Numerical simulation of mitigation for liquefaction-induced soil deformations in a sandy ground improved by cement grouting   总被引：4，自引：0，他引：4  

Yu Huang  Feng Zhang  Atsushi Yashima  Weimin Ye 《Environmental Geology》2008,55(6):1247-1252

This paper presents a numerical study of mitigation for liquefaction during earthquake loading. Analyses are carried out using an effective stress based, fully coupled, hybrid, finite element-finite differences approach. The sandy soil behavior is described by means of a cyclic elastoplastic constitutive model, which was developed within the framework of a nonlinear kinematic hardening rule. In theory, the philosophies of mitigation for liquefaction can be summarized as two main concepts, i.e. prevention of excess pore water pressure generation and reduction of liquefaction-induced deformations. This paper is primarily concerned with the latter approach to liquefaction mitigation. Firstly, the numerical method and the analytical procedure are briefly outlined. Subsequently, a case-history study, which includes a liquefaction mitigation technique of cement grouting for ground improvement of a sluice gate, is conducted to illustrate the effectiveness of liquefaction countermeasures. Special emphasis is given to the computed results of excess pore water pressures, displacements, and accelerations during the seismic excitation. Generally, the distinctive patterns of seismic response are accurately reproduced by the numerical simulation. The proposed numerical method is thus considered to capture the fundamental aspects of the problems investigated, and yields results for design purposes. From the results in the case, excess pore water pressures eventually reach fully liquefied state under the input earthquake loading and this cannot be prevented. However, liquefaction-induced lateral spreading of the foundation soils can be effectively reduced by the liquefaction mitigation techniques. An erratum to this article can be found at  相似文献   

Liquefaction analysis and soil improvement in Beydag dam     

Davut Yılmaz  Fatih Babuçcu  Serhat Batmaz  Fatih Kavruk 《Geotechnical and Geological Engineering》2008,26(2):211-224

Beydag dam is under construction on Kucukmenderes River for irrigation purposes. Due to the scarcity of core material and liquefaction of alluvium at the dam site, the original design was changed to Roller Compacted Concete (RCC) from rockfill dam with claycore. Although the new design was safer, it nearly doubled the cost of the dam, so the owner, State Hydraulic Works of Turkey, (DSI) set out to find more economical but equally safe alternative. Since jet-grouting is a cheap ground improvement tool in Turkey, such an alternative was developed for the ground improvement against liquefaction together with concrete face rockfill dam sitting on top of improved ground. This paper presents a detailed discussion of how the new alternative was developed and evaluated: it discusses the determination of jet grouting pattern, the placement of jet grouted blocks, and the assesment of liquefaction. On one hand the soil cement strength of jetgrout columns, internal friction angle of alluvium and rockfill were important in determining the dimensions of the blocks, on the other hand the location of the blocks were highly affected by the areas where liquefaction occurred. One of the most important parameter that has a considerable influence in delineating the boundary betweeen liquefaction and non-liquefaction was the value of stress reduction coefficient (r _d), being primarily sensitive to the weight of overburden, which is calculated by the height from the face of dam to the depth where the calculation was made. This approach is justified by two-dimensional ground response analysis. Most importantly, this paper shows that there exists an alternative solution for building dams on the liquefaction prone sites without removing alluvium by using a well known jet grouting technique for improving ground at only selected places.  相似文献   

A Consistent Soil Fatigue Framework Based on the Number of Equivalent Cycles   总被引：1，自引：0，他引：1  

Nii Allotey  M. Hesham El Naggar 《Geotechnical and Geological Engineering》2008,26(1):65-77

Cyclic soil degradation and hardening affects soil stiffness and strength, and is linked to an increase or decrease in the mean effective confining stress due to void ratio or pore pressure changes. This change of state can be explicitly modeled by using effective stress methods, or implicitly modeled using total stress methods. In the latter, this is achieved by using empirical functions based on the number of loading cycles that are derived from constant-amplitude stress or strain laboratory tests. To suite generalized loading conditions, these functions must be extrapolated to variable-amplitude loading. This falls under the general class of a fatigue-based problem. The main focus of this paper is to present a generalized consistent soil fatigue formulation for soils under cyclic loading. The paper then goes on to discuss the implementation of various cyclic soil degradation and hardening models reported in the literature, and highlights their important underlying assumptions, capabilities and limitations.  相似文献   

Liquefaction evidence for strong earthquakes of Holocene and latest Pleistocene ages in the states of Indiana and Illinois, USA   总被引：5，自引：0，他引：5  

S. F. Obermeier 《Engineering Geology》1998,50(3-4):227-254

Sand- and gravel-filled clastic dikes of seismic liquefaction origin occur throughout much of southern Indiana and Illinois. Nearly all of these dikes originated from prehistoric earthquakes centered in the study area. In this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the Holocene, and at least one during the latest Pleistocene. The recognition of different earthquakes has been based mainly on timing of liquefaction in combination with the regional pattern of liquefaction effects, but some have been recognized only by geotechnical testing at sites of liquefaction.

Most paleo-earthquakes presently recognized lie in Indiana, but equally as many may have occurred in Illinois. Studies in Illinois have not yet narrowly bracketed the age of clastic dikes at many sites, which sometimes causes uncertainty in defining the causative earthquake, but even in Illinois the largest paleo-earthquakes probably have been identified.

Prehistoric magnitudes were probably as high as about moment magnitude M 7.5. This greatly exceeds the largest historic earthquake of M 5.5 centered in Indiana or Illinois. The strongest paleo-earthquakes struck in the vicinity of the concentration of strongest historic seismicity. Elsewhere, paleo-earthquakes on the order of M 6–7 have occurred even where there has been little or no historic seismicity.

Both geologic and geotechnical methods of analysis have been essential for verification of seismic origin for the dikes and for back-calculating prehistoric magnitudes. Methods developed largely as part of this study should be of great value in unraveling the paleoseismic record elsewhere.  相似文献   

Study on wall-type gravel drains as liquefaction countermeasure for underground structures   总被引：1，自引：0，他引：1  

R. P. Orense  I. Morimoto  Y. Yamamoto  T. Yumiyama  H. Yamamoto  K. Sugawara 《Soil Dynamics and Earthquake Engineering》2003,23(1):114

One of the most dramatic causes of damage to engineering structures during earthquakes has been the development of soil liquefaction beneath and around the structures. In order to dissipate the excess pore water pressures near structures, gravel drains are usually employed. In this study, the use of recycled concrete crushed stones as gravel drain materials is addressed. In order to investigate the performance of wall-type gravel drains, two series of shaking table tests were performed. The test results showed that gravel drains, when appropriate grain size distribution is considered, effectively dissipate the excess pore water pressure underneath the structure, and consequently reduce the magnitude of uplift. To supplement the laboratory tests, finite element analyses were also performed. For specified structure, ground and earthquake conditions, there is a critical width of gravel drain at which no uplift of structure will occur. The results of the model tests and the finite element analyses were then employed in developing design charts for determining the critical width of gravel drain to prevent buoyant rise of structure when the surrounding soil mass liquefies.  相似文献   

砂土液化对设计反应谱和场地分类的影响   总被引：5，自引：0，他引：5  

孙锐  袁晓铭 《地震工程与工程振动》2003,23(5):46-52

本文采用有效应力原理分析了液化土层对设计反应谱的影响，分析中考虑了砂层的厚度、埋深和输入地震动等因素。选择Ⅱ类场地，将其标准反应谱合成的三条地震加速度时程在考虑土层非液化下反演到基岩，再正演计算存在液化层时的地面运动时程和反应谱。分析结果表明，从特征周期的变化来看，液化土层使Ⅱ类场地易变为Ⅳ类场地，对地震影响系数的作用则不是很大，但频谱上0．8s是一个分界线，液化土层对分界线以下的高频分量有一定减震效果，对分界线以上的低频分量有显著的放大效应。  相似文献   

Downslope volume enlargement of a debris slide–debris flow in the 1999 Hiroshima, Japan, rainstorm     

Gonghui Wang  Kyoji Sassa  Hiroshi Fukuoka 《Engineering Geology》2003,69(3-4):309-330

Following a heavy rainstorm on 29 June 1999, hundreds of slope failures occurred in granitic mountains in Hiroshima Prefecture, Japan. Among these events, a highly mobile landslide (termed the Kameyama landslide in this paper), which occurred in Kameyama area of Hiroshima city, was the most catastrophic, and was investigated in detail. The displaced soil mass from the source area of this landslide traveled about 300 m and deposited a volume more than 10 times as great as that in the source area. The landslide originated in and traversed a valley-shaped concave slope covered by pre-existing colluvial debris deposits. In addition, a spring was visible in the source area and very shallow ground water was observed in an observation pit dug in the source area. Thus, it is inferred that the ground-water table rose quickly during the rainfall, and that this rise triggered the slope failure in the source area. Based on a field survey along the landslide cross section, a possible explanation for the mechanism of the landslide was obtained: the displaced soil mass from the source area impacted the debris deposit in the path of the landslide, thus triggering liquefaction failure of the saturated part of debris. The original landslide and the liquefied debris then moved downslope as a single mass. To examine this assumption, ring-shear tests were performed on samples taken from the source area. Undrained ring-shear tests on the saturated samples showed that the sample is highly liquefiable, and liquefaction failure could have been triggered in the debris deposits by a very small impact from the displaced soil mass of the initial failure. In addition, laboratory tests simulating the impacts on the debris deposits at natural water content, i.e., unsaturated (at the survey time, 2 days after the failure) showed that although shear failure could be caused by the assumed impact force, the displaced soils stopped after a few centimeters displacement, indicating that existence of a saturated zone in debris deposits is prerequisite for this kind of failure.  相似文献   

Cyclic shearing and liquefaction of soil under irregular loading: an incremental model for the dynamic earthquake-induced deformation   总被引：1，自引：0，他引：1  

V. A. Osinov 《Soil Dynamics and Earthquake Engineering》2003,23(7):535-548

The paper presents a mathematical model for the deformation of soil under irregular cyclic loading in the simple-shear conditions. The model includes the possible change in the effective pressure in saturated soil due to the cyclic shearing, the reciprocal influence of the effective pressure on the response of the soil to the shear loading, and the pore pressure dissipation due to the seepage of the pore fluid. The hysteresis curves for the strain–stress relationship are constructed in such a way that they produce both the required backbone curve and the required damping ratio as functions of the strain amplitude. At the same time, the approach enables the constitutive functions involved in the model to be specified in various ways depending on the soil under study. The constitutive functions can be calibrated independently of each other from the conventional cyclic shear tests. The constitutive model is incorporated in the boundary value problem for the dynamic site response analysis of level ground. A numerical solution is presented for the dynamic deformation and liquefaction of soil at the Port Island site during the 1995 Hyogoken-Nambu earthquake.  相似文献   

基于内时理论的饱和黄土孔压增长模型的试验研究          下载免费PDF全文

刘红玫  袁中夏  王峻 《地震工程学报》2004,26(4):371-373

本进行了基于内时理论的动荷载下饱和黄土孔压增长模型的试验研究，结果表明：饱和黄土液化过程中其孔压的增长与土的干密度、饱和度以及动应力有着一定的相关关系。  相似文献   

Seismically induced landslide at Degirmendere Nose, Izmit Bay during Kocaeli (Izmit)-Turkey earthquake     

K. Onder Cetin  Nihat Isik  Berna Unutmaz 《Soil Dynamics and Earthquake Engineering》2004,24(3):189-197

This paper presents a study on the analyses of seismically induced landslide at Degirmendere Nose during the 1999 Kocaeli (Izmit)-Turkey earthquake. The paper discusses: (1) observed ground deformations and displacements after the earthquake, (2) the results of field investigations by means of borings and in situ index tests including standard penetration tests, static cone penetration tests (CPT) and piezocone tests, (3) analyses of observed landslide mechanisms by a suite of methods and (4) potential effects of soil liquefaction rupture on the observed landslide mechanism.  相似文献