Study on deformation of filling composite geological body in loess mountainous area

With the rapid expansion of urban area in mountainous areas of the Loess Plateau, the restriction of mountainous terrain on available construction land is becoming increasingly prominent. The man-made land is an effective way to solve this contradiction. The geological body produced by this way is composed of undisturbed soil and filling, and its deformation is complex. Deformation disasters are frequent and have serious harms. In order to explore the spatiotemporal deformation characteristics and stability analysis method of filling composite geological body in loess mountainous areas, the in situ tests were carried out. The settlement and horizontal displacement information were obtained by setting instruments in soil layers. The influence of undisturbed soil and interface interaction were considered. The main conclusions are as follows: (1) The settlement of composite geological body develops in a “J” shape with time, and the deformation of undisturbed soil under slope plane is significant. (2) The relationship between settlement and logarithm of time is piecewise linear, corresponding to primary and secondary consolidation sections, respectively. The settlement deformation capacity changing with overburden pressure in secondary consolidation section can be approximated by a straight line without passing through the origin. (3) The undisturbed soil also has obvious horizontal displacement. The horizontal displacement of composite geological body on the upper part of slope increases in a “round-trip fluctuation” pattern with time. Soil movement in depth direction is not coordinated, and there are “peaks and valleys” in the displacement curve. (4) The deformation stability time of horizontal direction is more than that of depth direction. (5) Stability analysis should take the stability time as focus and different threshold type should be taken for settlement and horizontal deformation, respectively. The adverse effect of deformation coupling in three directions should be considered, and the deformation difference between undisturbed soil and filling should be distinguished. The research conclusions are of great significance to the disasters prevention and control of filling composite geological body.