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1.
Amirali Mostafavi Moghadam Abbas Ghalandarzadeh Majid Moradi Ikuo Towhata Pouria Hajialikhani 《Bulletin of Earthquake Engineering》2011,9(4):1259-1288
This research is to study the efficiency of displacement reducer fuses, installed behind the caisson quay walls for controlling
the dynamic backfill thrust and minimizing the displacement, settlement and tilting of the walls. For this purpose, two types
of fuses, Displacement Reducer Panels (DRP) and Displacement Reducer Elements (DRE), were constructed and installed behind
the wall. The DRPs were constructed by hollow Polypropylene sheets to reproduce elastoplastic and plastic mechanical behaviors.
The DREs were cylindrical stainless-steel dampers, working upon friction mechanism that can reproduce perfect plastic behavior.
Here, two series of shaking table 1-g tests were performed with DRP and DRE applications. In this regard, different mechanical
behaviors and capacities were considered for fuses against demand thrusts of backfill in order to compare the mitigation tests
with no-mitigation cases. Harmonic base motions with constant amplitude and constant frequency were used in the model test.
The foundation soil and the backfill soil were constructed with the relative densities of 85 and 25%, respectively, to reproduce
non-liquefiable base layer and loose backfill situations in the model, respectively. The results showed remarkable reduction
in kinetic energy, dynamic backfill thrust and consequently seaward movement, settlement and inclination of the caisson quay
wall in case of using fuses with plastic behaviors behind the wall. 相似文献
2.
Evaluation of seismic displacements of quay walls 总被引：2，自引：0，他引：2
Sung-Ryul Kim In-Sung Jang Choong-Ki Chung Myoung-Mo Kim 《Soil Dynamics and Earthquake Engineering》2005,25(6):451-459
A new simplified dynamic analysis method is proposed to predict the seismic sliding displacement of quay walls by considering the variation of wall thrust, which is influenced by the excess pore pressure developed in backfill during earthquakes. The method uses the Newmark sliding block concept and the variable yield acceleration, which varies according to the wall thrust, to calculate the quay wall displacement.A series of 1 g shaking table tests were executed to verify the applicability of the proposed method, and a parametric study was performed. The shaking table tests verified that the proposed method properly predicts the wall displacement, and the parametric study showed that the evaluation of a realistic wall displacement is as important as the analysis of liquefaction potential for judging the stability of quay walls. 相似文献
3.
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
4.
In the last 50 years, there have been many incidences of failure of gravity quay walls. These failures are often associated with significant deformation of liquefiable soil deposits. Gravity quay wall failures have stimulated great progress in the development of deformation-based design methods for geotechnical structures. In this paper, the effective-stress analysis method has been used in conjunction with a generalised elasto-plasticity constitutive model implemented into a finite element procedure. Various monotonic and cyclic triaxial paths are simulated in order to demonstrate the capabilities of the constitutive model. The FEM is validated by back analysis of a typical Port Island PC1 caisson type quay wall, which was damaged during the 1995 Hyogoken-Nanbu earthquake. The numerical results are compared with the observed data obtained consisting of seaward displacement, settlement and tilting. In addition, both the influence of permeability, on the generation of pore water pressure and the influence of the relative density of the backfill and foundation layers, on the residual deformation of gravity quay walls are investigated. 相似文献
5.
Erol Guler Elif Cicek M. Melih Demirkan Murat Hamderi 《Bulletin of Earthquake Engineering》2012,10(3):793-811
Novel approaches to the dynamic analysis of the reinforced soil walls have been reported in the literature. Use of marginal soils reduces the cost of geosynthetic reinforced soil walls if proper drainage measures are taken. Therefore the affect of using cohesive marginal soils as backfill in geosynthetic reinforced retaining structures were investigated in this research. The dynamic response of reinforced soil walls was investigated in a similar focus, using finite element analysis. The results obtained from walls with cohesive backfill were compared to the results obtained from walls with granular backfill. The height of the wall was chosen as 6 m in the two-dimensional plane strain finite element model and the base acceleration was chosen to be a harmonic motion. The effects of various parameters like the backfill type, facing type, reinforcement stiffness, and peak ground acceleration on the cyclic response of reinforced soil retaining walls were investigated. After analyzing the wall response for end of construction and dynamic excitation phases, it was determined that the deformations and reinforcement tensile loads increased during the cyclic load application and that the amount of additional deformation that occurred during cyclic load application was strongly related to backfill soil type, facing type, reinforcement type and peak ground acceleration. It was determined that a cohesive backfill and geotextile reinforcement was a good combination to reduce the deformations of geosynthetic reinforced walls during cyclic loading for medium height walls. 相似文献
6.
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
7.
Base isolated buildings subjected to extreme earthquakes can exceed their design displacements and impact against the surrounding moat wall. To better understand the consequences of impact on the superstructure, an impact element considering moat wall flexibility is proposed based on impact theory and observations during experimental simulations. It is demonstrated that numerical simulations using the proposed impact element can capture the dominant characteristics of the contact force observed in experiments of base isolated buildings impacting various moat wall configurations including concrete walls with soil backfill and rigid steel walls. The contact force is dependent on impact velocity, geometry, and material properties at the contact surface, and the global dynamic characteristic of the moat wall. Properties of the moat wall impact element are derived based on mechanics‐based models considering material properties and geometric measurements of the experimental setup. For this purpose, the moat wall is modeled as a flexural column with a concentrated nonlinear hinge at its base and soil backfill considered through a damped elastic foundation then generalized into a single degree of freedom system. The resulting impact element is shown to accurately capture both local deformation and the vibration aspects of impact observed in experiments and the effects of impact on superstructure response. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
R. Uzuoka M. Cubrinovski H. Sugita M. Sato K. Tokimatsu N. Sento M. Kazama F. Zhang A. Yashima F. Oka 《Soil Dynamics and Earthquake Engineering》2008,28(6):436-452
The 1995 Kobe earthquake seriously damaged numerous buildings with pile foundations adjacent to quay walls. The seismic behavior of a pile group is affected by movement of quay walls, pile foundations, and liquefied backfill soil. For such cases, a three-dimensional (3-D) soil–water coupled dynamic analysis is a promising tool to predict overall behavior. We report predictions of large shake table test results to validate 3-D soil–water coupled dynamic analyses, and we discuss liquefaction-induced earth pressure on a pile group during the shaking in the direction perpendicular to ground flow. Numerical analyses predicted the peak displacement of footing and peak bending moment of the group pile. The earth pressure on the pile in the crustal layer is most important for the evaluation of the peak bending moment along the piles. In addition, the larger curvatures in the bending moment distribution along the piles at the water side in the liquefied ground were measured and predicted. 相似文献
9.
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
10.
11.
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
12.
13.
This technical note presents an analytical expression for the total passive pressure on a retaining wall from the c–? soil backfill subjected to both horizontal and vertical seismic inertial forces. The developed expression has been analysed for the special cases, and the results have been found identical to those proposed by earlier researchers on the subject. A numerical example, presented to illustrate the steps for the calculation of total dynamic passive pressure using the developed general expression, shows that the design value of total dynamic passive pressure as a resistance to the retaining wall movement should be obtained with upward vertical seismic inertial force in combination with the direction of horizontal seismic force towards the backfill. 相似文献
14.
Constantine A. Stamatopoulos Eleni G. Velgaki Arezou Modaressi Fernando Lopez-Caballero 《Bulletin of Earthquake Engineering》2006,4(3):295-318
Gravity walls retaining dry soil are modeled as a system of two bodies: (a) the gravity wall that slides along the wall-foundation soil boundary and (b) the critical soil wedge in the soil behind the wall. The strength of the system is defined by both the frictional and the cohesional components of resistance. The angle of the prism of the critical soil wedge behind the wall is obtained using the limit equilibrium method. The model accounts for changes in the geometry of the backfill soil behind the wall by considering the displacements at the end of each time step under limit equilibrium. The model shows that the standard (single) block model is over-conservative for the extreme case of critical-to-applied-seismic acceleration ratios less than about 0.30, but works well for cases where this ratio ranges between 0.5 and 0.8. The model is applied to predict the seismic displacement of gravity walls (a) tested in the shaking-table and (b) studied numerically by elaborate elasto–plastic analyses. 相似文献
15.
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
16.
Aldo Evangelista Anna Scotto di Santolo Armando Lucio Simonelli 《Soil Dynamics and Earthquake Engineering》2010
A stress plasticity solution is proposed for evaluating the gravitational and dynamic active earth pressures on cantilever retaining walls with long heel. The solution takes into account the friction angle of the soil, wall roughness, backfill inclination and horizontal and vertical seismic accelerations. It is validated by means of the comparison with both traditional limit equilibrium methods (e.g. Mononobe–Okabe equations) and static and pseudostatic numerical FLAC analyses. For numerical analyses the soil is modelled as an elasto-plastic non-dilatant medium obeying the Mohr–Coulomb yield criterion, while the wall is elastic. The solutions for the horizontal and vertical seismic coefficients are proposed, which allow one to determine the intensity of the active thrust and its inclination δ with respect to the horizontal. It is demonstrated that the latter also depends on the soil friction angle φ. The inclination in seismic conditions δE is greater than the one in static conditions, δS, usually adopted in both cases. As a matter of fact, since wall stability conditions improve with the increase of inclination δ, the present method gives solutions that are less onerous than traditional ones, producing less conservative wall designs. Finally pseudostatic results are compared with proper dynamic analyses (by FLAC code) performed utilising four Italian accelerometric time-histories as input ground motion. 相似文献
17.
This paper presents experimental results of a series of 1g shake table tests on mitigation measures for a model consisting of a 3×3 pile group and a sheet-pile quay wall in which the pile group was subjected to liquefaction-induced lateral spreading. First, general observations associated with the mechanism of lateral spreading and pile response are presented based on tests without remedial measures, followed by in depth discussions. Second, three remedial techniques were deployed to provide an adequate seismic performance of the pile group and the quay wall: (i) mitigating sheet pile of floating type, (ii) mitigating sheet pile of fixed end type, and (iii) anchoring the quay wall to a new pile row. The main objective of these mitigation methods was to restrict ground distortion behind the quay wall, enhancing seismic response of pile group and quay wall. This mitigation philosophy was decided based on the outcome of the first part, which consisted of a series of tests without mitigation measures. In addition, it should be noted that the proposed countermeasures were selected to be applicable for existing vulnerable pile groups, which are at risk of liquefaction and lateral spreading. Results of different mitigation tests are comparatively examined using a parameter called reduction factor, and the effectiveness of each countermeasure is discussed in detail. The results demonstrate that by applying the proposed mitigation measures the seismic performance of both pile group and quay wall can be improved, as a result of reduction in soil displacement and velocity of soil flow. 相似文献
18.
This technical note presents an analytical derivation of the expression for the total dynamic active thrust on a retaining wall from the c–? soil backfill considering both horizontal and vertical seismic coefficients. The derivation is based on the Coulomb sliding wedge concept, and it considers tension cracks, wall adhesion, and surcharge in order to make the expression useful for practical applications. It is found that the special cases of the general expression result in the expressions for total static and dynamic active thrusts presented by earlier researchers for different field conditions of soil backfills with and without seismic loadings. 相似文献
19.
At present, methods based on allowable displacements are frequently used in the seismic design of earth retaining structures. However, these procedures ignore both the foundation soil deformability and the seismic amplification of the soil placed behind the retaining wall. Thus, they are not able to predict neither a rotational failure mechanism nor seismic induced lateral displacements with an acceptable degree of accuracy for the most general case. In this paper, a series of 2D finite-element analyses were carried out to study the seismic behavior of gravity retaining walls on normally consolidated granular soils. Chilean strong-motion records were applied at the bedrock level. An advanced non-linear constitutive model was used to represent both the backfill and foundation soil behavior. This elastoplastic model takes into account both the stress dependency of soil stiffness and coupling between shear and volumetric strains. In unloading–reloading cycles, the non-linear shear-modulus reduction with shear strain amplitude is considered. Interface elements were used to model soil–structure interaction. Routine-design charts were derived from the numerical analyses to predict the lateral movements at the base and top of gravity retaining walls located at sites with similar seismic characteristics to the Chilean subduction zone. Thus, wall seismic rotation can also be obtained. The developed charts consider wall dimensions, granular soil properties, bedrock depth, and seismic input motion characteristics. As shown, the proposed charts match well with available experimental data. 相似文献
20.
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