Vibrating Wire NATM Stress Cells

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RST Vibrating Wire NATM Stress Cells are designed to measure stresses in concrete (shotcrete) linings in tunnels and other underground workings.

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Overview

RST Vibrating Wire NATM Stress Cells are designed to measure stresses in concrete (shotcrete) linings in tunnels and other underground workings. They feature a higher stiffness than Earth Pressure Cells, and are therefore more suitable for stress measurement in concrete.

The instrument name is associated with New Austrian Tunneling Method (NATM), which is also known as Sprayed Concrete Lining (SCL) and Sequential Excavation Method (SEM). Monitoring of radial and tangential stresses within and on shotcrete lining, along with measurement of tunnel convergence and deformation is an integral, very important part of the method and its successful implementation.

Vibrating Wire NATM cells are constructed of two rectangular steel plates welded around their periphery. The annular space between the plates is filled with fluid. The cell is connected via a stainless steel tube to a vibrating wire pressure transducer. The stress on the cell is then converted to a signal and may be read either with vibrating wire readout or a data logger. Each cell also incorporates a compensating tube that allows adjustment of the cell volume to compensate for shrinkage in the concrete. The compensating tube is squeezed to force more fluid into the cell. This increases the cell volume thereby assuring proper contact with the concrete around the cell.


VIBRATING WIRE NATM STRESS CELL SPECIFICATIONS

Tangential

MODEL CELL DIMENSION PRESSURE RANGES
VW3201-7 100 X 200 mm (3.9 X 7.8 in.) 7 MPa
VW3201-20 100 X 200 mm (3.9 X 7.8 in.) 20 MPa
VW3201-35 100 X 200 mm (3.9 X 7.8 in.) 35 MPa

Radial

MODEL CELL DIMENSION PRESSURE RANGES
VW3202-2 150 X 250 mm (5.9 X 9.8 in.) 2 MPa
VW3202-3 150 X 250 mm (5.9 X 9.8 in.) 3 MPa
VW3202-5 150 X 250 mm (5.9 X 9.8 in.) 5 MPa

 

PRESSURE TRANSDUCER SPECIFICATIONS

ITEM SPECIFICATION
Type Vibrating wire
Overrange 200% F.S.
Accuracy ± to 0.1% F.S.
Resolution ± 0.025% F.S. minimum
Signal Output 2000-3000 Hz
Signal Cable Two twisted pairs cable with polyurethane jacket

Vibrating Wire NATM Stress Cells are commonly used to monitor pressure on, and within, linings of tunnels and underground workings.

View illustrations on how Vibrating Wire NATM Stress Cells are used for:

Vibrating Wire NATM Stress Cell Ordering Info

MODEL CELL DIMENSION PRESSURE RANGES
TANGENTIAL VW3201-7 100 X 200 mm (3.9 X 7.8 in.) 7 MPa
TANGENTIAL VW3201-20 100 X 200 mm (3.9 X 7.8 in.) 20 MPa
TANGENTIAL VW3201-35 100 X 200 mm (3.9 X 7.8 in.) 35 MPa
RADIAL VW3202-2 150 X 250 mm (5.9 X 9.8 in.) 2 MPa
RADIAL VW3202-3 150 X 250 mm (5.9 X 9.8 in.) 3 MPa
RADIAL VW3202-5 150 X 250 mm (5.9 X 9.8 in.) 5 MPa

 

Accessories

MODEL DESCRIPTION
VW3250 Heavy Duty Crimper for NATM Stress Cells

 

Additional Ordering Info

Type and cell size
Length of signal cable
Pressure range
Accessories required

 

Optional Equipment

VW2106 readout
Data loggers
Terminal stations

Speak with an Expert

I’m very happy with the quality of the instrumentation and technical support from RST, as always. They worked with us from the initial stages of the project to ensure that we were fully prepared and equipped to use the RSTAR network for the first time. They delivered everything within the tight project time frame to ensure that there were no delays on site, and the submersible tilt meters looked like new even after over twelve months of being submerged in Thames water!
 
-Richard Lipscombe, BEng (Hons), Director & Principle Consultant - RL Geotechnical Ltd