某浅埋地下洞室围岩稳定及渐进破坏过程分析

以新疆乌鲁木齐市"世纪花苑"三期工程废弃人防地道为实例,在查明研究区浅埋洞室分布特征的基础上,结合现场及室内试验获取相关岩土体物理力学参数,利用快速拉格朗日差分分析程序FLAC研究浅埋洞室在拟建高层荷载作用下的稳定性及其破坏过程,通过系列模拟图,较真实地再现了洞室围岩变形破坏、尤其是塑性区发展变化过程。     

双剪统一强度准则改进及其在岩土工程中的应用

在分析Mohr-Coulomb强度准则和双剪统一强度准则的基础上,提出了主剪面应力对和主剪面应力对的作用这2个新概念,并以此为出发点,通过考虑十二面体单元主剪面上所有3个主剪面应力对的共同作用,在双剪强度准则的基础上提出了一个新准则,并对其作了极限线分析.应用该新强度准则研究了静水压力条件下圆形巷道围岩弹塑性分析和土压力计算问题.研究表明,该准则不仅能较好地非线性反映岩土的3个基本强度特征,还解决了双剪统一准则中存在的双重破坏角问题.     

Seismic horizontal pullout capacity of shallow vertical anchors in sand

The concept of the equivalent free surface has been extended to determine the seismic horizontal pullout capacity of shallow vertical strip plate anchors buried in sand. The analysis has been done rigorously by using the method of stress characteristics. The results have been expressed in the form of non-dimensional charts. The pullout resistance has been found to reduce quite extensively with increase in the magnitude of horizontal earthquake acceleration. The results were compared with the previously published data, and it was seen that the computed pullout resistance with the proposed method was found to be lowest. This revised version was published online in July 2006 with corrections to the Cover Date.     

Plastic flow strength of jadeite and diopside investigated by microindentation hardness tests

Microindentation hardness tests were performed on jadeite and diopside, being end members of the omphacite solid solution series. At temperatures between 300 and 750 °C, the hardness of jadeite ranges from 7.4 to 8.5 GPa, that of diopside from 4.9 to 6.1 GPa. Jadeite is significantly stronger than diopside in the low-temperature plasticity regime. Normalization of the hardness-derived yield stress with respect to the shear modulus considerably reduces the strength contrast. The normalized Peierls stress is identical for jadeite and diopside. This indicates that jadeite and diopside belong to the same isomechanical group. The hardness-derived yield stress for jadeite as well as for diopside is used to estimate flow law parameters for the low-temperature plasticity regime.     

Focal mechanism dependence of static stress triggering of earthquakes

We perform a global statistical investigation into the problem of Coulomb stress triggering of earthquakes by using the Harvard CMT catalogue of shallow earthquakes from 1976 to 2001. We consider ‘earthquake pairs’, i.e., pairs of successive earthquakes occurring near each other with similar focal mechanisms, and address the problem of whether or not the change of the Coulomb failure stress (CFS) produced by the first earthquake of the pair ‘encourages’ the occurrence of the second one. An interesting feature is that such a Coulomb stress-triggering phenomenon has an apparent focal mechanism dependence: for thrust earthquakes, a more evident triggering effect can be observed.     

Dynamics of an active rock glacier (Ötztal Alps, Austria)

The rock glacier Innere Ölgrube, located in a small side valley of the Kauner Valley (Ötztal Alps, Austria), consists of two separate, tongue-shaped rock glaciers lying next to each other. Investigations indicate that both rock glaciers contain a core of massive ice. During winter, the temperature at the base of the snow cover (BTS) is significantly lower at the active rock glacier than on permafrost-free ground adjacent to the rock glacier. Discharge is characterized by strong seasonal and diurnal variations, and is strongly controlled by the local weather conditions. Water temperature of the rock glacier springs remains constantly low, mostly below 1°C during the whole melt season. The morphology of the rock glaciers and the presence of meltwater lakes in their rooting zones as well as the high surface flow velocities of >1 m/yr point to a glacial origin. The northern rock glacier, which is bounded by lateral moraines, evolved from the debris-covered tongue of a small glacier of the Little Ice Age with its last highstand around A.D. 1850. Due to the global warming in the following decades, the upper parts of the steep and debris-free ice glacier melted, whereas the debris-covered glacier tongue transformed into an active rock glacier. Due to this evolution and due to the downslope movement, the northern rock glacier, although still active, at present is cut off from its ice and debris supply. The southern rock glacier has developed approximately during the same period from a debris-covered cirque glacier at the foot of the Wannetspitze massif.     

昆明市东川区泥石流信息系统的建立及其应用

根据东川区泥石流的成因、泥石流灾害信息源、各类数据的表达方式及泥石流信息系统的应用等，对东川区泥石流信息系统进行了系统分析，在此基础上利用3S技术，在ARCVIEW的AVENUE开发语言支持下，集成各类数据，建立东川区泥石流信息系统，最后讨论了该系统在泥石流危险度区划及灾害趋势分析中的应用。     

Estimating severity of liquefaction-induced damage near foundation

An empirical procedure for estimating the severity of liquefaction-induced ground damage at or near foundations of existing buildings is established. The procedure is based on an examination of 30 case histories from recent earthquakes. The data for these case histories consist of observations of the damage that resulted from liquefaction, and the subsurface soil conditions as revealed by cone penetration tests. These field observations are used to classify these cases into one of three damaging effect categories, ‘no damage’, ‘minor to moderate damage’, and ‘major damage’. The potential for liquefaction-induced ground failure at each site is calculated and expressed as the probability of ground failure. The relationship between the probability of ground failure and the damage class is established, which allows for the evaluation of the severity of liquefaction-induced ground damage at or near foundations. The procedure presented herein represents a significant attempt to address the issue of liquefaction effect. Caution must be exercised, however, when using the proposed model and procedure for estimating liquefaction damage severity, because they are developed based on limited number of case histories.     

Dynamic theory of rigid-plasticity

This paper deals with an analysis method for the response and motion of soil-like rigid-plastic bodies under seismic loading conditions. A continuity condition to determine the acceleration distribution within the rigid-plastic body when the failure occurs during seismic motions is proposed. Combining this continuity condition of acceleration and the ‘Generalized Limit Equilibrium Method (GLEM)’, the responses of the earth structure during seismic motions as well as the permanent displacements can be obtained, where GLEM is one of the limit equilibrium methods proposed by the authors for static problems and providing the approximate solution for Kötter's equation. The theoretical formulation of the method, the illustrative examples, and some comparisons between the analytical and experimental results are demonstrated.     

Signatures in flowing fluid electric conductivity logs

Flowing fluid electric conductivity logging provides a means to determine hydrologic properties of fractures, fracture zones, or other permeable layers intersecting a borehole in saturated rock. The method involves analyzing the time-evolution of fluid electric conductivity (FEC) logs obtained while the well is being pumped and yields information on the location, hydraulic transmissivity, and salinity of permeable layers. The original analysis method was restricted to the case in which flows from the permeable layers or fractures were directed into the borehole (inflow). Recently, the method was adapted to permit treatment of both inflow and outflow, including analysis of natural regional flow in the permeable layer. A numerical model simulates flow and transport in the wellbore during flowing FEC logging, and fracture properties are determined by optimizing the match between simulation results and observed FEC logs. This can be a laborious trial-and-error procedure, especially when both inflow and outflow points are present. Improved analyses methods are needed. One possible tactic would be to develop an automated inverse method, but this paper takes a more elementary approach and focuses on identifying the signatures that various inflow and outflow features create in flowing FEC logs. The physical insight obtained provides a basis for more efficient analysis of these logs, both for the present trial and error approach and for a potential future automated inverse approach. Inflow points produce distinctive signatures in the FEC logs themselves, enabling the determination of location, inflow rate, and ion concentration. Identifying outflow locations and flow rates typically requires a more complicated integral method, which is also presented in this paper.