Cyclic Simple Shear Apparatus

Product Code: 31-WF7500

The cyclic simple shear apparatus is generally used for research into the dynamic field of soil behaviour, and can simulate quite easily many different field loading conditions, as for example:

Stability under seismic events of submerged slopes on the continental shelf characterised by layered clays
Degradation of shear stress cohesive soils under cyclic loading
Evaluation of liquefaction parameters of non cohesive soil under cyclic loading

The cyclic simple shear is a plane strain device. The shear strain is induced by horizontal movement at the bottom of the sample relative to the top. The horizontal diameter of the sample remains constant, therefore any change in volume shall be as a result of vertical movement of the top platen.

This imposed distortion is termed “Simple Shear”
The system is designed to allow a sample to be consolidated, drained and then sheared.

Sample
The standard sample is 70 mm dia. The test can also be performed on 50 mm dia. samples using the conversion kit 31-WF7500/1.
It is positioned on a pedestal with a top cap the same as a triaxial sample and supported by a rubber membrane placed and secured with 0-rings. To maintain a constant diameter throughout the test the sample is supported by a series of slip rings.

Shear stage
During shear the rings slide across each other.
During the shearing stage of the test the vertical height of the sample is maintained at a constant height by the vertical actuator in a closed control loop with the vertical displacement transducer. The rings maintain a constant sample diameter.

Base system
The system consists of a simple shear load frame air receiver with vertical and horizontal loading control valves. It incorporates a control and data acquisition system as described below, with two 5 kN actuators, The system is mounted on a cabinet supporting all components. The horizontal and vertical actuators are fixed to the frame, which supplies the reaction to the forces applied. Each actuator has an internal displacement transducer, which relays the actuator piston position back to the computer. This is very important when setting up a sample; it allows you to set enough travel for the test duration.
The sample is set up in the machine, which has a rigidly fixed top half and a moving bottom half. The top half houses the 50 mm dia. vertical ram. This is housed in a linear bearing to allow vertical movement and prevent horizontal movement. The bottom half is mounted on roller bearings as in a standard shear box.

Integrated Multi-Axis Control System (IMACS)

The system is identical to that one which is part of the cyclic triaxial system, except for the input channels, which are 6 instead of 13.

Load cells
These two 5 kN load cells are fitted in-line with the horizontal and vertical actuators. The load cells are fitted with an in-line calibration module, allowing the transducers to be changed or moved within the data acquisition system without the need to recalibrate them. Accurate to 1 N.

Displacement transducer
This ± 25 mm displacement transducer is built into the actuator. It measures the actuator piston position and can also be used as the control transducer for the cyclic strain test.

Vertical displacement transducer
This transducer is calibrated over ± 2.5 mm for controlling the sample height. Accurate to 1um.

In-line signal conditioning
This normalises all the transducer outputs, allowing transducers to be moved from channel to channel without having to re-calibrate.

Actuators frequency up to 70Hz
Plane strain measurement
Shear at a constant height
Shear at a constant stress
Shear at a constant rate of strain

Main frame: floor mounted, steel box frame including integral double acting horizontal and vertical pneumatic actuators. Each with an internal displacement transducer. The top cap is fixed and the pedestal is mounted on roller bearings.

Sample size: 70 mm dia. (50 mm with conversion kit)

Maximum load: ± 5 kN vertical and horizontal

Actuators frequency range: 0 — 70 Hz

Overall dimensions: 1500x1200x700 mm (hxlxw)

Electrical specification: 240 or 110 V, 50-60 Hz, 1 ph.

Weight approx.: 350 kg

Conversion kit for 50 mm dia. samples

31-WF7500/1 50 mm dia. sample accessories including pedestal and top cap

Consolidation stage
The consolidation stage is simply the application of a static axial loading stress to the specimen while the lateral loading (shear) axis is held stationary Axial stress and specimen displacements (axial and lateral) data are measured over time and logged by the system. Logged data is also displayed to the operator in the form of charts and tables as the test stage proceeds. The consolidation stage is manually terminated by the operator once consolidation of the specimen is determined to be complete.

Cyclic simple shear stage
This stage of the test applies a lateral cyclic shear force, or optionally a displacement, to the specimen, while the axial axis is either maintained at the specified stress, or optionally, the specimen height is maintained. Both axial and lateral force and specimen displacements together with shear induced pore pressure are measured for each loading cycle. Measured data is obtained from 50 sample points captured over the cycle period. This data is displayed to the operator in the form of wave shapes, charts and tables and also logged by the system to an archive data file. The loading cycle shape is operator selectable from predefined functions but may also be a user generated shape.

Linear displacement shear stage
The linear displacement shear stage of the test applies a rate of lateral shear displacement to the specimen. Both axial and lateral force and specimen displacement together with shear induced pore pressure are measured for each loading cycle. Measured data is displayed to the operator in the form of charts and tables and also logged by the system to an archive-data file.

Cyclic Simple Shear Apparatus

Cyclic Simple Shear Apparatus

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