CVEN30010 Geotechnical Modelling and Design (2022)Lab Practical Instructions and Assignment Briefs1. IntroductionThe Lab Practical session is designed to facilitate the understanding of thefundamental concepts of water flow in soils, which include the seepage phenomenonand quicksand condition. A Cussons Technology permeability apparatus is to beused in the experiment, as shown in Fig. 1. The experiment is to be conducted inFrancis Lab of Melbourne School of Engineering, located at mezzanine level, BlockD, Building 176.Fig. 1 Test apparatus from Cussons Technology2 | P a g e2. Experimental apparatusAs can be seen from the detailed components shown in Fig. 2, the apparatus consistsof a glazed aluminum tank supported on a steel frame, which is designed to containthe permeable medium (e.g., sand). The front, back and sides of the tank are madeof clear toughened glass (giving scratch-free visibility without the risk of abrasionof the inner surfaces).Fig. 2 Components of the permeability apparatusFourteen piezometers are connected to the base of the tank with flexible tubes. Thespacing of piezometers is 120 mm as shown in Fig. 3. The left and right sides of thetank accommodate seven piezometers each, to read the water head. Thesepiezometers are provided to allow measurement of head at various points along thepermeability tank.Two removable end baffles are installed in the tank to retain the soil in the middlepart. Two header compartments are thus formed between the baffles and the twoends of the tank. In the figure, the left compartment is the inlet, whereas the right isthe outlet. The water height in the testing tank can be adjusted and maintained usingthe inlet and outlet header compartments.A water sump tank equipped with a variable speed centrifugal pump acts as a sourceof water supply. The water is circulated through the tank via header compartments3 | P a g eat each end of the tank. Weir tanks piezometer is provided to measure the dischargerate from the outlet head compartment located at the right-hand side of the tank.Fig. 3 Schematic of the setup (for illustration purpose and not in scale)3. Experimental setupA sheet pile is fitted in the tank (which seals against the front and back walls of thetank). Two tests were conducted, namely a seepage flow test with constant headdifference and a quick sand test with varying head difference. The first test isdesigned to help you understand the concepts of flow nets through tracing theseepage path and verify the theoretical formula based on Darcy’s Law. The secondis to observe quicksand (piping/ boiling) phenomenon, which helps you understandthe concepts of critical gradient and effective stress principle.4. Experimental procedure4.1 Test 1: Seepage flow experiment(1) Start the circulation pump and adjust the speed to achieve a level of 450 mm inthe left-hand header compartment (inlet) with a steady but small flow in to theoverflow pipe. Adjust the height of the overflow to maintain a water level of300 mm in the right header compartment (outlet).(2) Maintain the constant head difference between the two sides of the sheet pileas shown in Fig. 3.4 | P a g e(3) Measure the dimensions of the tank, the hydraulic heads and sand level basedon a datum (e.g., the base of the sand). Record the hydraulic head at eachpiezometer.(4) Inject a shot of red dye into the sand away from the glass (approximately in themiddle) on the upstream side and observe where and how the dye reappears.Please assess the type of the flow (laminar or turbulent) and give explanationsin your report.(5) Inject a shot of blue dye on the upstream side against the glass. Make sure thetip of the injection syringe is positioned just below the sand surface. Trace thepath of the flow line by marking the dye’s movement on the glass until the dyereaches the ground surface on the downstream side.(6) Repeat the above step at different spots on the upstream side to trace the flowlines on the glass. Observe the change in velocity of the flow as it travels. Pleaseexplain in your report how and why the velocity changes when the flow getscloser to the sheet pile or leaves away from the pile. Did you observe the flowlines intersecting each other? Please give your explanations.(7) Measure the discharge rate at the water outlet using a beaker (i.e. measuringcylinder) and a timer. Please convert this flow rate into litres per minute permetre width of the tank.In addition, the flow rate q can be calculated by using the following empiricalequation provided by the apparatus manufacturer:= 0.001269?2.353/where the flow rate q is in the unit of L/min and h is the head in the unit of mmwhich can be obtained from the weir tank piezometer. Please calculate the flowrate based on this empirical equation and convert this flow rate into litres perminute per metre width of the tank.(8) In your report, please sketch a flow net to represent the seepage flow in thesand. Please draw it on the graph paper (with squares) provided in Appendix C.Make sure the horizontal and vertical dimensions of your sketch are in samescale. The photo of the experimental flow lines needs to be included forcomparison in your report.(9) From your sketch of flow net, please calculate the discharge (litres per minuteper metre width of the flow net model) and compare your theoretical5 | P a g e10calculations with test results in step (7). The permeability coefficient of the sandcan be estimated from the Hazen’s Equation, k = 10 d2 , where k is in units ofmm/sec, and d10 is in units of mm (d10 can be estimated based on a particle sizedistribution curve). Please find the particle size distribution in Appendix A.(10) Based on your sketched flow net, please calculate the hydraulic head at eachpiezometer. Compare the calculated results with the measured ones in step (3).The numbering orders of piezometers in your report need to be consistent withthe experimental setup. Additionally, you are required to calculate thetheoretical hydraulic head at the positions marked with black dots (seeAppendix B) based on the flow net in step (8).(11) Please analyse the discrepancies between the calculated results and test resultsmentioned in step (9) and (10). Please give at least 3 reasons to explain it.4.2 Test 2: Quicksand experiment(1) The setup of this experiment is similar as that described in Section 4.1 except thatthe sheet pile has a shallower embedment (to facilitate the occurrence ofquicksand).(2) Instead of maintaining a constant head, gradually increase the hydraulic headdifference between the two sides of the test tank, until a quicksand phenomenonoccurs.(3) Explain the phenomenon by referring to the change in effective stress in the soilwhere quicksand occurs. Please give at least 3 methods to control seepage andavoid the occurrence of quicksand.5. GeoStudio modellingYou are required to model the experiment in 4.1 using the SEEP/W software andcompare the model outputs with your hand calculations and the experimental results.Please include sufficient evidence (i.e. geometry, material, boundary conditions andresults) from the SEEP/W outputs such as screenshots of the results to support yourinterpretation and analysis.6 | P a g e6. Report requirementLab Practical Report will be assessed individually. Students are required to preparethe report based on your own experimental data. For students attending thepractical remotely (i.e. online session P6), your experimental data will be providedseparately.1. Your report should cover all the tasks above.2. Your report should contain cover, content, seepage flow experiment,quicksand experiment and SEEP/W modelling. There is no need to repeat theexperimental setup and procedures.3. Page limit: 6 pages, single spacing, size 12 font. Page limit includeseverything in your report. If your report is beyond the 6-page limit, only thefirst 6 pages will be marked.4. If you have any question, please post it on the Discussion board under thesection of “Discussions on Lab practical”. Remember all technical questionsmust be asked on the Discussion board and will not be answered when sent topersonal emails.5. For Lab Practical related non-technical issues, you can contact Zeliang Li(zeliangl@student.unimelb.edu.au). Please include ‘CVEN30010’ in thesubject line in your email and remember emailing is for personal issue only.6. A one-hour online consultation session is scheduled on 4:00 pm Monday inWeek 8 (12th September). Please see Canvas->Zoom for further informationon the meeting.The due date for submission of the laboratory report is 11:59 pm on Sunday 18September 2022. Your report should be submitted electronically via the submissionlink in Canvas, which will be opened and announced in Week 7. Submissionsthrough email will NOT be accepted. Please note late submissions incur penalty of20% per day.7 | P a g eAppendix A: Sieve analysis resultTable 1 Sieve analysis result