海堤地震稳定性的概率分析

由于土坡稳定性分析实际上为一非确值性的问题，故一般通用的安全系数法分析海堤的稳定性不甚合理［１］。为考虑这一问题的随机性，文中引入概率分析的方法。最后基于所建议的概率方法分析了某实际海堤的地震稳定性，给出了该海堤稳定程度的定量评价。     

Fuzzy Probabilistic Analysis of Seismic Stability of Coastal Embankment

The stability of slope is affected by a number of factors, some of which have not only random property but also fuzzy characteristic. Therefore, the analysis of slope stability is really an uncertain problem. The customary safety factor does not in reality reflect stability scientifically, quantitatively and practically. In order to obtain more practical results, the slope stability is treated as a fuzzy random event for the evaluation of its fuzzy probability. Finally, the seismic stability of an existing coastal embankment is analyzed by means of the suggested fuzzy probabilistic method. It may be seen that the results of analysis can more fully represent the numerical assessment of the degree of slope seismic stability.     

Role of piles in mitigating the movement of pipes in soft grounds during embankment loading

Abstract

Pipes buried in soft ground can be damaged due to the vertical and lateral movement of the ground during the construction of the embankment. To investigate such a movement of the soft ground, full-scale tests using embankment piles and stabilizing piles were conducted for 70?days. A pile-supported embankment has been used to reduce the deformation of soft ground by transferring the embankment load through piles to the firm layer below the soft ground, whereas stabilizing piles have been employed to resist the lateral earth pressure that is induced in soft ground by embankment loads. The Coupling Area (CA), which was defined as the quantitative index to determine the resistance effect of both settlement and lateral flow of the soft ground when the embankment was reinforced, is adapted. The analysis results of the CA indicate that the piled embankment was more effective for preventing the damage to buried pipe installed near the embankment, while the stabilizing piles had almost the same effect as the piled embankment when the pipe was buried far away from the embankment.     

加筋软土海堤的稳定分析

本文对于淤泥质海岸上的路堤，采用竹筋土工布加固软基的处理方法，进行了三种作用机理的分析研究和不同方法的整体稳定性分析计算，提出了旋转式复合滑动和相应的稳定计算方法，同时还对竹筋格栅按弹性支承结构进行了力学分析与计算。结果表明，这种加筋效果既满足使用要求，又易于施工，比较经济，是一种较为理想的软土海堤的加固方法。     

Short-Term Stability Evaluation of an Embankment Constructed on Marine Clay Foundation at Kobe Airport

This article introduces the application of a stability analysis method that accounts for strength anisotropy on the embankment constructed at the Kobe airport. Shear strength anisotropy is induced by the in-situ state of stress along a potential slip surface of the embankment. In addition, the effects of the shearing rate on the undrained shear strength of the marine clay are examined in detail based on the results of a series of constant-volume direct shear box (DSB), triaxial compression (TC), and triaxial extension (TE) tests varying shearing rates. The most critical slip surface was selected from the deterministic slope stability analysis using unconfined compression tests of undisturbed clay samples from the field. For the most critical slip surface, the potential factor of safety of the embankment is estimated to be within the range of 1.21 to 1.28, as indicated by the results of the stability analyses using the strengths obtained from the DSB, TC, and TE tests and varying shearing rates.     

一种轻质硬壳海堤的断面设计和可靠性分析

针对软基堤坝易沉陷，滑移，倒塌，施工难，工期长的问题，提出一种新型的筑堤结构。该结构采用高强度材料作为外壳，以轻质材料放置于易沉滑的部位，以松散材料填充坝体，根据受力特性，构造要求，施工条件及抗滑稳定条件，拟解决结构断面设计的一些基本问题，并结合实例运用专业程序进行了对比计算分析，说明轻质硬壳堤坝比传统堤坝具有更高的可靠性。     

Properties of geogrid-reinforced marine slope due to the groundwater level changes

Evaluation of slope stability, especially in the absence of a proper bed such as marine soils, is one of the most important issues in geotechnical engineering. Using geogrid layers to enhance the strength and stability of embankments is regarded as a commendable stabilization method. On the other hand, groundwater level erratically fluctuates in coastal areas. Therefore, the aim of this research is to study the effects of groundwater level changes on stability of a geogrid-reinforced slope on loose marine soils in Qeshm Island, Iran. At first, geotechnical properties of the site were obtained by comprehensive series of geotechnical laboratory and in situ tests. Then, by simultaneous changes of groundwater level and several parameters such as embankment slope, loading, geogrid length, geogrid number, and tensile strength of geogrid, different characteristics such as embankment safety factor (SF), vertical and horizontal displacements at embankment top and embankment base were studied. It was observed that groundwater level had significant effects on behavior of the embankment. For most of the observations, by decreasing the groundwater level, the displacements decreased and consequently safety factor increased. Increasing the length, number, and tensile strength of geogrid led to the reduction of displacements and an increase in the safety factor.     

黄河三角洲莱州湾西岸防潮工程海堤断面块体稳定性实验研究

以黄河三角洲莱州湾西岸防潮工程海堤断面为工程实例，结合当地的水位及波浪参数，利用物理模型试验的方法，得出了护面块体稳定的极限条件及不同堤坝型式下海堤的冲淤状况，从而验证了海堤护面块体稳定性。     

轻质硬壳海堤断面设计初探

从海堤本身角度看，坝体过重与填料松散是影响其稳定性的主要因素，因此轻质硬壳堤坝是一种很好的选择。该结构采用高强度材料作为外壳，以松散材料填充坝体。根据受力特性、构造要求、施工条件及抗滑稳定条件拟解决结构断面设计的一些基本问题，并结合实例通过对比计算分析，说明轻质硬壳海堤比传统海堤具有更高的整体稳定性。     

The significance of earthquake-induced dynamic forces in coastal structures design

The dynamic forces of sea water and backfill soil acting on coastal embankments and the hydrodynamic forces on offshore breakwaters have been analyzed using a finite-difference scheme. A non-horizontal sea bottom is considered in the analysis. Both rigid and flexible embankments are included in the study. For a coastal embankment, the hydrodynamic pressure of sea water acting on the embankment face significantly increases as the slope of the sea bottom increases. On the other side of the embankment, the pore pressure and the interaction force between the soil and fluid will augment significantly when the backfill soil is compressed during earthquakes. When the sea-embankment-backfill soil interaction is included, the dynamic forces acting on a flexible embankment are much larger than those on a rigid one. The comparison of evaluating the sliding of a cassion in a case study of SPM by a conventional analysis and the present seismic analysis was made. The earthquake-induced dynamic pressures on both sides of the embankment (or breakwater) could be much larger than the force generated by the storm surge. The hydrodynamic (or seismic) analysis incorporating the effect of an earthquake should be included in the coastal embankment or offshore breakwater design, especially for the area with active earthquakes.     

Structural Types of Sea Embankment and Their Stability Analysis

In this paper based on investigation on the structural types of sea embankments in thesoutheast coastal area of China,as well as the related tidal stages,waves and strength of marine soils,thefinite element method(FEM)calculations for seepage flow stability,including the overall stability againstsliding and local stability of sloping surface under the action of tidal stage and waves are carried out.Acomparison of the computational results of FEM for single circular slip,composite circular slip andgeogrid reinforcement against sliding shows that for calculation of stability against sliding of marine softsoil foundation it is even more reasonable to use the composite circular slip.The stability of sloping typesea embankment against sliding is slightly better than that of the vertical face type;for the combination ofthree defences(wave,scour and seepage defences)the sea embankment structural type of a compositecross section with a platform should be a good one,but it still should be suitable to local condit     

Numerical Analysis of Seismic Performance of Embankment Supported by Micropiles

This paper presents a numerical model of the seismic behavior for the embankment constructed on micropile composite foundation. The effect of micropiles on soil reinforcement under static and seismic loading was studied. Embankments on the untreated and treated soil by micropiles were numerically simulated using an axisymmetric elastoplastic large deformation finite-element analysis code. The displacement caused by embankment static loading and acceleration of the embankment caused by seismic loading were calculated and compared. It was shown that micropiles can greatly reduce the settlement of the embankment and mitigate seismic response of the embankment. The main objective of this paper is to present a numerical model and to investigate the seismic behavior of micropile foundations subjected to seismic loading. A series of numerical simulations and parametric studies are presented.     

A statistical damage constitutive model based on unified strength theory for embankment rocks

Abstract

Fluctuant marine and reservoir water levels are the main failure-inducing factors for embankment slopes. The soft embankment rocks, e.g., red-bed mudstone, eroded by the reservoir water level in the Three Gorges Reservoir area greatly influence the stability of the embankment slopes. In this study, unified strength theory was innovatively applied for damage evaluation and combined with the Weibull distribution to obtain the strength statistics of micro units. Additionally, one damage constitutive model and one damage evolution model considering the initial damage, strain softening and damage weakening were proposed. Then, a series of tests, e.g., modified cyclic wetting and drying test, triaxial compression test and modified numerical simulation test for reservoir embankment red-bed mudstone, were conducted to verify the feasibility of the proposed models. In addition, grey system theory was originally used to evaluate the effects of the Weibull distribution parameters (m and w) and the confining stress on the peak stress. Finally, the proposed model was tentatively applied to the modification of the limit failure height model of the bedded rock slopes. The verification implies that the proposed model results are consistent with the testing results, especially in the simulation of compaction, elastic deformation and strain softening and in the prediction of peak strength. The results from grey system theory analysis indicate that the micro unit strength parameter (w) has the most obvious effect on the strength. Moreover, the modified method based on the damage evolution model for calculating the limit failure height of the bedded rock slopes is conservative.     

近年来横沙东滩围垦区前沿地形演化规律及驱动因素分析

河口大型滩涂演化关系到航运通畅、生态保护以及近岸工程的安全性,也是地貌学和工程界关注的热点。本文选择横沙东滩围垦区前沿5 m等深线包络区域作为研究区,2011–2017年间利用单波束测深系统对研究区进行持续性高精度监测,并结合近年来流域来沙、河口工程的建设和极端气候变化等影响因素分析其冲淤格局。结果表明:(1)近年来横沙东滩基本呈中间淤涨、周围冲刷的态势,整体由工程前“长大不长高”转化为工程后的“长高不长大”的演化格局;(2)海域来沙是此区域淤积的主要物源,研究区两侧涨落潮流路分异引起的环流是导致此区域淤积的主要动力;(3)深水航道堤坝工程、横沙东滩围垦工程等是导致研究区中间淤涨的原因;(4)人类活动可以直接影响滩槽的演化格局,工程建设的固定制约了河槽和滩涂的摆动,但也加剧了研究区局部的冲刷,未来应注意其内部串沟的发展,防止其连通威胁堤坝和滩涂的稳定。     

胜利油田孤东海堤外侧海底地形特征与变化分析

K10(总理台)~K16海堤是孤东海堤重点防护岸段。通过2004年5月、2005年5月以及2005年12月三次测量资料和资料比较分析,K10~K16海堤近岸,距堤百米内水深一般小于5m,有些地段受水动力作用形成冲刷凹坑及沟槽。但海底地形变化在不同的地段是不同的,且冲淤变化差异明显。从K13~K16之间水深地形变化较微弱,K14附近局部略有淤积。K12附近及沿堤以南地段出现强侵蚀岸段,距离岸堤20m左右处,顺堤形成水深7m左右的强侵蚀地形沟槽,严重威胁孤东海堤的安全。因此,分析研究该段地形变化,可以为该段海堤防护提供最佳对策。     

Piled embankment to prevent damage to pipe buried in soft grounds undergoing lateral flow

Lateral flow of soft ground occurs when embankment filling is performed on reclaimed land of foreshore. If a utility pipe is buried in soft ground undergoing the lateral flow, severe damage to the pipe can be caused. A pile-supported embankment has been used to support embankment to minimize lateral flow of the soft soil by transferring the embankment loads through the piles to the firm layer. To prevent damage to the buried pipe subjected to lateral force of the soft ground, full-scale field experiments on the piled embankment were conducted for 70 days. The test results show that the piled embankment effectively reduces both the settlements of the ground and the lateral displacements of the buried pipe. Although additional load was not imposed on the embankment after finishing embankment filling, the settlement and lateral displacement of soft ground simultaneously increased. This coupling behavior was observed at the toe of the embankment and the back of the buried pipe. To quantitatively evaluate the coupling effect of the movement, the coupling area (CA) was coined and analyzed with the efficiency of load transfer. The efficiency evaluated by the CA was in good agreement with the efficiency by the soil arching mechanism.     

Stability of jetties for channel protection in soft soils at Huanghua Port

This paper presents safety evaluations of jetties found on soft clays at Huanghua Port to protect the channel from deposition due to long shore transport. It is likely to be the most critical for the jetties during construction, as far as excess pore water pressure and its effects on the embankment stability are concerned. A rubble mound jetty and a caisson jetty are considered as design alternatives for comparison. Finite element analysis and limit equilibrium analysis are carried out to evaluate the stability of the jetties during construction. For the rubble mound jetty, effective stresses in the soft clays are calculated associated with consolidation, so as to estimate the shear strength increased thereby. With the effective stresses and shear strength, the critical situation of the rubble mound jetty is revealed by the limit equilibrium analysis. For the caisson jetty, wave action is concerned, which is transformed into distributed forces on the caisson. Both the finite element analysis and the limit equilibrium analysis indicate a potential general shear failure of the caisson jetty and the foundation.     

沿海大型工程海洋灾害风险排查山东省试点的方法及建议

为避免类似2011年日本"311"大地震的海洋灾害对沿海地区造成损失,中国海洋工程咨询协会开展了沿海大型工程海洋灾害风险排查工作。文章回顾了潍坊旅游度假区防护堤工程试点进行海洋灾害风险排查的具体做法,通过收集或实测更详细的潮位、波浪和地形等资料,经数值模拟方法分析,发现试点工程存在部分堤段不能满足设计要求的风险。通过本次试点,验证了风险排查规程的有效性和科学性,同时提出了增加试点工程堤顶高程或在试点工程外侧修建消浪潜堤的具有可操作性的建议。     

Limit analysis approach for accessing stability of three-dimensional (3-D) slopes reinforced with piles

The stabilization of slopes by placing piles is one of the most innovative and effective slope reinforcement techniques in the coastal engineering in recent years. Due to the simplicity and efficiency, limit analysis method is the most common approach for assessing the stability of slopes. However, the majority of existing limit analysis methods is limited to slope without the presence of piles. In this technical note, a novel upper-bound limit analysis method was proposed to access the stability of three-dimensional slopes reinforced with piles incorporating the admissible rotational failure mechanism where toe failure, face failure, and base failure were taken into account. The effects of key designing parameters, e.g., pile location, pile spacing, slope angle, slope width on the stability of earth slopes, and geometry of critical slip surface were presented and discussed. The results demonstrate that the proposed approach is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of piles stabilizing the unstable slopes.