Applicability of CPT for Construction Control of Seawall on Soft Clay Improved by Sand Drain Method

Abstract

A case study is presented of an application of the cone penetration test for construction control of a seawall construction on soft ground improved by sand drain. Effective construction control of such a soil structure requires a systematic way to collect accurate information about the progress of consolidation and gain in soil strength. An empirical correlation is proposed concerning cone resistance measured by a cone penetration test and the undrained shear strength of the ground. The relationship between cone resistance and the undrained shear strength is not affected by the state of consolidation of the ground. Based on the empirical correlation found in this study, gain in undrained shear strength during construction can be accurately evaluated by the cone penetration test. This paper also demonstrates the usefulness of cone penetration test to monitor the degree of consolidation of the improved ground. Also estimated by the cone penetration test are aging effect, classification of clay layer and strength increment ratio in normally consolidated state. Aspects geotechnical behavior of the ground are discussed such as the process of strength increment, aging effect, sequence of various shear tests to examine change in strength and considerations on shear strength of improved ground after deformation. The results of this study clearly show that the cone penetration test is a very useful investigation method and has high applicability for construction control.