隧道地质预报方法——以一工程为例

TUNNEL GEOLOGICAL PREDICTION: A CASE HISTORY

隧道地质预报是一个比较复杂的问题,本文以军都山隧道为例,对这一问题进行探讨。军都山隧道位于北京市北部,全长8.46km,由花岗岩、安山岩和黄土等组成,地质条件复杂。施工中遇到的主要问题是由断层、岩脉、侵入接触带和地下水引起的塌方和过量涌水。为减少这些灾害的产生,笔者选用地质方法(包括几何法、异常特征分析法和综合分析法)对该隧道中的断层、岩脉和侵入接触带进行了预报,取得了比较好的效果,预报成功率达70％。

The geological conditions are a major factor controlling tunnel cost, speed and excavation and support manners. It is necessary to predict tunnel geological conditions accurately in order to design tunnel and make cost budget. In this paper, the authors discuss tunnel geological prediction with reference to the Jundushan Tunnel example. The tunnel is located in Yanqing county of Beijing with a total length of 8.46 km. The tunnel passses through loess, andesite, granite, syenite dikes and so on. In the andesite and granite areas, there are many faults and dikes, andgeological conditions are complex. These rocks control construction when they contain a large amount of water. In the Jundushan Tunnel, collapses and excessive groundwater inflow caused by faults, dikes, intrusive contact zones and groundwater are main geological hazards. Therefore, emphasis is put on the prediction of faults for geological prediction. Three geological methods are selected for prediction of faults, a. the geometric method (including the surface projection method and face advance method): the fault is regarded as a plane and its exposed part is projected to the unexcavated position of the tunnel; b. the special features analytical method: the abnormal distributions of the attitude, spacing and filling of joints, groundwater and metamorphic minerals are considered as the indicators for the existence of faults, c. the synthetic analytical method: the synthesizes geometric method is coupled with the special features analytical method to predict the fault. These methods yield good results in the prediction of faults and contact zones in the middle and east sectors of the Jundushan Tunnel. The success rate of prediction attains 70%.