The results of the investigation on rock mechanical properties in Toki granite using cores from DH-6,7 and 8 boreholes

not registered ; Sato, Toshinori  

The rock mechanical investigations on Toki granite have been carried out from 1997 to 1998 as a part of the investigations in the regional hydorogeological study in Tono area. The objectives of the investigation are to supply the support data for developing of the conceptual geological/hydrogeological model in large scale (10km10km) The investigations in DH-6,7 and 8 consist of two part: (1)Laboratory tests for the physical/mechanical/thermal properties of rock matrix in Toki granite. (2)In-situ stress measurement in laboratory with AE and DRA methods. The results of the investigations are summarized as follows : (1)The distribution of rock physical/mechanical properties for DH-6,7,8 is not uniform from surface to 1000m depth. The trend of the distribution of the rock properties varies at about 400500m and 700800m. (2)The vertical component of stress tensors are almost equal to the overburden pressure based on the results of stress measurement with AE and DRA methods for DH-6,7 and 8. The results correspond with those in MIU-1. According to the both results, the vertical component of stress tensors can be assumed to be equal to the overburden pressure in Toki granite. The vertical component of stress tensors at several depth in DH-6,7,8 and MIU-1 boreholes is not equal to the overburden pressure. This result suggests that there are large discontinuities horizontally in the Toki granitic body. (3)There are no correlation between rock properties, fracture distribution and rock type. The results suggest that the complex variation of rock properties and fracture distribution with depth may be induced by the variation of regional stress field.