This paper describes the measurement results of site investigation and laboratory tests performed on soils sampled from the excavation slope.
The main concluding remarks derived from these studies are as follows; i) The inward soil of the excavation slope is neutral, on the other hand, the subsurface soil is strongly acidic. ii) The hydrogen-ion concentration exponent (pH) value of air drying soils decreases with an increasing elapsed time. iii) Unconfined compressive strength and deformation modulus increase corresponding to an increase of pH. Therefore, pH is the most important factor in considering strength-deformation characteristics of acid soils.