Full Scale Model Test of Soil Reinforcement on Soft Soil Deposition with Inclined Timber Pile

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1 Full Scale Model Test of Soil Reinforcement on Soft Soil Deposition with Inclined Timber Pile Suheriyatna 1, L. Samang 2, M. W. Tjaronge 3 and T. Harianto 4 1 Doctoral Student, Department of Civil Engineering, Hasanuddin University 2 Professor, Department of Civil Engineering, Hasanuddin University 3 Professor, Department of Civil Engineering, Hasanuddin University 4 Associate Professor, Department of Civil Engineering, Hasanuddin University Abstract This study aims to examine the behavior of full-scale embankment reinforcement on soft soil reinforced with inclined micro pile and simulate pattern deformation on full-scale Embankment with numerical validation. Fullscale test conducted by pre loading stage construction system to a height of 4.5 m, Reinforced with galam timber as micro pile 15 0 inclination, diameter of 10 cm, and a length of 6 m. Field observations were conducted by installing a Settlement Plate for settlement monitoring, piezometers to monitor the pore water pressure, and digital inclinometer to observed lateral movement the sub-soil. Field observations conducted every day for 3 months. Numerical Validation was performed using Plaxis 8.2. In the finite element method, Sub-soil and embakment were modeled as elastic-plastic solid materials using the Mohr-Coulomb failure criteria. Galam timber micro pile were modeled as elastic-plastic anchor, geotextile were modeled as tensile element with tensile strength 55 kn/m. Observation record of settlement plate that reinforced with geotextile, conventional micro pile, and micro pile 15 0 inclination be obtained total settlement are 113 cm, 54 cm and 40 cm, respectively. Trial embankment that reinforced with micro pile 15 0 inclination has effectively increased stability at once reduced settlement 65 % compared with geotextile reinforcement. Results also show that Observation records and numerical analysis are relatively similar with deviation <5 0. Keywords Galam Timber, Settlement, Soft Clay, Soil Improvement, Inclined Micro Pile I. INTRODUCTION Kalimantan island has many lowland areas and there are many locations soft clay, soil condition very specific, sometimes contaminated with coal. The problem of construction on soft clay is the low bearing capacity and differential settlement, therefore need a innovation in soil improvement. Recently, many researchers conducted field observation of full-scale model (e.g. Falorca et al., 2011; Won and Kim, 2007; Hatami and Bathurst, 2005, 2006; Bergado et al., 1995, 2000, 2003; Ling and Leshchinsky, 2003; Varuso et al., 2005). Nunes et al. (2013) reported that the settlement efficacy of pile-supported embankment is a reliable parameter to assess the overall performance of the rigid inclusion technique. Construction materials very limited in Kalimantan, especially in East Kalimantan. Most of the material constructions for road construction were inforted from outside the Kalimantan island, causing a very high cost construction and the timing of the construction is very less. Kalimantan many plants Galam and live longer at the time submerged in swamp, so the author think the need for an Innovation Technology Applied by utilizing local materials as an alternative to soft ground improvement. II. RESEARCH METHOD This research is to conduct experimental supported by the literature that is closely to the subject matter. Soil sampling conducted by deep drill to 30 meters at coordinates X: '17.3 "E and Y: '14.0" S. Galam timber (Melalucea Lencadendron Linn) comes from South Kalimantan. All testing parameters conducted at Soil Mechanics Laboratory, Hasanuddin University. Experimental results Validated by finite element method using PLAXIS 8.2. Settlement of soil and embankment were modeled as solid material, galam timber were modeled as anchor, the behaviour of embankment and sub soil were modeled as elastic-plastic material. Geotextile were modelled as tensile element with tensile strength 55 kn/m. Line Yield were modeled as Mohr-Coulomb criteria using shear strength parameters (cohesion and angle friction), and then deformation were modeled by young modulus of soil. Spring to modeling galam timber use the elastic-plastic model. Spring plastic conditions calculated from the ultimate capacity a galam micro pile divided by settlemet estimate needed to mobilizing ultimate capacity of galam timber as micro pile. III. MATERIAL PROPERTIES A. Soil Layer Properties On-site were conducted resistivity test to identify subsurface. Test results show the thickness of soft soil up to 30 m. The results resistivity test is shown in Fig. 1. Furthermore, also conducted CPT (Cone Penetration Test until hard soil to a depth of 30 m, and the graph result are shown in Fig. 2. The soil samples were collected from the borehole at the site. The subsoil properties are presented in Table , IJIRAE- All Rights Reserved Page -85

2 Fig. 1 Soil profile Cone Resistance, qc (kg/cm²) Resistance Ratio, Rf (%) Depth (m) 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0 10,5 11,0 11,5 12,0 12,5 13,0 13,5 14,0 14,5 15,0 15,5 16,0 16,5 17,0 17,5 18,0 18,5 19,0 19,5 20,0 20,5 21,0 21,5 22,0 22,5 23,0 23,5 24,0 24,5 25,0 25,5 26,0 26,5 27,0 27,5 28,0 28,5 29,0 29,5 30,0 30,5 31, Total Resistance, Tf (kg/cm) qc (kg/cm²) Tf (kg/cm) Fig. 2 CPT graph , IJIRAE- All Rights Reserved Page -86 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0 10,5 11,0 11,5 12,0 12,5 13,0 13,5 14,0 14,5 15,0 15,5 16,0 16,5 17,0 17,5 18,0 18,5 19,0 19,5 20,0 20,5 21,0 21,5 22,0 22,5 23,0 23,5 24,0 24,5 25,0 25,5 26,0 26,5 27,0 27,5 28,0 28,5 29,0 29,5 30,0 30,5 31,

3 Soil Type Layer 1 (0,00-4,00) m Layer 2 (4,00-6,00) m Layer 3 (6,00-12,00) m TABLE I SOIL LAYER PROPERTIES Layer 4 (12,00-18,00) m Layer 5 (18,00-25,00) m B. Timber Pile Properties The properties of timber (galam) which is used as a pile are presented in Table 2. Layer 6 (25,00-30,00) m g unsat [kn/m³] ,5 19 g sat [kn/m³] 14,5 14, k x [m/day] 6,89E-04 6,89E-04 6,89E-04 6,89E-04 6,89E k y [m/day] 1,38E-03 1,38E-03 1,38E-03 1,38E-03 1,38E E [kn/m²] v [-] ,35 0,35 Cc [kn/m²] 0,9 0,9 0,85 0,6 0,4 - - Cs [kn/m²] 0,13 0,11 0,13 0,09 0, e 0 [-] 2,2 2,2 2 1,8 1,5 - - j [ ] , c [kn/m²] Fill TABLE II CHARACTERISTIC OF TIMBER (GALAM) Characteristic of Galam Value Water Content 22,95% Compressive Strength // 23,3 Mpa Compressive Strength 14,4 Mpa Tensile Strength 17,9 Mpa Bending Strength 101,4 Mpa IV. EMBANKMENT CONSTRUCTION Full-scale trial embankment conducted in three types i.e. reinforcement with geotextile, reinforcement with conventional micro pile, and reinforcement with micro pile 15 0 inclination. Each type have length of 20 m, width of 30 m, slope of 1.5 horizontal : 1 vertical, and height of 4.5 m. Field observations were conducted by installing a Settlement Plate for settlement monitoring, piezometers to monitor the pore water pressure depth of 3 meters, 6 meters, and 20 meters, and digital inclinometer depth of 30 meters to observed lateral movement. Field observations conducted every day for 3 months. A. Reinforcement with Geotextile Trial embankment reinforced with geotextile reinforcement were conducted by installing 3 layers geotextile, which height of each layer is 0,7 m. A typical trial embankment reinforced with geotextile as shown in Fig ,50 m ±0,00 m Settlement Plate Piezometer Selected Sand and Gravel Geotextile Inclinometer -3,00 m -6,00 m Soft Clay -20,00 m -30,00 m Fig. 3 Reinforcement with geotextile , IJIRAE- All Rights Reserved Page -87

4 B. Reinforcement with Conventional Micro Pile Trial embankment reinforced with conventional micro pile implemented by galam timber length of 6 meters at a distance of 1,00 m. Each a micro pile group were 3 rods galam timber 10 cm. A typical trial embankment reinforced with conventional micro pile as shown in Fig ,50 m Settlement Plate Piezometer Selected Sand and Gravel Geotextile Inclinometer ±0,00 m -3,00 m -6,00 m Soft Clay -20,00 m -30,00 m Fig. 4 Reinforcement with conventional micro pile C. Reinforcement with Inclined Micro Pile Trial embankment reinforced with inclined micro pile using material of galam timber 6 meters length at a distance of 1,20 m. Each a micro pile group were 3 rods galam timber 10 cm and driven 15 0 inclination. A typical trial embankment reinforced with inclined micro pile as shown in Fig ,50 m ±0,00 m Settlement Plate Piezometer Selected Sand and Gravel Geotextile Inclinometer d=10 d=10 cm -3,00 m Timber Pile Length of 6 m -6,00 m -20,00 m Soft Clay -30,00 m Fig. 5 Reinforcement with inclined micro pile V. RESULT AND ANALYSIS A. Field observations According to the settlement plate observation result, total settlement of geotextile reinforcement was found 1,13 m, total settlement of conventional micro pile reinforcement was found 0,54 m, and total settlement of inclined micro pile was found 0,40 m. Measured of settlement by leveling control to a fix benchmark. Geotextile reinforcement indicated very low bearing capacity to supporting trial embankment with 4,50 m height. The bearing capacity Reinforcement with inclined micro pile has effectively increased stability at once reduced settlement 65 % compared with geotextile reinforcement, whereas reinforcement with conventional micropile only able to reduce a settlement of 52% compared with geotextile reinforcement. Galam timber as micro pile can be distributed weight of embankment to deep layer that better bearing capacity. The result of total settlement (3 months) are shown in Fig , IJIRAE- All Rights Reserved Page -88

5 Lateral movement were conducted by digital inclinometer which is installed vertically at the edge of embankment. Lateral movement occurs to a depth of 12 m, due to condition of the sub-soil is very soft. Lateral movement phenomenon influenced by vertical displacement, condutivity effect with partial drainage conditions as shown in Fig Preload Height (cm) Elastic Settlement Consolidation Settlement Elastic Settlement Consolidation Settlement Settlement (cm) GEOTEXTILE CONVENTIONAL PILE INCLINED PILE TIME (DAY) Fig. 6 Summary of time versus settlement observations of inclined pile reinforcement Profil Change in mm Embankment very soft clay soft clay Geotextile Reinforcement Conventional Micro Pile Reinforcement Inclined Micro Pile Reinforcement Sand Fig. 7 Inclinometer record day , IJIRAE- All Rights Reserved Page -89

6 Based on the piezometer record, the pore water pressure increases with the increasing of depth. The excess pore water pressure occurred due to embankment weight. pore There is no significant change of the amount of pore water pressure among the types of reinforcement as shown in Fig Stage 4 (+4,5) PRELOAD HEIGHT (M) Stage 1 (+1,2) Stage 2 (+1,5) Stage 3 (+3,0) Fig. 8 Piezometer record B. Numerical Validation Numerical analysis was conducted to predicted the total settlement during preloading. The effectiveness of the micro pile 15 inclination to reduced the settlement can be known by compared to the method with geotextile reinforcement and conventional micro pile reinforcement. Analysis was carried until 3 months. Total settlement for trial embankment reinforced with micro pile 15 inclination was found 0,47 m. Trial embankment reinforced with conventional micro pile obtained predicted settlement by 1,25 m. Trial embankment reinforced with conventional pile was found 0,60 m. The result of numerical analysis shows the trial embankment reinforced with micropile 15 inclination with a length of 6 meters and a distance of 1.20 meter installation can reduce the settlement about 60 % with when compared with geotextile reinforcement. While the trial embankment reinforced with conventional micropile with a length of 6 meters can reduce the settlement until > 50 % with a distance of 1,00 meter installation when compared with geotextile reinforcement. Comparison of the results between settlement plate record and numerical analysis is quite similar are shown in Fig. 9 and Table , IJIRAE- All Rights Reserved Page -90

7 Numerical Analysis (m) (a). Geotextile Numerical Analysis (m) (b) Conventional Micro Pile Numerical Analysis (m) (c). Inclined Micro Pile Settlement Record Settlement Record (m) Settlement Record (m) Fig. 9 Result comparison between settlement record and numerical analysis No Reinforcement Type TABLE III RESULT COMPARISON BETWEEN SETTLEMENT RECORD AND NUMERICAL ANALYSIS Total Settlement (m) Settlement Reduced Compared Geotextile Reinforcement Settlement Plate Record Numerical analysis Settlement Record Numerical analysis 1 Geotextile 1,13 1,25-2 Micropile upright 0,54 0,60 >50% >50% 3 Micropile (15 0 ) 0,40 0,46 >60% >60% VI. CONCLUSION The results of numerical analysis, it can be concluded as follows: 1. Galam Micropile 15 more effective to reduce settlement compared to Galam micropile upright reinforcement and geotextile reinforcement. 2. From the comparison between Galam Micropile 15 and galam micropile upright was obtained that Galam Micropile 15 effectively reduce settlement of> 60% with a distance of 1.20 meters and micropile upright can be reduce settlement of > 50% with a distance of 1.00 meters. This suggests the potential use of this type of construction to be applied to very large soft soil deposits are sufficient thick. REFERENCES [1] Bergado, D.T., Chai, J.C., Miura, N., FE analysis of grid reinforced embankment system on soft Bangkok clay. Computers and Geotechnics 17: [2] Bergado, D.T., Teerawattanasuk, C., Youwai, S., Voottipruex, P., FE modelling of hexagonal wire reinforced embankment on soft clay. Canadian Geotechnical Journal 37 (6): [3] Bergado, D.T., Youwai, S., Teerawattanasuk, C., Teerawattanasuk, C., Visudmedanukul, P., The interaction mechanism and behaviour of hexagonal wire mesh reinforced embankment with silty sand backfill on soft clay. Computers and Geotechnics 30: [4] Falorca, I., Gomes, L. and Pinto, M., A full-scale trial embankment construction with soil reinforced with short randomly distributed polypropylene microfibers. Geosynthetics International, 18(5): 280. [5] Hatami, K., Bathurst, R.J., Development and verivication of a numerical model for the analysis of geosynthetic-reinforced soil segmental walls under working stress conditions. Canadian Geotechnical Journal 42: [6] Hatami, K., Bathurst., R.J., Numerical model for reinforced soil segmental walls under surcharge loading. Journal of Geotechnical and Geoenviromental Engineering, ASCE 136 (6): [7] Ling, H.I., Leshchinsky, D., Finite element parametric study of the behaviour of segmental block reinforced soil retaining walls. Geosynthetics International 10 (3): [8] Nunez, M. A., Briancon, L. and Dias, D, Analyses of a pile-supported embankment over soft clay: Full- scale experiment, analytical ans numerical approaches. Engineering Geology, 153: [9] Varuso, R.J., Grieshaber, J.B., Nataraj, M.S., Geosynthetic reinforced levee test section on soft normally consolidated clay. Geotextiles and Geomembranes 23 (4): [10] Won, M.S., Kim, Y.S., Internal deformation behaviour of geosynthetics-reinforced soil walls. Geotextile and Geomembranes 25 (1): , IJIRAE- All Rights Reserved Page -91