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141Table 36: Stiffness ratio calculations for single piers of various compositionσ atσ atσ at δ topσ atσ atσ at δ topPier typeLength δ top = 2 δ top = 5 = 10Length δ top = 2 δ top = 5 = 10Pier type(mm) mm mm mm(mm) mm mm mm(kPa) (kPa) (kPa)(kPa) (kPa) (kPa)Aggregate 305 443 774 1,044 Loess + 305 483 794 1,062Pier –fiber +610 494 789 1,028 610 518 1,491 1,804Truncatedcementn. stiffnessCone- 1.3 1.5 1.5 n. - 1.4 1.5 1.5ratiostiffness- 1.4 1.5 1.5 - 1.5 2.9 2.6ratioAggregate 305 491 732 960 C(I) + 305 453 960 1,363Pier w/cem.610 341 904 1,304C(K)610 975 1,974 2,393bulbn. stiffness - 1.4 1.4 1.4 n. - 1.3 1.8 2.0ratiostiffness- 1.0 1.7 1.9 - 2.8 3.8 3.5ratioAggregate 305 509 958 1,385 C(I) + 305 667 1,028 1,200Pier w/cem.C(K) +610 740 1,341 1,726 610 1,247 1,749 1,944top 100mm.NS7n. stiffness - 1.5 1.8 2.0 n. - 1.9 2.0 1.7ratiostiffness- 2.1 2.6 2.5ratio- 3.6 2.0 2.8Loess + fiber305 211 475 667 C(I) + 305 523 1,044 1,327610 251 496 771NS7610 1,130 1,611 1,765n. stiffness - 0.6 0.9 1.0 n. - 1.5 2.0 1.9ratiostiffness- 0.7 1.0 1.1ratio- 3.3 3.1 2.6Loess + 305 729 1,258 1,570305 707 902 998Sandcement610 1,153 1,436 1,467 610 712 1,103 1,295n. stiffness - 2.1 2.4 2.3 n. - 2.0 1.7 1.4ratiostiffness- 3.3 2.8 2.1ratio- 2.1 2.1 1.9Loess — 347 521 689 Loess — 347 521 689Legend:δ top - deflection at the top of the pier (kPa)σ – stress on the pier (kPa)n –stiffness ratioCon<strong>version</strong>s:1 m = 3.3 ft1 mm = 0.0394 in1 kPa = 0.145 psi
142Table 36 outlines the amount of improvement in load support provided by unreinforcedmatrix soil versus load carried by the pier of the same cross section. In general the trend canbe outlined that the long 610 mm piers have shown a better performance in load carryingcapacity and improvement through stress increase and stiffening of the soil than short 305mm piers. As an exception, piers composed of loess and fiber demonstrated stiffnessbehavior results inconsistent with a general trend, where longer 610 mm pier has shown to beless effective in load bearing capacity.Another conclusion that was drawn from Table 36 has shown that the piers subjected tobulging or internal deformation mechanisms of failure, such as aggregate pier, sand, andloess, fiber composition piers featured a relatively unchanged or declined stiffness ratio asthe loads approached critical or ultimate conditions.Bearing CapacityWhile two primary modes of failure were considered where plunging and bulgingmechanisms were of a main concern, some of the piers featured a more complicatedmechanism of failure through combination of both plunging and bulging processes.Some of the piers, bearing capacities of which were not evaluated due to a complicatedmechanisms of failure, included partially cemented aggregate piers, loess and cementcomposition piers, as well as, piers composed of loess and fibers.Having partially cemented aggregate piers to undergo a more complex mechanism of failurewas attributed with the shift in zone of pier bulging for the aggregate piers with cemented100 mm top portion, and unknown impact of cementing of bulb on plunging mechanism offailure. Therefore, partially cemented aggregate piers could not be evaluated throughconventional methods of evaluating bearing capacity since no pure bulging or pure plungingwas observed.
Page 1:
Engineering behavior of small-scale
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viLIST OF FIGURESFigure 1: Concept
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viiiFigure 62: Stress-settlement te
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xLIST OF TABLESTable 1: Stiffness m
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xiiLIST OF EQUATIONSEquation 1: Ult
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xivSymbol Description Unitsγ dry l
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1CHAPTER 1: INTRODUCTIONIndustry Pr
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7MAKECAVITYPLACESTONE ATBOTTOM OFCA
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9Normal Stress, kPaShear Stress. kP
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11pier element for a maximum of 25
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13savings provided by the system (A
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15The bearing capacity accredited t
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17Equation 12: Load resistance prov
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19Soil conditions at the site were
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Settlement (mm)Settlement (mm)10202
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23Site soil conditions were describ
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25Article#ReferenceTable 2: Case st
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27Article#7ReferenceHughes andWithe
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29replaced with method of freezing
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UNREINFORCED COLUMNNO COLUMNREINFOR
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33The load carrying capacity was fo
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35Case 5 - Bachus and Barksdale, 19
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37full depth of the consolidated la
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39CHAPTER 3: RESEARCH METHODOLOGYCr
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41itself was designed to be support
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43While it is obvious that the chan
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45To perform all the required testi
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47In the areas where access was lim
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49CBR from DCPThe California Bearin
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305 mm610 mm305 mm610 mm305 mm610 m
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53The process of using the Shelby t
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15881556144815591597154915271586158
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57Table 14: Top and bottom UC loess
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59Data Collection and SensorsHaving
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61Micro Epsilon displacement transd
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63plate down the cavity through man
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65Beveled Tamper HeadsThe other asp
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67All, aggregate, cementitious and
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69DAQ Data CollectionWhile performi
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71space in the test bed (See Figure
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73(a)(b)(c)Figure 42: Test bed grou
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75CHAPTER 4: MATERIALSThe materials
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7710080LL = 31PI = 7Pass. #200 = 98
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79the second stage of testing. Mois
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81Knowing the gradation characteris
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83More importantly, the performed d
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85Figure 49: Cement type I compound
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87As the expansive and contractive
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89Figure 55: 19 mm polypropylene fi
Page 106 and 107: 91CHAPTER 5: TEST RESULTS AND ANALY
Page 108 and 109: 93Applied stress at top of pier (kP
Page 110 and 111: 95Figure 60: Stress-settlement test
Page 116 and 117: 101Figure 66: Stress-settlement tes
Page 120 and 121: 105Settlement (mm)024681012Applied
Page 122 and 123: 107to the maximum displacement of 1
Page 124 and 125: 109The failure mechanism of other p
Page 126 and 127: 1113000Measured Bearing Capacity (k
Page 128 and 129: 113Applied stress at bottom of the
Page 134 and 135: 119Settlement (mm)0246810Applied st
Page 136 and 137: 121The group efficiency results wer
Page 138 and 139: 123Pier typeAggregate PierUnit Cell
Page 146 and 147: 131Applied stress at bottom of the
Page 148 and 149: 133Table 33: Group efficiency compa
Page 150 and 151: 135Having a limited amount of exper
Page 152 and 153: 137Stiffness, kPa/mm600500400300200
Page 154 and 155: 139In case with the piers consistin
Page 158 and 159: 143Some of the loess composition pi
Page 160 and 161: 145Pier typeAggregatePierSingle Pie
Page 162 and 163: 147Another observation was made, wh
Page 164 and 165: 149As previously outlined, the stif
Page 166 and 167: 151pier group efficiency values wer
Page 168 and 169: Stiffness Ratio1538Figure 91: Stiff
Page 170 and 171: 155CHAPTER 7: SUMMARY AND CONCLUSIO
Page 172 and 173: 157MaterialsLoess-CementVery intrig
Page 174 and 175: 159Groups of PiersGroup of Aggregat
Page 176 and 177: 161CHAPTER 8: FUTURE RESEARCHThe fu
Page 178 and 179: 163Black, J.A., Sivakumar, V., Madh
Page 180 and 181: 165Hanlong, L., An, D., and Yang, S
Page 182 and 183: 167Randrup T.B., and Lichter, J.M.
Page 184 and 185: 169Yeh, Y.K., and Mo, Y.L. (2005).
Page 186 and 187: 171Group EfficiencyAggregate Pier G
Page 188 and 189: 173Aggregate Pier305mm Wedge HeadDC
Page 190 and 191: 175Loess + Fibers305mm Single PierD
Page 192 and 193: 177Sand305mm Single PierDCPI, mm/bl
Page 194 and 195: 179Aggregate Pier305mm Group of 4DC
Page 196 and 197: 181C(I) + C(K)305mm Group of 4DCPI,
Page 198 and 199: 183Aggregate Pier305mm Wedge HeadCB
Page 200 and 201: 185Loess + Fibers305mm Single PierC
Page 202 and 203: 187Sand305mm Single PierCBR, %0 2 4
Page 204 and 205: 189Aggregate Pier305mm Group of 4CB
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191C(I) + C(K)305mm Group of 4CBR,
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