Search

Rainfall is one of the most significant natural factors for inducing landslides. The shallow saturated zone formed in slopes during rainfall is an important factor in inducing shallow landslides. In this paper, the characteristics and influencing factors of the saturated zone in soil slopes, and the relationship between the soil surface permeability coefficient and the rainfall intensity are analyzed. In this research, the equation that characterizes the rainfall intensity by the soil saturation is built based on the Mualem-van Genuchten model, which mathematically describes the soil water characteristics of unsaturated soils. Using this model, the target saturation of the slope surface during rainfall can be determined accurately, with an average deviation of − 0.008. Based on the equations, the innovative critical curve model of the rainfall intensity−time required to form the shallow saturated zone is established and calculated. The influence of the soil material, slope angle, rainfall intensity and antecedent rainfall on the critical curve for the shallow saturated zone is analyzed. The results indicate that for slopes of 30°~40°, it is easy for the shallow saturated zone to form, and the previous rainfall after more than 16 days has little impact on the critical curve. Furthermore, an innovative landslide prediction model, based on the critical curve for the shallow saturated zone and I-D modeling, is proposed to provide benchmarks for the prediction-specific characteristics of deep or shallow landslides, which is verified by the case of the Madiwan landslide.

The effects of acoustic emission (AE) in soils during freezing and thawing under cyclic thermal and quasi-static mechanical loading have been studied. The composition and characteristics of the developed instrumentation set are presented. The informative AE parameters and primary data processing approaches were justified. The acoustic emission patterns of soil material behavior under the variable thermobaric conditions were obtained. The comparative tests were performed using static probing and ultrasonic scanning.

To explore the effect of drain board spacing on the vacuum preloading treatment effect, transparent soil material was selected to carry out indoor vacuum preloading model tests, and particle image velocimetry (PIV) technology was used to obtain the displacement field inside the soil under different drainage spacing. In this paper, a mixed solution of amorphous silica fume, white mineral oil and n-dodecane was used to prepare transparent soil, and model tests of vacuum preloading transparent soil were carried out under drainage spacing of 200 mm, 300 mm, and 400 mm. The test results show that the displacement field of soil with different spacing of drainage is obviously different. Obvious "concave" settlement will occur on the soil surface under 200 mm spacing, and obvious "W" type settlement will occur under 400 mm spacing. 300 mm is the best spacing of drainage; the range of the "soft soil zone" is small, and the uneven settlement of the soil surface is not obvious. According to the influence range of a single drainage, the spacing of drainage should be reasonably designed to ensure the lap and connection of "soil piles" and improve the effect of vacuum preloading treatment.

An expansive soil slope of a high-speed railway under construction in Yunnan suffered a local collapse after a heavy rainfall. The expansive soil on this slope surface is prone to slip and collapse under the action of rainfall. The analysis of water sensitivity reveals the attenuation law of the shear strength of the expansive soil. With the increase in the water content, the shear strength of the expansive soil decreases significantly. Wet–dry cycles also significantly lower the shear strength of the expansive soil. In addition, a high-density electrical method test is performed on the expansive soil slope to determine the structural characteristics of the internal soil. The test results indicate that the internal soil of the slope exhibits poor mechanical properties and contains fissures and cracks, which are also the factors that caused the landslide. The finite element software, ABAQUS, is used to analyze the impact of rainfall on the expansive soil slope. The results reveal that the soil at a depth of approximately 2 m below the surface reaches complete saturation after 24 h of rainfall, and the plastic failure zone is mainly distributed on the surface and toe of the slope. Based on the electrical test results, the slope soil material is classified into saturated, fissured, and non-fissured soil zones. The stability analysis results reveal that the sliding surface is circular and in the shallow layer of the slope, and the sliding depth is 2–3 m. Although the depth of the landslide mass is not large, almost the entire slope surface soil undergoes plastic failure, resulting in a large area of ​slippage.

Experimental studies on tunneling and other kinds of underground engineering using similar materials are an important technique for investigating relevant problems in civil engineering. Compared with case studies in real-world engineering construction, laboratory experiments have three distinctive characteristics: high maneuverability of the procedure, high accuracy of the monitoring data, and high repeatability of the experiments. Using this experimental method, numerous constitutive models of rock or soil material have been established, construction techniques and processes have been optimized, the principles and characteristics of rock deformation and failure have been studied, and various special conditions have been simulated. This paper presents a review of selected geomechanical experimental apparatus and techniques. First, five multiaxial loading techniques for similar-material experimental equipment are introduced, and the associated loading methods, suitable working conditions, and data analysis are illustrated. Second, the material selection and ratio of rock mass are discussed, and the data acquisition elements of model testing and a variety of monitoring methods are presented. Third, the rationality of the similar-material experimental techniques is investigated, several problems in excavation process similarity are examined, and potential research in simulating structurally controlled rock burst under hard rock conditions is discussed.

In this study, large-scale triaxial compression tests are conducted on gravelly soil material. The experimental investigation shows that gravelly soil exhibits complicated volume-dilatation/contraction behaviours that are dependent on stress level. To better describe the mechanical behaviours, an elastoplastic constitutive model is proposed within the frameworks of generalised plasticity and the critical state soil mechanics. An evolution equation of the void ratio is incorporated into the model to describe the effect of a relatively dense or loose state on the volume-change behaviours. The model has 10 material constants that could be determined using a few large-scale conventional triaxial tests. The model is then used to simulate the mechanical behaviours of gravelly soil. Comparisons between the numerical simulations and the test data show that the model is capable of capturing the mechanical behaviours of gravelly soil under various confining pressures. This research can be beneficial for understanding the mechanical behaviours of gravelly soils.

The requirements of regulatory documents imposed on the selection of control samples of coarse fragmental material often hamper the rate of erection of earth and rockfill dams and complicate operational assessment of work quality. Through the evaluation of the possibility of quality control of the stacking of coarse fragmental material in pits of reduced size by controlling the density of all the soil material relative to the density of fractions 200 mm, similar to the determination of the entire soil density relative to the density of fine material (5 mm), it becomes possible to optimize these types of operations without worsening their quality.

Stress reduction factor, λ, is a dimensionless coefficient in two-dimensional (2D) analysis based on convergence confinement method (CCM) of tunnel which represents stress relaxation in the tunnel walls at different excavation steps. The aim of this paper is to look into the influencing factors on parameter λ around the tunnel walls using finite difference code in order to improve the accuracy of the CCM. For this purpose, four different ground types with various tunnel radii, depths and cross section shapes are considered. Finally, the 2D analysis using uniform and variable stress reduction factors determined in this paper is compared with the 3D analysis of the tunnel. The results of this study enhance our understanding of the role of geometrical and soil material parameters of tunnel on stress relaxation around tunnel walls. The tunnel depth, soil type and tunnel shape have great influence on λ. Variable stress reduction factor enables the convergence–confinement method to predict the realistic behavior of third dimension of the tunnel and can also be used as the best alternative to 3D models.

Purpose The volume of dust deposition on the soil surface in Moscow is big enough and make several tens of grams per square meter annually. The role of dust as a soil-forming material is especially high in places with practically no other soil parent materials. It is necessary to consider solid atmospheric precipitation as a parent soil material in urban conditions and its impact on soil properties.

The yield criterion parameters of the soil material change with different values of the cohesion and the angle of frictionbecause of sustained rainfall infiltration. Based on the Mohr-Coulomb (M-C) and Drucker-Prager (D-P) yield criteria, some reasonable yield criteria selections were discussed for quantitative analysis of unsaturated soil slope stability. Moreover, a critical point was found at the effective angle of friction equaling to 16.5° by transformation of parameters related to unsaturated soil under sustained rainfall. When the effective angle of friction more than 16.5°through parameter transformation of different yield criteria under natural condition, the calculation result of the safety factor was such that: f(DP1) > f(M-C) > f(equivalent M-C) > f(DP2) > f(DP3). While the effective angle of friction less than 16.5° , through parameter transformation, the safety factors were in the following order: f(DP1) > f(M-C) > f(DP2) > f(equivalent M-C) > f(DP3). The calculated results from a case study showed that the equivalent M-C yield criterion should be the best at evaluating soil slope stability before rainfall; the DP2 yield criterion should be selected to calculate the soil slope stability at the effective angle of friction less than 16.5°under sustained rainfall. The yield criterion should be selected or adjusted reasonably to calculate the safety factor of unsaturated soil slopes before and during sustained rainfall.

Jointed Concrete Pavement (JCP) has been constructed in over half of the total expressway system in Korea due to its long service life and low maintenance costs. The JCP on a box culvert is susceptible to failure brought by the freezing and heaving phenomenon during winter. This contributes to the shortening of pavement service life and deterioration of road quality. In order to address this problem, several alternatives have been suggested. The results of temperature variation of the soil layer on a box culvert and the profile measurements show that the water in the soil freezes during winter. Furthermore, it is impossible to prevent this by a dummy ditch, however, a waterproof mat, a tent, and an elastic-asphalt mat can be effective. Based on measurements of moisture contents in the soil, a method to combine a waterproof mat and crack or joint sealing showed good performance. For a soil material and a crown at the top of a culvert, when 1% crown for anti-freezing material or 4% crown for subgrade was applied to the surface, the risk of freezing and heaving decreased.

Background and aims Tree root system structure and development are difficult to assess and poorly understood in natural conditions because of soil heterogeneity and the difficulty in extracting mature tree root systems without damaging them. The purpose of this study was to understand root system development plasticity according to biological and physical parameters: species, tree age and size, soil material, water availability, slope angle, and climate.

In this article, an attempt is made to construct a soil-material model which can be used over a wide range of soil densities. To construct such a model, an existing purely continuum-type soil material model (used in the high-density regime), within which the granular structure of the soil is neglected, is combined with an existing discrete-type soil material model (used in the low-density regime) within which soil is treated as an assembly of interacting particles. In order to enable it to be used in conventional transient, nonlinear dynamics, and finite element analyses, the new soil material model is cast using a continuum-type framework. Thus, while in the low-density regime soil behavior is fully dominated by the discrete-type soil-material model, soil has been treated as a continuum constituent properties of which are governed by particle geometrical parameters and particle-particle interaction laws. To demonstrate the utility and fidelity of the new soil material model, a series of uniaxial strain computational tests involving rectangular, parallelepiped-shaped soil-slug normal impact onto a rigid, fixed, flat surface is carried out. While these tests are of a one-dimensional character, they are generally considered as being representative of the loading and deformation histories experienced by mine-blast-ejected soil during its impact with the target structure. The results obtained using the newly proposed soil material model, in the low-density regime, are found to be fully consistent with their discrete-particle modeling and simulation counterparts, suggesting that the new model can be used in transient nonlinear dynamics, finite element simulations involving low-density soil.

Advanced numerical modes used for the description of performance of geosynthetic reinforced soil structures in terms of displacements corresponding to working loads well below collapse levels has created the need for material models for the geosynthetic and geosynthetic-soil interaction accounting for stiffness, yielding and strength properties. A direction dependent isotropic hardening, elastic-plastic-creep model for the geosynthetic, an elastic-perfectly plastic direction and normal stress dependent geosynthetic-soil interaction model, and a bounding surface plasticity model for soil material have been used in a finite element model of a geosynthetic pullout test. Predictions from the model have been compared to a series of pullout tests where it is seen that the model provides reasonable predictions of load-displacement pullout behavior. Systematic removal of material model components has shown that geosynthetic creep properties have a noticeable but minor impact on load-displacement predictions, while geosynthetic plasticity properties have a more significant role for load simulations where the material approaches rupture during pullout. Replacement of the bounding surface plasticity model for the soil material with a linear elastic model resulted in no significant differences in predictions.

Microamounts of thorium in soils can be determined by a differential-kinetic method based on the kinetic properties of the complex of thorium with 1,2-cyclohexanediaminetetraacetic acid (ThDCTA). The thorium content was determined spectrophotometrically upon decomposition of this complex in 0.1 M HNO3 in the presence of Arsenazo III. The method involves anion-exchange isolation of Th from solution obtained by degradation of the soil material; it allows thorium determination in the presence of a number of impurities, which poses less stringent requirements on thorium separation from these impurities.

The Bayesian probability model, using the weight-of-evidence method, was applied to the task of evaluating landslide susceptibility using GIS data. The location chosen for the study was the Janghung area in Korea, which suffered substantial landslide damage following heavy rain in 1998. Using the location of the landslides as well as topographic factors such as soil, forest and land use, the weight-of-evidence method was used to calculate each factor's rating. Tests of conditional independence were performed for the selection of the factors, allowing the large number of combinations of factors to be analyzed. For each factor rating, the contrast values, W+ and W–, were overlaid for landslide susceptibility mapping. The results of the analysis were verified using the observed landslide locations and, among the combinations, the slope, aspect, curvature, soil material and wood types show the best results.

To ascertain the feasibility of using 137Cs and 210Pb in soil erosion models a Compton suppression system with a Be window was used to simultaneous detect both of the naturally occurring isotopes. In particular, the system allowed the use of only 20 g of soil material instead of the usual needed 0.5-1.0 kg in similar soil studies.

A research facility is described for the integrated study of soil-root-shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight below-ground compartments; aligned along a corridor. A rain shelter automatically covers the experimental area at the start of rainfall. Compartments are 125 cm×125 cm and 200 cm deep. Each compartment has a separate drip irrigation system. Crop canopy photosynthesis, respiration, and transpiration can be measured simultaneously and continuously on four out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth [...]

We measure general activity of mice(Mus musculus) in a burrowing chamber from an ecological point of view. Natural topsoil or sand, however, is not suitable for long-term dwelling of mice, because burrows are likely to keep collapsing and to become rapidly rotten from being sprinkled with water to guard against collapse. For the present study, we devised a mixture of absorbent cotton and wood shavings as soil material. The mice burrowed in this soil just as they would in natural soil. About 104 cm3 of the cotton-shavings soil were durable for at least 40 days with 3 mice. These results suggest that this soil material can be a useful tool in not only the study of general activity but also other studies (e.g., the observation of maternal behavior of mice in burrows).

This investigation presents an analysis of the mobility of 37 organic solvents in saturated soil-water systems, focusing on adsorption phenomena at the solid-liquid interface This analysis was made, in part, by applying predictive expressions that estimate the potential magnitude of adsorption by soil materials Of the 37 solvents considered, 19 were classified as either “very highly mobile” or “highly mobile” and, thus, would have little tendency to be retained by soils to a significant extent, 12 were considered to have medium mobility and 6 low mobility None of these solvents were in the immobile class The limited information available indicates that these predictive expressions yield satisfactory first approximations of the magnitude of adsorption of these solvents by soil materials

A comparison between a tissue solubilization method and a sample oxidizer technique to measure14C in plant and soil material is described. The solubilization method although not quantitative gives good recoveries and reproducible values of14C-content with soil samples not exceeding 10 mg and should be of value for estimating the14C-content of soils in laboratories without a sample oxidizer.

1. The use of low-strength argillites and siltstones in the given dam showed that these soils can be used widely in dam construction. 2. The placement of soils of useful excavations in the dam, the bulk of which was composed of argillites and siltstones, markedly reduced transport costs on hauling the soil masses, and the location of the borrow pits in the flood zone reduced the area of lands allocated for construction and loss of agricultural production. 3. The possibility of year-round excavation and placement of argillites and siltstones in the dam accelerated the construction of the structures and delivery of water to consumers by means of the start-up complexes. 4. The observed operating settlement of the dam was considerably less than the predicted, which evidently is related to the gradual soaking of the Taurian soils from the reservoir as it filled during construction. 5. Owing to the scientifically developed specifications of placing the soils in the earth dam and high-quality performance of the construction works, the required calculated characteristics of the argillites and siltstones and also of the clay soils in its components were attained. This provided stability of the dam of new soil material.

A two-year experiment was conducted on the Black Mesa Coal Mine near Kayenta, Arizona to investigate the growth and establishment of seven plant species in unmined soil (undisturbed soil) and coal-mine soil (spoils). Natural rainfall (20 cm/yr) and natural rainfull plus sprinkler irrigation (50 cm/yr) were the irrigation treatments applied to each soil material.

Recent atmospheric chemistry studies have shown that substantial quantities of soil material are being transported out of Asia and across large regions of the North Pacific1,2. In the central North Pacific, the estimated1 (6–12×1012 g yr−1) and measured2 (20×1012 g yr−1) deposition rate of mineral aerosols could account for a substantial fraction of the non-biogenic portion of deep-sea sediments in this region, where sedimentologists have previously estimated that 75–95%3,4 of the surface sediment is derived from atmospheric dust fallout. The quantitative importance of wind-transported (aeolian) material to sedimentation in the North Pacific would be more firmly established if it could be shown that the composition of the present-day soil aerosol is similar to that of mineral particles in the underlying sediments, which have been deposited over a period of thousands of years. Here we compare the compositions of soil aerosols and sediments collected from the western North Pacific and find that their mineralogies are identical, except for one mineral. This supports the hypothesis that the sediments are heavily impacted by aeolian sources.

The purpose of this work was to determine the degree of oil retention from an oil spill area in view of natural physical weathering, and to evaluate the compositional changes of the natural oil retained in the soil material.

A DEFINITIVE and important characteristic of soil is its heterogeneity in fabric. This is evident in the great variety of spatial arrangements of components that have been established by the microscopic study of soil in thin section1. Chemical methods of soil analysis, however, usually involve the homogenization of soil material and therefore the destruction of its fabric by drying, sieving and representative sampling. Microchemical and mineralogical analysis of undisturbed soil fabric, on a scale comparable with the smallest recognizable components (that is, at least at the micron level), is therefore desirable to complement the existing chemical approach.