Application of dynamic and static cone penetrometer for characterization of railway substructure

The excessive loading generated from the train may cause the subgrade failure in the railway. Subsequently, the failure of subgrade leads to the change in the geometry of the rail. This paper represents the application of a dynamic and static cone penetrometer (DSCP) to evaluate the strength in the railway substructure. The DSCP, which consists of an outer pipe and an inner cone, is designed for the penetration into the ballast and subgrade, respectively. For the ballast, the outer pipe mounted with an accelerometer and four strain gauges is used to estimate the energy transferred into the head of pipe. During the penetration of the outer pipe, dynamic cone penetration indexs (DCPI) are recorded and can be corrected with the transferred energy. To evaluate the soil strength in the subgrade, the inner cone, which is mounted with four strain gauges, is used. For the field application of the DSCP, the dynamic and static cone penetration tests are performed at two positions. The results show that the corrected DCPI with the transferred energy is independent on the impact system. Furthermore, in the subgrade, the inner cone of the DSCP provides the soil strength profile with a high resolution, in terms of the cone tip resistance. This study suggests that the dynamic and static cone penetrometer may be effectively used for the characterization of the substructure in the railway.