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1.
This study was conducted to determine the stability of a quay wall under the combined action of an earthquake and tsunami. Adopting the limit equilibrium method, the stability of the quay wall was assessed for both the sliding and overturning modes under passive and active conditions. The variation in the stability of the quay wall was determined by parametric studies, including those for the tsunami wave height, seismic acceleration coefficient, internal friction angle of soil, wall friction angle, and pore water pressure ratio. The stability of the wall was also compared with the case of no earthquake and tsunami forces. When the earthquake and tsunami were considered simultaneously, the stability of the wall under the passive condition decreased significantly. The critical mode of the quay wall under the earthquake and tsunami forces was found to be that of the overturning mode. In the active condition, the safety factors for sliding and overturning increased, because the tsunami acted as a resisting force. However, it should be noted that, if a tsunami wave spills over the quay wall and then flows backward to the wall active condition, the tsunami no longer acts as a resisting force. 相似文献
2.
An analytical expression of a gravity retaining wall's seismic stability against sliding and overturning is proposed in this article. The derivation, aiming at the cohesionless soil with inclined backfill surface and nonvertical wall back, is based on limit equilibrium analysis and the pseudo-dynamic method. The variations of the sliding and overturning stability safe factors with the horizontal seismic acceleration are investigated for different seismic amplification factors, soil friction angles, wall friction angles, vertical seismic acceleration coefficients, wall back inclination angles, and backfill surface inclination angles. The results indicate that the soil friction and horizontal seismic action significantly impact the seismic stability. The increase of vertical earthquake action changes the curvature of stability factor curves. The wall friction and back inclination strengthen the gravity retaining wall's resistance to sliding and overturning failure while the backfill surface inclination plays a negative role in the seismic stability. We also found that the seismic stability safe factors calculated by the proposed method are larger but more reasonable than those by the Mononobe-Okabe method. 相似文献
3.
Waterfront retaining walls supporting dry backfill are subjected to hydrostatic pressure on upstream face and earth pressure on the downstream face. Under seismic conditions, if such a wall retains a submerged backfill, additional hydrodynamic pressures are generated. This paper pertains to a study in which the effect of earthquakes along with the hydrodynamic pressure including inertial forces on such a retaining wall is observed. The hydrodynamic pressure is calculated using Westergaard's approach, while the earth pressure is calculated using Mononobe-Okabe's pseudo-static analysis. It is observed that when the horizontal seismic acceleration coefficient is increased from 0 to 0.2, there is a 57% decrease in the factor of safety of the retaining wall in sliding mode. For investigating the effect of different parameters, a parametric study is also done. It is observed that if φ is increased from 30° to 35°, there is an increase in the factor of safety in the sliding mode by 20.4%. Similar observations were made for other parameters as well. Comparison of results obtained from the present approach with [Ebeling, R.M., Morrison Jr, E.E., 1992. The seismic design of waterfront retaining structures. US Army Technical Report ITL-92-11. Washington DC] reveal that the factor of safety for static condition (kh=0), calculated by both the approaches, is 1.60 while for an earthquake with kh=0.2, they differ by 22.5% due to the consideration of wall inertia in the present study. 相似文献
4.
By using the modified pseudo-dynamic method for submerged soils this paper explores the seismic stability of seawall for the active condition of earth pressure. Different forces such as seismic active earth pressure, seismic inertia forces of the wall, non-breaking wave pressure, hydrostatic and hydrodynamic pressures are considered in the stability analysis. Limit equilibrium has been used, and expressions for the factor of safety against sliding and overturning mode of failure have been proposed. The proposed methodology overcomes the limitations of existing pseudo-dynamic method for submerged soils. A detailed parametric study has been conducted by varying different parameters and results are presented in the form of design charts for computation of factor of safety against sliding and overturning mode of failures. It was noticed that the influences of soil friction angle, seismic acceleration coefficient, wall inclination and excess pore pressure are significant when compared to the other parameters. The value of factor of safety against the sliding mode of failure is increasing by about 62% when the value of soil frictional angle is increased from 30° to 40°. It was also found that the factor of safety against overturning mode of failure is decreasing by about 22% as the value of excess pore pressure ratio increases from 0 to 0.75. The proposed method with closed-form solutions can be used for the seismic design of seawalls. 相似文献
5.
B. Giridhar Rajesh 《Marine Georesources & Geotechnology》2017,35(7):930-938
The sparsity of examination of seismic passive earth pressure acting on retaining wall holding soil backfill with full submergence, which is more common in waterfront areas, can be noticed from the literature. In the current study, a closed-form solution to compute the seismic passive earth pressure on nonvertical rigid retaining wall retaining a backfill with full submergence is proposed using the modified pseudo-dynamic approach. A nonlinear rupture surface (logarithmic spiral?+?straight line) in a submerged backfill of viscoelastic nature has been assumed. The presented modified pseudo-dynamic method overcomes the limitations of the existing pseudo-dynamic method for submerged soils. The proposed methodology has been thoroughly validated with the available literature. The influences of seismic acceleration coefficients, excess pore water pressure ratio, wall inclination, and soil and wall friction angles have been studied. It has been noticed that the consideration of excess pore pressure ratio leads to significant decrease in seismic passive resistance of the soil which in turn lead to extra hydraulic pressure acting on the wall in submerged backfill. There is a 57% decrease in seismic passive earth pressure coefficient as the wall inclination changes from ?15° to 15°. 相似文献
6.
沉箱式防波堤静力与动力稳定性设计体型分析 总被引：2，自引：0，他引：2
将沉箱式防波堤滑移和倾覆稳定性设计方法分为三类：静力设计方法、不允许沉箱出现滑移和摇摆角的动力设计方法、控制沉箱滑移量和摇摆角的动力设计方法。建立了满足给定抗滑和抗倾安全系数条件下，按静力设计方法确定沉箱尺度的控制方程，研究了波浪条件和安全系数取值对沉箱长宽比的影响。通过动力数值计算分析了沉箱长宽比对沉箱滑移量和摇摆角的影响，并与传统静力设计理论进行了比较，讨论了控制沉箱滑移量和摇摆角的动力设计方法的可行性。 相似文献
7.
A numerical time-simulation algorithm for analysing highly nonlinear solitary waves interacting with plane gentle and steep slopes is described by employing a mixed Eulerian–Lagrangian method. The full nonlinear free surface conditions are considered here in a Lagrangian frame of reference without any analytical approximations, and thus the method is valid for very steep waves including overturning. It is found that the runup height is crucially dependent on the wave steepness and the slope of the plane. Pressures and forces exerted on impermeable walls of different inclinations (slopes) by progressive shallow water solitary waves are studied. Strong nonlinear features in the form of pronounced double peaks are visible in the time history of pressure and force signals with increasing heights of the oncoming solitary waves. The effect of nonlinearity is less pronounced as the inclination of the wall decreases with respect to the bottom surface. 相似文献
8.
研究门架式水力插板桩的抗倾覆稳定性,以确定其入土深度和工程安全以及工程造价。通过对目前较常用双排桩的稳定性计算分析,提出了1种新的桩土整体抗倾覆稳定计算模型,即将双排桩和桩间土视为1个整体,考虑双排桩桩间土的剪切破坏面随双排桩入土深度的变化,给出了门架式水力插板桩抗倾覆稳定性计算方法。并通过1个实例计算,验证了本文计算方法的可行性和一些有意义的结论。 相似文献
9.
极限平衡法仍是当前海底斜坡稳定性的主要工程评价方法,但该法只能给出稳定性分析的近似解答。基于极限分析运动学定理,假定海底斜坡发生对数螺线型滑移破坏模式,将滑体有效自重和简化波浪力等以外荷载形式叠加引入到虚功率方程中,与潜在滑动面上由黏聚力产生的内能耗散率相平衡,建立考虑一阶简化波浪效应的海底斜坡上限解法;利用多变量无导数求极值的逐级迭代方法与最优化技术,结合抗剪强度折减思想,求解波浪加载下不同时刻的海底斜坡稳定性与相应的临界破坏机构,并针对典型算例开展有限元数值解的验证。进而联合采用数值法与上限解,探讨波高、波长、水深等波浪参数对海底斜坡稳定性与滑动机制的影响。结果表明,本文提出的上限解与数值解吻合较好,获得的安全系数与破坏模式等符合一般规律,为波浪作用下海底斜坡的稳定性评价提供了新的途径。 相似文献
10.
Risk Assessment of Vertical Breakwaters -A Case Study in Turkey 总被引：1，自引：2，他引：1
In the reliability-risk assessment, the second order reliability index (βⅡ ) method and the Conditional Expectation Monte Carlo (CEMC) simulation are interrelated as a new Level Ⅲ approach for the analysis of the safety level of the Dalaman yacht harbor vertical wall breakwater in Turkey. The missing wave data of the Dalaman measurement station are hindcasted by use of multi-layer feed-forward neural networks with the steepest descent and conjugate gradient algorithms. The structural failure probabilities of sliding and overturning failure modes are forecasted by approximation of the failure sur-face with a second-degree polynomial of an equal curvature at the design point. in the new approach, for each randomly generated load and tide combination, the joint failure probability reflects both the occurrence probability of loading condition and the structural failure risk at the limit state. The approach can be applied to risk assessment of vertical breakwaters in short CPU durations of portable comput 相似文献
11.
Corresponding to the sliding and the overturning failure, the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion, the horizontal sliding-rotational oscillation coupled motion, the horizontal vibrating-uplift rocking coupled motion, and the horizontal sliding- uplift rocking coupled motion. The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson. The numerical models of four motion modes of caisson are developed, and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment. It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters. 相似文献
12.
Corresponding to the sliding and the overturning failure, the elementary motion modes of caisson breakwater include the horizontal-rotational oscillation coupled motion, the horizontal sliding-rotational oscillation coupled motion, the horizontal vibrating-uplift rocking coupled motion, and the horizontal sliding-uplift rocking coupled motion. The motion mode of a caisson will transform from one to another depending on the wave forces and the motion behaviors of the caisson. The numerical models of four motion modes of caisson are developed, and the numerical simulation procedure for joint motion process of various modes of caisson breakwater under wave excitation is presented and tested by a physical model experiment . It is concluded that the simulation procedure is reliable and can be applied to the dynamic stability analysis of caisson breakwaters. 相似文献
13.
Catastrophic failures of many tsunami barriers along the affected coasts during the 2011 Tohoku earthquake tsunami has prompted extensive investigation into improving and revising design codes for tsunami defence structures. To date, researchers and coastal engineers are investigating to understand the failure mechanisms and to find solutions so that the structures merely remain intact in the extreme event such as tsunami. Thus, the present work is motivated to experimentally study tsunami-induced bore pressures exerted on vertical seawalls; a solid vertical wall and a porous vertical seawall that consisted of a perforated front wall and a solid rear wall. Bores with various heights and velocities were generated by using the dam-break method. A porous seawall with 20% porosity of perforated front wall was used in this study. Bore pressures exerted on the solid rear wall and chamber oscillations that occurred in the experiments were also discussed. The experimental results showed that multiple peak pressures were observed during bore run-up phase in the time series of bore impacts. A predictive equation to estimate the maximum bore pressure on a perforated seawall was developed using multiple regression analysis. The proposed equation was also compared with previous empirical formulas. 相似文献
14.
Young-Suk Song 《Marine Georesources & Geotechnology》2013,31(1):34-52
The effectiveness of a simple method to estimate the lateral movement of piled bridge abutments due to lateral flow from the safety factor (Fs) of slope stability analysis was studied. This was accomplished through the construction and measurement of actual piled bridge abutments and its backfill, with and without piled slabs as a countermeasure. To do this, a computer program SLOPILE (VER 3.0) considering the lateral earth pressure acting on a row of piled bridge abutment was developed. SLOPILE (VER 3.0) can calculate the slope stability for both planar failure surfaces in infinite slopes and arc failure surfaces based on Fellenius or Bishop simplified methods. SLOPILE (VER 3.0) was utilized to design the piled bridge abutment reinforced by a piled slab at a real site. The piled slab can effectively prevent the lateral flow of soft ground and satisfy not only the safety factor of a slope but also the allowable bearing capacity of piles. To verify the design method, an instrumentation system was adapted. The instrumentation results from a case study clearly showed that the piled slab effectively resisted the lateral movement of a bridge abutment due to placement of backfill. Also, the surcharge loads due to backfill were supported by the piled slab and transmitted to the bedrock through the piled slab. 相似文献
15.
16.
The Tokachi-Oki earthquake was the strongest seismic event in 2003. The tsunami caused by the earthquake reached a height of four meters at the northeastern coast of Hokkaido. The JAMSTEC successfully recorded the variations of the near-bottom pressure in the region of the tsunami source. An analysis of the data reveals low-frequency (～ 0.15 Hz) elastic vibrations of the water layer. Estimates of the amplitude, velocity, and duration of the bottom deformation at the tsunami source were obtained. 相似文献
17.
WANG Yuanzhan 《中国海洋工程》2001,(2):205-216
The possible motions of a caisson breakwater under dynamic load excitation include vibrating, vibrating-sliding and vibrating-rocking motions. The models of vibrating motion and vibrating-sliding motion have been proposed in an early paper. In this paper, a model of vibrating-rocking motion of caisson breakwaters under breaking wave impact is presented, which can be used to simulate the histories of vibrating-rocking motion of caisson breakwaters. The effect of rocking motion on the displacement, rotation, sliding force and overturning moment of breakwaters is investigated. In case the overturning moment exceeds the stability moment of a caisson, the caisson may only rock. The caisson overturns only in case the rocking angle exceeds the critical angle. It is shown that the sliding force and overturning moment of breakwaters can be reduced effectively due to the rocking motion. It is proposed that some rocking motion should be allowed in breakwater design. 相似文献
18.
Yoshikawa Masashi Igarashi Yasuhiko Murata Shin Baba Toshitaka Hori Takane Okada Masato 《Marine Geophysical Researches》2019,40(4):467-477
When a subduction-zone earthquake occurs, the tsunami height must be predicted to cope with the damage generated by the tsunami. Therefore, tsunami height prediction methods have been studied using simulation data acquired by large-scale calculations. In this research, we consider the existence of a nonlinear power law relationship between the water pressure gauge data observed by the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) and the coastal tsunami height. Using this relationship, we propose a nonlinear parametric model and conduct a prediction experiment to compare the accuracy of the proposed method with those of previous methods and implement particular improvements to the extrapolation accuracy.
相似文献19.
自升式平台上外载荷的分析计算 总被引：3，自引：0，他引：3
海洋平台由于其作业的要求，而不可避免地受到各种海洋环境的考验。因此在设计平台时，必须考虑平台可能受到的各种外载荷，以保证平台海上作业的安全性。本文讨论了一种小型的自升式平台在外载荷作用下的受力分析，包括在外力作用下平台抗倾覆能力以及外载荷与平台承载力之间的关系。 相似文献
20.
Sliding is one of the principal failure types of caisson breakwaters and is an essential content of stability examination in caisson breakwater design. Herein, the mass-spring-dashpot model of caisson-base system is used to simulate the vi-brating-sliding motion of the caisson under various types of breaking wave impact forces, i.e., single peak impact force, double peak impact force, and shock-damping oscillation impact force. The effects of various breaking wave impacts and the sliding motion on the dynamic response behaviors of caisson breakwaters are investigated and the calculation of relevant system parameters is discussed. It is shown that the dynamic responses of the caisson are significantly different under different types of breaking wave impact forces even when the amplitudes of impact forces are equal. The amplitude of dynamic response of the caisson is lower under single peak impact excitation than that under double peak impact or shock-damping oscillation impact excitation. Though the disp 相似文献