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145Pier typeAggregatePierSingle PierTable 37: Stress concentration calculations for groups of aggregate piersσ atσ atσ atLength δ top = 2 δ top = 5 δ top =(mm) mm mm 10 mmPier type(kPa) (kPa) (kPa)305 129 247 406 AggregatePier Groupσ atσ atLength δ top = 2 δ top = 5(mm) mm mm(kPa) (kPa)σ atδ top =10 mm(kPa)305 867 2,254 3,406610 352 704 949 of 4 610 1596 3,105 3,947Loess - 67 158 285 Loess - 1028 1,891 2,719n. stiffness - 1.9 1.6 1.4 n. stiffness - 0.8 1.2 1.3ratio - 5.3 4.5 3.3 ratio - 1.6 1.6 1.5Aggregate 305 348 588 908 Aggregate 305 1,529 3,233 4,150Pier UnitCell 610 894 1,330 1,533Pier Groupof 5 610 3,511 4,375 4,825Loess - 278 685 1,101 Loess - 1,028 1,891 2,719n. stiffness - 1.3 0.9 0.8 n. stiffness - 1.5 1.7 1.5ratio - 3.2 1.9 1.4 ratio - 3.4 2.3 1.8Aggregate 305 483 1,345 2,146 Aggregate 305 3,073 4,100 4,898Pier Groupof 2 610 1,260 2,521 3,017Pier Groupof 6 610 3,134 5,361 7,068Loess - 642 1,055 1,609 Loess - 1,018 1,486 1,886n. stiffness - 0.8 1.3 1.3 n. stiffness - 3.0 2.8 2.6ratio - 2.0 2.4 1.9 ratio - 3.1 3.6 3.7Legend:δ top - deflection at the top of the pier (kPa)σ – stiffness of the pier (kPa)n –stiffness ratioCon<strong>version</strong>s:1 m = 3.3 ft1 mm = 0.0394 in1 kPa = 0.145 psiStiffness modulus results for groups of aggregate piers outlined in Table 30 have shown agreater amount of piers stiffening of the lab constructed piers comparing to the field stiffnessmodulus results. As the number of piers was to increase within the group the difference instiffness modulus between lab and field had also a trend to increase.
146Aggregate Piers – Bearing capacityObtained bearing capacity values were found to have a trend to increase in a non-linearfashion with the increasing number of piers within the group (Table 31). Single pier wasfound to bear 1.1 MPa - 1.9 MPa, while the group of 6 had a load capacity of 8.4 MPa – 15.5MPa. For most of the obtained results short piers were found to have similar bearing capacityas long piers within the same pier group, where only group of six was found to be an outlier.When performing comparative analysis between the lab and field bearing capacity results, itwas found that the values were to closely correlate. However, no particular trend wasnoticed. Figure 82 shows comparison between single piers, groups of four and groups of fiveaggregate piers. Full-scale piers are not necessarily of the same length as the lab 305 mm and610 mm piers and, therefore, additional field replicating testing would be required to identifythe field and lab correlation.Aggregate Piers - Group EfficiencyGroup efficiency calculations were performed at 2 mm, 5 mm and 10 mm top of the pierdisplacements. The group efficiency results with respect to single pier were summarized inTable 27 and with respect to unit cell were summarized in Table 28. Some of the majorconclusions were made based on the pier length, number of piers within the group andmagnitude of settlement at service and ultimate load conditions.Having the piers built at short 305 mm and long 610 mm lengths, the findings have shownthat the group efficiency with respect to single pier was consistently greater in magnitude forshort piers than for the long ones. In some cases the difference between short and long pierswas exceeded by a factor of two leading to a conclusion that some of the shorter groups ofaggregate piers were twice as efficient as the groups of piers of greater length.
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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
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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
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91CHAPTER 5: TEST RESULTS AND ANALY
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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 156 and 157: 141Table 36: Stiffness ratio calcul
Page 158 and 159: 143Some of the loess composition pi
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
Page 206 and 207: 191C(I) + C(K)305mm Group of 4CBR,
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