共查询到20条相似文献，搜索用时 234 毫秒
1.
Axi-symmetric Analysis of Geosynthetic-reinforced Granular Fill-soft Soil System with Group of Stone Columns 总被引：1，自引：1，他引：0
The paper presents a mechanical model to predict the behavior of geosynthetic-reinforced granular fill resting over soft soil
improved with group of stone columns subjected to circular or axi-symmetric loading. The saturated soft soil has been idealized
by spring-dashpot system. Pasternak shear layer and rough elastic membrane represent the granular fill and geosynthetic reinforcement
layer, respectively. The stone columns are idealized by stiffer springs. The nonlinear behavior of granular fill and soft
soil is considered. Consolidation of the soft soil due to inclusion of stone columns has also been included in the model.
The results obtained by using the present model when compared with the reported results obtained from laboratory model tests
shows very good agreement. The effectiveness of geosynthetic reinforcement to reduce the maximum and differential settlement
and transfer the stress from soft soil to stone columns is highlighted. It is observed that the reduction of settlement and
stress transfer process are greatly influenced by stiffness and spacing of the stone columns. It has been further observed
that for both geosynthetic-reinforced and unreinforced cases, the maximum settlement does not change if the ratio between
spacing and diameter of stone columns is greater than 4. 相似文献
2.
The paper presents a model for the analysis of granular foundation beds reinforced with several geosynthetic layers. Such
reinforced granular beds are often placed on soft soil strata for an efficient and economical transfer of superstructure load.
The granular bed is modeled by the Pasternak shear layer and the geosynthetic reinforcement layers by stretched rough elastic
membranes. The soft soil is represented by a series of nonlinear springs. The reinforcement has been considered to be extensible
and it is assumed that the deformation at the interface of the reinforcements and soil are same. The nonlinear behavior of
the granular bed and the soft soil is considered. Plane strain conditions are considered for the loading and reinforced foundation
soil system. An iterative finite difference scheme is applied for obtaining the solution and results are presented in nondimensional
form. The results from the proposed model are compared to the results obtained for multilayer inextensible geosynthetic reinforcement
system. Significant reduction in the settlement has been observed when the number of reinforcement layer is increased. In
case of inextensible reinforcements as the number of reinforcement layer is increased the settlement is decreased with a decreasing
rate, but in case of extensible reinforcement the reduction rate is almost constant. Nonlinear behavior of the soft soil decreases
as number of reinforcement layer is increased. The effect of the stiffness of the geosynthetic layer on the settlement response
becomes insignificant for multilayer reinforced system, but the mobilized tension in the reinforcement layers increases as
the stiffness of the geosynthetic layers increases. 相似文献
3.
Kousik Deb 《国际地质力学数值与分析法杂志》2008,32(10):1267-1288
The present study pertains to the development of a mechanical model for predicting the behavior of granular bed‐stone column‐reinforced soft ground. The granular layer that has been placed over the stone column‐reinforced soft soil has been idealized by the Pasternak shear layer. The saturated soft soil has been idealized by the Kelvin–Voigt model to represent its time‐dependent behavior and the stone columns are idealized by stiffer Winkler springs. The nonlinear behavior of the granular fill has been incorporated in this study by assuming a hyperbolic variation of shear stress with shear strain as in one reported literature. Similarly, for soft soil it has also been assumed that load‐settlement variation is hyperbolic in nature. The effect of consolidation of the soft soil due to inclusion of the stone columns has also been included in the model. Plane‐strain conditions are considered for the loading and foundation soil system. The numerical solutions are obtained by a finite difference scheme and the results are presented in a non‐dimensional form. Parametric studies for a uniformly loaded strip footing have been carried out to show the effects of various parameters on the total as well as differential settlement and stress concentration ratio. It has been observed that the presence of granular bed on the top of the stone columns helps to transfer stress from soil to stone columns and reduces maximum as well as differential settlement. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
《Geomechanics and Geoengineering》2013,8(3):185-194
In this paper, a model for the analysis of footings having finite flexural rigidity resting on a granular bed on top of stone columns improved saturated soft (clayey) soil has been proposed. Soft soil has been modeled as a Kelvin–Voigt body to represent its time dependent behavior. Pasternak shear layer has been used to represent the granular layer and the stone columns have been idealized by means of nonlinear Winkler springs. Nonlinear behavior of granular fill, soft soil and stone columns has been invoked by means of hyperbolic constitutive relationships. Governing differential equations for the soil–foundation system have been obtained and finite difference method has been adopted for solving these, using the Gauss-elimination iterative scheme. Detailed parametric study for a combined footing has been carried out to study the influence of parameters, like magnitude of applied load, flexural rigidity of footing, diameter of stone column, spacing of stone column, ultimate bearing capacity of granular fill, poor foundation soil and stone column, relative stiffness of stone columns and degree of consolidation, on flexural response of the footing. 相似文献
5.
Kousik Deb N. Sivakugan Sarvesh Chandra P. K. Basudhar 《Geotechnical and Geological Engineering》2007,25(6):639-646
In this paper, considering the plain strain conditions, a numerical study has been conducted to investigate the behavior of
multi layer geosynthetic-reinforced granular bed overlying a soft soil using the Fast Lagrangian Analysis of Continua (FLAC)
program. The granular fill, soft soil, and geosynthetic reinforcements are considered as linear elastic materials. The geosynthetic
reinforcements are modeled as cable elements fully bonded with the surrounding soil, thus neglecting any slip. The results
obtained from the present investigation showed very close agreement when compared with the results of finite element analysis
and lumped parameter modeling. The distribution of vertical, lateral and shear stresses in the soil are greatly affected as
the number of reinforcement layers is increased. If the tensile stiffness of geosynthetic layers increases and its value is
no more than 4,000–5,000 kN/m, the settlement of the reinforced foundation decreases significantly. The reduction in settlement
is insignificant when the tensile strength of the geosynthetics exceed the above value. 相似文献
6.
The present study pertains to the development of a foundation model for predicting the behavior of geosynthetic reinforcement railway track system rested on soft clay subgrade. The ballast and sub‐ballast layers have been idealized by Pasternak shear layer. The geosynthetic layer is represented by a stretched rough elastic membrane. Burger model has been used to characterize the soft clay subgrade. Numerical solutions have been obtained by adopting the finite difference scheme combined with non‐dimensioning the governing equations of the proposed model. The results confirm that the present model is quite capable of predicting the time‐dependent settlement response of geosynthetic reinforcement railway track system placed on soft clay subgrade. The surface settlement profile and mobilized tensile load of geosynthetics has been evaluated by considering variation in the wheel load, sleeper width, thickness of ballast and sub‐ballast layers and shear modulus of ballast and sub‐ballast layers. It has been observed that an increase in the sleeper width by 24% results in the reduction in central settlement and mobilized tensile load by 6.5% and 20.1%, respectively. It was found that with a 50% increase in the thickness of the ballast layer, the central settlement has decreased by 7.3% and the mobilized tension at the zone of maximum curvature has increased by 24.6%. However, with an increase in the thickness of the sub‐ballast layer, a considerable reduction in both central settlement and the mobilization of tension on geosynthetic has been noticed. The pattern of variation of settlement and mobilized tension for an increase in the shear modulus of ballast and sub‐ballast material was found to be almost similar. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
The use of geosynthetic-encased stone columns as a method for soft soil treatment is extensively used to increase the bearing capacity and reduce the settlement of raft foundations and the foundation of structures like embankments. Pre-strain is an effect occurring in the encasement during stone column installation due to the compaction of the stone material. The present study uses the finite element program Plaxis to perform a numerical analysis of the soft clay bed reinforced by geosynthetic-encased stone columns. An idealization is proposed for simulation of installation of geosynthetic-encased stone columns in soft clay based on the unit-cell concept. In the analyses, initially, the validity of the analysis of the single column-reinforced soil in the unit-cell model was performed through comparison with the group columns. Then, by considering a unit-cell model, the finite element analyses were carried out to evaluate the stiffness of the reinforced ground to estimate the settlement. The results of the analyses show that the improved stiffness of the encased stone column is not only due to the confining pressure offered by the geosynthetic after loading, but the initial strain of the geosynthetic that occurred during installation also contributes to the enhancement of the stiffness of the stone column and the reduction of the settlement. 相似文献
8.
Hormoz B. Poorooshasb 《Computers and Geotechnics》1989,8(4):289-309
The use of geosynthetic to reinforce soft-soils or peat in order to improve the load-settlement response is quite common. In such cases a layer of engineered fill, reinforced with a geosynthetic, is placed on the soft ground and the load is supported by the granular fill. In the present paper a procedure is outlined for the analysis of such a geothynthetic reinforced soil system. The granular fill is assumed to be rigid-strain hardening plastic and the soft soil is modeled by a Winkler type foundation. The grid is considered to be “rough” on its surfaces and be linearly elastic when subjected to tensile stresses. A simple transform function is used in the analysis. Through the analysis performed the influence of various factors such as the degree of overconsolidation (through compaction) of the fill, its dilatational properties, and the tangent modulus of the geogrid are investigated and discussed. 相似文献
9.
M. R. Dheerendra Babu Sitaram Nayak R. Shivashankar 《Geotechnical and Geological Engineering》2013,31(1):1-22
Stone columns have been used as an effective technique for improving the engineering behaviour of soft clayey grounds and loose silt deposits. The soil improvement via stone columns are achieved from accelerating the consolidation of weak soil due to shortened drainage path, increasing the load carrying capacity and/or settlement reduction due to inclusion of stronger granular material. This paper discusses the techniques, methods of construction of stone columns, mechanisms of stone column behaviour under load and associated design philosophies along with some practical findings from recent research programs. 相似文献
10.
In the present paper, a new foundation model has been proposed by introducing a stretched rough elastic membrane in the Pasternak shear layer sandwiched between two spring layers which is an extension of Kerr model. Considering the equilibrium of different elements, the equations governing the elastic settlement response of the model are derived. Finite difference scheme has been employed to solve the governing equations. The parametric studies carried out show the effect of several parameters on the elastic settlement response of the model. The proposed model is well suited for idealizing the behavior of geosynthetic-reinforced granular fill—soft soil system besides other applications. 相似文献
11.
In the present work, a simplified model has been developed to study the behavior of stone column-supported embankment under axi-symmetric loading condition. The rate of consolidation of stone column-reinforced soft ground under axi-symmetric condition has also been presented in the paper. Mechanical model elements such as Pasternak shear layer, spring–dashpot system are used to model the different components such as granular layer, soft soil, stone columns etc. The governing differential equations are solved by finite difference technique. Parametric study has also been carried out to show the effect of different model variables on the settlement, stress concentration ratio of the foundation system. It is observed that for lower diameter ratio, at a particular time, the degree of consolidation predicted by the present method for axi-symmetric loading condition is almost same or lower than the degree of consolidation obtained by unit cell approach, but as the diameter ratio increases present analysis predicts higher degree of consolidation as compared to the unit cell approach. The maximum settlement decreases as the modular ratio increases and beyond the modular ratio value 30, the reduction rate of settlement decreases. 相似文献
12.
In the present paper, soil-structure interaction analysis of an infinite beam resting on extensible geosynthetic reinforced
earth beds has been carried out for an applied load moving with constant velocity. The viscous damping of the soil-foundation
system has been given due consideration in the analytical procedure. The infinite beam has been treated as resting on a granular
fill layer overlying the naturally occurring weak soil layer. Geosynthetic layer has been provided in the granular fill layer
and has been considered as extensible. This extensible nature has been incorporated with the help of no slip and the compatibility
conditions at the interface between reinforcing layer and the neighboring soil. These conditions help in eliminating the two
interfacial shear stress parameters and in considering the tensile modulus of geosynthetic layer in the analysis. The influence
of various parameters, like magnitude and velocity of applied moving load, viscous damping, relative stiffness of granular
fill and tensile modulus of geosynthetic layer, on the response of soil-foundation system has been studied. It has been observed
that all these parameters affect the response significantly, however, the effect of velocity of moving load and viscous damping
has been found to be more significant especially at higher velocities. 相似文献
13.
土工布加筋基础的沉降和土工布拉力 总被引：1，自引：0，他引：1
给出解土工布加筋基础非线性模型方程组的差分选代格式。讨论了夹有土工布的砂层的荷载传递和模型参数对加筋基础的沉降及土工布拉力的影响。 相似文献
14.
根据某一大型油罐软基加固处理工程方案设计和优选需要,按照离心模型相似律,开展了三组模型试验,分别模拟了天然地基、土工合成材料袋装碎石垫层和既在填土层中设置袋装碎石垫层又在淤泥质粘土层设置土工合成材料排水板三种情况,以研究这一加固布置形式对减小高压缩性软土层地基上油罐罐底的差异沉降效果反应。模型油罐地基采用原型土重塑制备,现场土工合成材料袋装碎石采用柔性机织玻璃纤维细管塞装粗砂条模拟,并在不停机运转条件下模拟了多次充放水预压加载。试验结果表明,油罐软弱地基经土工合成材料袋装碎石加固后,罐底总沉降值和差异沉降值均明显小于天然地基情形下对应的沉降值,罐底畸变得到显著减小,就本文所述的土质条件、土层厚度和预压荷载强度,地基经加固处理后,油罐罐底畸变减小了近50 %。最后就土工合成材料在加固油罐地基布置形式的合理性进行了初步探讨。 相似文献
15.
It is common to use geosynthetics to reinforce soft-soils or peat with a view to improve their load — settlement response. A new foundation model element — the rough membrane, is proposed to represent the response of the geofabric. Combining this element with Winkler springs and Pasternak shear layers to model respectively the soft soil and the granular fills, a new foundation model is presented for the geosynthetic — granular fill — soft soil system. Analysis of results at small displacement indicates the effect of granular fill to be more and significant than that of the membrane thus confirming large scale model test results of Jarrett and results based on F.E.M. (Boutrup and Holtz). The effect of the membrane increases with the load or decreasing soil stiffness. 相似文献
16.
软土地基上填筑高路堤常常面临地基承载力不足、沉降和不均匀沉降过大等问题。桩承式加筋路堤能够有效地解决这些难题。通过理论分析和有限元数值模拟,研究了路堤填土-加筋材料-桩体-桩间土之间的相互作用机理,讨论了路堤填土中的土拱效率、桩体效率、路堤底面差异沉降和筋材拉力的变化规律。研究结果表明,填土中的土拱效应和筋材张力膜效应能够有效地提高桩体效率,防止软土屈服;筋材内部拉力呈非线性分布,桩顶边缘处筋材拉力最大。 相似文献
17.
Stone columns in soft soil improve bearing capacity because they are stiffer than the material which they replace, and compacted stone columns produce shearing resistances which provide vertical support for overlying structures or embankments. Also stone columns accelerate the consolidation in the native surrounding soil and improve the load settlement characteristics of foundation. In this paper, the finite element method is utilized as a tool for carrying out analyses of stone column–soil systems under different conditions. A trial is made to improve the behaviour of stone column by encasing the stone column with geogrid as reinforcement material. The program CRISP-2D is used in the analysis of problems. The program allows prediction to be made of soil deformations considering Mohr-Coulomb failure criterion for elastic–plastic soil behaviour. A parametric study is carried out to investigate the behaviour of standard and encased floating stone columns in different conditions. Different parameters were studied to show their effect on the bearing improvement and settlement reduction of the stone column. These include the length to diameter ratio (L/d), shear strength of the surrounding soil and, the area replacement ratio (as) and others. It was found that the maximum effective length to diameter (L/d) ratio is between (7–8) for Cu, between (20–40) kPa and between (10–11) for Cu?=?10?kPa for ordinary floating stone columns while the effective (L/d) ratio is between (7–8) for encased floating stone columns. The increase in the area replacement ratio increases the bearing improvement ratio for encased floating stone columns especially when the area replacement ratio is greater than (0.25). The geogrid encasement of stone column greatly decreases the lateral displacement compared with ordinary stone column. 相似文献
18.
Souhir Ellouze Zeineb Bensalem Mohamed Nadhir Znaidi 《Geomechanics and Geoengineering》2017,12(2):73-85
This paper addresses the installation effects of stone columns in soft soils. Focus is made on the lateral expansion of stone material using the vibro displacement and substitution techniques by means of numerical simulations. The behaviour of reinforced soil after stone column installation is investigated to show how the properties of soft soils can be improved prior to final loading. The effect of such an improvement on the prediction of reinforced soil settlement is evaluated. The axisymmetric unit cell model (UCM) served for the comparison between numerical predictions made by the Mohr-Coulomb and hardening soil constitutive laws adopted for the soft soil. An equivalent group of end bearing columns model was investigated in the axisymmetric condition to predict the settlement of reinforced soil by adopting the Mohr-Coulomb constitutive model for soft clay. The reduction of settlements predicted by the unit cell and group of columns models, due the improvement of the Young’s modulus of soft clay, were compared. It is concluded that a significant reduction of settlement is expected when the group of columns model is considered. 相似文献
19.
A. J. Choobbasti A. Zahmatkesh R. Noorzad 《Geotechnical and Geological Engineering》2011,29(5):675-684
Stone columns (or granular piles) are increasingly being used for ground improvement. This study investigates the qualitative
and quantitative improvement in soft clay by stone columns. Finite element analyses were carried out to evaluate the performance
of stone columns in soft clay. A drained analysis was carried out using Mohr–Coulomb’s criterion for soft clay, stones, and
sand. The interface elements were used at the interface between the stone column and soft clay. Analyses and calculations
were carried out to determine equivalent parameters of soil/columns system. The bearing capacity ratio (BCR) of the soil has
been estimated for homogeneous and heterogeneous soil. The results have shown that the values of BCR for homogeneous soil
are obviously higher than those for heterogeneous soil. 相似文献
20.
Settlement evaluation of soft clay reinforced with stone columns using the equivalent secant modulus 总被引：3，自引：2，他引：1
A method is proposed to evaluate settlement of soft clay reinforced with stone columns. Finite element analyses were carried out using 15-noded triangular elements with PLAXIS. A drained analysis was carried out using Mohr?CCoulomb??s criterion for soft clay, stones, and sand. The stress due to column installation has been considered in the analysis. At the interface between the stone column and soft clay, interface elements have been used. The settlement ratio (SR) of the soil has been estimated using the equivalent secant modulus. The results are compared with those available in the literature, and the advantages of the numerical analysis were highlighted. Based on the results of this analysis, the SR decrease with compaction surrounding soft soil, but decrease of SR is mainly due to a stiffer column material in soft clay. 相似文献