共查询到20条相似文献，搜索用时 15 毫秒
1.
In this study, a validated Finite Element procedure was used to investigate the similarities and differences of seismic performances between single- and multi-tiered reinforced soil walls. Three-tiered walls at a total height of 9 m were analyzed together with vertical walls at the same height. It was found from the Finite Element analyses that the resonant frequency of reinforced soil walls might increase with an increase in the tier-offset. The multi-tiered configuration could considerably reduce the residual lateral facing displacement and the average reinforcement load, and the reinforcement load distribution with height was different from that in vertical walls. With the same reinforcement length and spacing, the multi-tiered walls resulted in smaller reinforcement connection loads with the facing blocks. The study filled the gap of seismic behavior of multi-tiered reinforced soil retaining walls and revealed a few unique dynamic properties of this type of earth structures. 相似文献
2.
利用有限元软件对加筋土挡墙在地震荷载作用下的动力特性进行模拟分析,重点分析其在不同加筋长度、加筋间距以及峰值加速度条件下的动力响应特性。通过有限元分析一个高6m、底部为基础土的加筋土挡墙在地震荷载作用下的行为,针对理想化墙体研究加筋土挡墙的某些动力特性。模拟计算结果表明加筋土挡墙的加筋长度、加筋间距以及峰值加速度的变化对其水平位移、沉降及受力有较大影响。采用长度大的加筋材料可以有效减小加筋土挡墙的水平位移,但这样将导致加筋拉伸荷载的增大,同时也将导致加筋土挡墙的隆起增大。峰值加速度的大小对加筋土挡墙的水平位移有很大影响,当峰值加速度增大时水平位移也随之增大,但并不呈线性增长关系。减小加筋间距会有效地限制加筋土挡墙面板整体的水平位移,但在一定范围内减小加筋间距也会使加筋区域内土体底部挡墙的水平位移出现相对增大的现象,因此通过减小加筋间距来限制加筋土挡墙的位移在一定程度上具有局限性。 相似文献
3.
土工格栅加筋挡土墙是一种柔性挡土结构,目前尚未建立较严密的设计方法,作用在土工格栅加筋墙壁上的地震动土压力研究是抗震设计的重要内容之一。应用基于拉格朗日法的完全非线性动有限差分法研究整体面板式土工格栅加筋土挡壁在地震作用下各设计参数对挡壁动土压力的影响。采用弹塑性模型模拟填土,采用耦合弹性参数描述格栅与土接触界面特性,参数包括加筋间距、长度、刚度、地震强度和填土性质等,分析墙壁的动土压力沿墙身的分布特征,得出了影响地震动土压力的显著参数,证明了土工格栅加筋墙体的优异吸震能力,研究结果为整体面板式土工格栅加筋土挡墙抗震设计中的动土压力研究提供参考。 相似文献
4.
This paper examines in terms of seismic performance, the effectiveness of anchor reinforcement against gravity retaining walls used to stabilize a dry homogenous fill slope in earthquake-prone environment. Both analyzed stabilizing measures have the same design yield acceleration estimated from a limit equilibrium approach. The earthquake-induced displacements are calculated using a sliding block formulation of the equation of motion. Sliding failure along the base of the gravity retaining wall and rotational failure of the soil active wedge behind the wall, as well as rotational failure of the slide mass of the anchor-reinforced slope were considered in the present formulation. For the specific characteristics of the analyzed fill slope and input horizontal ground motion, the slope reinforced with anchors appears to experience vertical and horizontal seismic displacements at slope crest smaller by 12% and respectively, 32% than the vertical and horizontal earthquake-induced deformations estimated at the top of the active wedge behind the gravity retaining wall. 相似文献
5.
6.
Load and resistance factor design (LRFD) approach for the design of reinforced soil walls is presented to produce designs with consistent and uniform levels of risk for the whole range of design applications. The evaluation of load and resistance factors for the reinforced soil walls based on reliability theory is presented. A first order reliability method (FORM) is used to determine appropriate ranges for the values of the load and resistance factors. Using pseudo-static limit equilibrium method, analysis is conducted to evaluate the external stability of reinforced soil walls subjected to earthquake loading. The potential failure mechanisms considered in the analysis are sliding failure, eccentricity failure of resultant force (or overturning failure) and bearing capacity failure. The proposed procedure includes the variability associated with reinforced backfill, retained backfill, foundation soil, horizontal seismic acceleration and surcharge load acting on the wall. Partial factors needed to maintain the stability against three modes of failure by targeting component reliability index of 3.0 are obtained for various values of coefficients of variation (COV) of friction angle of backfill and foundation soil, distributed dead load surcharge, cohesion of the foundation soil and horizontal seismic acceleration. A comparative study between LRFD and allowable stress design (ASD) is also presented with a design example. 相似文献
7.
地基条件和墙高是影响挡土墙地震响应特征的重要因素。建立不同地基条件的仰斜式挡土墙有限元时程分析模型,以墙身外倾最大危险状态为最不利时刻,研究地基条件和墙高对挡墙动力响应及墙-土相互作用的影响特征,并以满足力学检算和墙身位移限值为出发点,提出同时考虑地基条件和地震峰值加速度PGA的仰斜式挡墙墙高控制建议。结果表明：岩质地基挡墙墙背动土压力沿墙高呈中部大、上下小的凸形分布,大震下土压力较中震时有小幅减小;基底反力呈墙踵为0、墙趾集中的三角形图式,且随PGA和墙高的增加踵部脱空趋势更为明显;土质地基挡墙因墙底地基土变形对墙后填土的牵连作用,填土跟随墙身运动的趋势加剧,墙背动土压力与PGA呈正相关并沿墙高近似呈线性分布,于墙底处最大;墙身往复摆动使踵趾端地基土体塑性变形较基底中部明显,基底反力峰值向中部转移;根据最不利时刻稳定性、承载力检算,考虑对墙身位移合理限制,提出地震区仰斜式挡墙的允许墙高在设防PGA不超过0.2g时为8 m, 0.4g大震下硬质岩地基挡墙可达8 m,软质岩地基挡墙不宜超过6 m,碎石土、砂质黏土地基挡墙不宜超过4 m。 相似文献
8.
The results of an experimental study conducted on two 1:2 reduced-scale geotextile-reinforced soil retaining walls are presented
and discussed. El Centro earthquake and sinusoidal harmonic motion excitations were applied to the 1.9 m tall models. The
design parameter investigated was the reinforcement length (L/H = 0.9 in the 1st model and L/H = 0.6 in the 2nd model). The
results were analyzed to evaluate the acceleration amplification, strains in the reinforcement layers and facing wall deformation.
The test results showed that in both experiments the walls were in fact designed to behave rigidly and almost no residual
displacements were observed on the front of the wall. The most important conclusion drawn from the experimental work was that
Geosynthetic Reinforced Retaining Structures designed according to the current specifications behave very successfully under
earthquake loading conditions. 相似文献
9.
The static and seismic sliding limit equilibrium condition of retaining walls is investigated, and analytical solutions for the angle of the active slip surface, the critical acceleration coefficient and the coefficient of active earth pressure are provided for different surcharge conditions. In particular, walls retaining a horizontal backfill without surcharge, walls supporting an extended uniform surcharge applied at different distances from the wall and walls supporting a limited uniform surcharge or linear uniform surcharge parallel to the wall are considered in the analysis.The solutions have been derived in the framework of the limit equilibrium approach, considering the effect of the wall through its weight, and accounting for the shear resistance at the base of the wall and the inertia force arising in the wall under seismic conditions.For the wall without surcharge the effect of the vertical component of the seismic acceleration as well as the effects of the inclination of the wall internal face and of the soil–wall friction were also investigated.The angle of the slip plane, the critical seismic acceleration coefficient and the coefficient of active earth pressure are given as functions of dimensionless parameters and the boundary conditions for the applicability of each solution are specified. The influence of soil weight, surcharge conditions and inertia forces on the active earth pressure coefficient is analysed. 相似文献
10.
In this paper the stability of a tied-back wall subjected to seismic loads is analysed for a predetermined mode of failure (rotation about the top of the wall) and the analysis is compared with data from tests on this type of wall using the seismic simulator at the State University of New York at Buffalo. We carried out a pseudo-static analysis of the problem using the Mononobe-Okabe earth pressure coefficients, wherein the dynamic effects due to the seismic loading are converted into equivalent static loads. The acceleration ratio at which the wall fails by rotation about the top was obtained by considering the moments due to the various lateral earth pressure resultants and the inertial forces induced in the soil due to the seismic loading. We found that the presence of wall friction on the passive side significantly enhances the stability of the flexible retaining wall under seismic loads. Thus, flexible retaining walls supporting dry cohesionless soil can be very efficient during earthquakes. Under moderate earthquakes, an increase in the depth of embedment increases the dynamic factor of safety significantly. However, beyond a certain acceleration ratio for a soil with a particular value of ø, any increase in the depth of emdedment has no effect in impeding failure, irrespective of any change in the geometry of the system. Seismic design charts are presented to evaluate the stability of, and to design, flexible retaining walls embedded in dry cohesionless soils under seismic loading. 相似文献
11.
Seismic stability analysis of gravity retaining walls 总被引：1，自引：0，他引：1
A new approach based on the category of upper bound theorem of limit analysis is presented in this study to consider the seismic stability of gravity retaining walls. The retaining wall and the backfill soil were taken as a whole system. For a translational failure mechanism assumed, formulas are provided to calculate directly the yield acceleration and the inclination of the failure surface. An example is shown to illustrate the method. Comparisons are made with limit equilibrium method, and the results are found consistent. Based on a limited parametric study, it is shown that the wall roughness has remarkable influence on the yield acceleration. 相似文献
12.
The Mononobe–Okabe (M–O) method developed in the 1920s in Japan continues to be widely used despite many criticisms and its limitations. The method was developed for gravity walls retaining cohesionless backfill materials. In design applications, however, the M–O method, or any of its derivatives, is commonly used for below ground building walls. In this regard, the M–O method is one of the most abused methods in the geotechnical practice. Recognizing the limitation of the M–O method, a simplified method was recently developed to predict lateral seismic soil pressure for building walls. The method is focused on the building walls rather than retaining walls and specifically considers the dynamic soil properties and frequency content of the design motion in its formulation. 相似文献
13.
Zhi-Fan Xia Guan-Lin Ye Jian-Hua Wang Bin Ye Feng Zhang 《Soil Dynamics and Earthquake Engineering》2010
It is known that a series of aftershocks might follow a mainshock, which may cause further damages on civil engineering structures. So it is necessary to investigate the dynamic response of structures undergone several shocks. This study presents a numerical analysis of repeated shake-consolidation process for an earth embankment founded on liquefiable foundation soils. Analysis is carried out using an effective stress-based, fully coupled, finite element method. The behaviors of the foundation soils are described by means of a cyclic mobility constitutive model which was developed at the bases of modified Cam-clay model by introducing concepts such as stress-induced anisotropy, over-consolidation, and structure. Results show that the cyclic mobility constitutive model can reflect the dynamic response of liquefiable soils. Special emphasis is given to analyze the result of excess pore water pressures, stress path, acceleration, and deformations during the two seismic excitation and consolidation process. 相似文献
14.
Fiber reinforced soil behaves as a composite material in which fibers of relatively high tensile strength are embedded in a matrix of soil. Shear stresses in the soil mobilize tensile resistance in the fibers, which in turn imparts greater strength to the soil. In this paper a study on the influence of synthetic fibrous materials in improving the dynamic response characteristics of fine sandy soil is reported. The project aims at converting fibrous carpet waste into a value-added product for soil reinforcement. A series of five shaking table tests using rigid box were carried out on Toyoura sand specimens reinforced with randomly distributed geotextile strips. The dynamic deformation characteristics of the reinforced sand are defined in terms of wall lateral deformation and rotation. The results clearly indicate the effectiveness of fiber reinforcement in improving dynamic properties of fine sand and deformation characteristics of fiber reinforced sheet pile retaining wall during shaking. 相似文献
15.
Effect of structural design on fundamental frequency of reinforced-soil retaining walls 总被引：1，自引：0，他引：1
The results of a numerical study on the influence of a number of structural design parameters on the fundamental frequency of reinforced-soil retaining wall models are presented and discussed. The design parameters in the study include the wall height, backfill width, reinforcement stiffness, reinforcement length, backfill friction angle and toe restraint condition. The intensity of ground motion, characterized by peak ground acceleration, is also included in the study as an additional parameter. The study shows that the fundamental frequency of reinforced-soil wall models with sufficiently wide backfill subjected to moderately strong vibrations can be estimated with reasonable accuracy from a few available formulae based on linear elastic wave theory using the shear wave speed in the backfill and the wall height. Numerical analyses showed no significant influence of the reinforcement stiffness, reinforcement length or toe restraint condition on the fundamental frequency of wall models. The strength of the granular backfill, characterized by its friction angle, also did not show any observable effect on the fundamental frequency of the reinforced-soil retaining wall. However, the resonance frequencies of wall models were dependent on the ground motion intensity and to a lesser extent, on the width to height ratio of the backfill. 相似文献
16.
Post-earthquake investigation on several geosynthetic-reinforced soil retaining walls and slopes during the Ji-Ji earthquake of Taiwan 总被引：1，自引：0，他引：1
Hoe I. Ling Dov Leshchinsky Nelson N. S. Chou 《Soil Dynamics and Earthquake Engineering》2001,21(4):3087
This paper gives an overview on the application of geosynthetic-reinforced soil structures in Taiwan. Taiwan has an unique topography and geotechnical conditions that rendered a less conservative and more challenging design compared to that of North America, Europe and Japan. The Ji-Ji (Chi-Chi) earthquake of 1999 gave an opportunity to examine the behavior of reinforced soil structures. The performance of several modular-block reinforced soil retaining walls and reinforced slopes at the vicinity of the fault was evaluated. Reinforced structures performed better than unreinforced soil retaining walls. The failure cases were highlighted and the cause of failure was identified. The lack of seismic design consideration could be a major cause of failure. The compound failure mode, the inertia force of the blocks, and the connection stiffness and strength relative to the large dynamic earth pressure, were among major items that would warrant further design consideration. 相似文献
17.
The effects of earthquakes on cantilever retaining walls with liquefiable backfills were studied. The experimental techniques utilized in this study are discussed here. A series of centrifuge tests was conducted on aluminum, fixed-base, cantilever wall models retaining saturated, cohesionless backfills. Accelerations on the walls and in the backfill, static and excess pore pressures in the soil, and deflections and bending strains in the wall were measured. In addition, direct measurements of static and dynamic lateral earth pressures were made. In some tests, sand backfills were saturated with the substitute pore fluid metolose. Modeling of model type experiments were conducted. The experimental measurements were found internally consistent and repeatable. Both static and dynamic earth pressure measurements were determined to be reliable. It was also observed that for the test configuration adopted, a special boundary treatment such as the use of duxseal is optional. Static and seismic modeling of models were also successful, which indicated that the assumed scaling relations were essentially correct. 相似文献
18.
Experimental evidence supporting the fact that results from quasi‐static (QS) test of low‐rise reinforced concrete walls may be safely assumed as a lower limit of strength and displacement, and energy dissipation capacities are still scarce. The aim of this paper is to compare the seismic performance of 12 reinforced concrete walls for low‐rise housing: six prototype walls tested under QS‐cyclic loading and six models tested under shaking table excitations. Variables studied were wall geometry, type of concrete, web steel ratio, type of web reinforcement and testing method. Comparison of results from dynamic and QS‐cyclic tests indicated that stiffness and strength properties were dependent on the loading rate, the strength mechanisms associated with the failure mode, the low‐cycle fatigue, and the cumulative parameters, such as displacement demand and energy dissipated. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
19.
Two correctly-scaled model cantilever retaining walls of different stiffnesses were tested under dynamic loading conditions in a centrifuge. A medium-dense fine sand was retained with a range of backfill slopes. For the centrifuge model, an earthquake-generating mechanism was designed to produce seismic shaking equivalent to that generated at ground surface in the epicentral area of an earthquake of approximate magnitude 5–5. The response of the model retaining walls to the input dynamic motion was measured by strain gauges, pressure transducers and accelerometers. From the measurements plots were constructed of moment, shear, pressure and displacement over the height of the walls as a function of time. The results are compared with calculations based on the quasi-static Mononobe-Okabe theory. Although the calculated resultant force is in reasonable agreement with the experiments, the moments can be substantially different. Residual values of all parameters at the end of shaking are considerably greater than the initial static values. It is recommended that dynamic behaviour be incorporated in the earthquake design of retaining walls. 相似文献
20.
Study of the liquefaction resistance of a saturated sand reinforced with Geosynthetics 总被引：1，自引：0，他引：1
This article presents various tests using a cyclic triaxial instrument, on samples of saturated Hostun RF sand, reinforced with circular sheets of geosynthetic material. Tests performed with different types of geosynthetics of different compressibility, rigidity and roughness characteristics indicate a significant increase in liquefaction resistance for samples reinforced with compressible, non-woven geotextiles. The undrained behaviour of saturated Hostun RF sand reinforced with non-woven geotextiles is analysed on the basis of different test series. This analysis highlights the influence of reinforcement compressibility on interstitial pressure distribution in the sample, thus showing the role of this type of inclusion in the increase in liquefaction resistance. 相似文献