北京市地铁暗挖施工沉降控制探讨

仅以北京市地铁4#线张自忠车站主体暗挖施工的沉降监控项目为研究背景,对穿越城市主干道的车站结构暗挖施工进行连续性的沉降变形监测;从地下构筑物暗挖施工的工序变化与地表沉降的关系进行试验研究.在预测基础上对获取的数据进行多层次的统计与分析,以研究其变形规律与稳定性,实现了信息化施工.     

广东省五华县地质灾害形成特征及防治对策

五华县主要地质灾害类型有滑坡、崩塌、地面塌陷、水土流失等。其中以滑坡、崩塌为主,多分布在东南、南部花岗岩区、北部花岗岩风化土区等广大中低山及丘陵区,具有点多面广,灾害点个体规模小,稳定性差,活动频繁,地质灾害发育呈明显的地域性与季节性分布等特点。五华县地质灾害的形成与发生是多种致灾因素相互作用的结果。地层岩性是其形成的内在要素,它在一定程度上决定着地质灾害的发育程度与类型;地形地貌与植被是地质灾害形成的外在条件,它制约着崩、滑、塌等致灾地质作用的形成;大气降雨是地质灾害形成与发生的激发因素,决定着地质灾害发生的速度和时间;人类工程活动是影响地质灾害形成与发生的最主要、最直接的因素。对地质灾害的防治应采用避让、预防、监测及治理措施,做到避让与治理结合,以群测群防为基本手段,点状灾害以工程治理与生物防治为主;面状灾害以生物防治为主;采用点、面结合综合治理的方法。     

基于权变理论的滑坡灾害监测预报思路探讨

文章简要评述了地质灾害基础理论与应用技术发展现状、滑坡灾害多种监测预报判据的利弊。利用综合信息处理决策方法,提出了基于权变理论的滑坡灾害监测预报新思路。分析了滑坡成灾的权变特征、环境因素和决策因素,建立了滑坡灾害预报决策概念模型。进一步探讨了在预报决策中应遵循的动态性及满意性原则,为提高地质灾害监测预报理论的科学性提供了新的理论依据与技术途径。     

A continuous/discontinuous Galerkin framework for modeling coupled subsurface and surface water flow

We consider conjunctive surface-subsurface flow modeling, where surface water flow is described by the shallow water equations and ground water flow by Richards’ equation for the vadose zone. Coupling between the models is based on the continuity of flux and water pressure. Numerical approximation of the coupled model using the framework of discontinuous Galerkin (DG) methods is formulated. In the subsurface, the local discontinuous Galerkin (LDG) method is used to approximate ground water velocity and hydraulic head; a DG method is also used to approximate surface water velocity and elevation. This approach allows for a weak coupling of the models and the use of different approximating spaces and/or meshes within each regime. A simplified LDG method based on continuous approximations to water head is also described. Numerical results that investigate physical and numerical aspects of surface–subsurface flow modeling are presented. This work was supported by National Science Foundation grant DMS-0411413.     

Probabilistic modeling of seismically triggered landslides using Monte Carlo simulations

The 2004 Chuetsu earthquakes of Niigata (Japan) triggered numerous landslides, and the most widespread types of landslides were highly disrupted, relatively shallow slides and soil (debris) flows. This paper presented a method to evaluate slope instability using Newmark displacement on a pixel-by-pixel basis in a given area. The proposed method was able to integrate Newmark displacement modeling and Monte Carlo simulations within geographical information systems. In the modeling, an empirical attenuation relationship was utilized to calculate Arias intensity over this study area, and the variability of geotechnical parameters was taken into account to calculate coseismic landslide displacement. Before deriving the displacement from related inputs, the Monte Carlo simulations ran 1,500 times and generated 1,500 displacement values for each grid cell, and then means and standard deviations of displacement were calculated and probabilistic distributions can be obtained. Finally, given 10 cm as a threshold value of displacement, estimated probabilities of displacement exceeding 10 cm were shown as a map of seismic landslide hazards. The resulting hazard map was classified into four categories from very low to high level.     

基于贡献权重迭加法的滑坡风险区划

贡献权重迭加法是对滑坡本底因子和承灾体因子在滑坡发育中的贡献率进行统计后,通过贡献率均值化、规一化处理,利用权重转换模型计算出每一个因子内部的权重——自权重W和因子相互之间的权重——互权重W＇。将滑坡因子、承灾体因子和两者的自权重、互权重分别相乘迭加,得到滑坡危险度和易损度区划结果,再将2项结果相乘得出滑坡风险区划。     

基于蒙特卡罗法的多级黄土滑坡可靠性分析

滑坡稳定性分析目前工程中一般采用极限平衡算法。为了确定滑坡的稳定性系数,在计算过程中要将岩土体、计算模型简化,忽略一些影响滑坡稳定的次要因素,把影响滑坡稳定的各种主要因素作为确定参数。由于滑坡岩土体本身的非均质性及其参数确定具有随机性和变异性,用唯一的稳定系数不能客观地反映整个滑坡的真实安全程度。以陕西省夏呀河滑坡为例,通过野外详细调查、工程勘探和室内土工试验,初步确定该滑坡存在四级滑动面,难以用简单的单一滑动面计算其稳定性。因此,先采用推力传递系数法对滑坡体上的四级滑坡分别进行滑坡稳定性计算,得到该滑坡体上的四级滑坡稳定系数。再采用蒙特卡罗法对该四级滑坡进行可靠性分析,得到其可靠度,定量地表达夏呀河四级滑坡的安全程度。同时对比分析夏呀河四级滑坡的稳定系数和失稳概率,综合评价该滑坡体上的四级滑坡的稳定性及其风险概率,为滑坡的工程治理及预测预警、灾害危险性评价提供依据。     

分布式光纤传感技术在滑坡监测中的应用

将分布式光纤传感技术引入滑坡监测,既可得到整个滑坡体的概要特征,又能提高监测效率。FBG与BOTDR是两种最具代表性的分布式光纤传感技术,FBG通过测量其反射光波长的变化获得应变或温度值。BOTDR通过测定后向布里渊散射光的频移实现分布式温度、应变测量。FBG传感器灵敏度高,但只能实现离散点的准分布式测量,BOTDR可实现分布式、长距离、不间断测量,但其空间分辨率不高。笔者提出FBG与BOTDR联合监测滑坡的方案。在巫山残联滑坡,在整个滑坡体上铺设监测光纤,利用BOTDR获得整个滑坡体的概要信息;在滑坡体变形的关键部位———变形缝安装FBG传感器,获得某些关键部位的应变信息,从而实现由点到线再到面的监测,获得滑坡体较完整的应变信息。     

A Block-Based Theoretical Model Suited to Gravitational Sliding

An original theoretical model has been devised to simulate mass flow over hill slopes due to gravitational sliding. The sliding mass is discretized into a sequence of contiguous blocks which are subjected to gravitational forces, to bottom friction and to surface resistance stresses that are generally negligible for subaerial flows, but are relevant for submarine slides. The blocks interact with each other while sliding down the hill flanks because of internal forces that dissipate mechanical energy and produce a momentum exchange between the individual blocks, yet conserving the total momentum of the mass. Internal forces are expressed in terms of interaction coefficients depending on the instantaneous distance between the block centers of mass, which is a measure of the deformation experienced by the blocks: the functional dependence includes three parameters, namely the interaction intensity ¯, the deformability parameter and the shape parameter , by means of which a wide range of interaction types can be fully accounted for. The time integration is performed numerically by solving the equations for the block velocities and positions at any time ti by means of the block accelerations at the previous time t_i-1, and by subsequently updating the block accelerations, which allows to proceed iteratively to the following times. The model has been tested against laboratory results available from literature and by means of several numerical experiments involving a simplified geometry both for the sliding body and the basal surface, with the purpose of clarifying the influence of the model parameters on the slide dynamics. The model improves the performance of the existing kinematic models for slides, moreover preserving an equivalent numerical simplicity. Future applications and possible improvements of this model are suggested.     

洛安江干渠老菁湾滑坡分析

洛安江水库灌溉工程是贵州黔北万亩以上骨干工程之一,中华人民共和国成立初期建成。１９９１年＂７．５Ｆ＂洪灾,连续大暴雨,河水暴涨,倒灌暗河,产生高静、动水压力作用。岸坡岩体受不利结构面组合,发生顺层岩质滑坡,破坏干渠,严重影响灌溉。本文根据滑坡破坏情况,对滑坡产生的地质环境、滑坡特征、滑坡形成机理（滑坡形式和破坏机理,各种稳定性分析与评价）,以及产生滑坡原因进行了初步分析。