康定地震地表破裂和震害特征

2014年11月22日,四川省康定县发生了6.3级地震,相关专家解释为一次左旋走滑事件,发震构造为鲜水河断裂带。以地震区地表破裂程度和震害特征为主,地震现场研究表明1地震没有形成明显的地表破裂;2烈度图长轴与鲜水河断裂走向一致;3农村房屋破坏比城里严重;414年11月25日5.8级强余震,加深了灾区破坏程度。     

建筑抗震设计问答

问:什么叫发震断裂?如何鉴定? 答:发震断裂这个名词,是由抗震工程研究人员,在国内历次大地震调查中提出来的。调查发现在构造地震中地面重新产生错动的断裂附近,建筑物震害明显加重,而位于其他一般断裂及其附近的建筑物看不出有明显加重的趋势。因此,为了在选择建筑场地时与普遍大量存在的断裂加以区别,而提出此概念。发震断裂是沿老断裂构造骤然释放能量,附近岩层突然错动而     

活动断裂工程危害、破裂参数评价与工程应用

本文针对"5.12汶川大地震"的震害调查结果,分析总结了活动断裂起因的隧道工程震害现象,着重分析了隧道与断裂带垂直距离对隧道的危害效应,对隧道破坏现象与断裂距离的相关性进行了归纳总结。通过整理分析汶川地震、雅安地震等西部地区68个不同类型地震,提出了将地震破裂数据按照走滑型、倾滑型与走滑兼倾滑型分别进行分析的统计方法,通过蒙特卡罗方法,对其进行最小二乘法分析,得出对应具有不同活动断裂机理的地震的震级(Ms)-地震破裂参数的回归关系式,为量化确定工程抗震设计的活动断裂位错量等破裂参数提供了依据,研究结果为基于活动断裂危害预测以及可量化的破裂参数开展针对活动断裂的工程抗震提供了依据。     

高密度电法探测在永古高速隧道工程稳定性评价中的应用

本文采用高密度电法对永古高速公路乌鞘岭隧道北洞口、安远隧道南洞口附近活动断裂带进行了探测,准确给出了隧道口附近毛毛山南麓活动断裂与毛毛山北麓活动断裂的具体展布、发育特征及与初选隧道位置的关系,为隧道地震工程条件与稳定性评价提供了可靠依据。探测结果表明。乌鞘岭隧道北洞口场地位于毛毛山南麓活动断裂下盘的影响带上,断裂最新活动面距隧道上行出口与下行进口最近距离约264m及284m,地震不会影响洞口安全,但须加强防护;安远隧道南洞口位于毛毛山北麓活动断裂全新世左旋正走滑活动区段断面及破碎带上,存在地裂的可能。应采取相应措施。     

汶川地震区路堑重力挡墙震害调查

中国四川省汶川县2008年5月12日所发生的里氏8.0级强烈地震,具有烈度大、持续时间长的特点,由于发生在山区,地震对山区公路边坡产生了严重的破坏作用,尤其是对路堑边坡的重力式挡墙产生了不同类别的损坏,根据对本次地震极重灾区国道G213都江堰－映秀段路堑边坡重力式挡墙损坏状况的震后全面调查,整理归纳了路堑边坡重力式挡土墙的不同震害特征,主要可以分为墙体开裂、墙体局部破坏、墙体部分节段外倾、墙体部分节段滑移、落石砸坏挡墙这5种破坏类别,统计归纳了墙体震害与墙高、墙体材料、墙体所在位置线路走向与发震断层走向之间的关系等重要因素之间的规律性特征,本文结果可为山区公路工程的抗震设计研究提供基础参考。     

广州地铁九号线田美断裂带之物探勘察

以广州地铁九号线田美断裂带专项勘察为例,探讨了物探技术在查明断裂带的位置及特征、查清断裂构造与隧道的空间位置、研究断裂带的岩性和水文地质特征、预测隧道在断裂带中开挖所遇到的工程问题、提出工程措施建议等方面的优越性,为工程设计和施工提供地质依据。     

"5·12"汶川地震典型桥梁震害分析

针对"5·12"汶川地震中公路桥梁破坏严重,且破坏形式在映秀-北川断裂带南北两段出现了显著差异的情况,从震源机制、断裂带运动方式和桥梁结构本身特点等方面分析了产生这一差异的原因;并在汶川地震典型的桥梁震害分析的基础上,对强震区梁桥和拱桥的抗震设防提出了一些建议.结果表明:在断裂带南段由于地震释放能量巨大,断层逆冲作用显著,桥梁结构在强大竖向和水平地震力的共同作用下出现了桥墩、拱圈断裂导致的结构垮塌等强度失效型破坏;在断裂带北段断层右旋走滑作用显著而逆冲作用微弱,桥梁结构在剧烈的地面水平错动下出现了上部结构的落梁和双曲拱的垮塌等位移型破坏.     

汶川地震中道路边坡工程震害分析

 发生在山区的地震对边坡工程所造成的危害,在致灾机制和破坏形式方面具有鲜明的特征。结合汶川地震灾区道路边坡工程震害实例,分析路堑、路堤以及与桥隧相连的各类边坡及相应支挡结构的震害机制和破坏形式。锚索(杆)地梁或预应力锚索抗滑桩加固的边坡具有较好的抗震性能,其原因是这些结构已与坡体联接在一起而形成一个整体,在地震波作用下结构与坡体的位移和变形能够很好地协调一致。铺设土工格栅或施加加筋材料的路堤边坡工程具有较好的抗震性能,一般填筑路堤特别是高路堤,其抗震性能较差。根据沙土液化和软弱黏性土层震陷造成的震害实例,提出含水沙质地层路堤边坡应注意坡脚沙土液化造成的震害,应采取措施防止软弱黏性土层地基震陷造成路面破坏以及坡脚震陷造成的边坡失稳。山区隧道洞口边、仰坡的抗震设计应重视支挡结构的耐震性。建于坡体上的桥台、桥基和桥路过渡段的安全性与坡体稳定性直接相关,应切实加强这些结构所在边坡的抗震设计。对于依山傍水而建的顺河桥,相关边坡的失稳危害桥梁时,应对其采取抗震措施。目前公路、铁路工程抗震规范涉及边坡工程及支挡结构的内容极少,研究成果可为规范的修改和补充提供有益的参考。     

集丹公路路堑边坡破坏类型及其机制分析

集丹线位于鸭绿江岩石圈深大断裂带上或其附近,地质条件复杂,构造较为发育,边坡失稳现象严重。通过对本区路堑边坡地质构造、地层岩性、水的作用以及人为作用等影响因素的介绍,进而对公路沿线不同的滑坡、崩塌边坡破坏类型进行了阐述,深入分析了其破坏机制,并针对不同的破坏类型提出了相应的治理方案。     

“5.12”汶川大地震触发地质灾害的 发育分布规律研究

 “5.12”汶川大地震具有震级高、震源浅、破坏性强、次生地质灾害严重的特点。通过灾后对地震地质灾害的现场调查和遥感解译,共获得地质灾害点11 308处,对地震地质灾害发育分布有了总体认识。在此基础上,利用GIS技术对地震地质灾害的分布与距发震断裂距离坡度、高程、岩性等因素的关系进行统计分析。研究得出：(1) 地震地质灾害在区域上具有沿发震断裂带呈带状分布和沿河流水系成线状分布的特点;(2) 地震地质灾害分布具有明显的上盘效应,发震断裂上盘地质灾害发育密度明显大于下盘,且上盘强发育带宽度约为10 km;(3) 地形坡度是地震地质灾害发育的控制性因素之一,绝大部分的灾害集中在坡度20°～50°的范围内;(4) 地震地质灾害与高程和微地貌具有很好的对应关系,大部分灾害发生在高程1 500～2 000 m以下的河谷峡谷段,尤其是峡谷段的上部(即宽谷向峡谷的转折部位),单薄的山脊以及孤立或多面临空的山体对地震波最为敏感,具有显著的放大效应,这些部位崩塌滑坡最为发育;(5) 不同的岩性与地质灾害的发育虽然没有显著的对应关系,但却决定了地质灾害的类型,通常情况下,滑坡多发生在软岩中,而硬岩中多发生的是崩塌。     

Assessment of damage in mountain tunnels due to the Taiwan Chi-Chi Earthquake

Tunnels, being underground structures, have long been assumed to have the ability to sustain earthquakes with little damage. However, investigations of mountain tunnels after the Chi-Chi Earthquake in central Taiwan revealed that many tunnels suffered significant damage to various extents. This work describes the findings of a systematic assessment of damage in the mountain tunnels in Taiwan after the earthquake. It was found that among the 57 tunnels investigated 49 of them were damaged. The damage patterns are summarized based on the characteristics and the distribution of the lining cracks. This systematic investigation, involving geological conditions, design documents, construction and maintenance records of these tunnels, has been conducted to assess the potential factors that may have influence on the various damage patterns and the earthquake loading for tunnels. The results show that the degree of damage is associated with the geological condition and structural arrangement of the tunnel. A tunnel passing through a displaced fault zone will definitely suffer damage. The extent of geological weak zones, distance from the epicenter, and the existence of a slope face are also significant influencing factors. The seismic capacity of the tunnel is influenced by its structural arrangement, type of lining, invert setup, lining reinforcement, and other parameters.     

Damage to mountain tunnels related to the Wenchuan earthquake and some suggestions for aseismic tunnel construction

Many tunnels along the Dujiangyan to Wenchuan highway, located near the epicenter of the 2008 Wenchuan earthquake in China, were damaged severely. The characteristics of the tunnel failures were analyzed and categorized as avalanches and landsliding near the tunnels, cracking of the tunnel portals, collapse of the liner and surrounding rock, cracking and dislocation of the liner, uplift and cracking of the ground, deformation and cracking of the preliminary bracing. The main geological factors influencing the tunnel damage are secondary fractures of earthquake faults, sudden change in soil and rock type, weak rocks and the variable geo-stresses in the host material. The tunnel portals and their slopes, unless fully integrated into the tunnel structures and sufficiently reinforced, are likely to suffer significant distress as a consequence of seismic events. The main mitigation measures proposed are the use of reinforced concrete in the secondary lining in the area of fault zones and injection grouting to reduce the differences where there are sudden changes in the character of the host material.     

隧道穿越断层破碎带震害机理研究

首先对汶川“5.12”等各次大地震中跨越断层破碎带隧道震害进行了资料调研,然后通过振动台模型试验及数值计算对跨断层破碎带隧道的动力响应进行了研究,研究内容主要包括围岩与隧道结构的加速度响应特性、地层变形及衬砌结构内力分布规律等。分析结果表明：震害调研结果、振动台模型试验和数值模拟结果有较好的吻合性,穿越断层破碎带隧道在地震中易于产生破坏;隧道断层带段围岩有较大的加速度响应特性,加速度响应在断层接触段不连续;地震过程中断层带段隧道结构对地层具有明显的追随性和依赖性;断层带隧道错动破坏主要由断层带隧道围岩与较好段围岩位移不同步性而造成的位移差值引起,且位移差值与断层带和隧道较好围岩类型有关;隧道断层破碎带段与较好围岩段衬砌结构横断面具有基本相同的内力分布规律,衬砌内力在共轭45°方向最大,但断层破碎带段衬砌具有最大的内力峰值,更易于在地震过程中产生破坏等。以上成果对于合理认识跨越断层破碎带隧道的地震响应特征具有重要意义,可为隧道实际工程设计和施工的抗震设防提供宝贵的基础资料。     

强震区软岩隧道大变形破坏特征及其成因机制分析

 对在建的穿越5•12强震区发震断裂带上广甘高速公路杜家山软岩隧道中多次出现的大变形及塌方等地质灾害特征、影响因素及其成因机制的分析表明：强震区软岩隧道变形破坏多以坍塌为主,且多数发生于掌子面附近;围岩自稳能力差及地下水对岩体的软化作用是隧道发生变形破坏的主要诱因,但5•12强震及后期余震作用形成的大量深部震裂损伤岩体也是产生上述现象的重要因素之一,复杂的区域环境造成设计、施工中类似经验不足也是引发上述现象不可忽视的重要环节。研究表明,对于强震区软岩隧道应结合现场实际情况适当调整围岩的预留变形量及安全控制基准,加强原有的支护参数,施工中重视各环节的工艺衔接,采用以三台阶+预留核心土的微台阶法可有效控制上述灾害的产生。     

隧道超前地质预报综合分析方法

 通过隧道介质物性差异特点分析和常见物探超前预报方法适宜性对比评价,提出“以地质分析为核心,综合物探与地质分析相结合,洞内外结合,长短预测结合以及物性参数互补”的综合预报原则,并建立较为完善的隧道超前地质综合预报方法体系和组织机构。针对隧道中断层、破碎岩体、富水情况、有无溶洞、软弱岩体5种常见不良地质情况,提出合理的预报工作流程,并提取相关地质参数和物探成果参数,建立综合分级评价体系。最后,采用模糊神经网络方法,实现隧道常见不良地质情况的综合预报,铜锣山岩溶隧道应用情况表明,综合预报结果准确率达80%。     

Interaction between tunnel and unstable slope – Influence of time-dependent behavior of a tunnel excavation in a deep-seated gravitational slope deformation

A back analysis of old tunnels in an unstable slope context leads to consider several situations of tunnel entering a slope: cross-cutting tunnel to the slope, oblique tunnel to the slope, or shallow tunnel parallel to the slope. Identified pathologies of structures vary depending on these situations. In the context of a shallow tunnel, the tunnel excavation leads to a slope destabilization due to a more or less important deconfinement of the surrounding massif. Construction techniques influence, on one hand, slope surface displacement acceleration, on the other hand, structural damages in the tunnel lining. Nevertheless, the interaction between tunnel and unstable slope depends on the distance between the slope surface and the tunnel lining plot according to the tunnel diameter (D) and on the geological, geomorphological, hydrological and seismic contexts of the slope. This research focuses on different mechanisms of slope instability in a glacial unloading context, especially in creeping contexts, and on damages affecting the structure of tunnels parallel to the slope. Through numerical simulations, the influence of the construction techniques was studied; so was the choice of the tunnel situation, more or less away from the slope surface. Mainly the delay time before tunnel structure implementation) on the damage lining processes, the interaction between tunnel and slope surface displacements and their time evolution have been taken into account for the most critical tunnel situation in the slope. The different situations of tunnel in the slope permit to set in evidence the safety distance from the slope in the context of a slow glacial unloading mechanism.     

跨海峡隧道风化槽围岩衬砌防排水技术研究

 采用钻爆法修建海底隧道必须采取有效措施预防塌方、涌水、突泥等地质灾害,海底隧道钻爆法施工时如何安全穿越断层破碎带是工程设计与施工的技术难点。结合厦门跨海峡隧道围岩的特点,研究钻爆法穿越断层破碎带的注浆加固、防排水技术,提出不同围岩条件下的隧道防排水和注浆设计方案。并根据实验室三轴试验结果得到强风化花岗岩渗透系数以及反演的围岩力学参数,分析风化槽隧道衬砌的外水压力分布特点和量值。研究成果为衬砌结构设计以及国内同类型隧道的衬砌防排水和衬砌支护技术设计提供可靠指导。     

Centrifuge experiments for shallow tunnels at active reverse fault intersection

Tunnels extend in large stretches with continuous lengths of up to hundreds of kilometers which are vulnerable to faulting in earthquake-prone areas. Assessing the interaction of soil and tunnel at an intersection with an active fault during an earthquake can be a beneficial guideline for tunnel design engineers. Here, a series of 4 centrifuge tests are planned and tested on continuous tunnels. Dip-slip surface faulting in reverse mechanism of 60-degree is modeled by a fault simulator box in a quasi-static manner. Failure mechanism, progression and locations of damages to the tunnels are assessed through a gradual increase in Permanent Ground Displacement (PGD). The ground surface deformations and strains, fault surface trace, fault scarp and the sinkhole caused by fault movement are observed here. These ground surface deformations are major threats to stability, safety and serviceability of the structures. According to the observations, the modeled tunnels are vulnerable to reverse fault rupture and but the functionality loss is not abrupt, and the tunnel will be able to tolerate some fault displacements. By monitoring the progress of damage states by increasing PGD, the fragility curves corresponding to each damage state were plotted and interpreted in related figures.     

Damage observation and assessment of the Longxi tunnel during the Wenchuan earthquake

The Longxi tunnel was one of the most damaged tunnels during the 2008 Wenchuan earthquake in China. What makes the case interesting is that the tunnel crosses a fault zone. Damage from small to heavy cracking was observed both at the portal and inside the tunnel, while sections close to the fault completely collapsed. A full three-dimensional dynamic finite element model of the tunnel and rock system is used to assess the seismic damage observed in the tunnel and to evaluate the influence of the longitudinal and vertical motions on the seismic response. A comparison between the numerical predictions and the damage reported shows a good agreement. The results indicate that the longitudinal earthquake motion has a significant effect on the response of the tunnel structure and should be considered for the structural design of tunnels in seismic zones. In contrast, the vertical seismic motions can generally be neglected.     

非可溶岩隧道突涌灾害预测研究及工程应用

 隧道等地下工程施工过程中,突涌事故一般发生在可溶岩隧道中,然而近些年非可溶岩隧道发生突涌事故的案例越来越多,给隧道施工带来重大灾难和经济损失。首先,通过3个突涌事故案例的剖析,揭示非可溶岩隧道突涌的本质是开挖或爆破扰动触发赋存在破碎带或软弱带中的水和碎屑物在自身压力作用下涌入隧道,其孕险环境必须同时具备物质条件、空间条件和触发条件,三者缺一不可。物质条件是充足的水和砾石、砂、泥等原地性或外源性的碎屑物;空间条件是突涌物的存储和运移的破碎带或软弱带等;触发条件是岩体的开挖扰动和爆破扰动。非可溶岩隧道施工过程中突涌灾害的预测就是对掌子面前方能够赋存潜在突涌物的破碎带或软弱带及其带内物质组成、固结程度的辨识。然后,针对突涌灾害的物质和空间条件给出基于地质、物探和钻探的综合超前预报体系;结合实践,重点建立地震波反射法(TGP)成果中的反射幅度比、波轴相似度等参数对异常地质体的地震动态响应特征。最后,将上述成果应用到岩前隧道的F17断层破碎带的预报中,通过宏观工程地质分析和已开挖段的地质调查及试验,全程动态追踪隧道揭露围岩的统计及力学特征;通过未开挖段长距离的TGP探测和短距离的地质雷达和水平钻孔探测,辨识隧道即将揭露区段突涌灾害的孕险环境,实现对断层破碎带位置、规模、空间展布的精确定位,对带内物质组成及胶结程度的确认,成功预测突涌事故的发生。实践证明,上述综合预报技术体系能够预测非可溶岩隧道的突涌灾害,其结果准确可靠,可为类似工程提供参考和借鉴。