井巷支护中被忽视的两个重要问题

TWO IMPORTANT ASPECTS NEGLECTED IN ROADWAY SUPPORT

开巷初期,围岩并不冒落,过了一段时间后方始冒落,这说明后期围岩强度降低了。大量事实表明,围岩强度降低是由围岩后期粘性位移造成的。原岩应力场由构造应力场和自重应力场两部分组成。仅以自重应力场计算,巷道埋深为200m 以下时,原岩应力值要大出支护抗力(不包括圆形整浇混凝土支护)几倍到几十倍,因而支护不能有效阻止围岩位移。成功的支护仅是维持了巷道整体稳定性。据以上分析,支护只要能满足围岩的位移条件(动载),并能承受可能冒落围岩的重量(静载),支护就可获得成功。

In the initial period of roadway development,the surrounding rocks do not collapse and the rocks begin to fall after a certain period.This shows that the strength of country rock reduces in the later period.Facts indicate reduced strength of country rock is due to adhesive displacement in the late period. The stress field of virgin rock consists of structural stress field and dead weight stress field.In the dead weight stress field calculation only,when the depth of roadway is greater than 200m,the stress of virgin rock is several times to several ten times greater than the support resistance,not including the circular insitu placed concrete support.Therefore,the supports can not stop effectively displacement of the rocks.The successful supports can only satisfy the conditions of rock displacement (dynamic load),and can support the weight of fallen rocks.