Bs 1377 part 7 pdf

NB mass of hanger = 5kg The apparatus, as shown above, comprises a square box construction in two separate pieces, an upper piece and a lower piece. The vertical normal load is applied directly through the upper pressure plate and it is divided by the plan area of the box to give the normal stress . The volumetric behavior of the soil is also determined during the test by measuring the amount of horizontal displacement and vertical displacement using dial gauges. Method: Assemble the empty shear box as shown, without the upper and loading platens. The two halves of the box should be screwed together with the screws marked by a cross cut into the heads; the two screws marked ‘L’ should be in position but clear of the joint between the two halves. Ensure that the apparatus is moving freely on its runners. Fill the box with loose sand and level it off about 1mm below the top of the box. Place the top platen, on the sand and the loading platen on the top platen. Put the ball bearing in place and the hanger on the ball bearing. Place a weight on the hanger. Adjust the apparatus to take up any slack, and then zero the proving ring dial gauge. REMOVE THE TWO SCREWS HOLDING THE UPPER AND LOWER HALVES OF THE BOX TOGETHER, then screw in those marked ‘L’ until resistance is just felt: give each one a further half turn to ensure that the two halves are slightly separated so that the normal

250

stress is being applied to the sand only, then remove them. Switch on the motor. Record the maximum reading on the proving ring dial gauge, then switch off and slacken off the apparatus. Dismantle the box entirely and pour all the sand back into the container. Repeat the test three more times, increasing the mass on the hanger. Record the results on the attached sheet. Results and Calculations:

• Sketch the failure mode(s) of the sample(s). • Calculate the values of effective normal stress (’) for each loading condition. • Plot  against horizontal movement for each loading condition. • Determine values for shear stress at failure (f) • Plot a graph of f against ’. Draw the straight line of best fit through the origin and

the points, and calculate the peak value of the angle of shearing resistance of the soil from the co-ordinates of any convenient point on the line.

• Plot vertical displacement against horizontal displacement. • Plot /’ against Δv/Δh for the section of the curve that defines the maximum rate

of dilation, derive the equation of a best-fit linear line through the data points and determine the value that this line intersects the vertical axis. From this determine the critical angle of friction, also calculate the angle of dilation.

Conclusion:

• Comment on the value of  for the sand you tested – explain how this value will be influcned by the density of the soil.

• Explain the main points to the vertical vs horizontal displacement plot. • Comment on the significance of the /’ against Δv/Δh plot. • Comment on the use and appropriateness of this test and your findings.

Indicative Reading: Manual of Soil Laboratory Testing Vol.1 – K.H. Head Basic Soil Mechanics – Whitlow, R. Laboratory Work in Soil Mechanics — B. Vickers (Chapter 4: Shear-strength test is available to download from My-Beckett).

251

LEEDS BECKETT UNIVERSITY
Results and Calculations:
Conclusion:
Indicative Reading: