Influence Of Initial Water Content Research Articles

A new framework for evaluating the virgin compression curves of reconstituted clays at different initial water contents

The influence of initial water content on the virgin compression of reconstituted clays is a topic of great importance. This study introduces a novel perspective based on the concept of intrinsic compression. It is demonstrated that the virgin compression curves of the reconstituted clays are similar in shape to the intrinsic compression line and can be obtained through vertical shifting and stretching. Building upon this concept, the intrinsic compression line is further extended to the compression curve cluster, enabling a direct evaluation of the influence of initial water content. The validity of the compression curve cluster is verified using independent data from the literature as well as data collected by our research team. In addition, a comparison with other relevant theories further underscores the superiority of the proposed framework.

Models for Considering the Thermo-Hydro-Mechanical-Chemo Effects on Soil–Water Characteristic Curves

The soil–water characteristic curve (SWCC) is widely used as a tool in geotechnical, geo-environmental, hydrology, and soil science fields for predicting and interpreting hydro-mechanical behaviors of unsaturated soils. Several previous studies focused on investigating the influence of initial water content, stress history, temperature, and salt content on the SWCC behavior. However, there is still limited understanding to be gained from the literature on how we can systematically incorporate the influence of complex thermo-hydro-mechanical-chemo (THMC) effects into interpreting and predicting the behavior of unsaturated soils. To address that knowledge gap, in this study, the coupled influence of temperature, initial stress state, initial density, soil structure, and chemical solution effects was modeled using established SWCC equations from the literature. The methodology for incorporating the coupled effects of these influential factors is presented herein. Furthermore, we evaluated the SWCC models proposed in this study, enabling us to provide a comprehensive discussion of their strengths and limitations, using the published SWCC data from the literature. The developments outlined in this paper contribute toward facilitating a rigorous approach for analyzing the THMC behaviors of unsaturated soils.

Experimental study on tensile strength of warm frozen soil based on hydraulic fracturing method

Tensile strength is one of the important parameters of frozen soil mechanics, which is widely used in engineering design of frozen soil and theoretical research of frost heave. At present, the research on tensile strength of frozen soil mainly focuses on low-temperature frozen soil, while that of warm frozen soil is less studied, thus limiting scientific evaluation of the tensile strength characteristics of warm frozen soil. In order to enrich the knowledge of tensile strength of warm frozen soil, the tensile strength experiments of silt clay from the Tibetan Plateau are carried out under various temperatures higher than −2 °C using the hydraulic fracturing method (HFM). Our results show that HFM can enable a reliable evaluation of the tensile strength of warm frozen soil, and the relationship between the tensile strength of warm frozen soil and negative temperature can be described by a power function. Compared with the results of uniaxial tension method (UTM) and radial splitting method (RSM), the feasibility of HFM can be regarded as an indirect tensile method in determining the tensile strength of frozen soil, and the suggestion for correcting the test results of indirect tensile method is given. In addition, the mechanism behind the influence of initial water content and temperature on tensile strength of warm frozen soil is analysed. Our results provide a new approach for researchers to analyse the tensile strength of warm frozen soil, thus can benefit the development of frost heave theory, and can reveal the influence of initial water content and temperature on the tensile strength of warm frozen soil.

Coupled hydro-mechanical behaviour of a Kaolin Clay in the context of the geothermal use of geotechnical structures

An experimental study regarding the hydro-mechanical behaviour of a Malaysian Kaolin is presented. Strain rate-controlled oedometer tests have been conducted on compacted samples. The influence of initial water content on the pore-size distribution (PSD) of compacted samples was investigated by Mercury Intrusion Porosimetry (MIP) tests. The drying path of the soil-water characteristic curve was experimentally determined for initially compacted samples and slurry samples. The preconsolidation stress was found to increase with increase in initial dry density and with decrease in initial water content. The compression curves merge into a single line, as soon as they have reached full saturation during loading. Samples at the dry side of Proctor water content showed a bi-modal PSD, whereas a mono-modal PSD was found for Proctor water content and at the wet side. The different initial compaction states of the samples were getting reflected in the drying SWCC until a suction of about 2 MPa, beyond which the drying paths were found to be identical.

Extreme low-temperature freezing process and characteristic curve of icy lunar regolith simulant

Water distribution uniformity is an important control criterion for icy lunar regolith samples during ground simulations and is easily influenced by the sample freezing process. However, the freezing process and characteristics of icy lunar regolith are rarely studied. Therefore, to address this issue, simulated samples of icy lunar regolith with two raw material ratios, various water contents and dry densities were prepared in this study, and the unfrozen water contents of samples at different freezing temperatures were tested by nuclear magnetic resonance instrument. The freezing process of icy lunar regolith from 20 °C to −192.8 °C was analyzed based on the variation of the T2 spectrum, and the influence of initial water content and dry density of the samples on the variation rules of unfrozen water content with temperature was discussed. The results show that the freezing process includes the subcooling stage, the fast freezing stage, the slow freezing stage and the stable freezing stage. Below −80 °C, the unfrozen water content in both unsaturated and saturated samples reaches a very small order of magnitude. However, at −190 °C, unfrozen water is still present in the pores (<1 nm) of the samples. Unfrozen water can be divided into bound water, capillary water and gravity water. Unfrozen water in samples with the water content of 5 wt% and 10 wt% is mainly bound water, and water migration occurs during freezing. The solid ice formed during the freezing process of saturated samples has similar adsorption or capillary effect on unfrozen water to rock particles. A lower dry density of the sample means a higher initial freezing temperature and can more significantly promote the formation of capillary and gravity water. Finally, a new freezing characteristic model was constructed based on the linear relationship between particle and pore radii. The model well predicts the four variation stages of unfrozen water content with temperature from room temperature (20 °C) to extreme low temperature (−190 °C). And the applicability of the model was verified by quantifying the available surface permafrost data.

Study on the Influence of Initial Water Content on One-Dimensional Freezing Process of the Qinghai-Tibet Silty Clay by Using Digital Image Technology

The water content of the foundation soil will change dynamically as a result of rainfall, snowfall, and ground surface evaporation, leading to a significant change in frost heave properties of the foundation soil in cold regions. One-dimensional freezing tests of the Qinghai-Tibet silty clay with three different initial water contents in an open system were carried out using CCD image acquisition technology and computed tomography (CT) scanning technology in combination with the traditional soil freeze-thaw test system. The heat conduct process, cryostructure formation, frost heave development, unfrozen zone consolidation, ice segregation, water migration, and redistribution during soil freezing are studied comprehensively. The results show that increasing the sample’s initial water content will lead to the increase of frozen depth, ladder-like cryostructures in vertical sections, more structural polygons in horizontal sections, and also more obvious ice lens segregation, unfrozen zone consolidation, and water migration during the freezing of soil samples.

Compression behavior and structure of undisturbed Q2 loess under wet-dry cycles

In the Loess Plateau of China, the undisturbed Q2 loess is in a state of wet-dry cycles due to seasonal rainfall and groundwater level fluctuations. The root cause of large deformation and poor stability of engineering foundation caused by wet-dry cycles or load compression lies in the distinctive structure of loess. In this paper, the effects of wet-dry cycles and initial water content on the compression deformation and compression coefficient of undisturbed Q2 loess were analyzed. Based on the structural parameter at the macro-level and the microscopic morphology and pore size distribution at the micro-level, the effects of wet-dry cycles and initial water content on the structure were analyzed from two aspects, and the influence mechanism was discussed. Meanwhile, based on the relationship between microstructure and unsaturation, the impact of wet-dry cycles on the soil–water characteristic curve was determined. The results show that the wet-dry cycles and initial water content were positively correlated with the compression deformation and compression coefficient of the undisturbed Q2 loess, but negatively correlated with the structural parameter and water retention. These parameters were stable under the 2 wet-dry cycles. With the increase in initial water content, the sensitivity of wet-dry cycles to the compression deformation, structural parameter, and water retention gradually decreased. The sensitivity of initial water content to the compression deformation, structural parameter, and water retention gradually reduced with the increasing wet-dry cycles. Moreover, the influence mechanism of wet-dry cycles and initial water content on the macro-parameters and structure was mainly weakening the particle cementation strength. With the increase in initial water content, the decreasing range of the inter-aggregate cementation strength and intra-aggregate cementation strength under the influence of wet-dry cycles decreased. With the increase in wet-dry cycles, the decreasing range of the inter-aggregate cementation strength and intra-aggregate cementation strength under the influence of initial water content decreased.

Tensile Strength of Compacted Clays during Desiccation under Elevated Temperatures

Abstract The tensile strength of unsaturated soils is a critical factor controlling the initiation and propagation of desiccation cracks, which can threaten the structural integrity of natural and man-made earthen structures and slopes. Several engineering applications involve unsaturated soils subjected to elevated temperatures (e.g., earthen structure-atmospheric interaction under prolonged droughts, nuclear water disposal, energy piles, ground source heat pumps). Although the temperature dependency of desiccation cracking is demonstrated in the literature, critical gaps remain regarding the characterization of the tensile strength under elevated temperatures. The main objective of this study is to investigate the effect of elevated temperature on the tensile strength of unsaturated clays during desiccation. To accomplish this objective, a novel testing setup that can be used to directly determine soil tensile strength during desiccation was placed in an oven to measure the tensile strength of two compacted clayey soils of medium to high plasticity under different temperatures ranging from 20°C to 60°C. The clays are compacted at 95 % of their respective maximum dry unit weights over a range of water contents from dry to wet of optimum to investigate the influence of initial water content on tensile strength. The results demonstrated that the tensile strength decreased with increasing temperature. At the optimum water content, a tensile strength reduction of 36 % and 27 % in the highly plastic clay and the medium plastic clay, respectively, was observed when the temperature increased from 20°C to 60°C. Additionally, for the partially saturated condition, the initial water content affected the tensile strength significantly. Temperature-induced changes in key factors contributing to the tensile strength of unsaturated clays are discussed to provide further insight into tensile strength of clays at elevated temperatures. The findings of this study can contribute toward a more realistic analysis and design of earthen structures subjected to elevated temperatures.

Influence of initial water content of dredged slurry on clogging effect under vacuum preloading

Influence of initial water content of dredged slurry on clogging effect under vacuum preloading

Characterizing saturation state of loess using P-wave velocity

A conventional approach to characterize the degree of saturation of soils uses the pore pressure parameter, also known as B-value in laboratory experiments. Given a recent advance that the P-wave velocity was derived as a function of the B-value with progressive saturation based on the poroelasticity theory, it sheds a light on applicability of the P-wave velocity to evaluate saturation of soils in an effective manner. Yet, previous studies in this regard often focus on granular materials, the feasibility of using the relationship for cohesive soils, such as loess, was less extensively studied and remained poorly understood. This paper presents an experimental study on the P-wave velocity of loess using a pair of piezoceramic extender elements at a sequence of saturation states. Moist tamping method was used to prepare loess samples of different water contents (5% and 14%), and the influence of initial water content on the relationship between the P-wave velocity and the B-value was examined. It was found that, in general, as the B-value increases, the P-wave arrives earlier for the loess specimen having a lower initial water content (5%). Though the P-wave velocity increases with the B-value, that is approximately in line with theoretical predictions, departures from predictions were observable at higher B-values. A relevant hypothesis was given that attributed the observed discrepancies to the local variation of pore connections and the associated distribution of air bubbles in the specimen. Correspondently, numerical evidences were also provided by using the program FLAC3D.

Influence of initial water content and strain rate on remolded yield stress in marine clay

Fifteen constant rate of strain consolidation tests were performed on Wenzhou clay specimens under various strain rates and initial water contents using an advanced oedometer to investigate the remolded yield stress during compression. The results for different initial water contents indicated that the remolded clay compression curves could be expressed by a unique trend line using the void index. The porosity parameter was proposed based on existing strain rate parameters to qualitatively describe the relationship between porosity and remolded yield stress. It was observed that the greater the strain rate, the smaller the strain under the same vertical effective stress.

Study on sedimentation characteristics of soft clay

There are large areas of soft clay distributed in coastal areas of China, which are often used as raw materials for hydraulic fill engineering in recent years, and its sedimentation characteristics have attracted more and more attention. In this paper, the influence of initial water content on the sedimentation characteristics of soft clay is studied through the experiment. The results show that: (1) the sedimentation process of soft clay can be divided into two stages: sedimentation stage and self weight consolidation stage. The sedimentation stage has a short time, and the soil property index tends to be stable quickly; the self weight consolidation stage is very slow, and the soil property index almost has no change; (2) the larger the initial water content of soft clay, the greater the sedimentation rate and the faster the sedimentation; (3) the higher the initial water content, the faster the sedimentation, the higher the water content and the void ratio, the smaller the density.

Influence of initial water content on unsaturated shear strength of compacted GaoMiaoZi (GMZ) bentonite

This paper presents an experimental study on the influence of initial water content on unsaturated shear strength of compacted bentonite. Isotropic loading and triaxial shear tests were conducted on compacted GaoMiaoZi (GMZ) bentonite specimens with different initial water contents. Isotropic loading test and triaxial shear test results show that the compression index increases and yield stress decreases with increasing water content, while the swelling index stays constant. For normally consolidated and lightly overconsolidated bentonite, unsaturated shear strength can be described by the critical state line. For highly overconsolidated bentonite, unsaturated shear strength can be described by the Hvorslev surface. The critical state line and Hvorslev surface are found to be linear for the specimens with different water contents. The critical state stress ratio and the Hvorslev surface parameters are found to decrease with an increase in water content of the bentonite studied.

Study on fluidity and strength of dredged sludge under water curing condition

Dredged sludge can be used in engineering by treating with flowing solidification method underwater, but the flow solidification characteristics of dredged sludge in underwater curing condition are not clear. The influence of initial water content, cement content and curing age on the fluidity and strength of solidified sludge was discussed through laboratory tests. The results show that the strength of solidified sludge under water curing situation increase linearly with cement content, decreases linearly with the initial water content, and increases logarithmically with the curing age. The relationship of unconfined compressive strength with liquid limit and initial water content for dredged sludge at 28 days curing age was proposed and verified, which provides an important basis for field application and strength prediction of flow solidification treatment.

MODELING OF THE KINETICS OF CRYOGENIC FREEZING OF LIMA BEAN SEEDS AS A FUNCTION OF INITIAL WATER CONTENT

ABSTRACT Cryopreservation is a technique used to preserve genetic material at ultra-low temperatures in cryogenic germplasm banks. In order to enable the cryopreservation of a seed, it is necessary to study its appropriate freezing temperature and its water content, because seeds reach maximum physiological quality with high water contents, and they tolerate drying when they are orthodox seeds, but they may not tolerate cryopreservation. Therefore, the objective of this study was to analyze the influence of initial water content (50 to 10% wet basis) on the kinetic behavior of the lima bean seed at the temperature of −150 °C, in addition to determining changes in its physiological quality (germination and vigor) when cryopreserved (−150 °C) for 30 days with the variation of initial water contents (50 to 10% wet basis). For this purpose, changes in lima bean size (length, width, and thickness), sphere-equivalent radius and volume, and kinetics of seed cryopreservation as a function of its water content. The Fourier model and the Cavalcanti-Mata & Duarte models I and II were used for cryopreservation modeling, in addition to proposing a new model for cryopreservation kinetics in which water content determines the kinetic behavior. The conclusion was that the water content of 10% wb should be used for the lima bean seed cryopreservation since its physiological quality was not affected by cryopreservation at −150 °C. The model that best represents the experimental data is Cavalcanti Mata & Duarte Model II.

Influence of initial water content of aggregates on the compressive strength and the shrinkage of High Performance Concretes

The time-dependent deformations of concretes, particularly in the case of high performance concrete (HPC) must be taken into account precisely when measurement of civil engineering works. theses deformations is essential for predicting the deflections, the stress distribution in statically indeterminate structures and the loss of pre-stressing force in elements of pre-stressed concrete. However, the experience shows a certain dispersion of values of instantaneous and delayed deformations measured and some significant differences with the values calculated using the building codes. The objective of the present paper focuses on the parameter which is not taken into account in building codes, which could causes the inaccuracies of their predictions: the initial water content of aggregates. The experimental program includes a comparative study of the mechanical behaviours (instantaneous deformations and shrinkage) of HPC with the same basic formulation (water cement ratio, volume of paste), differing principally in the initial water content of aggregates. The experimental results show that HPC made with wet aggregates has a higher resistance than others (dry aggregates). The pre-saturated aggregates would be a water reservoir in which the dough could slow the self-drying due to hydration in the capillary pores at the level of the Interfacial Transition Zone (ITZ). This would increase the amount of hydrates and improve the mechanical behaviour of this interface through better adhesion and less porosity. If the evolution of shrinkage of HPC with wet or dry aggregates can be distinct during the first months, the effect of this formulation parameter is not clear since it differs according to the type of aggregate. Moreover, in the long term, convergent shrinkage shows that this influence becomes insignificant. The comparisons with estimations of Eurocode 2 model were also performed and showed significant differences with the experimental values.

Influence of initial water content of aggregates on the compressive strength and the shrinkage of High Performance Concretes

Influence of initial water content of aggregates on the compressive strength and the shrinkage of High Performance Concretes

Pengaruh Kadar Air Awal Dan Surcharge Pressure Pada Uji Karakteristik Pengembangan Tanah Ekspansif

Expansive soils experience volumetric changes due to water content changes. These volumetric changes cause swell and shrink movement in soils, which in turn will inflict severe damage to structures built above them. A Proper understanding of how the expansive soil behaves during the wetting/drying process is essential for assessing the mitigation action of expansive soil hazard and design suitable foundation. The structures that build above expansive soil bed are susceptible to heave and to withstand swell pressure, thus the swell pressure must be considered in the design. This study focuses on swelling properties of two expansive clay from Ngawi, East Java and Wates, Yogyakarta. Laboratory test on disturbed samples is used to identified and to measured swelling properties. A series of swelling test was performed under constant soil dry density. The influence of initial water content and surcharge pressure on swelling properties (i.e swell percent and swell pressure) of compacted samples were investigated. The swelling properties test used ASTM standard 4546-03 method B. It was found that the lower initial water content the higher the swell percent, but the swell pressure seems not to be affected by initial water content. At the same initial water content, swell percent decrease with the increase of surcharge pressure, but swell pressure remains unchanged.

Permeability of the Mixture of Fine Grained Soil and Fly Ash from Fluidized Bed Combustion

Abstract Based on known correlations permeability was calculated for the mixtures containing various proportions of selected FBC fly ash, Speswhite kaolin and lime. The influence of initial water content of the mixtures was also considered. The study was limited to the first four weeks of curing time. Results of calculations were discussed on the background of previously obtained observations for mixtures of tested materials.

Influences of Initial Water Content and Roughness on Skin Friction of Piles Using FBG Technique

AbstractA series of pullout tests were conducted on a model pile in a soil with different initial water contents and different pile surface roughnesses to study their influences on pile skin friction. To measure axial strains and skin friction of the pile, fiber Bragg grating (FBG) strain sensors were used. Data were collected during the pullout tests and are analyzed in this paper. Test results indicate that the skin friction and axial strain of the model piles decrease with the initial water content of the soil but increase with the degree of surface roughness of the piles. The axial strain induced in the upper segment of the tested pile is considerably greater than that in the bottom segment of the pile. In addition, the skin friction is distributed nonlinearly along the length of the model piles.