Consolidation Characteristics Of Clay Research Articles

Laboratory study on the spacing effect of vertical drains on the consolidation characteristics of clay

Sand drains are extensively utilized to fasten the consolidation rate, especially in soft clay deposits. However, due to the scarcity of sand, it should be substituted with some cost-effective material. In view of this, in the current investigation, along with sand, waste materials like rice husk ash, coir pith, fly ash, and quarry dust were used as drain materials. The consolidation test was performed using Kuttanad clay, filled in a mould of 15 cm diameter and 10 cm height, allowing single drainage. A triangular pattern of three drain system was used in the study. A parametric study on the effect of the spacing of the drain on consolidation characteristics was investigated by varying the spacing/diameter ratio (s/d ratio). It was observed that the consolidation rate is more for coir pith and quarry dust drains compared to rice husk ash and fly ash drain used in the study. The consolidation rate reduces with the increase in the spacing of the drain. For achieving a particular consolidation rate, the required drain spacing has to be known. Correlations were developed to predict the spacing between the drains for attaining a particular coefficient of consolidation.

Strength and consolidation properties of clay modified by nano bentonite

Nano bentonite is a new kind of soil modification material, which can effectively improve the physical and mechanical properties of clay. The development of new soil modification technology has been a research hotspot in geological engineering, geotechnical engineering and road engineering. The purpose of this study is to test and analyze the strength and consolidation characteristics of clay modified by nano bentonite, and to explore the new clay materials applied in modern geological engineering. In this study, an installation test was carried out on the preparation of nano bentonite, and the compressive condition of the bentonite was observed. After that, the viscosity strength of nano bentonite was compared with that of undisturbed soil by the control variable method, and the nano bentonite was divided into experimental group and control group. The viscosity strength and consolidation characteristics of nano bentonite were observed and analyzed by changing temperature, nano bentonite content, pressure and pore ratio. The results show that the consolidation coefficient of the sample without adding nano bentonite is 8.7 × 10–3 cm2/s, which is 6.6 × 10–3 cm2/s lower than that of 2% nano bentonite. It shows that the consolidation coefficient decreases with the increase of consolidation pressure and the decrease of void ratio. The nano bentonite modified clay is also more stable in road or building construction. The method of this study has brought a certain value for the research of nano materials in soil materials.

Strength and consolidation characteristics of clay with geotextile-encased sand column

Installing sand columns in clays is a common ground improvement technique used to treat soft soils, and the inclusion of geotextile to encase the sand column can further improve the performance of the reinforced clay composite. In this work, the shear strength and consolidation characteristics of clay, clay with an ordinary sand column (OSC) and clay with a geotextile encased sand column (GESC) were investigated by carrying out laboratory direct shear and oedometer tests to study the response of the reinforced clay composite under both lateral and vertical loading conditions. It was found that the OSC and GESC significantly increased the shear strength of the clay, mainly by improving the friction angle, with little impact on the apparent cohesion. Furthermore, the OSC and GESC reduced the compression index, swell index, and recompression index of the clay to some extent. The secondary compression indexes obtained from the reloading stage were lower than those from the initial loading stage, indicating that over-consolidated clay has a lower secondary compression index than normally consolidated clay. The coefficients of consolidation showed an upward trend as the effective consolidation stress increased. In addition, the compressibility and hydraulic conductivity tended to decrease with increasing effective consolidation stress.

피압에 따른 연약지반의 압밀 거동

Vertical drain has usually been used to accelerate the consolidation of soft clay deposits with high moisture content. Busan thick clay deposits are subjected to artesian pressure from an aquifer in sand and gravel layers. However, effect of artesian pressure existing in drainage-installed soft ground on consolidation behaviors is not well known. This paper investigates the consolidation behavior of drainage-installed soft ground at the Nakdong river estuary with artesian pressure and without artesian pressure. A series of one-dimensional large size column test was carried out to find out the consolidation characteristics of clay. Test results indicated that total settlement of clay with artesian pressure was higher than that without artesian pressure because effective stress decreased due to upward flow. Dissipation rate of excess pore water pressure delayed and excess pore water pressure did not fully dissipate in clay layer with artesian pressure. Undrained shear strength of clay ground with artesian pressure was lower than that without artesian pressure.

対数体積比log <i>f</i> で表した圧密特性の再検討

対数体積比log <i>f</i> で表した圧密特性の再検討

Strain Rate Effect on Long-Term Consolidation of Osaka Bay Clay

The consolidation characteristics of clay, based on the isotache concept in which the strain rate effect is considered, have been studied by many researchers. Most of these studies are aimed at calculating the secondary consolidation with high accuracy in order to evaluate the long-term settlement of large structures. In this study, as the first step toward improving the accuracy of the evaluation of long-term settlement at the Kansai International Airport, the consolidation characteristics of Osaka Bay clay are examined and organized based on the isotache concept. This study proposes a simplified model based on the isotache concept by using a compression curve and the relationship between the consolidation yield stress and the strain rate. The former and the latter are obtained from the constant rate of strain consolidation (CRS) tests and long term consolidation (LT) tests, respectively. The latter is expressed by an equation with three isotache parameters. This model is very practical because it requires a minimum of only one CRS test and one LT test. It is widely applicable to the Osaka Bay clay. The isotache parameters used in this model can be commonly determined for the Osaka Bay clays retrieved from various depths at the Kansai International Airport.

Numerical assessment on the consolidation characteristics of clays from strain holding, self-boring pressuremeter test

The strain holding test (SHT), part of the self-boring pressuremeter test (SBPT), has been effectively utilized to determine the horizontal coefficient of consolidation ( c h ). However, the commonly used procedure proposed by Clarke et al. [Proc. 7th Eur. Comp. Soil Mech., Brighton 2 (1979) 207.] can lead to an erroneous estimation of c h , because of its simplified assumptions. This paper deals with numerical analyses based on realistic test conditions of the generally accepted testing procedure, and using the most commonly used type of pressuremeter. The effects of the pressuremeter geometry, the partial drainage during cavity expansion, and the cavity strain level for the holding test are investigated with the radial distribution of the initial excess pore pressure and its dissipation rate. Based on the results of the numerical analyses, the curve of the time factor for the 50% degree of consolidation ( T 50) needed to estimate c h is proposed with a modification method for soil permeability. Comparisons are made between c h values estimated from the SHT of the SBPT and those obtained from other in situ and laboratory tests performed at two sites in Korea. These results confirm the improved capability of the T 50 values proposed herein.

Consolidation characteristics of clays from self-boring pressuremeter tests : Clarke, BG Proc 24th Annual Conference of the Engineering Group of the Geological Society, Field Testing in Engineering Geology, Sunderland, 4–8 Sept 1988P19–35. Publ Sunderland: Sunderland Polytechnic, 1988

Consolidation characteristics of clays from self-boring pressuremeter tests : Clarke, BG Proc 24th Annual Conference of the Engineering Group of the Geological Society, Field Testing in Engineering Geology, Sunderland, 4–8 Sept 1988P19–35. Publ Sunderland: Sunderland Polytechnic, 1988

Mechanisms Controlling Compressibility of Clays

The consolidation characteristics of clays are controlled by mechanical and physico-chemical effects. Although these effects operate simultaneously one-dimensional consolidation tests indicate that one or the other usually dominates. The consolidation characteristics of sands, mica, and kaolinite are mechanically controlled whereas those of smectite are physico-chemically controlled. Illite occupies an intermediate position in that the virgin compression curve seems to be controlled by mechanical variables, whereas the swelling curve is influenced by both effects; the physico-chemical effect is more important when the adsorbed cations are monovalent and the pore water electrolyte concentration is low.

Mechanisms Controlling Compressibility of Clays

The consolidation characteristics of clays are controlled by mechanical and physico-chemical effects. Although these effects operate simultaneously one-dimensional consolidation tests indicate that one or the other usually dominates. The consolidation characteristics of sands, mica, and kaolinite are mechanically controlled whereas those of smectite are physico-chemically controlled. Illite occupies an intermediate position in that the virgin compression curve seems to be controlled by mechanical variables, whereas the swelling curve is influenced by both effects; the physico-chemical effect is more important when the adsorbed cations are monovalent and the pore water electrolyte concentration is low.