Abstract: Aiming at the limitation of stress relief method in vertical deep hole, an in-situ stress measurement technology suitable for vertical deep hole is proposed. A contact type aperture deformation measurement device based on the principle of micro optical imaging is developed, and a rapid in-situ stress measurement technology suitable for vertical deep holes is formed through the optimal connection of single acting double pipe drilling tools. The aperture deformation measuring device adopts key technologies such as aperture deformation perception, micro-imaging and directional measurement. This technology could simplify the test process, shorten the test time, realize multi-directional aperture deformation measurement under high temperature and high water pressure environment in vertical deep hole. A single acting double pipe drilling tool is introduced to optimize its drilling, coring and overflow, and an in-situ stress auxiliary testing device is formed. In-situ stress measurements are carried out at –410 m and –500 m levels in Jinshandian iron mine. The obtained annular core has stable inner diameter and high integrity, which verifies that the auxiliary test device has the technical advantages of accurate hole forming and complete coring, and provides a guarantee for the accurate measurement of borehole diameter deformation. The in-situ stress data at 4 points are obtained through measurement. The principal stress basically increases with the increase of depth, and the direction of the maximum horizontal principal stress is about NNW-NNE. The research shows that the in-situ stress measurement technology based on stress relief method proposed in this paper can realize in-situ stress measurement quickly and reliably in vertical deep holes.

Key words: stress relief, double pipe drilling tool, aperture deformation, annular core