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Treasure ’ s report of 1 st Lizzi Scholarship IWM2006 in Schrobenhausen, Germany: May 5th, 2006 Shingo MORIMASA Graduate Student, GeoMechanics Group, Toyohashi University of Technology

Treasure ’ s Report 1st Lizzi Scholarship (IWM2004) Date Type of Expense Total Rail fare from Toyohashi to Tokyo 8,190 yen 2004/08/24 Rail fare from Shibuya to Kachidoki 600 yen Rail fare from Kachidoki to Denen-chofu 410 yen 2004/08/25 Rail fare from Denen-chofu to Kachidoki 410 yen Rail fare from Kachidoki to Denen-chofu 360 yen 2004/08/26 Rail fare from Negishi to Kachidoki 710 yen Lodging charge for three nights 19,080 yen Rail fare from Kachidoki to Denen-chofu 360 yen 2004/08/27 Rail fare from Oyamadai to Oimachi 190 yen Rail fare from Tokyo to Toyohashi 8,190 yen TOTAL 38,500 YEN ($351.41)

Simulation of the Confining Effect on Bearing Capacity of Micropile Foundation; -- Field Loading Test and FEM Simulation -- IWM2006 in Schrobenhausen, Germany: May 5th, 2006 Shingo MORIMASA Graduate Student, GeoMechanics Group, Toyohashi University of Technology

Table of contents � Purpose � Field Loading Test � Prestressed micropile method � FEM simulation � Confining effect � Effects of network and prestress � Summary and future plan

The purpose of this study � Early studies (Otani, Tsukada, Miura et al) � “ Model Loading Tests on The Footing Reinforced with Prestressed Micropiles ” � “ Large-Scaled Field Loading Test on The Footing Reinforced with Prestressed Micropiles ” � Analytic clarification of the mechanism of the mobilization of load bearing capacity of foundation reinforced with prestressed micropiles

Field loading test � The boring log and the SPT N-value of the upper 10 meters � The subsoils are fill, loam, cemented clay, sandy clay, and fine sand, respectively. � The fill, loam and clay are soft; the SPT N-values are less than 5.

Field loading test The micropile is 3 m long, 100 mm in diameter, with a steel bar of 32 mm in diameter (a) S-MP (b) FT-MP/FT-PSMP

Loading apparatus Vertical Loading test Horizontal Loading test

The results of vertical loading tests Load (kN) 0 100 200 300 400 500 600 700 0 � Initial coefficient of 50 subgrade reaction 100 Settlement, S (mm) FT-PSMP: � FT-MP(non-prestressed) prestressed FT-PSMP 150 � 1.86 × 10 4 kN/m 3 � FT-PSMP(prestressed) 200 � 3.97 × 10 4 kN/m 3 FT+8MPs: 250 Summation of FT FT+8MPs FT-MP footing and FT-MP: non-prestressed 8 micropiles 300 Also in field loading test, network effect was mobilized. The settlement became half due to the effect of prestress.

The results of horizontal loading tests Horizontal load (kN) 0 5 10 15 20 25 30 0 � Initial coefficient of subgrade reaction 5 Horizontal displacement (mm) 10 � FT-MP(non-prestressed) FT-PSMP FT-PSMP: 15 � 1.01 × 10 3 kN/m 3 prestressed � FT-PSMP(prestressed) 20 � 17.1 × 10 3 kN/m 3 25 FT-MP: FT-MP non-prestressed 30 The effect of prestress was significant in the horizontal movement control.

FEM simulation � Footing: � rigid material � Micropiles: � elastic bending material � second-order FEM elements � Ground: � elasto-plastic model � Drucker-Prager Type � Ground - Micropiles: � bi-linear slider element

Analysis condition � Type of foundation � Footing, Micropile(MP), MP-footing, and prestressed MP-footing � Ground � Dense sand and Loose sand � Loading � Vertical and Horizontal Loading

Dilatancy angle ψ > 0 :positive dilatancy Input parameters ψ < 0 :negative dilatancy � Mechanical properties φ ( ° ) c ( N/m 2 ) ψ ( ° ) ρ (kg/m 3 ) ν E ( N/m 2 ) G ( N/m 2 ) 2.00 × 10 3 1.04 × 10 8 1.20 × 10 8 Dense sand 35 0 10 0.3 Loose sand 30 0 -10 1.90 × 10 3 0.35 × 10 8 0.40 × 10 8 0.3 Micropile 2.40 × 10 3 70 × 10 8 2.69 × 10 9 0.3 � Frinction angle between Ground and Micropiles � Internal friction angle of ground tan φ � Prestress � Approximately 30% of bearing capacity of micropiles

Vertical Loading Condition (Confining Effect) Loose Sand Ground Dense Sand Ground Load, q (kN) Load, q (kN) 0 50 100 150 200 0 100 200 300 400 0. 00 0. 00 Footing(FT) 0. 01 0. 01 Micropile(MP) MP footing(FT-MP) 0. 02 0. 02 Displacement , S (m) Displacement , S (m) 0. 03 0. 03 Network effect index 0. 04 0. 04 R= FT-MP FT+MPs 0. 05 0. 05 FT+MPs FT+MPs 0. 06 0. 06 FT MP FT+MPs FT-MP R Critical load + bearing capacity + Dense sand 124 45 169 307 1.82 Loose sand 64 35 99 123 1.24

Vertical Loading Condition (Effect of prestress) Loose Sand Ground Dense Sand Ground Load, q (kN) Load, q (kN) 0 50 100 150 200 0 100 200 300 400 500 0. 00 0. 00 with prestress 0. 01 0. 01 without prestress 0. 02 0. 02 Displacement , S (m) Displacement , S (m) 0. 03 0. 03 0. 04 0. 04 0. 05 0. 05 0. 06 0. 06 Loose sand Dense sand FTMP FT-PSMP FTMP FT-PSMP Critical bearing capacity 123 156 307 436 Initial Coefficient 19000 20000 31000 31000 of subgrade reaction

Horizontal Loading Condition (Effect of prestress) Loose Sand Ground Dense Sand Ground Load, q (kN) Load, q (kN) 0 10 20 30 40 50 0 10 20 30 40 50 60 70 80 0. 00 0. 00 0. 01 0. 01 wi th pr estr ess wi thout pr estr ess 0. 02 0. 02 Displacement , S (m) Displacement , S (m) 0. 03 0. 03 0. 04 0. 04 MP(Micropile) MP(Micropile) 0. 05 0. 05 0. 06 0. 06 Loose sand Dense sand FTMP FT-PSMP FTMP FT-PSMP Critical bearing capacity 23 38 31 67 Initial Coefficient 630 650 760 820 of subgrade reaction

Summary and future plan � The confining effects on the ground by the micropiles were clearly observed both in the loading tests and FEM simulations � The effect of the prestress which induced the confinement on the subsoil by the footing and the micropiles, was recognized not only in the loading tests but also in the FEM simulations.

� The FEM simulation must be modified � The yielding of micropiles under the horizontal loading on piles � The increase in shear modulus of ground due to the confinement � 3-D FEM simulation � network of micropiles � confining effect

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