膨胀土胀缩机理及其在控制隧道沉降中的应用

因黄土的膨胀特性导致的隧道地表沉降和变形坍塌事故屡见不鲜。为探究浅埋段膨胀土隧道地表沉降和变形控制技术,结合在建太兴铁路TXXS-2小河沟段膨胀土隧道施工,采用现场监测、理论分析和现场试验研究相结合的方法,对膨胀土的特性、胀缩机理及其影响因素进行研究,结合监控量测数据结果,提出地表沉降控制技术。通过对膨胀土微结构特征进行研究,引用了膨胀土的判别函数式,对膨胀土的膨胀潜势进行了分类,根据膨胀潜势情况指导施工;研究了膨胀土强度特性,建立了强度与含水量、干密度、饱和度的关系,并对有效蒙脱石含量对强度的影响进行研究,理论上分析了晶体胀缩的根本机理;根据对膨胀土胀缩特性进行研究,分析了隧道的膨胀潜势等级和隧道特殊地质特征,通过现场土工试验,确定了小河沟隧道胀缩影响因素及其曲线关系;通过对现场施工进行监控量测,结合关系曲线和现场情况,提出了控制地表沉降的处治措施,指导现场工程施工。

Application of Swelling Shrinkage Mechanism of Swelling Soil in the Tunnel Settlement Control

Deformation and collapse accidents of the tunnel caused by swelling characteristics of loess were encountered many times in tunneling. In order to explore the expansive soil tunnel surface subsidence and deformation control technology for shallow buried section, based on the expansive soil tunnel construction at TXXS-2 Xiaohegou section of Tai-Xing railway, a combined research of field monitoring, theoretical analysis and field test was carried out on the characteristics of swelling soil, shrinkage mechanism and influencing factors, in association with monitoring measurement results, the ground surface settlement control technology was presented. Through the study on micro structure characteristic of expansive soil, by introducing the discriminant function of expansive soil, the classification of swelling potential of expansive soil was set up to guide the construction by the expansion potential. Through the study of strength characteristics of expansive soil, the relations between strength and water content, dry density, saturation were found and the fundamental mechanism of crystal swell-shrink was theoretically analyzed. According to the research of the swell and contraction properties of expansive soil, the swelling potential grade and the special geological features of the tunnel were analyzed. Through the field test, the expansion and shrinkage factors and the curve of Xiaohegou tunnel were determined. Through monitoring on site measurement, analysis of measurement data, with combining the relationship curve and the site situation, some treatment measures were put forward to control the ground settlement for instructing the on-site construction.