The deformation of overburden soil induced by thrust faulting and its impact on underground tunnels

Overburden soil beds situated above a fault are often deformed by propagation of bedrock thrusting from the fault during large earthquake. The deformed beds formed a triangular shear zone. This coseismic faulting often causes damage to underground tunnels located in the shear zone. The present research studies the deformation behavior of the overburden soil beds and the tunnel, the associated mechanism and the impact on the safety of tunnel linings induced by a large blind thrust slip. Based on sandbox experimental and numerical studies, it is found that results from numerical analysis are in agreement with the sandbox model tests with regard to growths of the shear zones within the soil beds, location of the tunnel in this shear zone and deformations of the tunnel. The potential major shear zone may be bent or bifurcated into two sub-shear zones owing to existence of a tunnel inside the shear zone. Furthermore, the occurrence of back-thrust faulting will threaten the safety of nearby structures. It was also identified that stiffness of the soil and the fault dip angles are among the major factors controlling the configuration of shear zones, the stresses within the soil, and the loads on tunnel linings. Based on the identified mechanisms, the strategies for hazard prevention are accordingly suggested and discussed.     

Deformation characteristics and influential factors for the giant Jinnosuke-dani landslide in the Haku-san Mountain area, Japan

The Jinnosuke-dani landslide is a giant landslide 2,000 m long and 500 m wide in the Haku-san Mountain area, Japan. It was also the first landslide to be designated as a “Landslide Prevention Area” according to the “Japan Landslide Prevention Law.” This landslide consists of alternating layers of sandstone and shale in the Tedori Formation, which was deposited from the Jurassic period to the Early Cretaceous. Based on deformation monitoring results for more than 7 years, the landslide is divided into upper and lower blocks. The upper block has moved at a speed of 80 to 170 mm/year, while the lower block has moved more slowly (3 to 15 mm/year). Monitoring data show that the variation of the groundwater level has a great influence on the landslide movement. The deteriorating effect of the weathering of the alternating layers of sandstone and shale on the landslide deformation has been confirmed by borehole exploration and monitoring.     

A fault zone cause of large amplification and damage in Avcılar (west of Istanbul) during 1999 Izmit earthquake

Twenty seven buildings collapsed and 2076 buildings were heavily damaged during 17 August 1999 Izmit Earthquake in Avc?lar (west of Istanbul), which is nearly 100 km from the epicenter of the earthquake. The geology of Avc?lar consists of Upper Miocene poorly bounded conglomerate and sandstone (Çukurçe?me formation), claystone with sandstone and limestone interbedding (Güngören member) and limestone with sandstone and claystone interbedding (Bak?rköy formation). Lithological and geotechnical parameters of these formations in Avc?lar are not different from non damaged parts of the western Istanbul such as Zeytinburnu, Bak?rköy and Beylikdüzü, but these formations were cut by several faults in the damaged area. Collapsed and damaged buildings are located on this fault zone. Thus, cause of large amplification and damage in Avc?lar might be related with this fault zone because the fault zone behaves as a waveguide trapping seismic energy.     

混凝土动力本构模型的基础理论与建模应用综述

混凝土结构分析问题中动力荷载下混凝土的动力本构模型研究日益重要。为对建立混凝土动力本构关系的基础理论有系统的认知和了解其应用,对其进行了总结,简述了在建立混凝土动本构方面的应用,对混凝土动力本构模型的理论发展趋势作了展望。并对当前混凝土动力本构模型的应用做了概括评述,并指出了混凝土动力本构的可行研究方向,为建立混凝土动力本构模型提供指导。     

InSAR技术及其在地质灾害中的应用

InSAR是在太空对地球进行3维成像技术,它标志着空间遥感从2维信息获取进入到3维信息获取的新阶段,也为大地测量带来了一场革命。该技术为地质灾害的研究提供一个全新的工具。运用InSAR和D-In-SAR技术进行地面微位移监测,是近年来发展起来并得到日益重视的新方法。本文例举了InSAR技术在地震、火山喷发和滑坡等地质灾害应用的实例。表明它在形变监测研究中有广阔的应用前景,具有不可替代的优势。     

山西运城市城区主要桥梁的震害预测

采用经验统计法对山西省运城市的4座主要桥梁进行了震害预测计算,给出了4座桥梁的震害预测结果。认为,4座桥梁的破坏程度不同主要是由于桥主跨长度、桥墩高度、支座形式不同及在计算中采用的系数不同引起的,运城市桥梁的破坏程度较低,在遭遇Ⅷ度地震破坏时,中等以上破坏程度的桥梁占25%。     

山西形变台网映震能力分析

系统总结了山西形变台网对近年来5级以上地震的映震能力,分析了形变异常特征。认为,大部分地震均发生在异常转折或异常结束时段,异常持续时间一般为半年至1 a,震中距大多为200 km~300 km,并出现明显的丛集活动。     

Damage‐based design with no repairs for multiple events and its sensitivity to seismicity model

Conventional design methodology for the earthquake‐resistant structures is based on the concept of ensuring ‘no collapse’ during the most severe earthquake event. This methodology does not envisage the possibility of continuous damage accumulation during several not‐so‐severe earthquake events, as may be the case in the areas of moderate to high seismicity, particularly when it is economically infeasible to carry out repairs after damaging events. As a result, the structure may collapse or may necessitate large scale repairs much before the design life of the structure is over. This study considers the use of design force ratio (DFR) spectrum for taking an informed decision on the extent to which yield strength levels should be raised to avoid such a scenario. DFR spectrum gives the ratios by which the yield strength levels of single‐degree‐of‐freedom oscillators of different initial periods should be increased in order to limit the total damage caused by all earthquake events during the lifetime to a specified level. The DFR spectra are compared for three different seismicity models in case of elasto‐plastic oscillators: one corresponding to the exponential distribution for return periods of large events and the other two corresponding to the lognormal and Weibull distributions. It is shown through numerical study for a hypothetical seismic region that the use of simple exponential model may be acceptable only for small values of the seismic gap length. For moderately large to large seismic gap lengths, it may be conservative to use the lognormal model, while the Weibull model may be assumed for very large seismic gap lengths. Copyright © 2006 John Wiley & Sons, Ltd.     

Interaction of a Dynamic Rupture on a Fault Plane with Short Frictionless Fault Branches

Spontaneous bilateral mode II shear ruptures were nucleated on faults in photoelastic Homalite plates loaded in uniaxial compression. Rupture velocities were measured and the interaction between the rupture front and short fault branches was observed using high-speed digital photography. Fault branches were formed by machining slits of varying lengths that intersected the fault plane over a range of angles. These branches were frictionless because they did not close under static loading prior to shear rupture nucleation. Three types of behavior were observed. First, the velocity of both rupture fronts was unaffected when the fault branches were oriented 45° to the main slip surface and the length of the branches were less than or equal to ~0.75 R₀* (where R₀* is the slip-weakening distance in the limit of low rupture speed and an infinitely long slip-pulse). Second, rupture propagation stopped at the branch on the compressive side of the rupture tip but was unaffected by the branch on the tensile side when the branches were ~1.5 R₀* in length and remained oriented 45° to the principle slip surface. Third, branches on the tensile side of the rupture tip nucleated tensile ``wing tip' extensions when the branches were oriented at 70° to the interface. Third, when the branches were oriented at 70° to the interface, branches on the tensile side of the rupture tip nucleated tensile ``wing-crack' extensions. We explain these observations using a model in which the initial uniaxial load produces stress concentrations at the tips of the branches, which perturb the initial stress field on the rupture plane. These stress perturbations affect both the resolved shear stress driving the rupture and the fault-normal stress that controls the fault strength, and together they explain the observed changes in rupture speed.     

Probabilistic Assessment of Earthquake Insurance Rates for Turkey

A probabilistic model is presented to obtain a realistic estimate of earthquake insurance rates for reinforced concrete buildings in Turkey. The model integrates information on seismic hazard and information on expected earthquake damage on engineering facilities in a systematic way, yielding to estimates of earthquake insurance premiums. In order to demonstrate the application of the proposed probabilistic method, earthquake insurance rates are computed for reinforced concrete buildings constructed in five cities located in different seismic zones of Turkey. The resulting rates are compared with the rates currently charged by the insurance companies. The earthquake insurance rates are observed to be sensitive to the assumptions on seismic hazard and damage probability matrices and to increase significantly with increasing violation of the code requirements.