EXPERIMENT 11 CONSOLIDATION TEST

Transcription

1 119 EXPERIMENT 11 CONSOLIDATION TEST Purpoe: Thi tet i performed to determine the magnitude and rate of volume decreae that a laterally confined oil pecimen undergoe when ubjected to different vertical preure. From the meaured data, the conolidation curve (preure-void ratio relationhip) can be plotted. Thi data i ueful in determining the compreion index, the recompreion index and the preconolidation preure (or maximum pat preure) of the oi. In addition, the data obtained can alo be ued to determine the coefficient of conolidation and the coefficient of econdary compreion of the oil. Standard Reference: ASTM D Standard Tet Method for One-Dimenional Conolidation Propertie of Soil. Significance: The conolidation propertie determined from the conolidation tet are ued to etimate the magnitude and the rate of both primary and econdary conolidation ettlement of a tructure or an earthfill. Etimate of thi type are of key importance in the deign of engineered tructure and the evaluation of their performance. Equipment: Conolidation device (including ring, porou tone, water reervoir, and load plate), Dial gauge ( inch = 1.0 on dial), Sample trimming device, gla plate, Metal traight edge, Clock, Moiture can, Filter paper.

2 120

3 121 Tet Procedure: (1) Weigh the empty conolidation ring together with gla plate. (2) Meaure the height (h) of the ring and it inide diameter (d). (3) Extrude the oil ample from the ampler, generally thin-walled Shelby tube. Determine the initial moiture content and the pecific gravity of the oil a per Experiment 1 and 4, repectively (Ue the data heet from thee experiment to record all of the data). (4) Cut approximately a three-inch long ample. Place the ample on the conolidation ring and cut the ide of the ample to be approximately the ame a the outide diameter of the ring. Rotate the ring and pare off the exce oil by mean of the cutting tool o that the ample i reduced to the ame inide diameter of the ring. It i important to keep the cutting tool in the correct horizontal poition during thi proce. (5) A the trimming progree, pre the ample gently into the ring and continue until the ample protrude a hort ditance through the bottom of the ring. Be careful throughout the trimming proce to inure that there i no void pace between the ample and the ring. (6) Turn the ring over carefully and remove the portion of the oil protruding above the ring. Uing the metal traight edge, cut the oil urface fluh with the urface of the ring. Remove the final portion with extreme care.

4 122 (7) Place the previouly weighed Saran-covered gla plate on the frehly cut urface, turn the ring over again, and carefully cut the other end in a imilar manner. (8) Weigh the pecimen plu ring plu gla plate. (9) Carefully remove the ring with pecimen from the Saran-covered gla plate and peel the Saran from the pecimen urface. Center the porou tone that have been oaking, on the top and bottom urface of the tet pecimen. Place the filter paper between porou tone and oil pecimen. Pre very lightly to make ure that the tone adhere to the ample. Lower the aembly carefully into the bae of the water reervoir. Fill the water reervoir with water until the pecimen i completely covered and aturated. (10) Being careful to prevent movement of the ring and porou tone, place the load plate centrally on the upper porou tone and adjut the loading device. (11) Adjut the dial gauge to a zero reading. (12) With the toggle witch in the down (cloed) poition, et the preure gauge dial (baed on calibration curve) to reult in an applied preure of 0.5 tf (ton per quare foot). (13) Simultaneouly, open the valve (by quickly lifting the toggle witch to the up (open) poition) and tart the timing clock.

5 123 (14) Record the conolidation dial reading at the elaped time given on the data heet. (15) Repeat Step 11 to 13 for different preelected preure (generally include loading preure of 1.0, 2.0, 4.0, 8.0, and 16.0 tf and unloading preure of 8.0, 4.0, 2.0, 1.0 and 0.5 tf) (16) At the lat elaped time reading, record the final conolidation dial reading and time, releae the load, and quickly diaemble the conolidation device and remove the pecimen. Quickly but carefully blot the urface dry with paper toweling. (The pecimen will tend to aborb water after the load i releaed.) (17) Place the pecimen and ring on the Saran-covered gla plate and, once again, weigh them together. (18) Weigh an empty large moiture can and lid. (19) Carefully remove the pecimen from the conolidation ring, being ure not to loe too much oil, and place the pecimen in the previouly weighed moiture can. Place the moiture can containing the pecimen in the oven and let it dry for 12 to 18 hour. (20) Weigh the dry pecimen in the moiture can. Analyi: (1) Calculate the initial water content and pecific gravity of the oil.

6 124 (2) For each preure increment, contruct a emilog plot of the conolidation dial reading veru the log time (in minute). Determine D 0, D 50, D 100, and the coefficient of conolidation (c v ) uing Caagrande logarithm of time fitting method. See example data. Alo calculate the coefficient of econdary compreion baed on thee plot. (3) Calculate the void ratio at the end of primary conolidation for each preure increment (ee example data). Plot log preure veru void ratio. Baed on thi plot, calculate compreion index, recompreion index and preconolidation preure (maximum pat preure). (4) Summarize and dicu the reult.

7 125 EXAMPLE DATA

8 126 Conolidation Tet Data Sheet Date Teted: October 05, 2002 Teted By: CEMM315 Cla, Group A Project Name: CEMM315 Lab Sample Number: GB-08-ST Viual Claification: Gray ilty clay Before tet Conolidation type = Floating type Ma of the ring + gla plate = g Inide diameter of the ring = 6.3 cm eight of pecimen, i = 2.7 cm Area of pecimen, A = cm 2 Ma of pecimen + ring = g Initial moiture content of pecimen, w i (%) = 19.5 % Specific gravity of olid, G = 2.67 After tet Ma of wet ample + ring + gla plate = g Ma of can = 59.3 g Ma of can + wet oil = g Ma of wet pecimen = g Ma of can + dry oil = g Ma of dry pecimen, M = g Final moiture content of pecimen, w f = %

9 127 Calculation Ma of olid in pecimen, M (Ma of dry pecimen after tet) Ma of water in pecimen before tet, M wi =149.2 g = w i x M = 0.195*149.2 = g Ma of water in pecimen after tet, M wf (g) = w f x M = *149.2 = g M eight of olid, = = A G ρ w (ame before and after tet and note ρ w = 1 g/cm 3 ) = cm eight of water before tet, wi = A M wi ρ w = = cm eight of water after tet, wf = A M wf ρ w = = cm Change in height of pecimen after tet, Σ (Σ for all preure ee t v Dial Reading plot) =0.257 cm eight of pecimen after tet, f = i - Σ = = cm Void ratio before tet, e o = i = = Void ratio after tet, e f = f = = wi Degree of aturation before tet, S i = = 100 i =102.7 %

10 128 wf Degree of aturation after tet, S f = = f =105.08% Dry denity before tet, ρ d = M A i = = 1.77 g/cm =(110.6 pcf)

11 129 Table 1: Time - Settlement Data (1 unit on dial guage = inche) loading= ¼ tf loading=1/8 tf loading=1/2 tf loading=1 tf time dail reading time dail reading time dail reading time dail reading loading=2 tf time dail reading loading=4 tf loading=2 tf (unloading) loading=1 tf (unloading) time dail reading time dail reading time dail reading loading=1/2 tf (unloading) loading=1 tf (reloading) loading=2 tf (reloading) loading=4 tf (reloading) time dail reading time dail reading time dail reading time dail reading

12 130 loading=8 tf loading=16 tf loading=32 tf time dail reading time dail reading time dail reading

13 131 Dail Reading (x in) 0 D 0 = D 100 = Η = in Conolidation Tet (ASTM D 2435) Preure = 1/2 tf t 50 =10 min D + D D = = = Time (min) 170 Conolidation Tet (ASTM D 2435) Preure = 1 tf Dail Reading (x in) = in t 50 = 11.5 min Time (min)

14 132 Conolidation Tet (ASTM D 2435) Preure = 2 tf Dail Reading (x in) = in t 50 = 30 min Time (min) 300 Conolidation Tet (ASTM D 2435) Preure = 4 tf Dail Reading (x in) = in t 50 = 3.3 min Time (min)

15 133 Conolidation Tet (ASTM D 2435) Preure = 2 tf (Unloaded) Dail Reading (x in) = in t 50 = 1.9 min Time (min) 495 Conolidation Tet (ASTM D 2435) Preure = 1 tf (Unloaded) 490 Dail Reading (x in) = in t 50 = 3.5 min Time (min)

16 134 Conolidation Tet (ASTM D 2435) Preure = 1/2 tf (Unloaded) Dail Reading (x in) = in t 50 = 6.0 min Time (min) 440 Conolidation Tet (ASTM D 2435) Preure = 1 tf (Reloaded) Dail Reading (x in) = in t 50 = 1.2 min Time (min)

17 135 Conolidation Tet (ASTM D 2435) Preure = 2 tf (Reloaded) Dail Reading (x in) = in t 50 = 0.6 min Time (min) 445 Conolidation Tet (ASTM D 2435) Preure = 4 tf (Reloaded) 455 Dail Reading (x in) = in t 50 = 2.4 min Time (min)

18 136 Conolidation Tet (ASTM D 2435) Preure = 8 tf Dail Reading (x in) = in t 50 = 3.0 min Time (min) Conolidation Tet (ASTM D 2435) Preure = 16 tf Dail Reading (x in) = 0.02 in t 50 = 2.0 min Time (min)

19 137 Conolidation Tet (ASTM D 2435) Preure = 32 tf Dail Reading (x in) = in t 50 = 3.0 min Time (min)

20 138 Table 2: Analyi of Conolidation Tet Data Preure (tf) Time for 50% conolidation t 50 (min) D 0 (from graph) D 100 (from graph) D 50 = j = D 50 * (D 0 +D 100 )* (from graph) Σ * ** d ** Coefficient of conolidation C v (in 2 /min) *** *** v e *** E E E E E E E E E E E E E * Σ for applied preure = Σ of all previou preure + under applied preure j j ** d = ± and j = i ± (- for Loading and + for Unloading) j j d *** C v = 0.197, ( ) v v = i Σ and e = t 50

21 139 Conolidation Tet (ASTM D 2435) Void Ratio v Log Preure 0.49 Pc=3.5 tf C r =0.013 Void Ratio C c = Preure (tf) Final Reult: Compreion Index (C c ) = 0.11 Recompreion Index (C r ) = Preconolidation preure (P c ) or Maximum pat preure (σ vmax ) = 3.5 tf Coefficient of conolidation (C v )= 1.54x10-2 to 9.01x10-3 in 2 /min (depend on the preure) Coefficient of econdary compreion (Cα) = (It i the lope of time v ettlement curve beyond the end of primary conolidation)

22 140 BLANK DATA SEETS

23 141 Conolidation Tet Data Sheet Date Teted: Teted By: Project Name: Sample Number: Sample Decription: Before tet Conolidation type = Ma of the ring + gla plate = Inide diameter of the ring = eight of pecimen, i = Area of pecimen, A = Ma of pecimen + ring = Initial moiture content of pecimen, w i (%) = Specific gravity of olid, G = After tet Ma of wet ample + ring + gla plate = Ma of can = Ma of can + wet oil = Ma of wet pecimen = Ma of can + dry oil = Ma of dry pecimen, M = Final moiture content of pecimen, w f =

24 142 Calculation Ma of olid in pecimen, M = (Ma of dry pecimen after tet) Ma of water in pecimen before tet, M wi = w i x M = Ma of water in pecimen after tet, M wf (g) = w f x M = M eight of olid, = = A G ρ w (ame before and after tet and note ρ w = 1 g/cm 3 ) eight of water before tet, wi = M wi A ρ w = M wf eight of water after tet, wf = = = A ρ w Change in height of pecimen after tet, Σ = (Σ for all preure ee t v Dial reading plot) eight of pecimen after tet, f = i - Σ = Void ratio before tet, e o = i = Void ratio after tet, e f = f = Degree of aturation before tet, S i = i wi = Degree of aturation after tet, S f = f wf = Dry denity before tet, ρ d = M i A =

25 143 Time - Settlement Data Converion: inch = 1.0 on dial reading (confirm thi before uing) LOADING = tf ELAPSED DIAL TIME, min READING LOADING = tf ELAPSED DIAL TIME, min READING LOADING = tf ELAPSED DIAL TIME, min READING

26 144 Analyi of Conolidation Tet Data Preure (tf) Time for 50% conolidation t 50 (min) D 0 (from graph) D 100 (from graph) D 50 = j = D 50 * (D 0 +D 100 )* (from graph) Σ * ** d ** Coefficient of conolidation C v (in 2 /min) v *** e *** * Σ for applied preure = Σ of all previou preure + under applied preure j j ** d = ± and j = i ± (- for Loading and + for Unloading) j j d *** C v = 0.197, ( ) v v = i Σ and e = t 50