Borehole Pressure Cells • Stressmeters • Stress Cells • Borehole Deformation Gages

 

Photo of 3200

 

 

Model 3200 Hydraulic Borehole Pressure Cells
The standard Borehole Pressure Cell (BPC) is used to measure rock stress changes and is designed to be grouted inside a borehole. The BPC is manufactured from two steel plates welded together around their periphery. The plates are deformed into a “dog bone” configuration so that they can be expanded easily without damage to the welds. Hydraulic oil fills the space between the two plates and a high-pressure stainless steel tube connects the plates to a stainless steel pressure gage and/or a pressure transducer.

Specifications  
Standard Ranges 25, 35, 70 MPa
Sensitivity 0.25% of range (approximately)
Accuracy (gage) 0.25% F.S.
(VW transducer) 0.1% F.S.
Borehole Size 57 mm
Temperature Range –20°C to +80°C
L x W x H 210 x 51 x 6 mm

Photo of 4300-EX, 4300-BX and 4300-NX  

Model 4300 VW Borehole Stressmeter
The Model 4300 VW Borehole Stressmeters are designed to measure stress changes in rock and can be installed in boreholes up to 100 feet deep. The Stressmeter consists of a high strength steel proving ring wedged tightly across one diameter inside a borehole and a vibrating wire tensioned across the other diameter inside the stressmeter. Changes in rock stress cause a related change in the resonant frequency of vibration of the tensioned wire providing output which is read by the Geokon Model GK-403 Readout Box.

Specifications  
Range in Compression 70 MPa
Range in Tension 3 MPa
Sensitivity¹ 14 to 70 KPa
Temperature Range² –20°C to +80°C
Borehole Diameter (4300-EX) 37 to 39 mm
(4300-BX) 58 to 61 mm
(4300-NX) 74 to 77 mm
¹Depends on rock modulus
²High temperature versions (up to 200°C) available on request

Photo of 4350  

Model 4350 VW Biaxial Stressmeter
The Model 4350 VW Biaxial Stressmeter is designed to measure compressive stress changes in rock, salt, concrete or ice. Three or six VW sensors oriented at 60° intervals allow the principal stress changes to be measured in the plane perpendicular to the stressmeter axis. The stressmeter consists of a high strength steel cylinder which is grouted (or frozen, in the case of ice) into a BX (60 mm) size borehole.

Specifications  
Standard Range 70 MPa
Sensitivity¹ 14 to 70 KPa
Accuracy ±0.1% F.S.
Temperature Range² –20°C to +80°C
Borehole Diameter BX (60 mm)
¹Depends on rock modulus
²High temperature versions (up to 200°C) available on request

Photo of 4360  

Model 4360 VW Soft Inclusion Stress Cell (SISC)
The Model 4360 Vibrating Wire SISC is a larger version of the Model 4300 Borehole Stressmeters. The SISC is pre-loaded by wedging it into a large size diamond drill hole using an integral screw mechanism or hydraulic piston and can be set to measure both tensile and/or compression stress changes. It has been used successfully in 152 mm diameter overcoring holes (drilled to measure in situ stresses) to measure Aggregate/Alkali Reactions (AAR) in concrete dams.

Specifications  
Standard Range¹ ±35 MPa
Sensitivity¹ 35 KPa
Temperature Range –20°C to +80°C
Borehole Diameter² NX, PQ, HQ, 152 mm
¹Proportional to rock modulus; figures given are for E = 0.03 x 106 MPa
²Other diameters available on request

Photo of 5000  

Model 5000 Borehole Deformation Gage
The Model 5000 Borehole Deformation Gage is the proven USBM-style gage used to measure in situ rock stresses using the overcoring technique in rock that is competent and elastic. The measurement of in situ stresses is important in the design of underground openings such as power houses, crushing stations, mines, tunnels and the like. It is also useful for determining the inherent stability of pit slopes, foundation excavations, mine pillars and dam abutments. A full line of ancillary equipment is available including readout units, biaxial modulus chamber, setting rods, etc.

Specifications  
Borehole Diameter 38 mm EX-size diamond drill hole
Sensitivity 1.0 microstrain
Minimum Overcore Depth 203 mm (25 mm with reverse case)
Maximum Overcore Depth 15 m standard (60 m with extra cable)
Length x Diameter 267 x 35 mm