Large-scale Triaxial Tests On Soil-rock Aggregate Mixture Based On Orthogonal Design

With the rapid development of infrastructure construction in the mountainous area of the south, more and more soil-rock aggregate mixture are used as filling material in subgrade engineering, which are mainly from the excavating of the mountains in the construction of subgrade engineering. But considering the large range of variation of grain size, which usually is hard to control, and the water content is inhomogeneous extremely. The quality of subgrade engineering, of which uses the soil-rock aggregate mixture, usually can not be guaranteed in practical engineering. It often leads to the settlement a large amount of subgrade settlement, which causes destruction of the subgrade structure too early and the efficiency is also be influenced. The soil-rock-mixture foundation stand in a wet state over a long period of time because of the plenty of rain in southern mountain area of China, which affects the function of the soil-rock-mixture foundation. Therefore, aiming at the existing problem and in order to in-depth study deformation and intensity characteristics of soil-rock aggregate mixture, a series of studies is conducted in this paper. The main works are as follows:(1).A series of lab large-scale triaxial tests are conducted through YS30-3 large-scale triaxial test machine based on the orthogonal design. These tests take into account various factors such as water content, stone content, rock and soil property, etc. The tests results indicate that the shear strength of soil-rock aggregate mixture in the triaxial stress conditions does not exhibit obvious characteristics of strain softening. The cohesion of soil-rock aggregate mixture is generally low and the internal friction angle is relatively high. The internal friction angle is more susceptible to factors. The rock content is the primary factor for influencing for the strength of soil-rock aggregate mixture. With the increasing of rock content from 25% to 70%, the internal friction angle increases linearly from 34.54 to 46.35; The rock content and the confining pressure are respectively affect the internal cause and external cause of soil-rock aggregate mixture volumetric strain characteristics.That is to say, in the same water content, rock and soil property, the lower the rock content, the shear contraction of soil-rock aggregate mixture in the high confining pressure will be more obvious; the higher the rock content, the shear dilatation of soil-rock aggregate mixture in the low confining pressure will be more obvious.(2). A model of soil-rock aggregate mixture of high embankment is established by the software of FLAC 3D according to the test parameters which are obtained from the lab large-scale triaxial tests, which are used for numerical simulation analysis. In the progress of analysis, the influence of various factors to the stability of soil-rock aggregate mixture subgrade are considered. And some instructive advices about construction are also put forward.(3).Aiming at normal condition and sprinkler immersion condition, making the two groups soil-rock-mixture foundation model in a special model tank, and respectively applying graded load on the two foundation model to study the deformation behaviour of soil-rock-mixture when it is in the load-bearing state. The results showed:the model of soil-rock-mixture foundation showed better structural for normal condition, before reaching its ultimate load p-s curve is nearly linear development, with sudden destruction. But for sprinkler immersion condition, the settlement develops slowly and the obvious inflexion is of non-existent. The ultimate load is also smaller than that of normal condition. Besides, the water content has a very significant impact on its settlement and bearing capacity. Through the analysis of the measurement of earth pressure, the stress diffusion in the subgrade is asymmetric, and so does the depth of affected.