FIAT LUX UNIVERSITY OF LIVERPOOL SCHOOL OF ENGINEERING Year 2 Laboratories Shear Force SL-B Direct Shear Box Test Demonstrator Name: Normal Force Demonstrator Email: Normal Stress a Shear Stress T

CIVE220: Geomechanics 2 Sand Lecturers: Shear Force UNIVERSITY OF LIVERPOOL SL-B Lab Script // CIVE220 Health and Safety Lab coats must be worn at all times during the experiment and instructions by lab demonstrators should be followed exactly and information regarding the labs fire instructions made known. If the lab requires steel capped boots then they must be worn or admittance into the lab cannot be guaranteed. You are reminded that you are required by law to comply with the School's basic rules of lab safety, as outlined at the start of the first year. 1 1 UNIVERSITY OF LIVERPOOL Aims and Objectives SL-B Lab Script // CIVE220 1.1 Aims This laboratory experiment aims to help students understand how to measure the shear strength parameters of fine sand and its critical void ratio. 1.2 Objectives Prepare sand examples, and measure its shear strength parameters under both loose and dense packing respectively, by carrying out a series of direct shear box tests at different normal stresses. At the end of this lab experiment, students should be able to Carry out direct shear box test to measure shear strength parameters of a soil, and Determine its critical void ratio. 2 Experimental Procedure In order to prepare a loose specimen, carefully fill the shear box with sand to approximately 10 mms from the top, strike off the surplus sand to provide a level surface with the tool provided and carefully add the top plates. Note that any disturbance of the specimen before testing will cause some densification and will produce results unrepresentative of a loose specimen. In order to prepare a dense specimen, place the sand into the box in 3 layers, thoroughly tamping each layer with the block. For each test, place the shear box in the testing frame and position the load hanger on the box. Carefully add the appropriate weight to the hanger as follows: 5 kgs on lever hanger = Normal Stress of 55.01 kN/m². 10 kgs on lever hanger = Normal Stress of 104.05 kN/m². 20 kgs on lever hanger = Normal Stress of 202.12 kN/m². (NOTE: The shear box is 100 mms square in plan.) Move the shear box assembly close to the proving ring using the hand control and “zero” the dial gauges. Take a depth reading for initial height of the specimen. REMOVE THE TWO SCREWS HOLDING THE UPPER AND LOWER HALVES OF THE SHEAR BOX TOGETHER!!!!! Switch on the motor and engage the dog-clutch. Record proving ring and vertical deflection readings every 0.2 mms horizontal defection until WELL PAST the maximum shearing resistance as identified by the proving ring reading. After each test, carefully recover and weigh the sand to enable the initial unit weight of the specimen to be determined. 2 UNIVERSITY OF LIVERPOOL SL-B Lab Script // CIVE220 Complete the data sheet to enable results to be processed by the computer software provided. NOTE: The proving ring constant is marked on the inside perimeter of each proving ring. 3 Presentation and Interpretation of Results You are required to: a) Plot a graph showing the variation of shearing stress and volumetric strain with unit strain (relative horizontal movement / length of box) for tests on loose and dense sand (one for one normal stress). NOTE: The true relative movement between the upper and lower halves of the shear box is obtained from the difference between the movement of the bottom half and the proving ring deflection. b) Include the calculations of shearing stress and volumetric strain at failure for all the tests. c) Plot a graph showing values of maximum shear stress against normal stress for all the tests and determine the average angle of internal friction for the loose and dense packings of the fine sand. d) Plot a graph of initial void ratio against volumetric strain at failure (expansion positive) for all the tests and estimate the critical void ratio. e) Discuss the influence of normal stress and sand unit weight on the shearing behaviour of the sand. 3 UNIVERSITY OF LIVERPOOL 4 Technical Note Submission This laboratory activity requires short technical note. The principal aim of a laboratory note is to convey the substance of a piece of experimental work to another engineer and to draw attention to its practical significance. The subject matter of a laboratory technical note should be presented in the order shown below. 4.1 Assessment Criteria 1. Aim of the test 2. Results 3. 4. 5. 6. SL-B Lab Script // CIVE220 Appropriately tabulated experimental data and results. Calculations Appropriately calculations as well as any necessary graphs (and diagrams where appropriate). Discussion Your own comments on the work appear here. The values of shear strength parameters and the critical void ratio of the sand should be presented and discussed. Conclusions Presentation For overall layout and quality of figures 10% 20% 30% 20% 10% 10% 4.2 Submission Instructions Download the Technical Note Template for the Direct Shear Box Test section of the Year 2 Labs and Tutorials VITAL site. If you are having difficulty please contact the LTAs by email for help. Rename the document to include the date that you were in the lab and your name before submitting it - for example "SL-B Technical Note 21.11.14 John Smith.docx". The deadline is before midnight days from the date of the lab including the day of the lab, weekends, University holidays and bank holidays. So, if you did the lab on Monday the 2nd, the The Turnitin submission link will become available to you only after you have completed a short, anonymous survey for feedback on the lab. The School of Engineering takes your opinions seriously and feedback from last year's students informed significant changes to the labs which have been updated for this year. 4