Consolidation Of Soft Clay Research Articles

One-dimensional piecewise-linear large-strain consolidation model for soft clay with anisotropic creep behaviour

Viscous behaviour is a significant characteristic of soil, and to accurately capture this behaviour, a piecewise-linear model called ACLC has been developed specifically for modelling one-dimensional large-strain consolidation of soft clay. ACLC takes into account both the long-term deformation and anisotropy of the soil. Furthermore, it incorporates various factors such as soil heterogeneity, self-weight, time-dependent loading, vertical flows, and seepage force. In ACLC, the settlement of the soil layer is a result of both the net outflow of fluid from the soil element and the development of soil creep. To describe the creep behaviour of the soil, ACLC employs two yield surfaces: the Current State Surface (CSS) and the Normal Consolidation Surface (NCS). The creep rates are calculated based on the associated flow rule. To ensure the accuracy of ACLC, it is validated using the enhanced CS2 model, oedometer tests conducted on Xiaoshan soft clay, and observed data from the Murro test embankment. Finally, the influence of ACLC parameters on the consolidation behaviour of clay is thoroughly investigated. This analysis helps to understand the role of these parameters and their impact on the overall consolidation process.

Effect of smear zone on the consolidation characteristics under radial drainage

Vertical drains installed in soft clay deposits enhance the rate of consolidation in preloading projects. Using a mandrel to install the prefabricated vertical drains, its insertion and withdrawal will result in the remoulding of the soil zone surrounding it, called the smear zone. The extent of the smear zone is an important parameter that characterises the smearing effect. This paper describes this effect in terms of smear ratio (i.e. the ratio of the diameter of smear zone ds to the diameter of drain, dw) on the consolidation characteristics of soil with radial drainage. A series of radial consolidation tests with a predetermined smear zone in a model unit cell was conducted by varying the diameter of the smear zone. The experimental results show that beyond a smear ratio of 4, the soil behaves as if it is in a fully remoulded condition. The results were compared with some of the theoretical approaches reported in the literature. The analytical solution that predicts the time–settlement curve in a better way is identified. Also, it is observed that the gain in undrained shear strength due to the consolidation of soft clay decreases with the increase in the diameter of the smear.

Influence of periodic cyclic loading and rest period on soft clay consolidation

Railways are often subjected to periodic cyclic loading and intermittent rest periods. Excessive consolidation settlements can affect the performance of railway tracks built on the soft subgrade. The consolidation behaviour under railway loading conditions with rest periods has not been evaluated thoroughly. In this study, laboratory testing was conducted to investigate the influence of periodic cyclic loading and rest periods on the consolidation of Holocene soft clay from Ballina NSW. The specimens were subjected to a loading frequency of 1 Hz for 54 h with multiple rest periods. The recorded settlements and excess pore-water pressures (EPWP) during cyclic consolidation were employed to determine the corresponding hydraulic gradient, void ratio, resilient (dynamic) modulus and damping ratio. The settlement and accumulated EPWP can be observed during cyclic loading. In contrast, settlements do not occur within a rest period, despite the rapidly dissipating EPWP at the start of a given rest period. The maximum EPWP and settlements decrease as the number of resting period increases. An analytical model capturing the effect of cyclic loading and rest period is proposed where the unique relationships between the hydraulic gradient and the flow rate are established.

Modeling consolidation of soft clay by developing a fractional differential constitutive model in conjunction with an intelligent displacement inversion method.

Studying the constitutive relation of soft clays is of critical importance for fundamentally understanding their complex consolidation behavior. This study proposes a fractional differential constitutive model in conjunction with an intelligent displacement inversion method based on the classic particle swarm optimization for modeling the deformation behavior of soft clay. The model considered the rheological properties of soft clay at different consolidation stages. In addition, statistical adaptive dynamic particle swarm optimization-least squares support vector machines were implemented to identify the model parameters efficiently. The accuracy and effectiveness of the model were validated using available experimental results. Finally, the application results showed that the proposed model could efficiently simulate coupling properties of soft clay’s primary and secondary consolidations.

Consolidation of soft clay by cyclic and progressive electroosmosis using electrokinetic geosynthetics

Consolidation of soft clay by cyclic and progressive electroosmosis using electrokinetic geosynthetics

Reducing settlement of soft clay using different grouting materials

Abstract Different injection material types were tried in the injection of soft clay, such as lime (L), silica fume (SF), and leycobond-h (LH). In this study, experiments were made to study the effect of injection on soft clay consolidation settlement. A sample of natural soft clayey soil was investigated in the laboratory and the sample was injected with each of the grout materials used, L, SF, L + SF, and L + SF + LH. A 20 cm3 of each slurry grout was conducted into the soil, which was compacted in California Bearing Ratio (CBR) mold and cured for 7 days, and then the sample was loaded to 80 N load by a circular steel footing 60 mm in diameter. The settlement was recorded. The sample of each slurry grout, which provided minimum settlement, was chosen (L + SF + LH). To reduce soft clay settlement before and after footing construction, four cases were investigated. The impact of injection hole spacing and grout depth was studied. It was discovered that injecting a slurry of (L + SF + LH) into the soft clay beneath or surrounding the footing increased bearing capacity by 5–88%. Due to the shape of shear failure of the soft clay around the footing, grouting near the footing at a distance of 0.5 diameter of the footing is more effective than grouting at a distance of 1.0 diameter of the footing, and grouting near the footing at a distance of 0.5 diameter of the footing is more effective than grouting at a distance of 1.0 diameter of the footing.

Numerical analysis of one-dimensional consolidation of soft clays subjected to cyclic loading and non-Darcian flow

This paper aims in understanding the impact of the cyclic load on the one-dimensional consolidation of soft clays subjected to non-Darcian fluid flow. Three different cyclic loadings, namely, trapezoidal, triangular, and haversine, are considered with and without the rest period. The analyses are carried out using the fully implicit scheme of the finite difference method. The hydraulic boundary surfaces are considered either to be pervious or impervious. Unlike for conventional constant loading, negative excess pore water pressure develops during the unloading phase of cyclic load. With the continuation of load application and load removal, the soil reaches a certain equilibrium stage beyond which soil deformation remains confined within a specific elastic range. To verify the impact of flow law on the progress of cyclic-load-induced consolidation, the relevant curves are drawn for a few specific spatial points as well as for the entire layer. The deviation of the curves generated from the Darcian and non-Darcian flow is markedly visible, especially after the attainment of steady-state. The existence of a critical rest period, at which the chosen flow law influences elastic rebound most, is established.

Study on the Effect of Low-Temperature Anode Filled with FeCl3 Solution on Electro-Osmotic Reinforcement of Soft Clay

In order to study the effect of FeCl3 solution on the current, soil pH value, drainage volume, anode potential difference, energy consumption, and resistivity of electro-osmosis consolidation of soft clay with different moisture contents under a low temperature environment, we carried out 31 sets of model tests under different working conditions by using a self-made device and an improved Miller Soil Box. The test results showed that, under the same conditions, although the energy consumption coefficient of electro-osmosis had little change in the low temperature environment, the current, displacement, and electro-osmosis coefficient were obviously reduced, and the resistivity and anode potential difference was greatly increased, indicating that the low temperature environment reduces the efficiency of electro-osmosis of soft clay. After the anode was filled with FeCl3 solution, the current, water displacement, and electro-osmotic coefficient were clearly increased; the anode potential difference and electro-osmotic energy consumption coefficient were clearly decreased; and the resistivity was reduced to a certain extent, which indicates that the anode filled with FeCl3 solution is very beneficial in improving electro-osmotic efficiency and in saving energy. The electro-osmotic discharge after the anode filled with FeCl3 solution at low temperature was clearly higher than that after the anode was filled water at normal temperature, indicating that the effect of the anode filled with FeCl3 solution on electro-osmosis is greater than that of temperature. In the process of electro-osmosis of soft clay, the better the electro-osmosis effect, the smaller the pH value of the anode and the larger the pH value of the cathode. The pH value of the cathode and anode can be used as one of the indexes to reflect the electro-osmosis effect.

The effect of temperature on some engineering and consolidation properties of soft soil

This article defines the effect of temperature on some engineering and consolidation properties of soft soil. The purpose of this research, therefore, was to determine the technical characteristics of soft clay consolidation behavior, specifically in terms of temperature influence on varying values of soil established mechanical parameters, including soft soil compression index (Cc), swelling index (Cs), volume change coefficient (mv), consolidation coefficient (Cv), and the permeability coefficient (k). In this analysis, the use of soft clay in an undisturbed condition was sourced from a swampy location in South Kalimantan Province, Indonesia. Also, the temperatures applied to the specimens were 22o C, 40o C, 60o C, and 70o C. The results showed the influence of temperature modifications on soil compressibility, where extensive heat was responsible for abundant soil compressibility. In addition, the associated parameters, termed soil compression index value (Cc), consolidation coefficient (Cv), and the swelling index (Cs), observed an increase by 3%, 33%, and 22%, respectively. Furthermore, existence of high temperatures limited the unstable soil volume, where the volume change coefficient (mV) tends to decrease by 3%. Also, varying temperatures essentially altered soil permeability, where the seepage properties of soft clay showed the tendency to increase by 32%, with rising soil temperature.

Study of Strength Parameter for Different Drain Material using PVD for Consolidation of Soft Clay by Radial Flow

Study of Strength Parameter for Different Drain Material using PVD for Consolidation of Soft Clay by Radial Flow - written by Ruchi Shrivastava , Dr. A. V. Shroff published on 2020/09/30 download full article with reference data and citations

Effect of Stone Columns on the Behaviour of Single Pile in Soft Clay Soil

Soft clay is consolidated upon any slight change in the effective stress. Consolidation and settlement of soft clay surrounding a pile usually drag the pile down ward. The down drag movement adds additional loads to the already loaded pile. This force is expressed as a negative skin friction. Negative skin friction starts from the pile head to a neutral depth depending on the interface properties. This depth is referred to as the neutral plan. This paper presents a study on the effect of stone columns on the behaviour of piles during consolidation of soft clay soil. For this goal the experimental tests were done to study effect of stone columns on the behaviour of single pile embedded in soft clay. The study concluded that the neutral plane is located closer to the end of the pile as the end bearing increases. Stone columns are considered one of methods used to reduce the settlement of soft clay soil, and helps to speed up the rate of consolidation by shorting the length of drainage path within the soft clay layers, and then decrease the relative displacement between the pile and the surrounding soft soils. The use of stone columns reduced the amount of negative friction developed along the pile depth.

Performance and Energy Consumption of Electric Vertical Drains Used in Soft Clay Consolidation

With the advent of conducting polymers, electric vertical drains (EVDs) have been employed as electrodes in a small number of electro-osmosis trials. The design philosophy of EVDs is based on corrosion resistance, electric conduction, and drainage abilities. This paper summarizes the laboratory investigations of the electro-osmosis methods with different electrodes in kaolin clay. The electro-osmosis drainage time of EVDs was longer than the metal electrodes, which is beneficial to the strengthening effect. The filter membrane and drainage path of EVDs confers an obvious improvement on the drainage effect. The energy consumption of electro-osmosis by EVD is acceptable.

One-dimensional nonlinear consolidation behavior of structured soft clay under time-dependent loading

This research investigated the nonlinear compressibility, permeability, the yielding due to structural degradation and their effects on consolidation behavior of structured soft soils. Based on oedometer and hydraulic conductivity test results of natural and reconstituted soft clays, linear log (1+e) ~ log sigma\'v and log (1+e) ~ log kv relationships were developed to capture the variations in compressibility and permeability, and the yield stress ratio (YSR) was introduced to characterize the soil structure of natural soft clay. Semi-analytical solutions for one-dimensional consolidation of soft clay under time-dependent loading incorporating the effects of soil nonlinearity and soil structure were proposed. The semi-analytical solutions were verified against field measurements of a well-documented test embankment and they can give better accuracy in prediction of excess pore pressure compared to the predictions using the existing analytical solutions. Additionally, parametric studies were conducted to analyze the effects of YSR, compression index (lambda_r and lambda_c), and permeability index (eta_k) on the consolidation behavior of structured soft clays. The magnitude of the difference between degree of consolidation based on excess pore pressure (Up) and that based on strain (Us) depends on YSR. The parameter lamda_c/eta_k plays a significant role in predicting consolidation behavior.

Effect of electrochemical treatment on consolidation of soft clay

In this study, a method of electrochemical consolidation is applied. This method utilizes electro-osmosis, which is an effective ground improvement technique for soft clays, and soil treatment using lime, which is the oldest traditional soil stabilizer. The mechanism of lime treatment for soil involves cation exchange, which leads to the flocculation and agglomeration. Five representative laboratory tests-an electro-osmotic test and four electrochemical tests with various proportions of lime-were performed on dredged marine clay. The objectives of this study are to investigate the effect of electrochemical treatment and to determine the optimum dose for optimal consolidation performance of dredged marine clay. The results show that a better consolidation effect was achieved in terms of current, temperature, and vane shear strength by using electrochemical treatment. The best results were observed for the electrochemical test using 4% lime content.

Reassessment of Isotaches Compression Concept and Isotaches Consolidation Models

AbstractA substantial body of laboratory and field observations on compression and consolidation of soft clay and silt deposits as well as organic soils, suggest a soil behavior according to Hypoth...

One-dimensional large-strain consolidation of soft clay with non-Darcian flow and nonlinear compression and permeability of soil

Geometrical nonlinearity of the soft soil and the deviation of water flow in the soft clay from Darcy’s law have been well recognized in practice. However, the theory of consolidation, which can account for both the geometrical nonlinearity and the non-Darcian flow, has not been reported so far. In this contribution, a model for the consolidation of soft clay which can allow for these two factors simultaneously is proposed. Utilizing the finite difference method, the numerical model for this problem is developed. With the numerical model, the effects of the geometrical nonlinearity and the non-Darcian flow on the consolidation of the soft soil are investigated. The results show that when the self-weight stress is calculated by the same method, the rate of the non-Darcian consolidation for the large-strain case is larger than that for the small-strain case, but the difference between them is limited. However, the difference between the consolidation rates caused by the non-Darcian and Darcian flows is significant. Therefore, when the geometrical nonlinearity of the soft clay is considered in calculating the consolidation settlement, due to the complexity of the large-strain assumption, the small-strain assumption can be used to replace it if the self-weight stress for the small-strain assumption is calculated by considering its sedimentation. However, due to the aforementioned large difference between the consolidation rates with consideration of the non-Darcian flow in soft clay or not, it is better to consider the non-Darcian flow law for both the small and large stain assumptions.

Influence of Soluble Salt on Electro-Osmotic Consolidation of Soft Clay

A series of electro-osmotic consolidation laboratory tests was conducted to investigate the influence of soluble salt on the electro-osmotic consolidation of soft clay. Remolded soil samples with different salinities of KCl, NaCl, and CaCl2 were tested in the modified electro-osmosis oedometer experimental system. Final water content, vane shear strength, and pH value of test soil samples were analyzed by monitoring the changes in the electric current, volume of drainage, and vertical settlement during the tests. The results showed that addition of soluble salts can improve the electro-osmotic consolidation of soft clay. However, excessive salinity will reduce the efficiency of electro-osmotic consolidation. The optimal salinity of the soluble salt was determined for each type of salt. Moreover, an improved consolidation efficiency can be achieved by using CaCl2 rather than KCl or NaCl.

Numerical Analysis on Consolidation of Soft Clay by Sand Drain with Heat Injection

Numerical Analysis on Consolidation of Soft Clay by Sand Drain with Heat Injection

Experimental and numerical investigations into hydraulic behaviour of coir fibre drain

Over many decades, natural fibre bundles have been widely used for drainage and filtration applications because of their favourable hydraulic conductivity and abundance in Asian countries. In recent times, natural (biodegradable) coir and jute drains, which are environmentally friendly, have been considered in lieu of conventional geosynthetic wick drains for soft clay consolidation in Australian coastal regions. However, there is a lack of a computational framework to predict the hydraulic behaviour of fibre drains on the basis of micromechanical (fabric) characteristics. Employing computational fluid dynamics (CFD) coupled with the discrete element method (DEM) to model the hydraulic behaviour of fibrous materials has shown promise in an earlier 2016 study by Nguyen and Indraratna, which considered an idealized parallel arrangement of fibres for simplicity. This paper aims to broaden the application of the coupled CFD–DEM technique to real fibres (coconut coir) considering both nontwisted and twisted fibre bundles that have more complex porous structure. The hydraulic conductivity determined from the numerical approach is validated with the experimental results, and also compared with the analytical prediction based on the conventional Kozeny–Carmen (KC) approach. The current study shows that the CFD–DEM technique can capture well the fluid flow characteristics of a nonuniform fibrous structure, including dense twisted coir bundles.

Fractal properties of filter membrane for silt clogging evaluation on PVD improved soft clays

Soft clays are characterized by having large fine particle content, and prefabricated vertical drains (PVDs) are used to accelerate the consolidation of soft clays to improve foundation strength. During consolidation, the fine particles move and accumulate around the polyester filter membrane, which causes silt clogging of the PVDs, thereby reducing consolidation efficiency. The microstructure images of the polyester filter membrane before and after clogging were collected by applying electron microscope technology. The computer program processes the micro images, including preprocessing, binary threshold segmentation, pore distribution, and fractal properties analysis. Results show that the new fiber lines are clear, with no junk in the space and a certain sense of hierarchy. The clogged filter membrane is blurred, with black shadow lumps or sand-sized dots. The fractal dimension of clogged filter membrane is increased, particularly in the sand cushion. Thus, analyzing the fractal properties of the filter membrane is proposed as a new quantitative method for silt clogging on PVD-improved soft clays.