陕北地区黄土隧道围岩工程特性试验研究

对延安-延川(陕晋界)高速公路黄土隧道原状黄土进行了物理力学性质试验,结果表明:除液性指数外,黄土围岩物性参数的变异系数均小于力学参数;可将9个物性指标根据其相关系数和因子分析结果分为3组,并根据它们与土的强度指标的关系,选取天然含水量、干密度和塑性指数作为黄土隧道围岩分级指标;深埋饱和原状Q₂黄土的应力-应变曲线在低围压下为应变软化型,高围压下表现为应变硬化型;无侧限抗压强度试验为小应变脆性破坏,应力-应变关系曲线有两种形式:一种是土样直接发生脆性破坏,丧失承载能力;另一种是先发生局部脆性破坏,仍保留有一定的承载能力。

Experimental Study on the Engineering Properties of the Surrounding Rock in Loess Tunnel of Northern Shanxi

Physical and mechanical property tests were carried out based on loess tunnel surrounding rock in Yan'an-Yan'chuan (Shan Jin Boundary) highway.The tests results show that the variation coefficient of physical index of loess is less than that of mechanical parameters.On the basis of 9 physical property index and their correlation,three groups were obtained.Taking into account their relations with soil strength parameters,natural water content,dry density and plasticity index were selected as the classification index of loess tunnel surrounding rock.The deep-buried saturated undisturbed Q2 loess behaves strain-softening in low confining pressure and strainhardening in high confining pressure.The failure model in unconfined compressive strength tests displays small strain brittle fracture,and the stress-strain curve of the tests has two forms:the direct brittle failure,which causes the soil to lose bearing capacity completely,and the local brittle failure occurring first,but still remains a certain bearing capacity.