土石混合体力学特性的原位试验研究

土石混合体是由土体与不规则岩块混合形成的一种特殊地质介质,在我国山区广泛分布,但人们对其力学特性了解甚少。野外大尺度原位试验是揭示这类高度非均质和非均匀性复杂地质介质力学特性的一种有效办法。参照土体与岩体现场原位试验方法,首先提出并规范针对土石混合体的原位推剪与压剪试验仪器、方法、步骤及其关键问题等。结合三峡库区白衣庵滑坡典型的土石混合体,共进行23个大尺度的土石混合体原位推剪和压剪试验,获得不同含石量、不同尺寸大小和不同应力状态下土石混合体的剪应力与剪切位移曲线、剪切强度曲线、破坏模式以及相应的抗剪强度参数。试验结果表明,土石混合体具有典型的全应力–应变曲线、应变软化、高内摩擦角等特有特征,这也是其特殊的物质组成结构特征的体现。试验结果还表明,含石量是影响土石混合体强度与破坏形式的重要因素;而尺寸效应也是土石混合体的一个重要力学特性。该研究从试验方法与科学数据积累等角度为进一步研究这种非岩非土复杂介质的力学特性奠定了基础。

STUDY ON IN-SITU TESTS OF MECHANICAL CHARACTERISTICS ON SOIL-ROCK AGGREGATE

Soil-rock aggregate(RSA)is a special kind of geomaterial composed of soils and irregular rock blocks.The mechanical properties of RSA are rarely known although RSA distributes here and there in the mountainous area in China.In-situ large-scale test can explore the mechanical properties of RSA effectively since RSA is described as a kind of heterogeneous and nonuniform material.Here,the method of in-situ test for soils and rocks is referred;and a practical procedure of in-situ test for RSA is proposed and normalized including the method of push-shear test and press-shear test,equipments,steps,and some key points.Combined with the typical RSA at the Baiyian Landslide in the Three Gorges Reservoir area,23 large-scale in-situ tests(including push-shear and press-shear)are carried out.The curves of shear stress-displacement,curves of shear strength,failure mode,and shear strength parameters for RSA with different rock contents,sample sizes and stress states are obtained from tests.The results show that RSA has typical complete curves of stress-strain,strain softening,and high internal friction angle,which are caused by the special structure of RSA.It is also indicated that rock content is an important factor for strength and failure mode of RSA and that dimension effect is observed in the in-situ tests of RSA.The procedure of in-situ tests and results obtained from the tests can provide scientific data for further study of RSA.