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1.
In the present study, an approximate method has been suggested to calculate the ultimate bearing capacity of a square footing
resting on reinforced layered soil. The soil is reinforced with horizontal layers of reinforcement in the top layer of soil
only. The pre requisite to the method is the ultimate bearing capacity of unreinforced layered soil, which can be determined
from the methods already available in literature. The results have been validated with the model tests conducted on two layered
soil compacted at different densities and the top layer reinforced with horizontal layers of geogrid reinforcement. 相似文献
2.
In this paper, an analysis has been presented for calculating the pressure of an adjacent rectangular footing resting on reinforced sand for a given settlement. An approximate method has been suggested to compute the ultimate bearing capacity of adjacent footings resting on reinforced earth slab. The computation of normal force on the reinforcement area and estimation of interfacial friction coefficient at different layer levels are two essential steps in computation of pressure ratio. The process has been simplified by presenting suitable charts in non-dimensional form that can be directly used by practicing engineers. 相似文献
3.
Arvind Kumar Baljit Singh Walia Swami Saran 《Geotechnical and Geological Engineering》2005,23(4):469-481
A method has been proposed to obtain the pressure–settlement characteristics of rectangular footings resting on reinforced sand based on constitutive laws of soils. The confining effect of the reinforcement provided in the soil at different layers has been incorporated in the analysis by considering the equivalent stresses generated due to friction at the soil– reinforcement interface. The prerequisite of the method is the value of ultimate bearing capacity, which can be obtained from the approaches already available in literature. The value of settlement may be read directly from pressure–settlement curves for the given pressure intensity. Therefore, the rectangular footing resting on reinforced sand can be proportioned satisfying shear failure and settlement criteria. 相似文献
4.
《Geomechanics and Geoengineering》2013,8(2):107-111
The stability of eccentrically loaded strip footings on slopes was investigated using the method of finite element analysis based on the theory of elasto-plasticity. The analysis was done for two different soils involving three levels of slope angle, six footing locations, and two levels of load eccentricity plus central vertical loading. The strip footing analysed was a 3-ft (0.9 m) wide reinforced concrete footing embedded to a depth of 3 ft (0.9 m). The analysis focused on footing settlement, plastic yielding of soil, and ultimate bearing capacity. The results of analysis show that the influence of load eccentricity on footing pressure vs. footing centre settlement is negligibly small. However, the progressive soil yielding and ultimate bearing capacity are greatly affected by load eccentricity. Furthermore, the effect of load eccentricity differs considerably with the load location relative to the footing centre and slope crest. The ultimate bearing capacity for the eccentric load located on the slope side is significantly greater than that for the load located on the other side of the footing centre. For a 2(H): 1(V) slope in silty clay, the effect of slope on footing stability decreases with increasing footing location from slope crest as would be expected, and diminishes when the footing is located from the crest at about 5-times the footing width. 相似文献
5.
《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
6.
基于传统的极限平衡条分法,利用临界滑动场法计算了条形基础的加筋地基极限承载力。假定土体处于极限平衡状态时,土体与筋材间存在均匀的摩擦力,通过建立土体条块极限平衡方程,推导了地基承载力的递推关系式。首先,设定计算土体范围,并划分条块和离散状态点;其次,根据递推公式计算各个状态点的参数,并搜索临界滑面;最后,根据搜索出的滑面计算地基承载力。通过实例比较进一步验证了计算结果的可靠性,并分析了首层筋带埋深、铺设层数和长度对地基承载力和滑面位置的影响。研究结果表明：地基承载力随着筋带埋深的增加先增大后减小;随着层数和长度的增加先逐渐增大,最后趋于稳定;滑面位置的变化规律主要是垂直影响深度和水平影响范围增大或减小。该方法原理简单、易于编程,为条形基础加筋地基承载力的计算提供了一种新思路,是临界滑动场法在地基承载力计算中的推广应用。 相似文献
7.
Swami Saran Surendra Kumar K.G. Garg Arvind Kumar 《Geotechnical and Geological Engineering》2007,25(1):123-137
In the present paper, a method of analysis for calculating the pressure intensity corresponding to a given settlement for
eccentrically and obliquely loaded square and rectangular footings resting on reinforced soil foundation has been presented.
The process has been simplified by presenting non-dimensional charts for the various terms used in the analysis, which can
be directly used by practicing engineers. An approximate method has been suggested to find out the ultimate bearing capacity
of such footings on reinforced soil. The results have been validated with the model test results. The procedure has been made
clear by giving an illustrative example. 相似文献
8.
The ultimate bearing capacity of a strip footing on soil reinforced with geogrids has been studied analytically. The reinforcing mechanism of the soil bearing on lateral surfaces and shearing over soils through the apertures of the grids was considered. The passive resistance against transverse ribs of geogrid was calculated using the Prandtl mechanism. The proposed equation incorporated the traditional Nγ factors, unit weight of soil, soil shear strength angle, footing width, and the geometry of the geogrid. The accuracy of theoretical predictions was verified by the experimental and analytical results from the existing literatures. The mean bias of the theoretical model was found to be about 10%. 相似文献
9.
L. G. Tham 《Computers and Geotechnics》1988,5(4):249-268
A numerical method is proposed for the analysis of rectangular footing resting on an elastic soil layer. The footing is represented by double spline elements and the elastic soil medium by finite layers. The effect of the rigidity of footing and the non-homogeneity of the soil on the behaviour of such foundation system is investigated, and the results are presented in form of design charts such that they may be used for hand calculation for the estimation of the settlement of footings for a wide range of practical cases. 相似文献
10.
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
11.
The stress characteristics method (SCM) has been used to compute the bearing capacity of smooth and rough ring foundations. Two different failure mechanisms for a smooth footing, and four different mechanisms for a rough footing have been considered. For a rough base, a curvilinear non-plastic wedge has been employed below the footing. The analysis incorporates the stress singularities at the inner as well as outer edges of the ring footing. Bearing capacity factors, Nc, Nq and Nγ are presented as a function of soil internal friction angle (ϕ) and the ratio (ri/ro) of inner to outer radii of the footing. 相似文献
12.
Bearing Capacity of Strip Footings Near Slopes 总被引：2，自引：1，他引：1
In the last decades a great attention was given by many authors to the evaluation of the static and seismic bearing capacity
of footings near slopes. In this paper a model has been developed based on the limit equilibrium method, considering a circular
surface propagates towards the slope until the sloping ground is reached. The bearing capacity is investigated considering
either the distance of the footing from the edge of the slope and/or the effect of the footing embedment. A validation of
the proposed model was made by a comparison with solutions taken from literature regarding the evaluation of the bearing capacity
for a footing adjacent to a slope and for an inclined load. The loading conditions consist in vertical and horizontal stress
on the footing and on the soil below the footing. Both the inertial and kinematic effects of the seismic loading have been
analyzed, and a simple equation has been derived for the evaluation of the seismic bearing capacity. The static and seismic
bearing capacity has been investigated as a function of the soil friction angle, of the seismic coefficient, of the sloping
ground. Finally, the influence of the distance of the footing from the edge of the slope was taken into consideration in the
evaluation of the bearing capacity, and a threshold distance at which the reduction of the bearing capacity due to the sloping
ground vanishes has been defined. 相似文献
13.
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
14.
This paper examines the drained bearing response of circular footings resting on structured soil deposits. Numerical simulations have been carried out using a finite element formulation of the Structured Cam Clay model. A parametric study was conducted by varying the parameters that govern the behaviour of structured soils and guidelines are given for designers to identify when effects of the soil structure are important. Under fully drained conditions, deformation within the structured soil supporting the footing usually occurs as a local or punching shear failure due to high compressibility of the structured soil and the mobilised bearing pressure increases with the footing movement, without reaching an ultimate value. A novel approximate method is presented to obtain the load–displacement response of a rigid circular footing resting on the surface of a structured soil deposit. This requires the properties of the soil in the reconstituted state and two additional parameters, which govern the natural structure of the soil. The proposed method has been applied to a published case study, where plate load test results are given for rigid circular steel plates resting on structured soil deposits. Fair agreement is observed between the computed and experimental results, suggesting the approximate method may be useful in design studies of foundations on structured soil deposits. 相似文献
15.
加筋带布置对地基承载力的影响 总被引：2，自引：3，他引：2
现场原位载荷试验表明：素碎石薄垫层(Z/B=0.2)地基经土工带加筋后，能提高地基承载力。通过承载力比BCR分析加筋层数Ⅳ、加筋首层间距U、加筋带间距H、加筋线密度LDR对地基承载力的影响，并对极限稳定时筋带的设计拉力进行了讨论，提出用筋带的设计强度预估加筋地基极限承载力。 相似文献
16.
《Geomechanics and Geoengineering》2013,8(4):235-251
The bearing capacity of footing has been studied by both conventional and numerical methods by many researchers. However, degradation of the microstructure of material, that is, a change in the microstructure of the soil, has not been adequately taken into account. Degradation of microstructure causes strain softening of materials and it leads to strain localization such as shear bands and slip bands. From an engineering point of view the strain localization is crucial because it is a precursor of failure. In the present study, finite element analyses of the bearing capacity of a shallow foundation on homogeneous and inhomogeneous saturated clay strata have been conducted using an elasto-viscoplastic soil constitutive model of microstructure change. A series of analyses of footing on clay deposit with different microstructure parameters have been carried out. Numerical results show that strain localization can be predicted during the loading of rigid footing on highly structured soil and strain localization affects the footing–soil interaction. The effects of footing roughness on the failure mechanism are also discussed in the study. 相似文献
17.
This paper examines the potential of least‐square support vector machine (LSVVM) in the prediction of settlement of shallow foundation on cohesionless soil. In LSSVM, Vapnik's ε‐insensitive loss function has been replaced by a cost function that corresponds to a form of ridge regression. The LSSVM involves equality instead of inequality constraints and works with a least‐squares cost function. The five input variables used for the LSSVM for the prediction of settlement are footing width (B), footing length (L), footing net applied pressure (P), average standard penetration test value (N) and footing embedment depth (d). Comparison between LSSVM and some of the traditional interpretation methods are also presented. LSSVM has been used to compute error bar. The results presented in this paper clearly highlight that the LSSVM is a robust tool for prediction of settlement of shallow foundation on cohesionless soil. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
Reliability analysis of bearing capacity of a strip footing at the crest of a simple slope with cohesive soil was carried out using the random finite element method (RFEM). Analyses showed that the coefficient of variation and the spatial correlation length of soil cohesion can have a large influence on footing bearing capacity, particularly for slopes with large height to footing width ratios. The paper demonstrates cases where a footing satisfies a deterministic design factor of safety of 3 but the probability of design failure is unacceptably high. Isotropic and anisotropic spatial variability of the soil strength was also considered. 相似文献
19.
This paper presents the method proposed to calculate the bearing capacity of a square footing under oblique and eccentric oblique loading condition (satisfying both shear failure and settlement criteria) resting on fiber reinforced sand layer underlain by sand with geosynthetic/fabric sheet at the interface. Large direct shear tests were carried out to investigate the shear strength parameters of sand and randomly distributed fiber reinforced sand (RDFS) and soil-plastic fabric sheet bond. The ultimate bearing capacity of RDFS was determined using direct shear results. Non-dimensional charts proposed by Kumar (Behaviour of eccentrically–obliquely loaded footing on reinforced earth slab. Ph.D. thesis, University of Roorkee, Roorkee, India, 2002) were used to consider the contribution of plastic fabric sheet in increasing the bearing capacity. Also, for calculating the settlement, horizontal deformation and tilt at a given pressure the regression analysis of plate load test data have been carried out. The predicted values of ultimate bearing capacity, settlement, horizontal deformation and tilt are compared with the experimental values which are in good agreement with each other. There appeared to be an increase in the residual shear strength and angle of internal friction of RDFS. 相似文献
20.
By means of a semi-analytical FE approach an embedded circular footing under monotonic horizontal and moment loading is studied.
In a non-homogeneous soil whose shear modulus is characterized by a power law variation with depth, horizontal, rocking and
coupled modes of displacement, expressed in terms of influence factors are thoroughly examined. The exponent α that controls
the shape of the stiffness variation with depth is termed shear modulus factor. Surface influence coefficients are considered
for the situations where the interface between the soil and the footing is either perfectly rough or perfectly smooth. First,
results of semi-analytical FE analysis in the case of rough footing are established and compared with those of another numerical
method. Results of comparison show good agreement. Then, for different values of α the surface influence coefficients are
presented for an embedded footing in perfect smooth contact with soil. The metacentre is referred to as the depth at which
there is no coupling between the sliding and the rocking modes of footing deformations. Expressions for location and horizontal
influence coefficient corresponding to this particular depth are developed and their variations with α examined. The paper
finishes by showing the effect of interface conditions on the soil normal stresses developed beneath the embedded circular
footing for the case of loading applied at the footing top. 相似文献