Digital Microprocessor Based Direct Shear, Residual Shear Apparatus
VSLIC-S131
Copyright @2023 Vertex Group
Copyright @2023 Vertex Group
short info
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.
Standard
IS2720 Part XXXIX and BS1370
Model
VSLIC-S131
Origin
Indian
Make/ OEM
VERTEX
Warranty
This Warranty covers the defects resulting from defective parts, materials or manufacturing, if such defects are revealed during the period of 12 months since the date of purchase.
Picture
All pictures shown are for illustration purpose only. actual product may vary due to product enhancement.
The unit is same as VSLIC-S133 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.
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.
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.
COMPUTER
Dedicated Computer with Data Acquisition card with latest configuration will be supplied.
FEATURES
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.
COMPUTER
Dedicated Computer with Data Acquisition card with latest configuration will be supplied.
PRODUCT VIDEO
WORKING PRINCIPALNew
Shear Strength of Soil by Direct Shear Test
Shear strength of a soil is its maximum resistance to shearing stresses. The shear strength is expressed as
Where C’ = Effective cohesion
= Effective stress = Effective angle of shearing resistance
Using direct shear test, one can find out the cohesion and angle of internal friction of soil which are useful in many engineering designs such as foundations, retaining walls, etc.
This test can be performed in three different drainage conditions namely unconsolidated-undrained, consolidated-undrained and consolidated-drained conditions. In general, cohesionless soils are tested for direct shear in consolidated drained condition.
Apparatus Required for Direct Shear Test
Apparatus required for conduction direct shear test are
Shear box
Shear box container
Base plate with cross groves on its top
Porous stones (2 Nos)
Plain Grid plates (2Nos)
Perforated grid plates (2Nos)
Loading pad with steel ball
Digital weighing machine
Loading frame with loading yoke
Proving ring
Dial gauges (2 Nos)
Weights
Tampering Rod
Spatula
Rammer
Sampler
Fig 1: Direct Shear Test Apparatus
Test Procedure of Direct Shear Test
Test Procedure of Direct shear test contains following steps:
Collect the soil specimen which is either undisturbed or remolded. The sample should be taken using sampler and Rammer. If cohesionless soil is taking then sampler and rammer are not required.
The inner dimensions of sampler should be 60 mm x 60 mm in plan which are also the inner dimensions of shear box. The Thickness of box is about 50 mm while the thickness of sample should be 25mm.Fig 2: Shear Box,Porous Stones, Grid Plates, Loading pad
Now attach the two halves of the shear box with locking pins and place the base plate at the bottom.
Above the bottom plate, Place the porous stone and above it place the grid plate. Plain grid plates are used for undrained conditions while perforated grid plates are used for drained conditions.
Now we have baseplate, porous stone and grid plate in the shear box. Weigh the box at this stage and note down.
After that place the soil specimen above the grid plate. Undisturbed sample is directly transferred to shear box. If sandy soil is using, place it layers wise and tamper the each layer to get the required density.
Note down the weight of shear box with soil specimen.
Above the soil specimen, place the upper grid plate, porous stone and loading pad one above the other.Fig 3: Different Layers Positions in Shear Box
Now the whole box is placed in a container and mounted on the loading frame.
Proving ring is arranged in such a way that it should contact the upper half of the shear box.
Loading yoke is placed on the steel ball of loading pad of shear box.
Two dial gauges are fitted one to the container for measuring shear displacement and other one is to the loading yoke for measuring vertical displacement.
Now locking pins are removed from the shear box and spacing screws are placed in their respective positions of the box.Fig 4: Applying Load on Specimen
The upper half of the box is raised slightly with the help of spacing screws. The spacing is decided depending upon the maximum size of particle.
Now apply the normal stress which is generally 25 kN/m2. Also apply the shear load at a constant rate of strain.
Now the box starts reacting to loads applied and for every 30 seconds note down the readings of proving ring and dial gauges.
If the proving ring reaches maximum and suddenly drops it, means the specimen is failed. Note down the maximum value which is nothing but failure stress.
For some soils, failure point is taken at 20% of shear strain.
Finally remove the box and measure the water content of the specimen.
Repeat the same procedure for different normal stresses of 50, 100, 150,200,250,300,400 kN/m2
Observations and Calculations for Direct Shear Test
Calculations are to be done using the observations taken from the test as follows:
Size of the box =
Area of the box =
Thickness of specimen =
Mass of specimen =
Volume of specimen =
Bulk Density of soil =
Dry density of soil =
Void ratio =
Mass of box + base plate + porous stone + grid plate =
Mass of box + base plate + porous stone + grid plate + Soil specimen =
Calculate the shear stress using below tabulated observations:
S.No
Elapsed time
Horizontal dial gauge reading
Horizontal displacement
Vertical dial gauge reading
Vertical displacement
Proving ring reading
Shear force
Shear stress
Now determine the shear stress at failure for different normal stress values:
Test no.
Normal stress(kN/m2)
Shear Stress at Failure (kN/m2)
Shear Displacement at Failure
Initial Water Content
Final Water Content
Now plot a graph between normal stress and shear stress by taking normal stress on abscissa and shear stress at failure on ordinate. The graph looks like as shown below.
Fig 5: Graph plotted between Normal Stress and Shear stress
From the graph cohesion intercept (c’) and angle of shearing resistance () can be known and shear strength (s) can be calculated from the formula.
Result of Direct Shear Test
Shear strength of the given soil sample is = ______________ kN/m2.
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