Borehole Pressure Cells

Borehole Pressure Cells OVERVIEW

• Borehole Pressure Cells have a long term track record of stress monitoring in both elastic and viscoelastic rock. Product development is largely the result of research done by the U.S. Bureau of Mines (Panek & Stock 1964, and Smith 1972).
• Cells are available in two basic configurations: a miniature flatjack version (BPC) and a cylindrical pressure cell (CPC). Due to the flat design, the BPC responds primarily to the stress in the plane perpendicular to the cell, and is only slightly affected by stress in the same plane. Two BPCs mounted at right angles to each other in the same borehole will monitor the principal stresses in the plane perpendicular to the borehole. Biaxial stress measurement will require three BPCs in the same borehole.
• While not appropriate for anisotropic stress conditions, the CPC will measure the average change in the principal stresses in the plane perpendicular to the borehole.

OPERATING PRINCIPLE

• Both the BPC and CPC are two stainless steel plates welded together around their periphery. The space between the plates is filled with de-aired fluid and leads to the borehole collar via a high-pressure stainless tube. Attached to this tube is a check valve and hydraulic coupler to facilitate pumping up the cell and either a gauge or pressure transducer type readout. In a typical installation, the BPC is grouted into the borehole. Once the grout has set, the cell is pressurized to slightly over the estimated stress. The hydraulic pump is then disconnected, with the pressure being held by the integral check valve. The system is then allowed to stabilize. In elastic rocks, given the modulus of the rock, the stress change may be determined by the corresponding change in hydraulic pressure. In rocks that exhibit plastic creep, the cell will not only measure stress change, but the final equilibrium pressure approximates the in situ stress.

FEATURES

• Low cost.
• Simplicity of operation.
• Field rugged and reliable..
• Stainless steel construction.
• Remote readout available.
• Data logger compatible.

BENEFITS

• Increase Safety
• High Accuracy

APPLICATIONS

• Monitor stress in elastic and viscoelastic rock

ORDERING INFO

INSTALLATION TOOLS

SPECIFICATIONS

• Installation Manual_borehole-pressure-cell