Investigations and numerical analysis at pre-excavation stage of machine excavation effects experiment

not registered; not registered; Sakaki, Toshihiro; not registered

Excavation of a shaft or a horizontal drift in a rock mass probably affects the rock mass around the openings. It is necessary in the design, construction and safety assessment of underground facilities to consider the properties and extent of the EDZ (Excavation Disturbed Zone; the zone where rock properties and rock conditions have been changed due to excavation). PNC has carried out the in-situ experiments in the Tono mine and has identified the controlling factors in the generation and extent of the EDZ due to blasting. In order to evaluate dependence of the generation and extent of the EDZ on excavation method, Machine Bxcavation Effects Experiment has been started. In FY 1992, a horizontal drift for measurements (measuring drift) was excavated. A horizontal drift parallel to the measuring drift (test drift) is scheduled to be excavated by a machine in FY 1994. The investigations and numerical analysis before excavation of the test drift were carried out in FY 1993. The objectives of the investigations and numerical analysis carried out in FY 1993 are as follows: (1)to measure and evaluate the rock properties and the rock conditions around the test drift before excavation, and (2)to predict by numerical analysis the displacements and stress change during excavation of the test drift. The investigations and numerical analysis in FY 1993 consist of the following items: (1)laboratory tests to measure the compressive strength, deformation modulus, seismic wave velocity, electric resistivity, and so on, (2)in-situ tests to estimate deformability and permeability, (3)borehole wall observation, (4)measurement of the initial stress, (5)seismic tomography and resistivity tomography, and (6)numerical analysis to predict the displacements and stress change by the Finite Blement Method. This report describes the details of these investigations and numerical analysis carried out in FY 1993.