Abstract
Recently the collapse accidents of the existing steel towers, due to natural disasters such as large earthquakes and large-scale typhoons, are regarded as the important problems for the safety managements of the infrastructures. Particularly, the steel tower facilities, built before the 1970s, should be reinforced for prevention of the deterioration. Practical use of the non-destructive exploration of their foundation with easy handling and low coat is expected for maintenance and management of the facilities effectively and properly. We performed the laboratory tests simulating the electrical exploration of foundations of steel tower and the field experiments of real-scale foundations made of steel reinforced concrete by using the electrical exploration. As a result, it was confirmed that we can distinguish the reversed T-shaped foundations from the mat-type foundations by using the 2D electrical exploration while the size of the foundation is indistinct. On the other hand, the size of the foundation (5.2m×5.2m×1.5m) can be estimated more clearly as the low resistivity zone with approximate accuracy of 25cm (5% of the foundation size) by using the 3D electrical exploration. The large low resistivity zone can be seen as a false image on the apparent resistivity section, because the current flows through a part of the steel tower above the ground surface at some electrode arrays. It is necessary to use the electrode array such as the dipole-dipole to evade the influence. As a future problem, we examine the applicability for the foundation of plain concrete.
