This paper analyzed the earth pressure, pore pressure, and surface settlement of the Luoyang urban rail transit tunnel in a sandy gravel stratum (Henan Province, China) under different burial depths by using field measurement methods. The results showed that the earth pressure as well as pore pressure of the soil layer above the working surface increased sharply and reached their maximum values when the cutter head of the shield gradually crossed the working surface. During the completion of synchronous grouting, the earth pressure and pore pressure increased slightly; when shield tunneling passed through the working surface, the earth pressure is smaller than the original earth pressure due to the unloading effect. The surface settlement curve above the tunnel took on a “V” shape after the completion of the left-side tunnel excavation, conforming to the normal distribution pattern. The surface settlement curve above the two tunnels took on a “W” shape after the completion of the right-side tunnel excavation, which is in good agreement with the proposed theoretical calculations. The findings of this study can help for better understanding the control of safety risk during shield construction.

A convection-diffusion transport model of soluble contaminant suitable for one-dimensional homogeneous unsaturated three-layered soils is established. The transport processes of soluble contaminant are analyzed by a semi-analytical method, which takes into account the boundary conditions of pond infiltration. Various combined soil layers and various absorption models (e.g. linear or nonlinear adsorption) are discussed. Studies show that, under pond infiltration, the immigration velocity in coarse grained soil will be greater than that in fine grained soil; furthermore the diffusion ratio of the former will also be higher than the latter. Besides, the influence of initial pressure head on immigration velocity can be neglected; however the concentration peaks of contaminant will increase with the decrease of initial pressure head.

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Tangshan stadium is located in downtown Tangshan, Hebei province， China. In this area, there are many karstic fissure zones and several karst collapses have happened, causing serious damages to the buildings on top of them. In this paper, the engineering geological and hydrogeological data was acquired through comprehensive investigation methods, and the distribution of karst collapses was determined and their forming mechanism and main influence factors were explored. The results indicate that the distribution characteristics of karst collapses in the stadium are mainly as follows: (1) a relatively thin silty clay layer, (2) a thin eluvial red clay layer or the layer is missing，and (3) located near the fault zone, especially near the intersections of the faults. The study indicates that the effect of penetration erosion is the key factor contributing to the karst collapse and the destruction soil structure caused by several earthquakes in history may aggravate the erosion. The present study can provide guidelines to the prevention and management of karst collapses in Tangshan, as well as other areas in China.