The Force Analysis Of The Underground Box-Shaped Concrete Structure Under The Interaction Of Vehicle-Soil-Groundwater

At present, it is still relatively rough that the design method of the underground small or medium box-shaped concrete structure of the urban hydropower working well in China. The general design always adopt the simplified design theory designed by plane which does not consider the space effect. Vehicle load is equivalent to a simplified static load (considering power factor) applied to the structure. The effect of thickness on the structure is not sufficiently taken into account when design. Therefore, it is necessary to improve the existing design method.This article is based on the existing research results and taking the practical engineering underground cable well for example. Under the interaction of the earth pressure and groundwater pressure and the vehicle moving load, the article is to study the actual force of the underground box-shaped concrete structures and made design suggestions. With ABAQUS finite element software, the article establish a three-dimensional finite element model taking into account the combined effect of these three factors, and considering the sequence of excavation and backfill, and through the existing literature data to demonstrate the correctness of the results. The main conclusions are as follows:(1) The bending moment value calculated through culvert structure theory is significantly larger than the value obtained from finite element. The value calculated through culvert structure theory is about 2.2-3.5 times as the value obtained from finite element. The bending moment ratio of the lateral wall is the largest, more than 7 times. Visually, compared with the finite element software which considers the spatial effect, the structure has great safety reserves when it calculates through culvert structure theory which considers the plane effect. When overloaded or more automobile traffic, the jointly force is advantageous for security of structure.(2) The horizontal vehicle moving load has very little impact on the cable box-shaped structure under the road. It is desirable that the vehicle load only consider the vertical load, ignoring horizontal load when designers design. When the road is good, that is, when the road surface is smooth, the higher the speed, the less the bending moment value (absolute value). Thus, when the road surface is smooth, it is save that the vehicle dynamic load is replaced by static load when design.(3) Under the same vehicle load, the dead load increasing effect of the upper soil is large than the live load reduced effect of the vehicle load. Therefore, the thicker overburden, the greater the bending moment value of the cable well. And when the overburden depth is greater than lm, it is stable that the variation bending moment value of the cable well caused by vehicle load. At this moment, the bending moment value (absolute value) increases obviously. Thus, when designers select the depth for the underground cable wells or the similar box-shaped structure, the depth as much as possible shallow, and try to select the overburden depth within lm.(4) Groundwater level changes has great impact on the bending moment value of the roof span, spacers span and floor seat in the cable well. Therefore, if the box-shaped structure in the area that the underground water level constantly changing, designers should consider the effect by underground water level fluctuation.