Degree Of Water Saturation Research Articles

Ultrasonic S-wave responses of single rock joints filled with wet bentonite clay

Clay minerals are prevalent in rock discontinuities and have significant effects on mechanical, hydraulic and seismic properties of rock masses. Understanding seismic behaviours across individual clay-rich rock joints is of great importance in the fields of geology and earth sciences. However, the wave responses of individual clay-rich rock joints have not been well understood until now. This paper reports a laboratory investigation of ultrasonic S-wave propagation and attenuation across single rock joints filled with bentonite clays with varying degree of water saturation. In this study, a series of acoustic measurements were conducted on specimens of the bentonite clay-filled rock joint using a self-developed ultrasonic pulse-transmission test system that equipped with a S-wave transducer pair with a dominant frequency of 250 kHz. Based on the obtained laboratory data, the wave velocity, transmission ratio and the time-frequency-energy distribution of the S-waves transmitted through the bentonite clay-filled joint were calculated and evaluated. The experimental results show that the degree of water saturation of the bentonite clay greatly affects S-wave responses of the filled rock joint. In particular, an increase in the degree of saturation causes a nonlinear decrease in S-wave velocity. In addition, as the water saturation of the bentonite clay increases, the wave attenuation decreases; the minimum wave attenuation is reached at a saturation degree of 71.4% and then the attenuation increases slightly. Additionally, with the increase of the water saturation, the magnitudes of the S-wave energy transmitted across the bentonite clay-filled joint firstly increases and then decreases. The S-wave energy is mostly stored in the frequency range of 150 - 300 kHz regardless of the degree of water saturation of the bentonite clay. This finding indicates that the frequency partition of the transmitted S-waves rarely changes with the changing water saturation. The present work could not only compensate for the lack of laboratory-based research on wave behaviours across clay-rich rock joints but also provides insights into the interpretation of acoustic data from field tests for detecting, characterizing and monitoring rock discontinuities.

A model tank investigation of the electrical resistivity response over a simulated forensic target

The electrical resistivity response of a simulated clandestine buried weapon box-laden ammunition tank was carried out. This was with the aim of determining the adoptability of the resistivity method in search for similar forensic targets. The experiment was carried out in a model tank of dimension 207x160x50 cm3. The model tank was filled with compacted and un-compacted sand and a weapon box-laden ammunition tank was buried within the compacted sand. The ammunition tank was made of stainless steel while the weapon box was metallic. Resistivity measurements were taken on the crest of the tank along five (5) traverses before and after the burial of the ammunition tank. The Electrical Resistivity Imaging (ERI) technique in conjunction with the dipole-dipole array was adopted for the measurements. The data were quantitatively interpreted by inversion and the results were presented as 2-D resistivity structures, maps and stacked profiles. During the pre-burial measurements, resistivity values generally increased with increasing depth and three (3) resistivity classes (101–266, 275–835 and 2113–23,944 Ω-m) resulting from the variation in compaction and/or degree of water saturation were observed. The resistivity classes were present within the depth ranges of 0–8 cm, 8–16 cm and 16–40 cm respectively. A drastically reduced resistivity regime, however characterized the post-burial measurements. The post-burial images of the traverses straddled by the region of burial had their resistivity values decreasing with increasing depth as against the pre-burial pattern. The presence of the stainless steel ammunition tank was attributed to the resulting higher resistivity values introduced within the overburden after its burial. A major low resistivity anomaly coincident on the position of burial of the metallic weapon box indicated its presence. The study demonstrated the potential of the electrical resistivity method in the delineation of similar targets that may have forensic implications.

Modelling the pyrite oxidation level in a refractory gold-bearing stockpile to assess its potential for gold recovery by direct cyanide leaching

This study presents a three-dimensional numerical modelling method for predicting the pyrite oxidation level in refractory gold-bearing stockpiles under various conditions. The physical and chemical processes incorporated into the model include oxygen transport, heat transfer, air convection and pyrite oxidation. Different reaction rate models based on the shrinking core model are used to quantify the oxidation of pyrite grains in rock particles considering the influence of oxygen concentration, degree of water saturation, temperature and pH conditions. The extent of pyrite oxidation is a function of the oxygen concentration gradient within rock particles and is determined by the diffusion–reaction equation using the polar-coordinate system. Particle size distributions for both pyrite grains and rock particles are incorporated in the modelling of pyrite oxidation and oxygen consumption. Several scenarios with different parameters were examined and the simulation results show that after ten years, the pyrite oxidation level over the stockpile is up to 50% depending on the location within the stockpile, the rock types and stockpile properties such as porosity and water content. The model can simulate the overall pyrite oxidation level as well as the oxidation profile of the pyrite grains, i.e., the oxidation depth of pyrite grains of different sizes and at different locations within the rock particles. These are essential inputs required for the estimation of gold recovery by direct cyanide leaching for possible reclamation of the partially oxidised stockpile without incurring expensive pre-treatment of the material.

Simulation of non-stationary two-phase mass transfer in a large reservoir

The Kuibyshev Reservoir was formed on the Volga River and is the largest in Eurasia. The length of the reservoir along the Volga is 510 km with its maximum depth of 41 m and average depth of 8 m; the area of water mirror is 6,450 km2. Conditions of runoff formation in catchment area, as well as seasonal and daily regulation are the reasons for unsteady regime of the reservoir. Specificity of flow control in the Kuibyshev Reservoir predetermines water masses motion, flow speed pattern, as well as degree of water saturation with suspended sediments and, therefore, reservoir bed siltation intensity. The lowest flow velocity in the reservoir is observed in summer-autumn period of year; at this time, the reservoir bottom is reshaped least actively. During spring filling, flow velocity in the reservoir is at maximum, hence, favourable conditions to transfer small and large fractions of suspended sediments are created. Most of them enter the reservoir during its spring time filling, although sometimes, sediments maximum was observed earlier, before reaching the peak of flood wave in the reservoir. Flow pattern unsteadiness leads to increase or decrease in flow transfer capacity and, hence, changes in bottom levels. Complex configuration of banks, large depth gradients and basin morphology’s particulars pre-determine instability of sedimentation processes in water area. 3D hydrodynamic model of the reservoir (A. Rakhuba) forms the basis for calculating bottom level motions of the Kuibyshev reservoir. This model is supplemented with analytical formula for sediment consumption (M. Shmakova) and hydraulic ratios to calculate erosion and sediments accumulation (M. Shmakova). Four ice-free months runoff simulation of the Kuibyshev reservoir includes the following main water content phases: low water period and periods of snow flood and rain floods. The study of spatial and temporal patterns of bottom reshaping has shown that greatest intensity of such reshaping occurs during the period of large level gradients, i.e. high water. Flood swelling is featured by intensive bottom erosion. When flood recesses, transfer capacity decreases that leads to sedimentation. The greatest motions in bottom reshaping occurs in the places of channel contraction, which is explained by sharp changes in channel capacity.

Review of investigations into the vadose zone’s variable state of saturation in connection with the assessment of radon potential in Bulgaria

Natural radon (222Rn) is a radioactive noble gas that occurs as the immediate decay product of radium (226Ra), part of the 238U family, in the lithosphere. Radon is driven by advection and diffusion with soil gas throughout connected and water-unsaturated pores and/or cracks in permeable rocks and soils. The aim of the present study is to do a review of the existing so far research activities in Bulgaria in connection with the observation and/or evaluation of the degree of water saturation of the near-surface layer, and on that base to distinguish the up-to-date achievements in regards to the radon potential in situ evaluation. Due to this review, the studies in Bulgaria concerning moisture dynamics in the near-surface layers can be divided mainly into two groups. The first one investigates the hydraulic characteristics (parameters) of soils in the vadose zone. Based on that, conclusions or computer simulations for the saturation degree estimation can be drawn. The other group includes in situ observations by sensors on the change of moisture with time. The results of these studies may serve as a base for more precise moisture dynamics assessment at sites with specific radon potential tendencies.

Forecasting the viscosity properties of water-oil systems

In article possibilities of predicting the viscosity of stable multicomponent water-oil systems in practice, when it is impossible, for a number of reasons, to obtain their experimental values, are considered. A predictive model is proposed to describe the change in the viscosity properties of various oil-water emulsions depending on the degree of water saturation. It is shown that the proposed formula allows to determine the effective viscosity of water-oil systems in the entire range of variation of the velocity gradient in the absence of experimental data and is acceptable for engineering practice. Keywords: viscosity; water-oil emulsions; matematical description; water saturation degree; heterogeneous systems.

Influence of the degree of saturation on carbon steel corrosion in soil

The corrosion behaviour of carbon steel was investigated in artificial soils of various saturations with 3% NaCl solution. The carbon steel corroded uniformly at slower rates in saturated soil and non-uniformly at higher rates in unsaturated soils. The corrosion current density (icorr) was measured by electrochemical impedance spectroscopy, and the percentage of corroded surface area (Aanode) was evaluated using a laser displacement metre. The corrosion current density (icorr(a)) of the corroded surface area was determined by dividing the icorr by (Aanode/100). Based on the results obtained, the influence of the degree of water saturation on carbon steel corrosion is discussed.

Thermal conductivity of undisturbed soil – Measurements and predictions

Soil thermal conductivity, λ, is decisive for a range of soil ecosystem services related to soil temperature. Soil functions affected by temperature comprise microbial as well as abiotic processes of importance to crop growth, leaching of nutrients, carbon sequestration, and emission of greenhouse gases. Models for crop production and climate change include λ for simulation of heat transfer in the natural environment. Nevertheless, most prediction equations for λ are based on measurements deriving from physically disturbed soil. We identified nine Danish soils with a gradient in clay from ~ 0.03 to 0.35 kg kg−1 and measured λ in situ at six soil depths from 5 to 85 cm with the heat pulse method. Soil cores were collected and used for measurements of λ at a range of moisture conditions in the laboratory. The degree of soil water saturation, S, ranged from 0.01 to 0.98, and measured λ was in the range 0.18–2.98 W m−1 K−1. A model for λ identified by multiple regression across all laboratory measurements explained 87% of the variation in data and pointed out a convex polynomial relation between S and λ. It included significant positive effects of bulk density (BD) and soil organic matter (SOM), while λ decreased with soil clay content for a given S. The stochastic model predicted λ for three independent data sets from the literature with little bias and root mean square errors in the range 0.15–0.23 W m−1 K−1. A polynomial regression of λ versus S was performed for combinations of site and soil depth. By this λ was estimated at completely dry conditions, λdry, and at the fully saturated state, λsat. The estimates of λdry as well as λsat had a wider range than reported in the literature. This study calls for re-evaluation of existing pedotransfer functions for λdry. Measurements of λ in soil of undisturbed structural conditions are encouraged.

Coupled model for water, vapour, heat, stress and strain fields in variably saturated freezing soils

Although many frost heave and freezing soil models have been developed in the past decades, saturated conditions are commonly assumed and/or the behavior of pore ice rather than ice lenses are conventionally predicted. This study presents a fully coupled thermal-hydraulic-mechanical (THM) model for variably saturated freezing soil, which examines a number of processes. These include heat conduction and convection, phase change, water (moisture) movement through cryosuction, and the development of independent ice lenses. Instead of directly solving for the pore pressure distributions, the void ratio is considered as a dependent variable related to the degree of water saturation. Both the stress-deformation and ice lens segregation are inextricably linked to the evolution of the void ratio as well. The coupled mechanism and performance of the model is first verified by comparison with laboratory freezing experiment observations obtained from literature and then is further evaluated by a series of parametric analyses. The results show that the calculated profiles of temperature, water content and frost heave are in good agreement with literature experimental data, demonstrating that the proposed THM coupling model appropriately represents the mechanisms of heat-moisture-deformation in variably saturated freezing soil. In addition, the sensitivity analysis illustrates that in the test cases considered, thermally-induced cryosuction due to phase change is the main driving force for water migrating towards the freezing front. Also, ahead of the freezing front, a significant increase in effective stress developed due to the elevated negative pore pressure and expansion of ice lenses causing substantial consolidation and reduction in porosity in the unfrozen zone. As the freezing front penetrated with time, the temperature, moisture, vapour and stress-strain fields interact with each other. The distribution of water vapour was mainly controlled by the temperature gradient and location of the freezing front. Both the initial degree of saturation and hydraulic conductivity affected the distribution of pore pressure and displacements. Higher compression moduli and lower overburden load led to greater frost heave but exerted little influence on the temperature field. Finally, the two-sided freezing scenario for soils underlain by permafrost made the middle ice-poor zone highly compacted with ice lenses accumulating near both freezing boundaries.

Determination on pore size distribution by a probabilistic porous network subjected to salt precipitation and dissolution

Pore system strongly affects durability of building materials. Therefore, representative models for pore system and evolution of the pore system during aging are important for understanding physical processes that affect durability of building materials. In this study, a porous network model was developed based on a probabilistic method to describe pore size distribution, and three transformation laws were employed to establish relationship between the initial pore sizes and modified pore sizes (after salt precipitation and dissolution) regarding the waterfront. Proposed model illustrated evolution of pore size distribution due to salt precipitation and dissolution based on overall porosity and water saturation degree. Moreover, the model can be used to implement the filling/emptying ratio of pores at vicinity of waterfront. Successive transformations were introduced into the model to illustrate evolution of pore size distribution due to long-term salt intrusion. Lastly, parametric studies on the model were performed to further elucidate the modifications on pore size distribution due to salt precipitation and dissolution.

Settlement and bearing capacity of water-saturated soils of foundations of finite width under static impact

Introduction. In case of brief exposure to static loads or dynamic loads, in conditions of absence of drainage, distribution of total stresses between the skeleton of soil and pore gas-containing water should be taken in account. The situation of the stress-strain state of the base is further complicated when we consider the degree of water-saturation of soil of the foundation (0.8 < Sr ≤ 1). The aim of the study is to pose and solve problem of the stress-strain state of a water-saturated soil massif, Including settlement and bearing capacity of a water-saturated base of a foundation of finite width, depending on the degree of water saturation of soils, taking into account the linear and nonlinear properties of the skeleton of soil and the compressibility of pore gas-containing water.
 Materials and methods. Henckyʼs system of physical equations are used as a calculation model to describe the relationship between deformation and stresses of soil, which takes into account the influence of the average stress on the deformation and strength properties of the soil. This system allows us to represent the linear deformation of the soil as the sum of the volumetric and shear components of the soil of this deformation. In addition allows us too to determine the deformation of the layer of soil, as part of the compressible thickness of the base of foundation with finite width under conditions of free deformations.
 Results. Depending on the linear and nonlinear deformation parameters, the settlement can be developed with a damped curve (S – p) and stabilize, and can be developed with a non-damped curve (S – p) and moved to the stage of progressive settlement.
 Conclusions. Solutions have been made for cases when the water-saturation of the base soils changes in the range of 0.8 to 1.0. It is shown that the settlement and bearing capacity of a water-saturated base significantly depends on the degree of water saturation of soils.

Numerical simulation study of influencing factors for 3D coal seam gas drainage efficiency

Gas drainage from the coal seam can not only decrease gas pressure, content, and gas emission but also prevent gas outburst and explosion; however, the gas drainage efficiency is low. In this study, numerical simulations were conducted on 3D coal seam gas drainage based on the gas–solid–liquid coupling model using COMSOL Multiphysics. The application of different initial conditions of the coal seam on gas drainage showed that the initial permeability, water content, and gas pressure of the coal seam all had influence on gas drainage efficiency. The decreasing velocity of gas pressure in the coal seam accelerated dramatically, and the outburst elimination range where the residual gas pressure decreased below 0.74 MPa increased dramatically at the same time during gas drainage with the increase of the initial permeability. An increase of the water content in the coal seam indicated that the larger the water saturation degree in the coal seam, the more slowly the coal seam gas pressure decreased at the same time and position, and the smaller the outburst elimination range. Moreover, the larger the initial gas pressure, the larger the residual gas pressure, and the more difficult the realization of the regional outburst elimination.

Frost resistance of internal curing concrete with calcined natural zeolite particles

In this paper, the frost resistance of internal curing concrete with calcined zeolite particles was studied, comparing with ordinary curing concretes. Concrete specimens with compressive strength of 50 MPa and 100 MPa were prepared. Firstly, the pore structure characteristics of the concrete specimens were tested by mercury intrusion porosimetry. Then freeze–thaw test was conducted, residual deformation, weight loss and strength loss of concrete specimens during freeze–thaw cycles were measured to investigate the frost resistance of the specimens, and water saturation degree of the specimens during freeze–thaw cycles was tested to analyze the mechanism of frost resistance. Results show that, the porosity and pore structure of concrete can be improved by prewetted zeolite particles with the development of curing age. For the same water absorption time, the water saturation of zeolite curing concrete is higher than that of ordinary curing concrete in the initial stage of freeze–thaw cycles, but the growth rate with the development of freeze thaw cycles is much slower. The frost resistance of concrete using calcined zeolite is slightly worse than that of ordinary curing concrete in early stage of freeze–thaw cycles, while it is much better in the middle and later stage.

ВИЗНАЧЕННЯ НОРМАТИВНИХ ЗНАЧЕНЬ МЕХАНІЧНИХ ПОКАЗНИКІВ ЗВ’ЯЗНИХ ҐРУНТІВ ЗА ДАНИМИ ДИНАМІЧНОГО ЗОНДУВАННЯ

In the work on the basis of analytical analysis of tabular data, both current and previous domestic regulatory documents on civil engineering, for mechanical indicators of bonded soils of natural occurrence graphic and analytical (formula) interpretation of these values in relation to the values of the dynamic probing index of Pd, MPa, and yield index IL, units, for the degree of water saturation of these soils Sr ≥ 0.8 units is given. Correlation with the value of dynamic probing of Pd, MPa allows not only to differentiate engineering and geological (geotechnical) cross-sections, more or less detailed, but also to estimate the load-bearing capacity of selected layers of bonded soils accurately enough. The theoretical analysis has shown that the values of mechanical indicators of natural bonded soils adopted in the current regulatory documents, even taking into account their structural strength, can not be directly used as a prototype to assess similar indicators of compacted technogenic soils of artificial structures in the form of embankments of hydraulic dams, road embankments or airfields. This is due to the fact that in the vast majority of cases in civil construction assessed the properties of soils in the plastic state, which tend to have a lower density of dry soil than at the border of rolling, and a mandatory condition for the use of such soils in artificial soil structures is their compliance with the requirements of the so-called standard compaction, that is, the density of dry soil there should be more than the density of dry soil at the border of rolling. These soils are in a solid state (their concentration is ≥ 85 %) and indeed (through direct contact between the soil parts) work as an elastic body and can be characterized by a modulus of elasticity with a corresponding small elastic deflection lmax and a sufficiently large design critical resistance value of R0 ≥ 0.6 MPa, which must be determined at each laboratory test of the samples before they fracture or disproportional movement of the stamp. Keywords: regulatory documents, tabular data, bonded soils, natural, mechanical properties, graphical interpretation, analytical dependencies.

Experimental study of thermomechanical effects in water-saturated limestones during their deformation

Stability control of elements of stone constructions of various structures is a prerequisite for their safe operation. The use of modern methods of non-destructive diagnostics of the stress-strain state of such constructions is an effective, and in many cases the only way to control it. Studies of thermal radiation accompanying the processes of solid bodies deformation allowed to justify and develop a method that allows to obtain non-contact information about changes in the stress-strain state in various types of geomaterials, including limestones. However, studies of the water saturation influence of rocks on the thermal radiation parameters recorded in this way are currently superficial. Taking into account the water saturation degree of rocks is necessary when monitoring the mechanical condition of stone structures that are in direct contact with water. The main purpose of this work is to study the dependences of changes in the intensity of thermal radiation from the surface of limestone samples with different humidity under conditions of uniaxial compression. The obtained results showed the expected significant decrease in the mechanical properties (uniaxial compressive strength and elastic modulus) of water-saturated samples in comparison with dry ones. At the same time, a significant increase in the intensity of thermal radiation of limestone samples subjected to compression with an increase in their water saturation was recorded, which makes it necessary to take into account the revealed regularity when identifying changes in the stress state of stone structures established according to non-contact IR diagnostics in real conditions.

Multiple ions transport and interaction in calcium silicate hydrate gel nanopores: Effects of saturation and tortuosity

The durability of cement-based materials is significantly influenced by the transport ability of multiple ions in gel nanopores of calcium silicate hydrate (C-S-H) that is directly associated with the degree of water saturation. In this study, the mechanism of ions transport in unsaturated C-S-H gel pores was revealed by the molecular dynamics simulation at the nanometre scale. The ions transport behaviour in gel pores was investigated via the establishment of different types of simulation models, which had different initial saturations, pore sizes and bending numbers of gel pores. The thickness of the electrical double layer was determined by the analysis of the distribution of ions, and the ions transport in C-S-H gel pores was affected by the electrical double layer. The percolation effect would appear in gel pores during the simulation from the dry state to saturated state, and it could promote the transport ability of ions significantly. However, it affected the extreme value of ion diffusion coefficient rather than the maximum value. Another result is that the bending numbers of gel pores would hurt the transport of ions. It is noted that the incorporation of Ca2+ will weaken the diffusion capacity of ions in the NaCl solution, while the reverse phenomenon is observed when K+ is incorporated.

Water Retention and Saturation Degree of Peat Soil in Sebangau Catchment Area, Central Kalimantan

Water is an essential factor in forming, utilization, management, and sustainability of peat soil. This study was to obtain characteristics of water retention and porosity of peat soil. Peat samples were taken from the Natural Laboratory of Peat Forest, Central Kalimantan at shallow, medium, and deep peat at 0-50cm (surface) and 50-100 cm (subsurface), while laboratory analyses carried out at Soil Laboratory, Universitas Gajahmada. The result shows that volumetric moisture content at the surface lower than subsurface, except for deep peat. The total pore for the surface was 84.67-86.98%, while subsurface layers were 83.53-86.93%. For surface layer, saturated degree (S) medium peat higher than shallow and deep peat, while for shallow subsurface peat higher than medium and deep peat. S value all pF levels of surface for medium and deep peat higher than the subsurface. Bulk density for surface was 0.094g.cm-3 (rb(wet)) and 0.22g.cm-3(rb (dry)) for shallow peat while medium peat are 0.084–0.087g.cm-3(rb(wet)) and 0.18–0.20g.cm-3(rb(dry)), deep peat 0.064–0.090g.cm-3(rb(wet)) and 0.11–0.16g.cm-3(rb(dry)). For subsurface, bulk density of medium peat are 0.094–0.107g.cm-3 (rb(wet)) and 0.16–0.20g.cm-3 (rb(dry)), deep peat are 0.067–0.090g.cm-3 (rb(wet)) and 0.10–0.17g.cm-3 (rb(wet)). The particle density of surface and subsurface for shallow peat higher than medium and deep peat, with values 0.67-0.77g.cm3, 0.61-0.66g.cm3, and 0.53-0.63g.cm3 for shallow, medium, and deep peat, respectively. Total pores for the surface layer decrease with increasing dry bulk density (R = 0.624) and particle density (R = 0.375). This fact seems to confirm a directly proportional relationship between parameters bulk and particle density with total pores.

Numerical Modeling of Water and Gas Transport in Compacted GMZ Bentonite under Constant Volume Condition

During deep geological disposal of high-level and long-lived radioactive waste, underground water erosion into buffer materials, such as bentonite, and gas production around the canister are unavoidable. Therefore, understanding water and gas migration into buffer materials is important when it comes to determining the sealing ability of engineered barriers in deep geological repositories. The main aim of our study is to provide insights into the water/gas transport in a compacted bentonite sample under constant volume conditions. The results of our study indicate that water saturation is obtained after 450 hours, which is similar to experimental results. Gas migration testing shows that the degree of water saturation in the samples is very sensitive to the gas pressure. As soon as 2 MPa or higher gas pressure was applied, the water saturation degree decreased quickly. Laboratory experiments indicate that gas breakthrough occurs at 4 MPa, with water being expelled from the downstream side. This indicates that gas pressure has a significant effect on the sealing ability of Gaomizozi (GMZ) bentonite.

Evaluation of groundwater effects on tunnel engineering in loess

Tunnels are commonly constructed in loess with a high water content or saturation degree, which can lead to large ground deformation, structural cracking, and even tunnel collapse during construction, in addition to tunnel leaks, sidewall settlement, and frost damage. A complete understanding of the distribution, source, and effects of groundwater in loess is therefore of critical importance, particularly to comprehensively consider loess landforms and material properties and tunnel design and construction practices. This paper presents a review and analysis of previous studies and 27 typical loess tunnels in China, which indicates three different types of water-rich loess surrounding rocks: natural water-rich loess (type I); excavation disturbance-induced water-rich loess (type II); and surface rainfall infiltration water-rich loess (type III). The formation mechanism, seepage field characteristics, and consequent stress and deformation characteristics of the surrounding rock are explained in detail. Key problems, strategies, solutions, and countermeasures are proposed as a helpful reference for theoretical research, design, construction, and maintenance of tunnel engineering in loess.

Deformation and pore water pressure change during static and cyclic loading with subsequent shearing on soils with different textures and matric potentials

Soil deformation on arable lands due to heavy machine traffic always results in compaction and stress dependent shearing. The deteriorated effects of compaction on soil pore functions have been often reported, but less is known about the shearing-induced deformation. To better understand the combined effect of compaction and shearing on soil deformation and pore water pressure uw, measurements were performed on repacked soils with three textures (silt loam, sandy loam, and sand) and two matric potentials (-60 hPa and -300 hPa). Soils were sheared after two types of loading (static loading and cyclic loading) with three compaction levels (50, 100, and 200 kPa). Compaction was the main stress accounting for the loss of soil void ratio e and volume, on the contrary, shearing slightly increased void ratio and volume due to particle rotation in the shear zone. At -60 hPa, soil water ratio stepwisely decreased with compaction and subsequent shearing process. The soil volume change induced by compaction and shearing resulted in an obvious increase in uw. The higher the stress levels and initial matric potential, the more prominent changes in soil deformation and uw. Compared with static loading, further decrease of soil volume and increase of uw were observed under cyclic loading. Soils pre-compacted by cyclic loading always showed high and relatively constant uw values during shearing. The results demonstrated that compaction increased uw by decreasing e and increasing the degree of water saturation while shearing enhanced these effects by means of rearranging particles and blocking the water-filled pores. Therefore, after shearing, soil pore functions were further deteriorated compared with the initial state before compaction.