Soil Strength Parameters Research Articles

Influence of acid rain climate environment on deterioration of shear strength parameters of natural residual expansive soil

Shallow landslides often occur on expansive soil cutting slopes especially during continuous rainy, causing traffic disruptions and enormous economic losses. This study experimentally investigated the effects of acid rain climate environment on the shear strength parameters of natural residual expansive soil (NRES). Firstly, the effects of the acid rain (pH = 3, 5, and 7) and wet-dry (W-D) cycles (n = 0, 2, 4, and 6) on the shear strength parameters of the NRES were studied by the direct shear test. Secondly, the changes in the microstructure and mineral composition of the NRES was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Finally, the mechanisms behind the shear strength loss of the NRES under acid rain and W-D cycles were considered. The direct shear test results revealed that acid rain and W-D cycles could accelerate the decline of shear strength of NRES, with the most apparent decrease under the first two W-D cycles. After two W-D cycles, the cohesion (c) of the soil samples under the acid rain with pH = 5 and 3 is 15.2 % and 31.2 % lower than that under the solution with pH = 7, respectively, while the internal friction angles (φ) of the soil samples decreased slightly. The results from XRD and SEM indicated the acid rain infiltration could cause different degrees of dissolution and leaching of free cementitious substances in NRES, resulting in the formation of loose structures with larger voids. This trend is more pronounced after the superposition of W-D cycles. Therefore, the integrity of the soil microstructure unit is reduced and the ability to resist vertical stress is weakened. In the direct shear test, the soil structure is more likely to form a shear fracture surface, eventually leading to the decline of shear strength.

Ultimate Bearing Capacity Calculation of Soil With Finite Element Method

Ultimate bearing capacity calculation is one of the most important factor to design foundations in geotechnical engineering. In this paper, ultimate bearing capacity values were calculated with finite element and analytical methods and compared. A case study of Bozozuk (1972) article is used for ultimate bearing capacity evaluations. On 30 September 1970, 600-ton weight concrete silo suddenly overturned and failure. After failure, in-situ Vane shear test and laboratory tests carried out to determine soil strength parameters for back analysis. In finite element analysis, Plaxis 2D was use. From analytical method maximum factor of safety FS= 1,09 from Terzaghi (1943) and minimum factor of safety FS= 0,97 from Meyerhof (1963). According to finite element analysis results, factor of safety was calculated as FS=0,64. All these results indicate that especially for complex and sensitive soil profiles, finite element analysis method may be used instead of analytical method.

Effective stress and shear strength parameters of unsaturated soils as affected by compaction and subsequent shearing

AbstractWheeling induced compression and shearing forces are main stresses accounting for soil deformation and changes of hydraulic, gaseous and thermal properties. There are reports about the combined effects of compaction and subsequent shearing on soil hydraulic properties, but their consequences on soil strength properties (i.e., effective stress and shear strength) need to be further analysed. This study investigated the dynamics of soil mechanical properties as affected by pore water pressure () during compaction and shearing. Soil samples from an A‐horizon of Gleysols derived from glacial sediment and a Stagnic Luvisol from loess were analysed. The repacked and structured samples were compressed under static and cyclic loading and then sheared at two speeds (0.3 and 2.0 mm min−1) with three loading levels (50, 100, and 200 kPa). During each stress application, the , chi factor (χ) and effective stress () were measured and calculated. The shear strength (), angle of internal friction () and cohesion (), were determined and fitted by the Mohr–Coulomb failure criterion. The results showed that compaction and shearing increased and χ in all homogenized soils while on structured soils this phenomenon only occurred when the applied loading stress exceeded the soil precompression stress. The increased resulted in soil hydraulic and mechanical stresses, which ultimately reduced the , especially at −6 kPa initial matric potential. Soils with finer texture, higher loading stresses and faster shear speed normally exhibited more reduced values. The structured soil had higher values with higher and compared to the homogenized soils. The changes of at high loading stress (i.e., 200 kPa) may overlap the normal pattern of the Mohr–Coulomb failure line that results from the theoretical Mohr envelope. Thus, to minimize the destruction of soil structure and stability induced by wheeling, it is important to consider field water content, traffic loading and wheeling speed.

Study of soil reinforcement in the east of Mashhad using glass granule

As waste production has increased, these materials have been put to their best use to help reduce pollution. Glass bottles account for more than 5% of municipal waste in Mashhad, according to statistics. This study attempted to look into the impact of using glass granule recycled materials on soil parameters. The impact of adding glass granule materials on the properties of weak soil and the need for improvement in the east part of Mashhad was studied. The dominant soil in the east of Mashhad was determined using samples collected from‌ 54‌ different locations. Finally, two experimental relations for determining soil strength parameters were presented. The results show that adding glass granule (GG) lowers the optimum moisture content, and CBR testing on the samples revealed that adding GG by 5% water content increases CBR capacity. Adding GG reduces the CBR in saturated conditions with high densities. According to the obtained results, adding 5% of glass granule is the optimal state that increases CBR and adding more than 5% of additive amounts does not have such an effect. Also, by examining the effect of GG on the shear strength of the soil, it was obtained that the addition of GG increases the internal friction angle of the soil by at least 30% and reduces adhesion by about 40%, as determined by a direct shear test. Adding glass granule in cyclic CBR has no effect in low cycles and has a negative effect in high cycles.

Sensitivity Analysis of a Physically Based Model to Assess Rainfall-Triggered Shallow Landslides

Rainfall-triggered shallow landslides are one of the most frequent geomorphological processes in tropical mountainous terrains, and they deserve special attention due to their potential negative consequences in society. Such processes involve several variables including those regarding precipitation, terrain morphology, and hydraulic and shear strength parameters of saturated and unsaturated soils. A spatially distributed and physically-based model for transient rainfall infiltration and grid-based regional slope stability analysis (TRIGRS), was implemented. It was used to analyze the influence of the mentioned variables on the triggering of shallow landslides by rainfall. A robust sensitivity analysis was carried out to quantify the influence of parameter variation on the change of the factor of safety (Delta f_textrm{s}) for shallow landslides, including a one-parameter-at-a-time analysis of a unique cell representing the simplest model space. Four combinations of saturated/unsaturated models and finite/infinite infiltration models were analyzed. The interaction among the hydraulic parameters was analyzed through small-multiple plots to observe their influence on Delta f_textrm{s}. It was found that Delta f_textrm{s} is most sensitive to variation in the maximum depth at which the landslide can be triggered, the slope angle, the cohesion, and the friction angle. In addition, it was found that the parameters of the soil–water characteristic curve for unsaturated soils have little influence on Delta f_textrm{s}. Finally, the interactions among the remaining parameters determine the impact of each one of these on Delta f_textrm{s}. Thus, the results showed that when the baseline set of parameters is changed, the influence of each parameter is modified.

Probabilistic back analysis of rainfall-induced slope failure considering slope survival records from past rainfall events

Many rainfall-induced landslides occur on slopes that have limited, or even no, site investigation data before failure. Probabilistic back analysis of slope failure provides an effective tool to back analyze possible pre-failure soil parameters, thus gaining insights into the mechanism of slope failure. For a slope failure induced by rainfall, the actual factor of safety (FS) is time-variant when time-variant rainfall and infiltration are explicitly modeled. This study proposes a novel probabilistic back analysis method that models explicitly the rainfall triggering mechanism for a rainfall-induced slope failure. Unlike existing methods that are based on a constant FS = 1, the proposed method utilizes FS inequality information for probabilistic back analysis, including slope failure record with FS < 1 and slope survival records from past rainfall events with FS > 1. The proposed method is suitable for high-dimensional problems when soil hydraulic properties are also back analyzed. The proposed method converges to the conventional methods with FS = 1 when the time span of slope failure is narrowed down to a few hours and slope survival records are ignored. Incorporating both slope failure and survival records effectively reduces uncertainties in soil strength and hydraulic parameters.

An Experimental Study on the Effect of Plastic Waste Powder on the Strength Parameters of Tuff and Bentonite Soils Treated with Cement

This experimental study investigated the effect of plastic waste powder on the strength and swelling behavior of tuff and bentonite soils treated by cement since the plastic powder is highly compressible and does not absorb much water. This study aimed to improve the tuff and bentonite soils used in construction by adding plastic waste powder in various ratios (5, 10, 20, and 25%) and a low cement content (2.5%). Atterberg limit, swelling consolidation, and loading-unloading tests were performed to determine the optimal composition of the mixture. The results demonstrated that as the plastic powder content increases, the liquid limits, swelling pressure, swelling potentials, and duration to swelling peak decrease. This reduction is particularly notable for the soil with the highest swelling potential. Compression and recompression indices increase significantly with the content of plastic powder due to its high compressibility. The findings suggest that plastic powder with low cement can be utilized as a soil modification reinforcement material, but with a content that shouldn't significantly alter the compressibility of the mixture.

Calculation of Risk Probability of Levee Landslide Based on Three-dimensional Lequilibrium Theory

Sliding instability is a common form of failure of embankments, and traditional dike safety evaluation often uses the safety factor value to judge whether it is safe or not. However, due to the uncertainty of the rock and soil characteristics of the embankment, the evaluation results of the safety factor method sometimes fail to reflect the reality, and it is reasonable to use the risk analysis of sliding instability considering these uncertainties. In this paper, the uncertainty of rock and soil strength parameters and the randomness of seepage field are considered, and the risk probability of sliding instability of the embankment is solved by relying on the reliability analysis method. In the reliability analysis, a three-dimensional bin method combining slope stability analysis and gradient optimization method of reliability analysis are proposed, which consider the safety performance, so that the stability evaluation is not too conservative, and the corresponding sliding risk probability can be obtained while obtaining reliable indicators. Finally, the calculation program is prepared for the proposed method, and the proposed method is verified to be reasonable and correct through the example.

Effect of Electric Arc Furnace Slag on the Engineering Properties of Lateritic Soil

It is imperative for geotechnical engineers to harness ways of improving lateritic soil with industrial waste materials in other to satisfy the required highway pavement construction. This work investigated the effect of Electric Arc Furnace Slag (EAFS) on the engineering properties of Lateritic soil. Tests to determine the X-Ray Florescence (XRF), X-Ray Diffraction (XRD), grain size analysis and specific gravity of the soil sample and EAFS and the lateritic soil stabilization with varying percentages (0%, 4%, 8%, 12% and 16%) of EAFS using Atterberg limits, Compaction and Shear Strength were carried out. The soil sample was classified as A-7-5 (6) and ML according to American Association of State Highway Transportation Official (AASHTO) and Unified soil classification system while the silica-sesquioxide ratio and mineral contents showed that the soil is a lateritic soil as they contain both swelling and non-swelling clay minerals. The stabilized soil sample revealed that EAFS increases the maximum dry density (20.0KN/m3 to 25.0KN/m3) and decreases the optimum moisture content (18.50% to 13.00%) which could be attributed to the lower affinity of EAFS to water thus, improving the compaction properties. Also, the EAFS has significant effect on the strength parameters of the lateritic soil as it increases the shear strength from 551.11KN/m2 at virgin state to 974.44KN/m2 at 16% EAFS. Conclusively, electric arc furnace slag has positive influence on the geotechnical properties of the lateritic soil as it will not only solve the waste disposal problem but can be used as additive to improve the engineering properties of lateritic soil.

Numerical analysis of the effect of replacing the start-up frictional coefficient with soil strength parameters for granular flows

Numerical analysis of the effect of replacing the start-up frictional coefficient with soil strength parameters for granular flows

Soil Improvement Using Blends of Coal Ash and Plantain Peel Ash as Road Pavement Layer Materials

The management of waste and its environmental impact remains an issue. Thus, various strategies are being explored to mitigate this problem. For this research case, the ash of plantain peel and coal was harnessed to enhance soil for usage in designing road pavements. The form of the soil, as regards its plasticity and grain assortment, positions it as a sandy lean clay material. Geotechnical parameters of the natural soil were established before being treated with coal ash (CA) and plantain peel ash (PPA), and subjected to tests for the Atterberg limits, California bearing ratio (CBR) and compaction, as well as investigations pertaining to its crystallinity and morphology. These assessments showed that strength parameters of soil increased on adding CA and PPA. However, the inclusion of these admixtures should be conducted until optimal strength is achieved as seen in 9% CA + 6% PPA. The use of soil stabilised with CA and PPA is suitable for general fillings and embankments. These findings revealed that integrating CA and PPA together would have the potential of stabilising soil as pavement layer material while also eliminating the pollution that emerges from the improper disposal of coal and plantain peels from the environment.

Experimental Study on Shear Strength Parameters of Round Gravel Soils in Plateau Alluvial-Lacustrine Deposits and Its Application

The shear strength parameters of conglomerate soils are crucial to the stability analysis of foundation support when excavating and supporting ultra-deep foundation pits in the highland alluvial lacustrine layer. The difference in water content of conglomerate soils in different regions will directly affect the values of shear strength parameters. At the same time, more research on the shear strength of conglomerate soils under different water contents is required. In this study, a series of large-scale direct shear tests were carried out on the round gravel soil in the plateau alluvial-lacustrine deposit, and the round gravel soil’s shear strength curves under natural and saturated conditions and water content were obtained. The influence of different water content on the shear strength characteristics of the round gravel soil was discussed, and the shear strength parameters of the round gravel soil with different water content were used in the numerical simulation of ultra-deep foundation pit excavation and support. The stress and deformation laws of the foundation pit support were analyzed. The results show that the peak strength of the round gravel soil in the natural water content state appears between 30% and 45% of the shear displacement, while the peak strength in the saturated water content state appears around 45–55% of the shear displacement. The shear strength tends to be stable or slightly weakened with the increase of the shear displacement. The angle of internal friction and cohesion of round gravel soil in the natural water content state is greater than those in the saturated water content state. The simulation of the foundation excavation support shows that the shear strength parameter of the round gravel soil influences the force deformation of the support structure. The higher the water content of the round gravel soil, the more the shear strength parameter affects the soil displacement. The research results can provide some reference for optimizing project design parameters.

İnce Toprak İçeriğin Zeminin Kayma Mukavemeti Parametrelerine Etkisi

The shear strength of the soil is a crucial factor in the structure's failure. Before any engineering structure is built on the soil, the shear strength characteristics must be thoroughly examined in order to reduce the calamity of structural collapse. The current study investigates the influence of varied percentages of fine material on soil shear strength. The soil sample consists primarily of sandy and clay soil. The study looked into the impact of fines on shear strength metrics (friction angle and soil cohesion). Several journal papers and articles were reviewed for this study. Based on the findings of several papers, the flow chart was created to describe the effect of the percentage of fine content in the soil and how it affects shear strength parameters. The shear strength parameters of sandy soil are significantly dependent on the percentage of fines in the mixture and the type of fine mineralogical composition. Both soil shear strength parameters increase at a substantial and apparent pace as compared to the particle content and additive increases in clay soil.

Soil water diffusivity as function of the pore size distribution and precompression stress

The idea of the study was to combine the saturation-dependent hydraulic conductivity, K(Se), as intensity parameter with the volume fraction related to the fractional capillary potential for each of the characteristic pore size classes that based on the matric flow potential, φ, and the soil water diffusivity, D(θ). The analysis is focused on the soil hydraulic properties of differently textured soils with differences in the pore size distribution, PSD. The soil-moisture retention, θ(h), and K(Se) as function of the effective saturation were determined with undisturbed samples for each soil profile and horizon and fitted by Mualem–van Genuchten type analytical function. The results indicate a strong linear relationship between φ values and the soil water diffusivity, D(θ), of soils with its volume fractions of macropores (r2: 0.65–0.91), wide coarse pores (r2: 0.55–0.77), and medium pores (r2: 0.83–0.85). The precompression stress, Pc, as mechanical soil strength parameter affects the soil water diffusivity of the chosen datasets especially in the wide coarse pore range (r2: 0.85). The results suggest that the PSD’s-related φ and D(θ) values are affected by both textural and structural effects. The soil water diffusivity itself strongly depends on the PSD and is an effective link between soil’s intensity and capacity parameter.

Mapping of Slope Failures on Highway Embankments using Electrical Resistivity Imaging (ERI), Unmanned Aerial Vehicle (UAV), and Finite Element Method (FEM) Numerical Modeling for Forensic Analysis

Highway Embankment Fill Slope is one of the significant components of transportation geo-infrastructures assets. Embankmets failure is a common problem that occurs due to various geotechnical, climatological, and environmental contributing parameters. Major influential factors include high temperature, high rainfall volume, and type of soil or a combination of all the above. For instance, when a slope built on high swell-shrinkage clay soil fails abruptly, it is due to the weakened self-retaining ability of the soil due to excess pore water pressure from high rainfall events. In Mississippi, rainfall is very intense, and lately, it is often characterized by aggressive showers. This rainfall generates significant soil strength losses that can endanger the safety and durability of embankments. Most embankments in the Jackson metro areas are constructed using Yazoo clay which is a typical High Swell-Shrinkage Clay Soil. These embankments have been found to experience shallow to deep failures a few years after construction due to the shrink-swell cycles during seasonal variations. These frequent failures have caused a significant maintenance problem for the Mississippi Department of Transportation (MDOT). Therefore, methods and approaches to evaluate embankment failures have been subject to careful examination by the MDOT by employing multiple investigations means, including Non-Destructive Testing (NDT) methods. To this end, in this study, Unmanned Aerial Vehicle (UAV), Electrical Resistivity Imaging (ERI), and Finite Element Method (FEM) numerical modeling were used to analyze shallow failure mechanisms within slopes. Several failed slopes located in the Jackson metro area in Mississippi were considered as references. The objective of the current study is to highlight the differences between pre and post-monitoring, evaluative, and analytic actions regarding embankments experiencing failure. During this study, four failed embankments were investigated using ERI and UAV to identify and locate the failed geometry, including slip surfaces. To better understand the failure mechanism, the identified embankments failure slip surfaces were numerically modeled using the FEM software package Plaxis 2D. Soil-strength parameters at failure were extracted through back calculation, and failure/slip surface depth was numerically characterized. The finding of this study helps post-embankments failure forensic evaluations significantly in terms of understanding failure mechanisms, identifying contributing failure parameters, better managing the decision-making process, and selecting an optimized stabilization technique.

Effect of freezing soil temperatures on strength parameters of clayey sand soils stabilized by poly propylene and poly vinyl alcohol fibers

Applying synthetic fibers is one of the most effective physical methods for soil improvement and stabilization. In this paper, we determine the effects of polypropylene (PP) and poly vinyl alcohol (PVA) fibers contents (0.2, 0.5, 1.0 and 1.5%) at environment temperature (25 °C) and various freezing soil temperatures (0, −5, −10 and − 15 °C) on stabilization of the clayey sand soil (SC) samples. The results show that for both types of fibers, by simultaneous increasing of fiber content and lowering the temperature, the values of the unconfined compressive strength (UCS), elastic modulus (EM), ductility and California bearing ratio (CBR) increase, and they all reach their maximum values for 1.5% fiber content at −15 °C. Moreover, we show that PVA fibers perform better compared to PP fibers in increasing of UCS, EM, ductility and CBR values for different fiber contents and temperatures. This can be attributed to the fact that PVA has higher tensile and flexural strength compared to PP fiber.

Laboratory Experiments on Soil Stabilization to Enhance Strength Parameters for Road Pavement

AbstractClay soils can cause significant distress in road construction due to their low strength. Stabilizing such soil improve with binder agents prior to the geotechnical works can significantly its performance and ensure safety and stability of roads while exploitation. This research envisaged the use of five different binders (lime, energy fly ash, bio fly ash, slag, cement) as an additive stabilizing agents to improve the strength parameters of soil as required in engineering industry standards. The variations of strength was assessed using measurements of P-wave velocity of the elastic waves propagating through soil specimens stabilized by different combination of binders. Measurements were performed on 28thday of soil treatment. The best effects of added binders were noted in the following combinations: cement / energy fly ash / bio fly ash (P-waves &gt;3100 m/s), followed by combination lime / energy fly ash / GGBFS (P-waves &gt;2800 m/s) and cement / lime / energy fly ash (P-waves &gt;2700 m/s). Adding lime is effective due to its fixation and chemical bond with particles. The study contributes to the industrial tests on soil strength for constructing roadbed.

Study on the influence of spatial variability of soil strength parameters on reliability and slip surfaces of cofferdam slope reinforced by geosynthetic reinforcement

How to guarantee the stability of the cofferdam slope during and after construction is a difficult problem. In this article, a practical procedure is developed to implement probabilistic stability analysis for reinforced slope considering the spatial variability of soil strength. In the proposed procedure, the improved random limit equilibrium method is adopted to calculate the safety factor and particle swarm optimization is adopted to search critical sliding surface of slope. The influence of different reinforcement positions, lengths, and number of layers on the reliability of reinforced slope and critical sliding surface is studied. The results show the variability of soil, the length, location, and the number of layers of geosynthetics are important factors affecting probability of failure (Pf ) of reinforced slope. The location and the number of layers of geosynthetic reinforcement play an important role in the statistical characteristics of FOS and slip mass volume. The reinforcement length has a greater impact on the safety factor.

Risk assessment of a layered slope considering spatial variabilities of interlayer and intralayer

While many studies have analyzed the effects of spatial variabilities of intralayer soil parameters on the probability of failure and risk of layered slopes, there is a paucity of research on the effects of interlayer variability. This paper is intended to investigate the influence of interlayer variability on the mechanical responses of a layered slope, as well as the effects of spatial variabilities of strength parameters of intralayer soils. To characterize the uncertainty of intralayer and interlayer spatial variabilities of layered geologic profiles, an integrated random field is developed using the program of FLAC based on both the two-dimensional random field theory and one-dimensional random process theory. Particularly, the random field for the interlayer transition zone is generated by a linear interpolation technique. Within the framework of Monte-Carlo simulation, a large number of stochastic calculations for a two-layered slope are conducted to evaluate the influences of spatial variabilities of both interlayer and intralayer on the stability and risk of the slope. The results show the failure mode of a two-layered slope changes greatly due to the stochastic layered boundary. It is also noted that the probability and risk of slope failure might be underestimated if ignoring the uncertainty arising from layered boundary and layered transition zone. The proposed equations can provide helpful information when investigating the probability and risk associated with layered slopes.

Influence of Different Industrial Waste Residues on Engineering Properties of High Liquid Limit Soil and Its Microscopic Mechanism

High liquid limit soil has unfavorable engineering geological characteristics, such as strong disintegration, dry shrinkage and easy cracking, and easy uplift when encountering water, which will cause various problems to the engineering. At present, the relationship between the physical and mechanical properties of high liquid limit soil and the characteristics of water-soil interaction is still not clear enough. In this study, the high liquid limit soil of Zhanjiang Avenue was selected to explore the influence of different ratios of three kinds of industrial waste residues (blast furnace slag, carbide slag, and tailing sand) on the high liquid limit soil. Aiming at the common adverse engineering geological phenomena of high liquid limit soil, such as easy disintegration, dry shrinkage crack, and easy uplift in water, the effects of different industrial waste residues on the water-soil interaction characteristics of high liquid limit soil are explored through disintegration and crack tests. In addition, the effects of different kinds and ratios on the free expansion rate, pH, unconfined compressive strength, and shear strength parameters of high liquid limit soil were studied. The improvement mechanism of different industrial waste residues on the engineering properties of high liquid limit soil is discussed in terms of mineral composition and microstructure. Based on the experimental results of this study and considering the cost and engineering practice, it is suggested that the modified carbide slag optimal ratio of high liquid limit soil of Zhanjiang Avenue is 8%. The results can provide certain guidance for the improvement and application of different industrial waste residues on high liquid limit soil to achieve the effect of sustainable development.