Surface Excavation Assessment in Non-bedded Rock Mass Based on Borehole Information and Seismic Survey

Abstract

One of the most popular indirect methods for investigating the subsurface information is through borehole record. The information obtained from a bore log will provide the subsurface scenario with regard to the soil and rock mass profile, stiffness of the material, weathering grade and quality of the rock material. It is wise to obtain as much as possible useful information from it for any civil engineering design including its excavatability assessment. On the other hand, seismic velocity is also commonly used to describe subsurface information as it furnish actual profile of the subsurface along the survey line. Seismic survey is assumed to be relevant geophysical method to characterize the boundary of soil-rock. Although the field borehole information and seismic method has been widely applied in the ground investigation, their applicability in assessing excavation performance is still debatable, especially when it involves thick soil-rock interaction zone in tropical region. The objective of this study is to investigate the applicability of ground profile obtained from the field borehole information and the seismic survey in surface excavation works. Field studies were carried out ontwo on-going excavation sites namely Nilai and Kota Tinggi involving non-bedded -bedded rock masses, namely granite. This study aims to present the relationship between seismic refraction method and boreholes were to investigate their effectiveness in assessing the ground information for excavation purpose. A sets of boreholeswere drilled approximately on the same path of seismic linesto obtain relationship between those methods. The seismic survey results are evaluated with Standard Penetration Test (SPT), strength index, core recovery (CR) and Rock Quality Designation (RQD) information. Upon obtaining that information, trial excavation were carried out using different size of excavator machines to determine its productivity rate. This study provides useful information on the excavatability of ground materials by using various type of excavating machines, based on the most commonly used of ground investigation tools, which are boreholes and seismic velocity method.