Dae-Soo Lee

Exploration of underground utilities using method predicting an anomaly

Rapid urbanization and industrialization have caused increased demand for underground structures such as cable, and other utility tunnels. Recently, it has become very difficult to construct new underground structures in downtown areas because of civil complaints, and engineering problems related to insufficient information about existing underground structures, cable tunnels in particular. This lack of information about the location and direction-of-travel of cable tunnels is causing many problems. To solve these problems, this study was focused on the use of geophysical exploration of the ground in a way that is theoretically, different from previous electrical resistivity surveys. An electric field analysis was performed on the ground with cable tunnels using Gauss’ law and the Laplace equation. The electrical resistivity equation, which is a function of the cable tunnel direction, the cable tunnel location, and the electrical conductivity of the cable tunnel, can be obtained through electrical field analysis. A field test was performed for the verification of this theoretical approach. A field test results provided meaningful data.

Load-Settlement Characteristics of Drilled Shafts Reinforced by Rockbolts

This paper describes the load distribution and settlement of reinforced drilled shafts subjected to axial loads. The emphasis was on quantifying the reinforcing effects of rockbolts placed from the shafts to surrounding weathered rock based on a numerical analysis and 1/8 scale load tests performed on instrumented piles. The piles with and without rockbolts were instrumented with strain gages, load cell and tell tale, and load tests were performed on four piles: tension and compression. The results of the four load tests are presented in terms of top load-top movement curves. In addition numerical analyses are performed for the major influencing parameters on the behavior of reinforced drilled shafts such as the number of rockbolts, the positions on the shaft, reinforcement level, and the inclination angle at which the rockbolts are placed. As a result, the parametric study is highlighted. It was found that as the number of reinforcing levels increases, the incremental effect of reinforcement tends to increase, whereas the reinforcing effect on relative positions is negligible. In addition there is a reinforcing effect as the inclination angle increases up to 30 degrees.