地热系统作用下红层软岩力学性能试验研究

地热能源是目前绿色建筑的发展趋势，但红层软岩分布地区出现的系列建筑地基病害问题与地源热系统关系尚不清楚。依托成都某建筑群事故调查项目，研究了有无地热系统作用下泥岩、石膏岩的工程特性，并基于室内试验模拟，研究了不同加热方式、不同温度及不同浸水时间等因素下岩石宏观力学特性和微观结构特征。结果表明：（1）同一场地有无地热系统对岩石力学性质影响甚微，但有地热系统时岩体中裂隙发育数量明显增多，累积张开度明显增大；（2）随着浸泡时间增加，泥岩最大含水率可达30%以上，石膏岩含水率超不过15%，泥岩浸水软化效应较石膏岩显著，二者力学指标随含水率增加呈负指数型下降，石膏岩因晶粒大小不同，离散性大；（3）天然状态下石膏岩呈脆性破坏，泥岩呈延性破坏，石膏岩水岩界面溶蚀作用效应显著，随着石膏岩由表及里溶蚀加剧，温度变化效应对岩体内生裂隙萌发起一定促进作用；（4）在20～50 ℃温度变化范围内，石膏岩抗压强度随温度呈抛物线变化，而泥岩单调升高；（5）地热管与岩体间填筑不密实容易形成渗水通道，改变水动力条件，动水作用下使石膏岩裂隙及软弱夹层溶蚀加剧，形成更大空洞，从而诱发沉降。

Experimental study on mechanical properties of red-layer soft rock in geothermal systems

Geothermal energy is the development trend of green building. However, it is not clear about the relationship between the problems of building foundation impairment and the geothermal system in red-layer soft rock areas. Based on an accident investigation project of building clusters in Chengdu, the engineering characteristics of mudstone and gypsum rock with or without geothermal system were studied, and the macro-mechanical and micro-structural characteristics of rock under different heating methods, different temperatures and different soaking times were studied as well. The results show that: 1) At the same site, there is little influence of geothermal system on rock mechanical properties, but when geothermal system is in place, the number of fissures and the cumulative opening has an obvious increase. 2) With the increase of soaking time, the maximum water content of mudstone can reach more than 30%, the water content of gypsum can not exceed 15%, the water softening effect of mudstone is more obvious than that of gypsum, and the mechanical index of mudstone decreases with the increase of water content. 3) In the natural state, the gypsum rock is brittle and the mudstone is ductile; the water-rock interface of the gypsum rock has a significant effect of dissolution, and the dissolution of the gypsum rock is intensified from the surface to the interior. 4) In the temperature ranges from 20 °C to 50 °C, the compressive strength of gypsum rock parabolically changes with temperature, while that of mudstone monotonously increases. 5) The loose filling between geothermal pipe and rock mass is easy to form seepage pathway and change the hydrodynamic condition. Under the action of flowing water, the rock mass at the crack of gypsum rock and the weak interlayer dissolves, forming big cavity and inducing building subsidence.