The stability of bell shaped caverns in soft and discontinuous chalk is studied, jointly with M. Talesnik of the Civil Engineering Dept. at the Technion, using rock testing, numerical analysis, and Block Theory analysis. The caverns were excavated about 1000 years ago for extraction of building materials. The caverns have an elliptical cross section with a span of up to 40m and height of 17m, the openings roof is about 5 m below ground surface.
The mechanical behaviour of the chalk is studied using uniaxial, radial, and triaxial tests performed on both solid cylinders (at BGU) and on hollow cylinders (at the Technion) and the influence of anisotropy on elastic behaviour and strength is analyzed.
Stress distribution around the openings is studied using FLAC. Particular emphasis is given to the stress concentrations at side walls which are common to two or more adjacent caverns.
Block theory analysis is performed in conjunction with a statistical joint trace generation code which was developed by Gen-Hua Shi for the determination of the removable key block area in unrolled tunnel surfaces. The results are used to generate optimized support scheme where expected support pressure is regressed against joint spacing.
In order to detect the performance of the opening in real time joint displacement meters (LVDT’s with a sensitivity of 0.01mm) are installed on removable blocks. Temperature and humidity gages are installed in each studied cavern. 9;
Graduate Student: Michael Tsesarsky, M. Sc.
Supervisors: Dr. Yossef H. Hatzor
Click here to see images of the Beit Gubrin Bell Caves and some of our activities there