Direct Shear Apparatus

In a direct shear test, the failure of the soil sample in shear is caused along a predetermined plane. Test is performed as per IS 2720 part XIII The normal load, strain and shearing force are measured directly during the test. It is also used to estimate residual stress of soil. The apparatus utilizes a square box divided horizontally into two halves. The box containing the sample is placed in a water jacket and subjected to constant normal load while a horizontal force is applied till the specimen fails along the plane of juncture of the two halves. A number of specimens are tested under different loads and from the data obtained the angle of internal friction and shearing strength of the soil can be evaluated. Following pages give details of both hand operated and motorised versions of direct shear test apparatus conforming to different Indian Standard Specifications.

Direct Shear Apparatus, Hand Operated IS:2720 (Part XIII)

HS 24.05

The unit confirms to IS:2720. It has a hand operated horizontal loading system for shearing the specimen. Hangers are provided for creating normal stress.

It comprises :-

  • Shear box assembly, 60 mm square, complete with a U-bracket, guide pins and spacing screws, made of brass.
  • Gripper assembly consisting of two plain grid plates, two perforated grid plates, one base plate and one loading pad, all made of brass.
  • Two porous stones, each 6 mm thick, fitting the shear box.
  • Shear box housing of brass, complete with two ball roller strips.
  • Loading unit with normal loading of 8 kg/cm² on 60 mm square specimen.
  • Specimen cutter for a specimen size of 60 mm x 60 mm x 25 mm.
  • Set of weights to give a normal stress upto 3 kg/cm² through lever, comprising 4 of 0.05 kg/cm², 1 of 0.1 kg/cm², 1 of 0.2 kg/cm², 3 of 0.5 kg/cm² and 1 of 1 kg/cm². Complete as above but without dial gauges and proving ring.

Direct Shear Apparatus, 12 speed, Motorised IS:2720 (Part XIII) IS:11229

HS 24.15

The unit is same as HS24.05 except that it is motorised. It is provided with a turret type gear box to get 12 different constant rates of strain i.e 1.25, 0.625, 0.25, 0.125, 0.05, 0.025, 0.01, 0.005, 0.002, 0.001, 0.0004, and 0.0002 mm/min. and arrangements to carry out residual shear strength tests. Suitable for operation with 220V, 50 hz, single- phase supply.

Electronic Direct Shear Apparatus, 12 Speed, Motorised with Microprocessor based Touch Panel electronic unit, As per IS:2720 (Part-XXXIX/Sec-1)

HS 24.515

The unit is same as HS 24.15 except that the transducers like displacement sensors and load cell with micro-processor based touch panel display system are provided instead of dial gauges and proving rings. Total loading capacity of the apparatus is 8 kg/cm². It is provided with standard 60mm shear box assembly. Set of weights to give a normal stress up to 3 kg/cm² on the specimen through lever is provided as standard. Additional weights are to be ordered separately.

Electronic Data Acquisition System For Direct Shear Test Equipment

The three-channel micro controller based signal conditioning and touch panel display unit is suitable to measure Horizontal load, Horizontal Displacement and Vertical displacement directly indicated in their respective engineering units during Direct Shear Testing. The system receives the output signal from the sensors i.e. Load cell and Displacement Sensors attached to the Direct shear Test apparatus. The data of all three channels of Direct Shear Test can be transferred to computer through RS-232/ Ethernet and can be online monitored. The Unit also provides the facility of online monitoring of data of all the sensors on Touch Panel Display provided at the front.

Broadly the following facilities are incorporated in the system:-

  • Touch panel is provided to perform various operations such as TARE, PROGRAMMING, START, STOP etc.
  • Independent Taring of each channel
  • Data transfer interval is programmable (between 1 second to 1 hour)
  • Automatic data saving on stop button.
  • There are 25 set results having a maximum of 200 data points per set can be stored in the electronic unit .The sample number can be programmed.
  • Online date and time of test will be stored along with the data.
  • On line (while the test is in progress) data transfer to the computer through RS-232/ Ethernet.

Sensors Specification:-

1. Load Cell :
    •   Capacity : 200kg/ 2000N
    •   Resolution : 0.1kg/ 1N

2. LINEAR VARIABLE DIFFERENTIAL TRANSFORM ER (LVDT) 2 No.
    •    Stroke : ± 20mm
    •    Resolution : 0.01mm

Software Specification

  • Data Acquisition from Signal Conditioning Unit to Computer
  • Off-Line Data Analysis Software that does all the calculations of Direct Shear Test.
  • Has option for manual as well as automatic recording of data.
  • Calculates Area, Volume, Bulk density, Dry density, Moisture content etc. of the specimen
  • Display the following Plots (Graphical)
        (a) Horizontal Displacement vs Shear Force
        (b) Horizontal Displacement vs Vertical Displacement
        (c) Normal stress vs Shear Force
        (d) Maximum value of the Dilation Angle

The software is windows based and user friendly. It is easy to operate and has the flexibility to enter different sizes of test specimen up to 1000mm X 1000mm
Note : Computer does not form part of the supply.

Direct/Residual Shear Test Apparatus (Confirming to IS2720 Part XXXIX and BS1370)

HS 24.617

An automatic system enables performing of Direct Shear and Residual Shear tests through a total computer control. It is a table-mounted model and has stepper motors controlling shearing load. Stress levels can be maintained with in the limits of ±0.5% through set of weights. Vertical and horizontal displacements and shearing load are all displayed in their respective engineering units on LCD display.

Board specification of the unit are:-

  • Rate of strain: 0.0001-9.9999 mm/min
  • Load range capacity : ±5 kN

Electronic Sensors

The unit includes :-

  • Load cell Universal type : 2000N
  • Displacement sensor horizontal : ± 20mm
  • Displacement sensor vertical : ± 20mm Supplied complete with weight upto 3kg/cm²

COMPUTER
Dedicated Computer with Data Acquisition card with latest configuration will be supplied. 

Computer Controlled Direct Shear Apparatus

HS 24.620

Conforming to IS: 2720 (Part XIII) & BS 1377 The unit is totally computer controlled, it has 2 servo motors, one for shear load and the second for maintaining normal load. Circuit for normal load is based on closed loop principal.

Salient Features

  • Enables Direct shear tests through a total computer controlled operation
  • Conforms the test requirement of IS-2720 (Part-XIII) & BS 1377
  • Programmable Normal stress from 0.01N/mm2 to 0.5N/ mm² and maintain \ Stress level with in the limit of ±0.5%
  • Strain rate programmable form 0.00001 mm/min– 9.9999 mm/min.
  • Shear box suitable for 60×60 mm sample (Optional 100x100mm sample)
  • Online plotting of Load vs Displacement, Load vs Time and Displacement vs Time curves and dis play of data for all the channels
  • Advanced Analysis Software

Direct Shear Apparatus, Large, Motorised IS: 2720 (Part XXXIX/Sec. I)

HS 24.20

This is required for testing 300 mm x 300 mm x 150 mm soil sample containing gravel with particle size more than 4.75 mm.

Optional
100mm shear box assembly complete with porous stone and gripper plate The unit provides 72 different constant rates of strain for shear load ranging from 0.0014 mm/min. to 10.16
mm/min and is suitable for carrying out residual shear strength test.

The equipment comprises of the following :-

  • Loading Unit having a normal load capacity of 3 kg/cm² through lever and shearing load capacity upto 5000 kg maximum.
  • Shear box assembly in two halves, complete with two guide pins and three spacing screws.
  • Shear box housing, complete with two ball roller strips.
  • Two perforated gripper plates.
  • Two plain gripper plates.
  • Two plain grid plates, one for top and one for bottom.
  • Two perforated grid plates one for top and one bottom.
  • One base plate.
  • One loading pad with lifting handles.
  • One set of slotted weights to give a maximum ormal stress intensity of 3 kg/cm² on the specimen through lever system.

Suitable for operation on 220 V, 50 Hz, single phase supply. Supplied without Proving Ring and dial gauges which are to be ordered separately.

Electronic Direct Shear Apparatus, Large, Motorised IS: 2720 (Part XXXIX/Sec. I)

HS 24.520

Same as HS24.20 except that the unit is provided with electronic digital system & sensors for vertical displacement, & horizontal displacement & load cell for shearing load.
Broad specification of digital display unit is given below.

Sensor
Displacement sensors ±50mm -2 Nos.
Load Cell 30kN -1 No
Digital display system with RS232 -1 No

Digital Direct Shear Apparatus

HS 24.622

This unit is similar to HS 24.620 except that it can accommodate sample size of 300*300*150 mm. Servomotor can create power to give a shearing load of 50kN. Additional Stepper motor is provided for normal stress. This stepper motor can create a maximum stess of 5kg/sqcm. Total controlling is through the computer. Parameters like shearing load, vertical strain and horizontal strain is shown on the monitor.

Operation is based on the close loop Principle the specimen to be sheared can be loaded either on strain basis or stress basis.

Selection of this mode has to be made at the beginning of the test. Maximum strain rate that can be achieved is 9.9999mm/min where as the minimum strain rate could be programmed as low as 0.0001mm/min.

Loading System
For Horizontal strain controlled through micro stepper motor:

  • Rate of strain : 0.0001-9.9999mm/min.
  • Load range capacity : ± 50kN
  • Displacement range : ±50mm

For Vertical Consolidation:

  • Capacity : 5kg/cm2
  • Range : 0-20 mm

Electronic Sensors

  • Load cell Universal type : 50kN
  • Displacement sensor horizontal : ±50mm
  • Displacement sensor vertical : ±50mm

Salient Features of software and graphical plots

  • It is supported by user-friendly windows based software for graphical plotting and numerical tabulations.
  • Horizontal displacement vs. Vertical displacement
  • Normal stress vs. Shear stress
  • Displays maximum value of dilation angle along with c and ø values.