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1.
A series of coupled thermo-hydraulic simulations were performed on a soil–geotextile column to understand the effect of temperature on suction distribution throughout the soil column and on the hydraulic performance of the geotextile as a drainage/capillary barrier layer. Two different constant temperatures of 0 °C and 38 °C and a temperature gradient of 4 °C along the column were modeled. Changing the temperature from 0 °C to 38 °C did not have a significant effect on the suction head distribution in the soil–geotextile column. The temperature gradient resulted in appreciable thermal vapor flow and changes in suction head and hydraulic conductivity of the geotextile. During drainage, the temperature gradient and lower temperature at the top of the column increased suction in the geotextile and its ability to function as a capillary barrier. During capillary rise, the temperature gradient and lower temperature at the top of the column decreased the suction in the geotextile and its ability to function as a capillary barrier. Changing the direction of the thermal gradient reversed the water vapor flow direction and its effect on the suction in the geotextile. A temperature gradient did not have a noticeable effect on the suction head of the geotextile when positive pore pressure was developed in the geotextile and adjacent soil during drainage. 相似文献
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在软土地基加筋路堤稳定性分析方法中,传统分析方法(如瑞典法和荷兰法)因对加筋材料的加筋作用估计不足,导致计算结果过于保守,与实际不符。本文在充分考虑加筋体的加筋作用下,提出了新的加筋路堤稳定性分析计算方法,并采用小生境遗传算法搜索临界滑动面和最小安全系数。算例计算结果表明,本文提出的加筋路堤稳定性分析方法与工程实际情况吻合较好,并且小生境遗传算法能有效地搜索到边坡所有的临界滑动面。 相似文献
3.
It has been widely accepted that reinforcement made of polyethylene and polypropylene is susceptible to creep and soil’s hydraulic conductivity varies with its void ratio. However, unfortunately there is no available sensitivity analysis on time-dependent embankment behaviour taking either reinforcement viscosity or time varying hydraulic conductivity of subsoil into consideration. The influence of geosynthetic reinforcement viscosity and decreasing hydraulic conductivity with consolidation on the time-dependent performance of embankments with floating columns is investigated using a fully 3D coupled model. For an embankment at the working height corresponding to a post-consolidation polypropylene geotextile strain of about 5%, it is shown that the assumption of constant hydraulic conductivity and the failure to consider the viscous behaviour of geosynthetic reinforcement can underestimate time-dependent embankment deformations (including differential crest settlement and horizontal toe movement). The effects of factors including the foundation soil, reinforcement stiffness, column stiffness, column spacing, column type (floating and fully penetrating), and construction rate, on the time-dependent behaviour of column supported embankments are explored. 相似文献
4.
Performance of quasilinear elastic constitutive models in simulation of geosynthetic encased columns
Past numerical simulations of geosynthetic encased columns (GECs) using different versions of the quasilinear elastic hyperbolic model for the encased granular material have, in certain cases, yielded unrealistic results. In this paper the cause of such results is investigated by performing three-dimensional finite element analyses of GECs in soft clay, utilizing three common functional forms of the hyperbolic model for the encased granular material. Results indicate that one form of the hyperbolic model can predict an unrealistic lateral response for GECs during application of load to the column. In addition, the inability of hyperbolic models to properly account for soil behavior near failure compromises their ability to realistically capture the behavior of encased granular soil in GECs. Modeling the behavior of soil near failure is essential for properly simulating the behavior of GECs, as soil shear failure is necessary to mobilize the tensile stresses in the encasement and improve the stress–displacement response of the GEC. Although this type of hyperbolic model behavior was demonstrated for the specific case of encased soil in a GEC, the limitations of the hyperbolic model described herein apply equally to other geotechnical problems in which some portion of the soil mass is at or near failure. 相似文献
5.
In this paper a study on the improvement of liquefaction strength of fly ash by reinforcing with randomly distributed geosynthetic fiber/mesh elements is reported. A series of stress controlled cyclic triaxial tests were carried out on fly ash samples reinforced with randomly distributed fiber and mesh elements. The liquefaction resistance of reinforced fly ash is defined in-terms of pore pressure ratio. The effects of parameters such as fiber content, fiber aspect ratio, confining pressure, cyclic stress ratio, on liquefaction resistance of fly ash have been studied. Test results indicate that the addition of fiber/mesh elements increases the liquefaction strength of fly ash significantly and arrests the initiation of liquefaction even in samples of loose initial condition and consolidated with the low confining pressure. 相似文献
6.
AbstractShort waste fibers are used to suppress the expansion and improve the tensile strength of cement-stabilized marine clay (CMC). The fiber-reinforced mechanism and characteristics are revealed by experimental and numerical methods. First, the curing effect of the CMC when adding a composite curing agent is observed by scanning electronic microscopy, as is the contact surface between the fiber and the matrix. Then, the expansion rate and the tensile strength of fiber-reinforced cement-stabilized marine clay (FCMC) are illustrated by an expansion experiment and a direct tensile experiment, respectively. The results show that the sample with the cement content of 0.1% and the fiber length of 10?mm is the best in terms of strength enhancement and expansion inhibition. Finally, the mechanism of fiber reinforcement is discussed following a single fiber pullout experiment and some comprehensive explanations are proposed to verify the results of the tensile experiment. A numerical simulation of a single fiber pullout from a matrix is established by using a cohesive contact model. The comparison between the numerical results and the experimental results shows that the two models can be in good agreement, indicating that the calculation model of the interaction between the fiber and the matrix is realistic. 相似文献
7.
A new type of quay wall structure has been proposed to improve the seismic resistance capability of existing sheet pile quay wall structures. The new structure adopts a combination of stabilized soil and geogrid, and this structure is referred to simply as “SG-WALL”. This paper presents a numerical comparative study on the seismic performances of quay wall structures between the newly developed SG-WALL and the traditional anchor pile-reinforced structure. The calculated results, including displacement of sheet pile, ground settlement, bending moment and stress of sheet pile, and excess pore water pressure, were analyzed and discussed. It was shown that both types of improvement methods can effectively reduce the residual displacements of sheet piles after earthquakes. The residual displacements at the top of the sheet piles in SG-WALL structure and the anchor pile-reinforced structure decreased by 35.6 and 38.2%, respectively. In addition, the SG-WALL structure can more significantly reduce the ground settlement due to earthquakes. The maximum ground settlement in SG-WALL structure and the anchor pile-reinforced structure decreased by 67.3 and 58.9%, respectively. 相似文献
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9.
S. Scheiner B. Pichler Ch. Hellmich J. Eberhardsteiner 《Computers and Geotechnics》2006,33(8):371-380
Oil and gas pipelines covered with a mixture of sandy gravel and square-edged stones are subjected to abrasive shear loading steming from temperature-induced displacements of the pipeline in longitudinal direction. This requires wear protection of the outer anti-corrosion film of such pipes. In order to assess appropriate means for protection, adverse settlements on both sides of the soil-covered pipeline are assumed as relevant loading scenario. A nonlinear, elastoplastic, cap model-based Finite Element model delivers the radial stresses exerted onto the pipeline, due to settlement-induced load re-arrangement within the cohesionless soil body. Given a cover height of 1.5 m, the aforementioned load re-arrangement leads to an increase of force action onto the pipe by up to 200%. Based on the grain size of the filling material, radial stresses are integrated as to estimate the maximum normal forces exerted by single stone corners onto the pipe’s anti-corrosion film. These forces, when analyzed through Archard’s law, allow for calculation of the service life of the protection layer enveloping the pipe, once the wear resistance of that layer is determined from experiments, as is done for geosynthetics. Since the service life of a geosynthetic protection layer of the anti-corrosion film turns out to be distinctively smaller than the standard service life of a soil-covered steel pipeline, protection through geosynthetic layers is insufficient. Hence, more effective means for protection are suggested. 相似文献
10.
Experimental Study of Bearing Capacity of Granular Soils,Reinforced with Innovative Grid-Anchor System 总被引：1，自引：0，他引：1
Mansour Mosallanezhad Nader Hataf Arsalan Ghahramani 《Geotechnical and Geological Engineering》2008,26(3):299-312
The pull-out resistance of reinforcing elements is one of the most significant factors in increasing the bearing capacity
of geosynthetic reinforced soils. In this research a new reinforcing element that includes elements (anchors) attached to
ordinary geogrid for increasing the pull-out resistance of reinforcements is introduced. Reinforcement therefore consists
of geogrid and anchors with cubic elements that attached to the geogrid, named (by the authors) Grid-Anchor. A total of 45
load tests were performed to investigate the bearing capacity of square footing on sand reinforced with this system. The effect
of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance
that anchors are effective, effect of relative density, low strain stiffness and stiffness after local shear were investigated.
Laboratory tests showed that when a single layer of reinforcement is used there is an optimum reinforcement embedment depth
for which the bearing capacity is the greatest. There also appeared to be an optimum vertical spacing of reinforcing layers
for multi-layer reinforced sand. The bearing capacity was also found to increase with increasing number of reinforcement layer,
if the reinforcement were placed within a range of effective depth. The effect of soil density also is investigated. Finally
the results were compared with the bearing capacity of footings on non-reinforced sand and sand reinforced with ordinary geogrid
and the advantages of the Grid-Anchor were highlighted. Test results indicated that the use of Grid-Anchor to reinforce the
sand increased the ultimate bearing capacity of shallow square footing by a factor of 3.0 and 1.8 times compared to that for
un-reinforced soil and soil reinforced with ordinary geogrid, respectively. 相似文献