retention and mechanical support in plant cell, we develop a multifunctional biomass soybean meal (SM) adhesive by combining the rigid internal boron-nitrogen coordinated boronic esters structure for reinforcement with the flexible zwitterionic polymer for water retention. Such a design provides good dry (2.03 MPa) and wet shear (1.14 MPa) strengths and demonstrates durable adhesion in various harsh environments for up to 80 days. The adhesive exhibits the anticipated water retention property, extending the plywood shaping manufacturing time to 60 min due to the ability of the water-retaining polymer to convert free water into a bound state and suppress water evaporation. Additionally, the adhesive demonstrates a 10-fold increase in mildew resistance compared with the SM adhesive and exhibits good flame retardancy. This study presents a versatile and efficient approach for developing durable, water-retaining, and sustainable aqueous adhesives for various bonding techniques and shaping materials.

BEARING CAPACITY AND FOUNDATION QUALITY OF SUBSOILS IN PARTS OF THE MAIN CAMPUS OF AKWA IBOM STATE UNIVERSITY, IKOT AKPADEN, AKWA IBOM STATE, NIGERIA

The study of the Foundation quality of Subsoils in parts of the main campus of Akwa Ibom State University, Ikot Akpaden, Eastern Niger Delta, Nigeria was carried out with the aim of determining the bearing capacity of the subsoils and designing suitable foundations for the construction of structures. Through field and laboratory investigations carried out, the geophysical study revealed four geo-electric layers namely; the top soil, silty clay, sand, and clayey sand. Six geotechnical boreholes were drilled in the field to a maximum depth of 15m each, with standard penetration tests and cone penetration tests carried out. Soil samples were extracted at 1meters each for different laboratory tests including; moisture content, liquid limit, plastic limit, bulk density, specific gravity, particle size distribution, shear box test, undrained shear strength and Consolidation test. The subsurface stratigraphic profile consists of clayey silty sand (0-7m), sandy silty clay (2-14m) and sand (10-15m) from top to bottom. The clayey silty sand are soft to firm, low to medium compressibility clays with liquid limit, plastic limit and average cohesion values of 23% to 41.5%, 14% to 24% and 14KN/m2 to 64KN/m2 respectively. Ultimate bearing capacity values of the clayey silty sand range from 152.65KN/m2 to 667.94KN/m2. The sandy silty clays are soft, intermediate to high compressibility clays with liquid limit, plastic limit and average cohesion values of 44% to 83%, 25.5% to 51% and 10KN/m2 to 32KN/m2 respectively. Ultimate bearing capacity values of the sandy silty clay range from 269.43KN/m2 to 582.4KN/m2.The sand is poorly graded, medium dense with standard penetration N- values ranging from 13-16. The ultimate bearing capacity ranges from 7878.12KN/m2 to 11423.36KN/m2 respectively. Standard penetration tests and pile bearing capacity analysis indicate that the sands are suitable foundation materials for construction. A Pile foundation terminated within the sand substratum is recommended for large structures.

Analysis of Road-Cut Slope in Calcareous Rocks and Stabilisation by Shotcreting and Rock Bolting, Dehradun-Mussoorie Road, Uttarakhand

In this study, analysis and stabilisation of four road-cut slopes in the lesser Himalayan region near Mussoorie, along Dehradun- Mussoorie Road, are investigated using the shotcreting and rock bolting technique. The rocks studied are calcareous in nature with varying rock mass properties. The exposure is along the road cuts with slope varying from 700 to 900, showing toppling to wedge failure. The stability analysis is performed through the Finite Element Analysis (FEA) and Factor of Safety (FOS) is evaluated using the Shear Strength Reduction Technique. The evaluation considers various conditions, including unreinforced slopes and slopes reinforced with rock bolts and shotcrete, to thoroughly assess the effectiveness of rock bolting in enhancing stability. The results indicate that rock bolting combined with shotcreting improves slope stability by approximately 10–40% across the different slopes analyzed.

Soil Stabilization by Using Raw Plastic

The best method for improving the physical properties of the soil like; increasing strength such as shear strength, bearing capacity etc. is the process of soil stabilization. This process includes addition of the admixtures into the soil in order to increase the properties of the soil. The admixtures such as; cement, lime ad waste materials like fly-ash, phosphor gypsum, etc. are very expensive materials. The cost of these kind of admixtures is increasing day by day as the technology is improving around the every corner of the society. In recent technology research, utilization of the waste materials likes plastic, bamboo etc. The widely used thing in today’s society is the plastic. The disposal of these plastic wastes causes the ecological hazards, a big is a useful thing in stabilization. In the modern world, there is a scarcity of a good soil. Since the low availability of un-stabilized soils makes it difficult admixtures to the soil. These plastic waste materials like plastic bottles are used in this project. For this to happen the plastic bottles are cut down into small strip like pieces. The addition of these small strips in the soil by different percentage and conduct tests such as liquid limit, plastic limit, compaction test, CBR test etc. Then soil becomes stabilized i.e, increasing the load bearing capacity of the soil and also strength properties such as shear strength with a controlled compaction. Soil stabilization by using waste plastic bottles which significantly enhance the strength properties of the soil. KEY WORDS: Soil Stabilization, Lime, Portland Cement, Raw Plastic, Plastic bottles.

Shear Mechanical Properties of Rock Joints Under Non-Uniform Load Based on DEM

Previous joint test studies have mainly been conducted under the condition of uniformly distributed loads, but in engineering, overlying loads are often non-uniformly distributed. It is necessary to investigate the shear mechanical properties of joints under non-uniform loads. This paper establishes three typical mechanical models: far-field concentration (FFC), near-field concentration (NFC), and focus on center (FOC). Direct shear test simulations using the DEM software PFC reveal that the location of load concentration affects main shear parameters. The closer the load concentration is to the far end along the shear direction, the greater the deformation of rock mass during failure is, the higher the proportion of shear cracks is, and the greater the strength and energy required for failure are. Compared to a uniformly distributed load (UD) condition, FOC shows similar mechanical properties; NFC yields inferior outcomes, while FFC results in superior mechanical performance compared to UD. By utilizing machine learning, five prediction models for non-uniform load shear strength are developed, with the Genetic-XGBoost algorithm demonstrating the highest accuracy. Weight calculation results indicate that load distribution form is the most critical factor influencing shear strength.

OPTIMIZATION OF WELDING PARAMETERS IN SPOT WELDING OF AISI 316L AND IF 7114 DISSIMILAR JOINTS

This study investigates the optimization of welding parameters in spot welding of dissimilar materials, AISI 316L stainless steel and IF 7114 steel. The objective is to enhance the mechanical properties of the welded joints, particularly the tensile shear strength, by optimizing welding parameters such as electrode force, welding current, and welding time. Using the Taguchi method, an experimental design was developed, and spot resistance welding was performed on 18 different parameter combinations. The results indicate that increased electrode force, welding current, and welding time led to a significant improvement in tensile shear strength. The highest tensile shear strength of 7.877[Formula: see text]N was achieved with 6[Formula: see text]kN electrode force, 9[Formula: see text]kA welding current, and 50 cycles of welding time. Additionally, the weld core diameter and depth increased with higher heat input, and significant grain coarsening was observed in the heat-affected zone of IF 7114 steel. The study concludes that optimizing welding parameters enhances the mechanical properties of dissimilar joints, with the Taguchi method providing an effective approach for determining the ideal welding conditions.

Prediction of Shear Strength of Steel Fiber-Reinforced Concrete Beams with Stirrups Using Hybrid Machine Learning and Deep Learning Models

The shear behavior of beams cast with steel fiber reinforced concrete and provided with stirrups is a complex phenomenon that depends on various factors. In the present research effort, a hybrid support vector regression model combined with a particle swarm optimization algorithm is provided, to explore the relationship between the material and dimensional characteristics of a concrete beam and its shear strength. A database with diverse material properties associated with the shear strength of a steel fiber reinforced concrete beam was established from numerous reliable published research articles and was utilized for the development and evaluation of the model. The obtained results from the hybrid support vector regression model were then validated through the results of the artificial neural network and convolutional neural network models combined with the particle swarm optimization algorithm. In conclusion, the adopted hybrid support vector regression approach was proven to be a successful engineering technique that can be used in structural and construction engineering problems.

Experimental investigation and image-based analysis of clay slurry consolidation with prefabricated horizontal drain

Abstract The characteristics of the consolidation facilitated by prefabricated horizontal drains (PHDs) combined with vacuum loading, and the evolution of the soil column surrounding the PHDs, which significantly affects the acceleration efficiency, remain insufficiently understood. This study conducts experimental investigations into PHD-assisted consolidation, employing an enhanced digital image correlation (DIC) technique. A novel texture seeding method for slurry, essential for DIC measurements, was developed and applied to consolidation model tests with varying PHD pave rates. Data on vacuum-discharged water reveal that the consolidation rate increases with the pave rate, albeit non-linearly. The DIC-observed plane strain fields exhibit distinct non-uniform features, with zones closer to the PHD consolidating significantly faster than other regions. The shape of the soil column observed through the DIC method is approximately elliptical, and its dimensions are characterized using empirical equations, highlighting the feasibility of optimizing PHD spacing in engineering design. The void ratio distribution was derived from strain information, validating the findings related to the soil column. Additionally, excess pore pressure distributions suggest that the effective range of vacuum transfer lies between 20 and 30 cm. Water content and undrained shear strength distributions provide key insights into the non-uniformity of PHD-improved consolidation. Further studies are recommended to quantify the optimal pave rate and the effective transfer distances of vacuum pressure and incorporate the observed soil column information into PHD-assisted consolidation analysis.

Zinc Oxide Nanowire‐Enhanced Interlocking Interfaces in Mechanically Robust Basalt Fiber/Epoxy Lamellar Composites

ABSTRACTThe contradiction between the widespread application of basalt fibers (BFs) and their poor interfacial interaction with polymers has become an urgent issue for the preparation of BF/thermosetting polymer composites. In this study, zinc oxide (ZnO) nanofibers were successfully grown on the surface of BFs through a surface modification process involving polydopamine (PDA) coating, followed by a two‐step hydrothermal method to create an interfacial interlocking structure. As a result, the interfacial interaction between the modified BFs and epoxy resin was significantly enhanced, as evidenced by the increase in interfacial shear strength from 13.3 to 22.4 MPa, greatly improving the mechanical properties of the resulting composite. The impact toughness and flexural strength of the modified composites increased from 46.4 kJ/m2 and 278.4 MPa to 59.6 kJ/m2 and 347.5 MPa, respectively. This not only addresses the issue of weak interfacial interaction between BFs and polymers to expand the application potential of BFs, but also provides an effective strategy for the other inorganic fibers to enhance the interfacial interaction with polymer.

Predicting shear performance of Co-cured CFRP composite joints with covered lamination: an artificial neural network and optimization approach

Co-curing, a highly efficient bonding technique, is key to joining similar and dissimilar materials in aerospace, aircraft, and marine applications. This research delves into the shear strength of co-cured CFRP composite joints fabricated using the covered lamination technique with multiwalled carbon nanotubes (MWCNT) modified adhesive. The experimental results revealed that the incorporation of 0.25 wt.% MWCNT-modified adhesive into the covered lamination with a co-cured CFRP composite joint resulted in a shear strength of 25.95 MPa. This value represents a substantial increase of 80% compared to the pure epoxy-based joint and a remarkable 119% increase compared to the neat joint. The practical implications of these findings are significant, as they can enhance the performance and reliability of structures in various applications. Finally, the shear performance was accurately predicted using the Levenberg Marquardt Artificial neural network model and optimised using the least square fit method.

Correction: 3D-Printed Continuous Basalt Fiber-Reinforced Polylactic Acid Composites: Effect of Printing Parameters on Impact and Interlaminar Shear Strength

Correction: 3D-Printed Continuous Basalt Fiber-Reinforced Polylactic Acid Composites: Effect of Printing Parameters on Impact and Interlaminar Shear Strength

Graphene Oxide Pre-Installed with a Covalent Adaptable Network Resulted in a "Nacre-Like" and "Self-Healable" Multi-Layered Interface in Carbon Fiber Laminates.

This study presents the development of a thermally stable carbon fiber-reinforced epoxy (CFRE) laminate incorporating functional graphene oxide (hGO) and a covalent adaptable network (CAN) to improve interfacial adhesion. Traditional methods, such as nanoflake dispersion or fiber surface modification, have limitations in achieving optimal mechanical reinforcement. The laminate features a multi-layered, "nacre-like" interface stabilized through non-covalent interactions, as supported by density functional theory (DFT) studies. DFT indicates that both polar (electrostatic) and non-polar (π-π) interactions are key to enhancing interfacial strength. A polyetherimide-based sizing agent (BA) with dynamic disulfide bonds is synthesized and applied to carbon fiber (CF) mats to improve bonding. The laminate (BA-CFRE-hGO) is fabricated via vacuum-assisted resin transfer molding, combining BA-coated CF mats with hGO-dispersed epoxy. BA increases CF surface roughness, enhancing mechanical interlocking, while dynamic bonds in BA and hGO strengthen CF-epoxy interactions, creating a "cemented" interface. Optimal BA and hGO concentrations yield a 37% increase in interlaminar shear strength (ILSS), 38% in flexural strength (FS), and a 190% improvement in storage modulus. SEM confirms improved adhesion, and the laminate shows self-healing (57% ILSS recovery), high electromagnetic shielding (∼48 dB at 8.2 GHz), and fast deicing performance, indicating strong potential for aerospace applications.

Microstructure and Shear Strength of SiC Ceramics Diffusion Bonded with Ti Foils by Spark Plasma Sintering

This study systematically investigated the diffusion bonding of SiC ceramics using Ti interlayers via spark plasma sintering. The effects of holding time (5 min, 10 min, 20 min), joining temperature (1300 °C, 1400 °C, 1500 °C), and Ti foil thickness (5 μm, 10 μm, 20 μm) on joint microstructure and shear strength were characterized through SEM, TEM, XRD, and EDS. The results revealed that the joining temperature was the key factor influencing joint performance, while the holding time and Ti foil thickness had relatively minor effects. When joined at 1300 °C, the primary reaction products in the interlayer consisted of TSC, TiC, and Ti5Si3 phases. Prolonged holding times improved the shear strength, but inhomogeneous phase distribution adversely affected the stability of mechanical properties. In joints with thinner Ti interlayers (5 μm and 10 μm), Si-rich phases tend to aggregate in the central region, leading to stress concentration and reduced joint strength. As the joining temperature increased to 1400 °C and 1500 °C, the Ti5Si3 phase was gradually consumed, and the interlayer primarily contained TSC and TiC phases, leading to a significant enhancement in shear strength, with a maximum value of 127.67 MPa achieved at 1400 °C. These findings provide important experimental evidence and theoretical support for optimizing the joining process of SiC ceramics.

Effect of hydrated lime and guar gum treatment on the geotechnical behaviour of a Ligurian sandy silt

Biopolymers emerged in recent years as promising soil stabilisers and are increasingly investigated by the scientific community for the treatment of earthworks. The literature on the subject has mostly focused on shear strength in unsaturated rather than saturated conditions, while only a handful of studies have investigated the effect of biopolymer treatment on soil compressibility and consolidation. Moreover, there is little research about soil treatments that synergically combine biopolymers and conventional chemical stabilisers (e.g. cement or lime). The objective of the present study is to fill these gaps of knowledge by investigating the hydromechanical behaviour of a silty sand, treated with a blend of hydrated lime and biopolymer guar gum, by way of a laboratory campaign of saturated direct shear box and oedometer tests. Results indicate that the lime-treated soil exhibits the highest peak strength, while guar gum increases the strength at critical state. Under normally consolidated conditions, treated samples exhibit higher void ratio than untreated ones at any given vertical effective stress. However, this difference in void ratio reduces as the stress increases because of the progressive deterioration of bonds through loading. Finally, soil stabilisation by guar gum produces a decrease of both hydraulic conductivity and consolidation coefficient.

Formulation optimization and synergistic effects of flocculation–solidification–vacuum preloading on sludge treatment

Rapid infrastructure development generates large volumes of high-water-content sludge, creating an urgent need for efficient recycling and management strategies. This study introduces the flocculation–solidification–vacuum preloading (FSVP) method to enhance dewatering efficiency and strength development, facilitating subsequent mechanical construction requirements. To enhance solidification and reduce cement consumption, the response surface method was used to determine the optimal composite curing agent, which consists of 53% cement, 32% rice husk ash, and 15% sodium silicate. Vacuum dewatering was applied to sludge samples treated with different flocculants and curing agents to assess their synergistic effects on soil improvement. The mixed flocculant of polyaluminum chloride and anionic polyacrylamide significantly increased the micropore content and compactness, with pore sizes primarily concentrated around 0.01 μm. While the flocculant facilitated efficient drainage, required unconfined compressive strength could only be achieved with the further addition of a curing agent. The optimal composite curing agent formulation induced hydration and pozzolanic reactions, filling larger pores with cementitious materials and enhancing soil strength. As a result, the vane shear strength reached 58 kPa and unconfined compressive strength reached 365 kPa at 7 days, further increasing to 586 kPa at 28 days.