共查询到20条相似文献，搜索用时 15 毫秒
1.
Seong-Bae Jo Jeong-Gon Ha Mintaek Yoo Yun Wook Choo Dong-Soo Kim 《Bulletin of Earthquake Engineering》2014,12(2):961-980
In the design procedure for a retaining wall, the pseudo-static method has been widely used and dynamic earth pressure is calculated by the Mononobe–Okabe method, which is an extension of Coulomb’s earth pressure theory computed by force equilibrium. However, there is no clear empirical basis for treating the seismic force as a static force, and recent experimental research has shown that the Mononobe–Okabe method is quite conservative, and there exists a discrepancy between the assumed conditions and real seismic behavior during an earthquake. Two dynamic centrifuge tests were designed and conducted to reexamine the Mononobe–Okabe method and to evaluate the seismic lateral earth pressure on an inverted T-shape flexible retaining wall with a dry medium sand backfill. Results from two sets of dynamic centrifuge experiments show that inertial force has a significant impact on the seismic behavior on the flexible retaining wall. The dynamic earth pressure at the time of maximum moment during the earthquake was not synchronized and almost zero. The relationship between the back-calculated dynamic earth pressure coefficient at the time of maximum dynamic wall moment and the peak ground acceleration obtained from the wall base peak ground acceleration indicates that the seismic earth pressure on flexible cantilever retaining walls can be neglected at accelerations below 0.4 g. These results suggest that a wall designed with a static factor of safety should be able to resist seismic loads up to 0.3–0.4 g. 相似文献
2.
This paper outlines the results of an experimental program carried out on centrifuge models of cantilevered and propped retaining walls embedded in saturated sand. The main aim of the paper is to investigate the dynamic response of these structures when the foundation soil is saturated by measuring the accelerations and pore pressures in the soil, displacements and bending moment of the walls. A comparison among tests with different geometrical configurations and relative density of the soil is presented. The centrifuge models were subjected to dynamic loading in the form of sinusoidal accelerations applied at the base of the models. This paper also presents data from pressure sensors used to measure total earth pressure on the walls. Furthermore, these results are compared with previous dynamic centrifuge tests on flexible retaining walls in dry sand. 相似文献
3.
砂土自由场地震响应的离心机试验研究 总被引：3，自引：1，他引：2
离心机模型试验是研究岩土地震工程问题的有效手段。本文使用层状剪切箱,通过干落法制备了均匀的砂土模型,进行了离心机振动试验;观测了振动过程中孔隙水压力的发展,土体的加速度响应、侧向变形以及竖向沉降。结果表明,土体的运动和变形与孔隙水压力的发展密切相关,但离心机中的试验现象和现场观测的现象存在显著区别。研究结果增强了对振动过程中土-水之间相互作用机理的理解,同时为自由场地震响应分析方法的验证提供了基础数据。 相似文献
4.
Evolution of the shear wave velocity during shaking modeled in centrifuge shaking table tests 总被引：2，自引：1，他引：1
Chung-Jung Lee Chung-Ru Wang Yui-Chen Wei Wen-Yi Hung 《Bulletin of Earthquake Engineering》2012,10(2):401-420
Two in-flight shear wave velocity measurement systems were developed to perform the subsurface exploration of shear wave velocity
in a centrifuge model. The bender elements test and the pre-shaking test used in the study provided reliable and consistent
shear wave velocity profiles along the model depth before and after shaking in the centrifuge shaking table tests. In addition,
the use of the bender elements measurement system particularly developed here allowed continuous examination of the evolution
of shear wave velocity not only during and after the shaking periods in the small shaking events but also during the dissipation
period of excess pore water pressure after liquefaction in the large shaking events. The test results showed that the shear
wave velocity at different values of excess pore water pressure ratio varied as the effective mean stress to the power of
0.27, to a first approximation. Consequently, a relationship between the shear wave velocity evolution ratio and the excess
pore water pressure ratio is proposed to evaluate the changes in shear wave velocity due to excess pore water generation and
dissipation during shaking events. This relation will assist engineers in determining the shear stiffness reduction ratio
at various ru levels when a sand deposit is subjected to different levels of earthquake shaking. 相似文献
5.
Two dynamic centrifuge model tests were performed to simulate dry or saturated sand deposits subjected to 1 Hz base shaking. This experimental study investigated the boundary effects of a laminar container on the seismic response acquired from accelerometers and from pore pressure transducers, both of which were embedded in the sand bed at various depths and distances from the end walls. Under the tested configurations and the employed input motion used in the study, the test results revealed minimal boundary effects on the seismic responses. The measured maximum amplitude, main frequencies, phase lags of acceleration, and the profiles of the calculated RMS acceleration amplification factor were not affected by the boundaries if the instruments were positioned at a distance of more than one-twentieth of the model length from the end walls and were not positioned on the ground surface. No obvious discrepancies were observed in the time histories of excess pore water pressure, measured at a distance of one-fourth of the model length from the end walls. These results infer that variations in the seismic response at the end walls were minimal; hence the laminar container used in the study may be used effectively to simulate 1D shear wave propagation in centrifuge shaking table tests. However, for other testing configurations, a similar study should be undertaken for evaluating the boundary effect of the laminar container on the seismic responses. 相似文献
6.
Evaluating the seismic active earth pressure on retaining walls is currently based on pseudo-static method in practices. In this method, however, it is not simple, choosing an appropriate value for earthquake coefficient, which should fully reflect the dynamic characteristics of both soil and loading is an important problem. On the other hand, by using only two extra dynamic parameters that are shear wave velocity of soil and predominant frequency of probable earthquake, one can benefit from another more accurate tool called pseudo-dynamic method to solve the problem of earth pressure.In this study in the framework of limit equilibrium analysis, pseudo-dynamic method has been applied into horizontal slice method of analysis to account for the effect of earthquake on lateral earth pressure history behind rigid retaining walls. The pressure history resulted from a number of analyses shows that before and after reaching the peak resultant force, different pressure distributions occur behind a wall that put more local pressure than the same at peak. This method would be a tool to control this phenomenon in wall design. 相似文献
7.
桩板式挡土结构由抗滑桩发展而来,可用于一般地区、浸水地区和地震区的边坡工程支挡;对于地震区边坡,采用单排或双排支挡结构的形式及其支挡效果尚缺少深入研究。本文基于地震力作用下单排、双排桩板结构在不同加载等级时的桩身土压力、土体加速度、桩身位移等变化的振动台模型试验结果,对比采用单排、双排桩板结构边坡的支挡效果,得出静力状态和不同加速度峰值地震力作用桩前后土压力分布、桩后土体加速度分布和桩体位移的一些规律,为今后边坡桩板式支挡结构的抗震设计提供参考。 相似文献
8.
Centrifuge modeling of seismic response of layered soft clay 总被引：1，自引：0，他引：1
Centrifuge modeling is a valuable tool used to study the response of geotechnical structures to infrequent or extreme events
such as earthquakes. A series of centrifuge model tests was conducted at 80g using an electro-hydraulic earthquake simulator mounted on the C-CORE geotechnical centrifuge to study the dynamic response
of soft soils and seismic soil–structure interaction (SSI). The acceleration records at different locations within the soil
bed and at its surface along with the settlement records at the surface were used to analyze the soft soil seismic response.
In addition, the records of acceleration at the surface of a foundation model partially embedded in the soil were used to
investigate the seismic SSI. Centrifuge data was used to evaluate the variation of shear modulus and damping ratio with shear
strain amplitude and confining pressure, and to assess their effects on site response. Site response analysis using the measured
shear wave velocity, estimated modulus reduction and damping ratio as input parameters produced good agreement with the measured
site response. A spectral analysis of the results showed that the stiffness of the soil deposits had a significant effect
on the characteristics of the input motions and the overall behavior of the structure. The peak surface acceleration measured
in the centrifuge was significantly amplified, especially for low amplitude base acceleration. The amplification of the earthquake
shaking as well as the frequency of the response spectra decreased with increasing earthquake intensity. The results clearly
demonstrate that the layering system has to be considered, and not just the average shear wave velocity, when evaluating the
local site effects. 相似文献
9.
A two-dimensional (2D) finite element analytical model is developed to analyze the seismic response of rigid highway bridge abutments, retaining and founded on dry sand. A well verified finite element code named FLEX is used for this purpose. The proposed model has the following characteristics: (1) The soil (dry sand in this study) is modeled by a 2D finite element grid; (2) The bridge abutment is molded as a rigid substructure; (3) The strength and deformation of the soil are modeled using the viscous cap constitutive model. This model consists of a failure surface and hardening cap together with an associated flow rule. The cap surface is activated for the soil under the wall to represent compaction during wall rocking. In addition, viscoelastic behavior is provided for representing the hysteretic-like damping of soil during dynamic loading; (4) Interface elements are used between the wall and the soil (at the backface of the wall and under its base) to allow for sliding and for debonding/recontact behavior; (5) The finite element grid is truncated by using an absorbing boundary approximation. Using this boundary at both sides of the grid simulates the horizontal radiation of energy scattered from the wall and the excavation. Shear beams are placed adjacent to the lateral boundaries from each side which give the far-field ground motion, for comparison with those computed adjacent to the boundaries. The analytical model is verified comparing predictions to results from dynamic centrifuge tests, with satisfactory agreement. The proposed model is used to study the dynamic response of an 8.0 m high and 3.0 m wide rigid bridge abutment (proportioned using the traditional approach to design) for different sinusoidal and earthquake acceleration input motions. The results from the analysis show that outward tilting of rigid bridge abutments is the dominant mode of response during dynamic shaking and that these abutments end up with a permanent outward tilt at the end of shaking. The results from all the analyzed cases of the 8.0 m high gravity retaining wall together with those from the analysis of the tilting wall centrifuge tests are discussed and used for proposing a practical method for evaluating the seismic response of rigid abutments during earthquakes. 相似文献
10.
An overview of past and recent developments on the subject of seismic earth pressures on yielding, gravity-type walls, retaining cohesionless backfill, is first presented, focusing on available data on the issue of phase difference that develops between the peak values of wall inertia and seismic earth thrust increment. The results of a FEM parametric study are next presented regarding the dependence on the resulting dynamic earth thrust reduction – acting on the time of peak wall inertia – on backfill rigidity, wall height, and shaking characteristics. The reliability of the numerical analyses was verified by modeling centrifuge tests reported by Nakamura [24] and successfully comparing measured vs. computed behavior. The results of the parametric analyses indicate that the seismic active earth thrust, acting on the wall at the time of maximum wall inertia, is significantly reduced (compared to its peak value) with increasing shaking intensity of backfill, increasing wall displacements, increasing wall height, and decreasing backfill rigidity. No systematic dependence on the ratio of input motion frequency to the natural frequency of the backfill (f/f1) was observed. The above findings: (1) verify earlier experimental and numerical results, (2) explain the reported lack of damage to retaining walls under strong ground shaking, and (3) indicate the need for revising the pertinent provisions of current seismic codes. Graphs summarizing the results of the numerical analyses are presented which may be used as a guide for selecting the magnitude of seismic active earth thrust that needs to be taken into account in the design of the examined type of earth retaining walls. 相似文献
11.
A series of 2-D centrifuge modeling tests with an in-flight shaker were carried out in order to model both the deformation characteristics of backfill and the seismic responses of caisson-type walls embedded in soils with various permeabilities. The rotational and translational modes were found to be in phase or various degrees out of phase with each other for quay walls embedded in soils with varying permeabilities. The alternative pumping and suction processes in excess pore water pressure that are caused by a wall's vibrations increase the level of damage because large amounts of backfill are forcedly leaked into the sea. The test results show that the rotational mode makes the dominant contribution to the changes in excess pore water pressure and in the earth pressure in the deep layers of soil, but the translational mode makes the dominant contribution to these pressures in the shallow layers. The average shear wave velocities were found to decrease rapidly to values as low as 1/8th of the velocity measured at the beginning of shaking. 相似文献
12.
Dynamic response of dams is significantly influenced by foundation stiffness and dam-foundation interaction. This in turn,
significantly effects the generation of hydrodynamic pressures on upstream face of a concrete dam due to inertia of reservoir
water. This paper aims at investigating the dynamic response of dams on soil foundation using dynamic centrifuge modelling
technique. From a series of centrifuge tests performed on model dams with varying stiffness and foundation conditions, significant
co-relation was observed between the dynamic response of dams and the hydrodynamic pressures developed on their upstream faces.
The vertical bearing pressures exerted by the concrete dam during shaking were measured using miniature earth pressure cells.
These reveal the dynamic changes of earth pressures and changes in rocking behaviour of the concrete dam as the earthquake
loading progresses. Pore water pressures were measured below the dam and in the free-field below the reservoir. Analysis of
this data provides insights into the cyclic shear stresses and strains generated below concrete dams during earthquakes. In
addition, the sliding and rocking movement of the dam and its settlement into the soil below are discussed. 相似文献
13.
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
14.
15.
面板堆石坝的动力离心模型试验研究 总被引：1，自引：0，他引：1
为研究面板堆石坝的地震响应规律,采用Parkfield波作为地震动输入,在清华大学50g-t土工离心机上进行了动力离心模型试验.试验在50倍重力加速度条件下采用电液伺服离心机振动台系统完成,采用加速度传感器测量了模型不同位置动力响应的加速度时程并且测量了面板的变形.结果表明,地震最大响应发生于坝顶,该处地震动放大系数接... 相似文献
16.
Static and dynamic behavior of hunchbacked gravity quay walls 总被引：2，自引：0，他引：2
Abouzar Sadrekarimi Abbas Ghalandarzadeh Jamshid Sadrekarimi 《Soil Dynamics and Earthquake Engineering》2008,28(2):99-117
One of the parameters that can affect the lateral pressures behind a retaining wall is the back-face shape of the wall, which can be controlled by the designer, and has not been investigated experimentally. Therefore, in order to study this behavior, a set of 1g shaking table tests was carried out on hunched back gravity type quay walls made of concrete blocks. Crushed stone and silica sand were used in the backfill and subsoil, respectively. The subsoil was prepared by moist tamping. The models were fully instrumented and beside each earth pressure transducer a pore water pressure sensor was also installed behind the wall therefore the lateral effective stress acting on the wall could be calculated. Tests were performed with various base accelerations on models with different subsoil relative densities. The results show that the earth pressure increases at upper portions of the wall and decreases by the leaning slope at lower elevations. Depending on the back-face shape of the wall the total thrust and overturning moment would be increased or decreased after an earthquake. However, the hunched back-shape of the wall tends to raise the point of application of the total thrust exerted on the wall. Other advantages of hunched back walls are demonstrated as well. 相似文献
17.
土-地铁车站结构动力相互作用大型振动台模型试验研究 总被引：12，自引：5，他引：12
以南京地铁为背景,开展了深厚软弱场地土-地铁地下结构动力相互作用的大型振动台模型试验研究。在试验中获得的主要数据有:模型体系的加速度反应时程、模型结构的应力反应时程和结构表面的土压力时程等。本文对试验反映的地铁车站结构的动力反应规律及其周围模型地基的地震反应规律进行了分析。结果表明:车站结构的中柱应变反应明显大于别的构件,同时,深厚软弱地基上车站结构侧墙底部的应变反应也明显大于侧墙顶部的反应,其中,车站结构顶板、中间层楼板和底板的应变反应都很小;输入地震动的频谱特性对车站结构应变反应的影响是不同的,在同一加载情况下,在台面输入傅氏谱频宽最大的南京人工波时车站结构应变反应最大。 相似文献
18.
An analytical model is developed to analyze the seismic response of gravity walls retaining and founded on dry sand, with special emphasis on tilting behaviour. A well verified two-dimensional finite element code is used for this purpose. The analytical model is verified by comparing predictions to results from three dynamic centrifuge tests, with satisfactory agreement. Moreover, sensitivity analyses are carried out for one of the centrifuge test conditions to understand how the results would change if the boundary conditions and rotational stiffness of the wall were changed. 相似文献
19.
Seismic behaviour of flexible retaining systems subjected to short-duration moderately strong excitation 总被引：2，自引：0，他引：2
G. Gazetas P. N. Psarropoulos I. Anastasopoulos N. Gerolymos 《Soil Dynamics and Earthquake Engineering》2004,24(7):537-550
Using finite-element modelling, this paper explores the magnitude and distribution of dynamic earth pressures on several types of flexible retaining systems: L-shaped reinforced-concrete walls, piled walls with horizontal or with strongly inclined anchors, and reinforced-soil walls. The utilized base excitation is typical of earthquake motions of either high or moderately low dominant frequencies having a peak ground acceleration (PGA) of 0.40 g and relatively short duration. Linear as well as non-linear (Mohr–Coulomb) soil behaviour is investigated, under dry conditions. The results show that, as the degree of realism in the analysis increases, we can explain the frequently observed satisfactory performance of such retaining systems during strong seismic shaking. 相似文献
20.
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