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107to the maximum displacement of 12 mm due to testing limitations were still included inTable 24, however, the ultimate amount of settlement was substituted with settlementobtained at maximum point of stress-settlement curve.The pier stiffness modulus was calculated for each tested pier and obtained only at 2 mm topof the pier displacement. The modulus was evaluated by taking a ratio between the appliedstress and corresponding 2 mm displacement:Equation 18: Stiffness modulusk = ∆σ / ∆δ top (Equation 18)The ratio δ tell-tale / δ top between top and bottom of the pier settlement values was calculated inorder to interpret the amount of bulging that occurred within the tested pier. The evaluationwas made at the point of failure or at ultimate load, therefore, the top of the pier deflectionδ top was taken at 10 mm:Equation 19: Top of the pier tell-tale deflection ratioRatio = δ tell-tale / δ top = δ tell-tale / 10mm (Equation 19)Bearing CapacitySupplemental bearing capacity calculations were also performed for the piers of differentcomposition. Two different bearing capacity calculation approaches were taken where failureby bulging (Table 25) and failure by plunging (Table 26) mechanisms were applied.The piers that were deemed to fail by bulging were limited to long 610 mm aggregate pierand sand pier. Due to the pier length and having the bulb portion of all 610 mm piers to beplaced against a stiffer layer of soil, the plunging mechanism of failure for the noncementitiouspiers was limited and the failure through shearing of the material was induced.Having the failure of long aggregate pier and sand piers to occur through shearing of the
108aggregate, the friction angle was of the essence. Aggregate pier friction angle of 44 degreewas evaluated from the direct shear test as outlined in Materials Section. For the frictionangle of sand material the value was assumed to be 35 degree as per Holtz and Kovacs, 1981,where the dense state of Ottawa sand friction angle was used as a reference. Densification ofsand was inevitable in the process of ramming material in even size lifts inside the cavityand, therefore, the dense state of sand friction angle was selected to be used to performcalculations (details are provided in the appendix).Table 25: Ultimate bearing capacity due to bulging failure for single piersPier type H shaft (mm) γ dry loess (kg/m 3 ) C u (kPa) σ v ’ (kPa) σ r,lim (kPa) q ult (kPa)Aggregate Pier -TruncatedAggregate Pier w/cem.bulbAggregate Pier w/cem.top 100mm.Loess + fiberLoess + cement610 1,556 33 1.5 175 970COMPLICATED MECHANISM OF FAILUREFAILURE BY BULGING, HOWEVER FRICTION ANGLE OF LOESS ANDFIBER COMPOSITION IS UNKNOWNBRITTLE FAILURE BY SHEARING AT TOP PORTION OF THE PIERLoess + fiber + cementC(I) + C(K)C(I) + C(K) + NS7FAILURE BY PLUNGINGC(I) + NS7Sand305 1,561 35 1.5 185 683610 1,559 39 1.5 206 760Legend:φ p AGGREGATE PIER = 44°φ p sand = 35°H shaft - length of the pier (mm)γ dry loess - dry unit weight of matrix soil (kg/m 3 )C u - undrained shear strength (kPa)σ' v - overburden stress at the bottom of the pier (kPa)σ r lim - limiting radial stress (kPa)q ult - ultimate bearing capacity due to pier bulging (kPa)Con<strong>version</strong>s:1 m = 3.3 ft1 mm = 0.0394 in1 kPa = 0.145 psi1 kg/m 3 = 0.0624 pcf
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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
Page 72 and 73: 57Table 14: Top and bottom UC loess
Page 74 and 75: 59Data Collection and SensorsHaving
Page 76 and 77: 61Micro Epsilon displacement transd
Page 78 and 79: 63plate down the cavity through man
Page 80 and 81: 65Beveled Tamper HeadsThe other asp
Page 82 and 83: 67All, aggregate, cementitious and
Page 84 and 85: 69DAQ Data CollectionWhile performi
Page 86 and 87: 71space in the test bed (See Figure
Page 88 and 89: 73(a)(b)(c)Figure 42: Test bed grou
Page 90 and 91: 75CHAPTER 4: MATERIALSThe materials
Page 92 and 93: 7710080LL = 31PI = 7Pass. #200 = 98
Page 94 and 95: 79the second stage of testing. Mois
Page 96 and 97: 81Knowing the gradation characteris
Page 98 and 99: 83More importantly, the performed d
Page 100 and 101: 85Figure 49: Cement type I compound
Page 102 and 103: 87As the expansive and contractive
Page 104 and 105: 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 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 156 and 157: 141Table 36: Stiffness ratio calcul
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
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157MaterialsLoess-CementVery intrig
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159Groups of PiersGroup of Aggregat
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161CHAPTER 8: FUTURE RESEARCHThe fu
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163Black, J.A., Sivakumar, V., Madh
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165Hanlong, L., An, D., and Yang, S
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167Randrup T.B., and Lichter, J.M.
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169Yeh, Y.K., and Mo, Y.L. (2005).
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171Group EfficiencyAggregate Pier G
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173Aggregate Pier305mm Wedge HeadDC
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175Loess + Fibers305mm Single PierD
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177Sand305mm Single PierDCPI, mm/bl
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179Aggregate Pier305mm Group of 4DC
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181C(I) + C(K)305mm Group of 4DCPI,
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183Aggregate Pier305mm Wedge HeadCB
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185Loess + Fibers305mm Single PierC
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187Sand305mm Single PierCBR, %0 2 4
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189Aggregate Pier305mm Group of 4CB
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191C(I) + C(K)305mm Group of 4CBR,
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