公路隧道外水压力的相似模型试验研究

针对确定公路隧道衬砌外水压力的技术难题,利用自行设计的模型试验装置,采用相似理论,进行了38组工况试验。试验主要研究了水头高度、渗透系数、隧道排放量以及组合排放系统等因素与外水压力和折减系数的关系。通过对相似准则的分析得出,进行工程类比时应注意水头高度的相似关系为平方关系。试验结果表明:水头高度越小、隧道排放量越大、围岩渗透系数越小,隧道外水压力则越小;无论隧道是否完全封堵,只要周边存在排水点,且隧道在其渗流影响的范围之内,隧道外水压力就可折减。此外,深入分析组合排放系统的试验结果,提出了对于隧道周边富水洞穴应采用"复合回填"的处治方式的理念。最后指出,采用这种相似模型试验确定的外水压力是岩石隧道外水压力的上限值。

Study on Similar Model Test for External Water Pressure of Highway Tunnel

In order to solve technical problems of determination of external water pressure for highway tunnel,thirty eight tests were made with own designed apparatus by similarity theory.The relationships among different factors,including water head height,permeability coefficient,discharge amount and combined drainage system,and external water pressure and discount coefficient were mainly studied.Similarity criterion analysis reveals that the similar relationship of water head heights is square relation on engineering analogy.Test results show that(1) the less water head height is,the more discharge amount is,the less permeability coefficient is,and the less external water pressure is;(2) external water pressure can be discounted so long as there is drainage drop around tunnel and tunnel is within its seepage impact scope,no matter whether absolute plugging measures is taken for tunnel.Furthermore,the deep analysis result for combined drainage system points out that the concept of composite backfill method should be used for curing abundant water cavities around tunnel.Finally it was suggested that the value of external water pressure through the similar model test should be the upper limit of it.