与城市地下生命线工程有关的双层地质结构中的几个问题

SOME PROBLEMS CONCERING DUAL GEOLOGICAL TEXTURE IN URBAN UNDERGROUND LIFELINE ENGINEERING

近代城市地下生命线工程要求对埋藏基岩中的活动断裂作出工程评价,以判断其是否有出现地表破裂的可能。 本文提出了对研究活动断裂的3项内容,即:“活动断裂的活动时间下限、地震复发周期及活动断裂的活动速率;对不同的断裂活动机制,即蠕动和粘滑,从覆盖层厚薄两种情况分析了对地基所产生的影响。 作者通过超声地震模型实验对覆盖层横向非均一性影响地下生命线工程的特点进行了研究,结果表明,横向非均一的覆盖层在地震过程中对地下生命线工程影响显著,不可忽视。

<ABSTRACT> Underground lifeline engineering (ULE for short) in modern city demands to make the appreciation of active fault in buried bedrock. Generaly speaking, a large number of urban geological texture of basement may be all simplified into a dual geological texture model, i. e. . the upper part of the basement consists of loose covering layer and the lower part consists of bedrock. The study of active fault should include three parts of contents, the first, to determine the lower time limit of activity of the fault, and the time limit must be recognized by both of the designing engineers and the geologists, the second, on the basis of studying repetition periods of earthquake occurrence, to determine whether the fault moves or not during the allowed time of efficiency of buildings and construction; the third, for the sake of engineering practice, the active rate of the fault and possible scale of the surface rupture must be given. The authors studied the effect of lateral non niform overburden site on the ULE by means of supersonic earthquake modelling and considered that the lateral non-uniformity of the overburden sediments lying on the bedrock has considerable effect on the strength distribution of earthquake ground motion. Owing to the lateral non ?uniformity of the covering sediments, there occurs an obvious jump of amplitude by the seismic wave propagation near the contact surface of the two different sediments. In addition, from the modelling experiment curves it may be seen that the different focus mechanisms and different medium characters may also exert an effect in different degrees.