Laboratory Experiment 2: Strength of Sails 2. 1. Objective To examine the strength of clay (by performing undrained tria

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Laboratory Experiment 2 Strength Of Sails 2 1 Objective To Examine The Strength Of Clay By Performing Undrained Tria 1 (67.37 KiB) Viewed 27 times

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Laboratory Experiment 2: Strength of Sails 2. 1. Objective To examine the strength of clay (by performing undrained triaxial tests on normally consolidated and overconsolidated samples) and sand (by performing drained shcar box tests on dense and loose samples). Triaxial test 2.1 Apparatus The triaxial test is a routine test used for determining the strength and stress-strain behaviour of soils. A cylindrical sample of soil, usually 38mm in diameter and 76mm long, is covered with an impermeable rubber membrane and placed in a cell so that a fluid pressure may be applied all round it. The fluid pressure equals the total radial stress acting on the soil and also provides a component of axial stress. An additional component of total axial load is applied to the top of the sample by a loading ram passing through a bush in the top of the cell. Drainage from, or pore pressure in the sample is controlled through a dise of porous stone placed on the lower pedestal of the cell. With the connections to the porous stone closed, drainage from the sample is prevented, the sample volume change is zero and the test is termed undrained. In this case, a transducer is connected in the line to measure the pore pressure in the sample. With the drainage valve open water may drain from or into the sample, the pore pressure will remain constant and the test is termed drained. In this case a volume gauge is connected in the line to measure the volume changes. In the most common triaxial test the loading ram is driven at constant speed (strain controlled) and the variation in ram load is measured. The cell pressure is held constant during the strain controlled loading 2.2 Procedure Two samples of saturated Speswhite kaolin clay have been consolidated in triaxial apparatus, depending on the timing of your examinations, you may only test one of these, but you will be given results for both samples. The samples dimensions at the start of the test are given in the Excel files. The samples have been consolidated under different stress histories and consequently are at different states defined by effective stress and specific volume). Both samples are currently under a cell pressure of 300kPa and a pore pressure of 200kPa. However, one sample has been consolidated isotropically to a mean effective stress of 400kPa before being unloaded to its current state. This is explained in detail in the accompanying video or will be explained by the demonstrator of the laboratory The drainage tap will be closed, and the position of the cell will be adjusted so that the loading ram is just touching the top of the sample and the axial force and axial displacement readings are then zeroed. The initial cell pressure and pore pressure are given in the Excel file. The data logger is started when you start the test. The data logger will take a series of readings. Loading is continued until the axial displacement transducer reaches a reading equivalent to 13%. 3. Shear Box Two sets of tests will be undertaken. Tests on loose sand and tests on dense sand. 3.1 Sample Preparation a) Tests on loose sands

200g of dry sand are weighed and the shear box is filled carefully so as to avoid vibrating the box and compacting the sand, this will be explained in the laboratory and can be viewed on the video. The top platen is positioned horizontally on the sample, and the sample is placed in the apparatus. The hanger is placed in position and the required weights added for an initial total normal stress of 151 Nim as per the table below. These operations must be done with great care to avoid accidental compaction of the sand b) Tests on dense sands 200g of dry and are weighed. The shear box is filled in three approximately equal layers, compacting cach layer in turn, as explained in the laboratory or shown in the video. The top platen is placed horizontally on the sample and the sample is placed in the apparatus. The hanger is then placed in position and the required weights added for an initial total normal stress of 151 km as per the table below 3.2 Test Procedure (loose and dense sandsk:- The height, h mm, of the top of the platen above the top of the box is measured the height of the sand sample is then ch - 24.6mm. The horizontal and vertical displacement transducers are adjusted so that they are within their linear range. The readings of the horizontal and vertical displacement transducers and the proving ring transducer are zeroed. The logging programme is then started and a sensible filename entered when one is requested. The motor is started and the test continued until the sample has reached a critical state when it continues to shear but with no further change of state - or until the shear box has travelled horizontally by 6mm. The motor and the computer logging program are then stopped. The appropriate sample preparation (1.e. for loose or dense sand) and the test procedures is repeated. For the second test, the dense sample should be tested at the lower stress of S6kN/m' and the loose sample at the higher stress of 315kN/ mas per the table). 201 544 1133 5.5 5.5 5.5 Normal force on sample (N) Load due to hanger (kg) Added Load (kg) Normal Stress (kN/m) x! 15 x10 - 5 11 315 56 151 4 Report Your report should be handwritten, and should address cach of the numbered points below. Please plot graphs on graph paper or squared paper ensuring that both axes use the same scale. You may use the graph sheet given below: 1. Triaxial test (a) For each test, use the data in the Excel file to calculate the axial strain, deviator stress, 4. mean effective stress, p.radial effective stress, a, and axial effective stress, c. Plot the data as q vst, and u vst, in Excel and interpret these graphs to establish whether the final state is a critical state and to find the peak state

(b) In your report list the values of q. p... and c. in the format given below at the start of each test and at peak and critical states 4 p State (kN/m) (Nm) (Nm) kN/m) Peak Final marks awarded for completing tables correctly. 2 marks for the grupet) (c) Plot Mohr's circles for the final state and peak state of the two tests given above. (2 marks) (d) Identify a line tangential to the Mohr's circles representing the final state of the tests and through the origin. Calculate the angle that this line makes to the horizontal. This is the critical state angle of friction. Show your calculation (e) Identify 2 lines tangential to the Mohr's circles representing the peak state of the tests and through the origin. Calculate the angles that these lines make to the horizontal. These are the peak angles of friction. If one of your curves does not have a peak there is no need to calculate an angle. (1 mark) 2. Direct Shear Test Results (a) For all tests provided in the Excel file you have been sent, calculate the shear stress, r, and the normal stress o' (allowing for the current area of the sample) and the shear strain.y. Use a graph showing's y to find points of maximum me' and the critical (ultimate) state (if this is different to the point of maximum 1). Complete a summary table using the format given below (assume a value of 263 for G). Note that only two data points from cach of four tests need to be reported in the table. (3 marks) Sample Area, A Initial vertical stress (kNm) Vertical effective stress, c'(kN/m) Voids ratio Shear stress, (kN/m) peak ultimate state state peak peak initial final ultimate state ultimate state state state 56 LOODENSE 151 151

315 (b) Plot the peak and critical state values of t' against o for all four tests and determine the peak strength envelope and critical state failure envelope (note: there should be one best-fit line for the critical state angle of friction, some guidance is shown below). (2 marks) on (c) State the values of 'peak and 'crit obtained. In three or four sentences comment on whether the data conform with theory? (2 marks) (d) In three or four sentences, comment on the accuracy of the data obtained. (2 marks)

Some useful relations for the triaxial test: Area, Ao AH 0.-FJA+O Oro Area, A AV V. H. -- AAd1 - .)(1-.) 6.- ALL -- AV/V. N.B. sign convention compression positive q' =(G-6)=4 p = (: + 20')3 =p-u LOR D 6 0.0 u

Graph sheet Mohr's circles for le) 150 100 06 100 30 200 250 OGE -40 05 50 -400 -350 Peak and critical states for 2(b) 400 350 300 250 (kNim) 200 150 100 50 O 0 50 100 150 200 300 350 400 450 500 Nim

Height of Palce 7.3mm Mass of Sample 200.02 Times) Load() 1 2 1 4 5 6 7 * 6 10 1510100 I! 12 13 15 16 17 19 OC 21 23 9 26 27 ARAMARBRE PISHIED 30 Vertical (m) Horuscatal (mm) 0 -0.002036 -0.004072 0.001018 -0.007126 0 -0.011214 -0.0010 -0.011 -0.002036 -0.00016 -0.007126 -0.012216 -0.007136 0.0012 -0.00140 0.007126 -0.007126 0.005145 -0.000 -00050 0016289 -0.004072 0.019343 -0.003054 0.040721 -0.007126 0.045811 -0.008144 0.070044 -0.01018 0.073298 -0.011195 08536 -0.014352 0.120127 -0.01018 0.121145 -0.009162 0.121145 00012216 0.131325 00101 0.155757 -0.006105 0100147 017144 -18418512 0206658 -13.353 0.247379 -13.264791 0_275854 -13.267845 0.291154 -13.2955 -13.269881 0.322713 -13.267845 01100 -13.267545 156.107 -13.267845 0.370577 -13.263 0.37565 -13.268863 0.40619 -13.269881 0.418 -13.264791 0.42 -13.271917 044611 -13.2753 0.475463 -13274971 0.49174 -13.27025 0.50392 -13.282097 0.52428 -13.284133 0534461 -13.284133 0510 -13.221951 0 56700 -13.279171 0.570001 -13.271917 0.589434 -13.270899 474 -13.2001 0.617918 -13.270921 0.625052 -13.28061 09312 -13.27025 06162 -1323119 0.69 -13.289223 0.695304 -13.290041 0.713632 -13.288205 0.743144 -13.280061 0.754353 -13.283115 078492 -13.280061 0.824595 -13.27943 0854119 -13.274971 3263 -33.279999 0.863281 .13.279043 0867353 0.711721 2.491022 2.491022 2.846862 3.202742 4.982014 53374014 9.97 10.675807 14 507 16.011711 20.284034 24.910217 26333655 28.468819 3024812 31621561 12.027422 35.230164 33,50672) 34 518443 36.297744 35.38124 35581034 39 500467 35.941884 41.635645 41.635645 43.050 43.414999 4519425 45.908971 50-532154 $4.502477 36.225913 55.500 601408 61 561821 67.257585 66.901725 56.545565 67/613445 67.257585 67611445 67.909305 86 70.101467 7112208 7L1720 70,460027 72.599489 7437479 72.951300 72.9513 70.816188 69.743607 69006886 69392747 68 681006 66701225 67. 70327 70.316188 70.460327 70104467 70460327 63 121 33 34 35 36 37 18 ME 30 41 42 1 EP SACO ST 97 4 67 OS IS LS 54 55 56 57 59 09 8328 3296 61 62 63 19 65 0914542 -13.286305 -13.307546 09 WOO I SI 0940

JIS 19 59 99 60 1426.06 32 353 $ERN 70.460327 70 101467 70.466327 683351 71.527905 75.440391 79.356833 82 353 8932092 ESTOS SO 1.5803 ICO -13-2017 -11 -13.305 13303512 -14 -13.39769 -13.294313 -13.297367 -1330146 13 2014 -13.305512 -13.297367 -13.30449 -13.10347 -13: 30 -13.20385 -13101476 -13.30347 70 71 72 23 74 75 76 77 INST 16 90X264 89 13092 8896506 96.7979 A1293 12092 1041434 1055704 LASON HOT90101 LWS 11 IM1 ON L.123894 1146 LIS RI MEER NOSTI 1019 106.758072 113.875276 114586907 116.722158 116.222148 117.67015 116366295 115298719 12001 L111741 L15993 1.25335 1.395.40 122976 87 ES CI SKICE CESSIT -33353 -23313 -13.3.2002 -13.3049 11.13656 -13. -13003456 -13.54 - 12.1945 1303075 -13.315692 -13314678 -13164 -13.31671 -11-323656 -13313655 16 ועוד 1381300 90 122.415922 123.339365 93 123.339363 134.19522) 90 124.19922) 95 122.415922 124.551083 97 124 123 1 16 CE 96 ENDISS PI 1354136 139417 1.3834 1397741 1643 1.400 1.46 OLDOVEI 66 COOTER 168CCSET 1 16954 141213 SOL STEET -1331160 -1123656 -13315692 -13.374 13:32 -13.33318 -1239948 -13.30 -13.332995 -131 - 11.19 -1.915 -13.3213 1.248 154 SALES ILISE MESE MUSCE ET 15162 156775 ISTRU 1.50 100 13344789 101 102 137.006192 103 138.40633 104 141.276515 14:411676 106 146 258558 107 142.699956 103 145546835 109 146.970278 110 150.171021 111 154.799204 112 1976 111 160492 114 160 SSSS 115 161016405 116 166.166731 117 166 16731 118 167.966033 119 168 321893 120170-457054 121 170312914 122 169 189473 123 170812914 124 172236355 125 173.303936 136 172260155 127 176 508 177.574290 129 179 15356 130 154.691464 13 1875336 132 187.18345 133 186.470765 114 127 134 1941 1517156 169512 $63364 LAS 1 TS 1991 SICUT -23334354 -13 -13.33948 -13.312 -13.33707 -13344196 -131925 -13.350304 -13.126 -13725 -13353359 -130351322 -13.353354 - 13.355395 -13.36045 -13364559 -13.374737 -13 - - 1396115 1.727579 10156 121174 17506 2.183ST TORT 15.4579 14723 DEN ITETER

Initial dimensions 78.94 mm Diameter 1947 mm Cell Prese 100 LP Vert Dup Times) Force (N) Pore Pressure Imm) Pa) 1 0 0 220.6132 210.972012 -0.00038 221.6514 3 15.362425 0.000876 222.503314 4 17.121875 0.010 223.129166 $18.26509 0.054151 223 60577 19.045624 0,054166 224.063790 7 19.706004 0.072951 224.513755 8. 20:405595 0.124563 224946539 920x52327 0.126111 225.336953 10 21.243763 0,130351 225.696484 11 21.544294 0.13118 226 07150 12 22.151555 0,119771 226.488721 13 2223223 0.170440 226 22795 14 22.784573 0.181494 227.188618 15 22.16416 0.14212 222.539050 16 23.35325 0.19946 32701609 17 23.871878 0.246 223.251378 18 24.180703 0.25312 228.567331 19 24.625141 0.271127 22949211 20 24.677194 0.29366 229,306066 21 25.138849 0.313169 229.642649 22 25.592368 0.328834 229.956184 23 25.689641 0.359997 230,313753 24 25.99793 0.3653 230.6125229 25 2626364 0.373961 231.037867 26 26.418137 0.386394 231331531 27 26.704341 0.400194 2.31.35644 28 26.36179 0428911 211.96 29 27.13549 0.410154 2.12.310605 10 27 236292 0.40 2.12.202744 31 27 048199 233.00992 $ 27.975836 0.49555 211 251666 33 28.135862 0.518418 233,609266 34 28.331078 0.353062 233.928851 35 28.270335 0.57886 234.216661 36 28.488339 0.5X147 214.489046 37 288288 0.5887 234.38322 38 29.092165 160415 235.138219 39 29.156511 0.663011 235.400759 40 29.361564 0.661324 235.672627 41 29.636541 0.092217 235.9772 42 29.795107 0.9272 236.271839 43 30.001100 0,72314 216.554067 44 29.42713 0,706118 216.17954 45 10.12209 0.758158 217.0794664 46 30.290636 0.77117 27.404876 47 30.436185 0.779805 2175622 48 30.031946 0.794846 217.912375 49 30.739261 0.622372 22.18471 50 30.710189 0.8336 238.433526 51 30.357563 0.85854 238.7003 52 31.033425 0.192518 23.9619 33 31.163205 0.91983 239,205295 54 31 295164 0.893934 239.461959 SS 31.38229 0.934946 239.727279 56 31.481000 0.945246 239.462372 57 31.628538 0,972541 240.17827 58 31.739215 0,985417 240.445204 59 31.918763 0,936807 240.644378 032.006425 1.002213 240.199253 61 32.182178 1.051456 241.12173 62 32.43042 1.056470 241.60864 6032.48.2018 241.6151

1.056679 1.0605 1,0634 1.663631 L11629 ESGEPIT SRESTE 1.165723 1.197502 1209533 1211443 1.219319 1.2407 1.343307 1.26041 1.100414 1.314967 1.129077 1.14952 13672 1.393142 241.364 241.6151 341.835399 242.037753 242 21636 201527492 242.728993 342.935692 243.1142 243389513 243.621242 243.822475 24.000326 244.15705 244 401147 SENESTE SISTENT 62 32.43043 63 12.452033 64 32.43679 65 32.995648 66 32.693005 67 32.039948 6 32.771626 69 33.010543 70 33.022943 TI33.135129 72 33.421919 73 33.252966 74 13 16432 75 $1.485511 76 13.5642 72 105193 78 33.74415 79 3.811679 O 1.049289 RI 34.077105 34.15251 R3 34.364198 84 34.31639 55 34.4022 56 34.564305 17 34.659064 34.65323 19 1.89914 9 14.690557 91 94.911922 92 35.128251 93 35.236161 24 25.105545 35 35 110408 15.227199 99 15.177515 15.217672 115335919 100 35.39753 105 35.536694 102 35.551859 103 35.63715 104 35.604978 105 35.744142 106 35.970357 107 36.063775 103604359 109 36109 110 36.256393 111 36.321911 112 36134 113 16.457232 114 16.427542 115 16.442192 116 16,447419 117 16.555751 118 36 562956 119 36.746106 120 36,642048 121 36.833409 122 369220 123 37.023597 124 370148 125 37033199 126 37.13519 127 37.173736 128 37.142904 129 37.144747 110 37.195939 131 37.22133 244756 344919544 345 111376 245 345.472438 245.652403 249.845204 246,048634 246.225379 246355262 246.35640 246.73996 246.927832 247055409 247.235533 347.4101 347.581912 247.718211 2475004 348067776 348 21947 248 141522 248 SOL 365 345.673805 248.852031 24897748 249.0 201 249.238704 249.426711 299 249.66067 29.840617 229.997984 250.1.2005 250.245544 250380402 250 545218 250657113 250.77549 250.89835 251 051685 251 2004 25131030 251.417913 251,615423 251.737857 251.818404 251.914379 252.925 252.20953 252.110791 252.407300 252550301 2526SOK 1.44113 1.442699 1.445258 1.453937 1.477894 1496894 1.517507 1.353576 1.56784 1.573271 1.591671 1608119 1.634772 1.658742 1.681663 1.682545 1.687858 1.701354 1.715381 1.736256 1.774149 1.7813 1.803416 1.2650N 1967 1.81 1.689023 189275 1.195126 1.909158 1.927015 1.946483 1.978331 1986) 1.995194 2.007291 2.035613 2.065732 2.070327 2,077555 2.098574 2.126093 2.1-40516 2.162236 2.17446 2.180979 2.189593 2.228376 ISCS 「