Study on Estimation Method of Base Layer in Construction of Water Stop Wall for Subsurface Dam

Abstract

In order to secure the storage performance of the subsurface dam, it is necessary to secure the water-stopping performance of the wall by constructing the water-stopping wall without clearance and by securely grounding it to the base layer (impermeable layer) below the aquifer. In this paper, in order to ensure the grounding to the foundation layer, we investigated a method of estimating the depth of the foundation layer from the data of the load and the current of the speed reducer by the ground improvement machine at the time of constructing the water stop wall by the SMW method. It was confirmed that the relationship between the suspension load and the electrical current changed. In addition, it was confirmed that the injection pressure of the drilling fluid tended to increase when the auger penetrated into the base layer. The method of estimating the depth of the base layer from the change of the injection pressure of the drilling fluid was also examined. From the above examination, it was suggested that the depth of the foundation layer could be estimated from the data acquired from the ground improvement machine at the time of constructing the water stopper wall.