Field Experimental Study On Expansion Characteristics And Strength Properties Of Expansive Soils At Yun Gui Railway

Due to expansive soils have the behavior of swelling and softening when absorb water, and other features that when dehydrated they will shrink and rend, which has been the difficulty in engineering application for long time. China is one of the country that expansive soils are widely distributed, in which many civil engineering construction including railway, highway, water conservancy and building, often encounter the problem caused by expansive soils. The indoor study on expansive soils has been made a lot of results, but the research on the strength, the deformation and the mechanical properties of in-situ expansive soils are very little.Relying on the subject of Key Technology Research on Expansive Soils and Karst Lots of Yun-Gui Railway (Code:2010G016-B), which is supported by Science and Technology Department of Railway Ministry, China, this paper conducted a field investigation about the distribution of expansive soils along Yun-Gui railway; besides, through a series of field trials of expansive soils at Yun-Gui Railway, the paper studied the force, the deformation and the shear strength behavior of in-situ expansive soils, the main contents and conclusions are as follows:1) Through a field investigation about engineering geological conditions and expansive soils distribution of Yun-Gui Railway, choose the medium to strong expansive soils test section and the weak to medium expansive soils test section.2) Through the vertical swelling pressure of the medium to strong expansive soils and the weak to medium expansive soils in-situ experiments, the paper acquires the vertical limit swelling pressure of the two soils, and studys the relationship between the vertical swelling pressure and the time, the water content, the swelling volume.3) Based on the experiment of a large area of water immersion test for the medium to strong expansive soils in the long-term, this paper acquires the final swelling amounts of the these soils on condition of immersed in water in long terms, studys the law of development of swelling contents over the time. In addition, the paper learns the water content variation of soil with depth and time under long-term and large-area immersion.4) Through the in-situ direct-shear tests, the paper acquires the push-displacement curve, obtains the shear strength of undisturbed soils in the case of the real force and compares the changes of the soil shear srength before and after soaking.