包气带隧道气相释压效应与气相释压集聚水

摘要

研究目的:地下水位以上包气带隧道施工或运营期间出现渗水或小股涌水现象的成因和机理一直困扰着人们,且往往对工程有着重要且长期的影响.本文通过对隧道开挖后土体固、液、气三相变化的分析,找出与隧道周边水分变化相关的主要影响因素,揭示隧道周边围岩形成饱和含水带并出现渗水的成因和机理,合理解释明确处于地下水位以上且无上层滞水地段隧道渗水问题,并提出关于隧道气相运移以及关于围岩局部地下水的全新概念.研究结论:(1)包气带气相压力随高程降低增加的梯度在年内约多数时间段大于大气压力的增加梯度,亦即隧道围岩岩土体气相压力周期性大于同高程大气压力;(2)隧道开挖后在气相与大气压力差驱动下,导致产生岩土体气相收敛集聚运动,以及与之相伴的一系列水汽运移、吸附、转化现象,本文称为隧道开挖的气相释压效应,并认为该效应为隧道开挖所产生的除应力场变化以外的另一重要变化;将由此产生的局部饱和地下水称为气相释压集聚水,该地下水的溢出是包气带除局部为上层滞水导致以外的隧道渗水的主要原因;(3)本文研究内容主要用于隧道等地下工程的工程地质及水文地质勘察.%Research purposes:The people be nagged by cause of tunnel leakage and little water burst in vadose zone in long times during tunnel construction or operation.This paper finds out the main factor that affect moisture change of tunnel periphery through analysis of three phase changing of soil after excavation,reveals the cause of tunnel leakage and the formation of saturated zone,reasonably explains the question of tunnel leakage that tunnel located in the underground water level and no perched water,and puts forward new concept about gaseous phase migration and part underground water around tunnel.Research conclusions:(1) The pressure increase grads of gaseous phase in vadose zone are greater than the pressure increase grads of atmosphere in about most mouths of one year.(2) After excavation of the tunnel,converging movement of gaseous phase in vadose zone appears,and moisture of gaseous phase generates movement,adsorption,conversion,this phenomenon is named as the effect of pressure release of gaseous phase in vadose zone in this paper.This paper thinks that this effect is another important influence except the surrounding rock change of stress field when tunneling.Partial saturated underwater in surrounding rock produced by the effect of pressure release of gaseous phase is named pressure released gather underwater of gaseous phase in vadose zone,this underground water overflowing is main reason of tunnel leakage and little water burst in vadose zone.(3) This paper ean be used for the survey of engineering geology and hydrogeology in tunnel engineering and other underground engineering.