EXPERIMENTAL STUDY OF SANDY CLAY REINFORCED BY GROUTED SAND COLUMN Authors: Lawalenna Samang A.B. Muhiddin, A. Arsyad, R. Abdullah, and N. Dhani PAPER ID: GE58 DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY 9 th International Symposium on Lowland Technology September 29 – October 1, 2014 in Saga, Japan

PRESENTATION OUTLINE  INTRODUCTION  RESEARCH METHODLOGY  RESULTS AND DISCUSSION  CONCLUSION DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

INTRODUCTION  The ground condition in Indonesia largely comprises of soft soil such as peat, soft clay, and peat over soft clay Map of Soil Characteristic Distribution in Indonesia DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

INTRODUCTION  Due to the increasing demand of land use, it is inevitable to avoid the construction of infrastructure on the soft soil.  Soft soil is commonly known as type of soil which has low bearing capacity and high sensitivity. This leads to the ground deformation which directly causes potential damage to the structure above the ground. This may lead to the formation of crack to the building, road construction and many more. It is commonly observed that after the placement of road embankment, the ground deforms and follows the pattern of local shear failure which basically suggest that the heaving occurs.  The ground may deform vertically and horizontally. It is expected to reduce both types of deformation to minimize the potential damage towards the infrastructure in the future. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

INTRODUCTION  In order to deal and solve the problem, it is proposed to conduct a research to analyze and observe the efficacy of grouted soil cement column to minimize the displacement occurred on the embankment.  Deep mixing of cement with soil and water, normally forming soil-cement columns in situ, is a widely used soft ground improvement (e.g., Broms and Boman 1979; Bergado et al. 1994).  Compressive strength of grouted soil-cement column characteristic which are: 1. Compressive Strength, 2. Stress, Strain, and 3. Elastic Moduli are significant to analyze the strength of soil-cement column to hold the magnitude of the soil pressure vertically or horizontally which located on the subgrade layer of the ground. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

INTRODUCTION  Soft ground improvement is commonly undertaken by grouting technique and deep mixing.  Relevant Past Researches: 1. Model test on granular soil columns for ground improvement of very soft soil was developed by Rackwitz et al (2010). 2. Reinforced granular column for deep soil stabilization was also investigated by Tandel et al. (2012) who developed granular column wrapped with Geosynthetic. 3. Settlement evaluation of soft clay reinforced by stone columns with considering the effect of soil compaction was examined by Zahmatkesh et al (2010).  The performance of sand column is still necessary to be evaluated particularly for sandy clay. This study evaluated the performance of grouted sand column in sandy clay by conducting experimental tests and numerical modeling for results validation. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

Testing Apparatus DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY RESEARCH METHODOLOGY

 Experimental model was conducted by setting a soil model with a grouted sand column. Four models were set up with different depth of sand column.  Cylinder box with 500 mm high and 600 mm in diameter was filled with sandy clay soil, compacted until a certain degree of compaction density.  A sand column with a 100 mm diameter was grouted into the soil as reinforcement.  Bearing plate was set on the top of the sand column and then the plate was subjected to a hydraulic jack as a load. Four dial gauges were installed in the soil  Gauge 1 was set on top of bearing plate to read bearing capacity and deformation pattern, and gauges 2, 3, and 4 were set in between the edge of soil model and sand column, to read deformation DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

 First test was conducted on the soil model without reinforcement of sand column. After that, the model was deconstructed and the soil was later used for the soil model with reinforcement of sand column with the penetrated depth of 200, 300, and 400 mm.  Bearing plate was on the top of grouted sand column and then hydraulic jack was applied on the bearing plate. Dial gauges were set to read ultimate load and settlements pattern in the soil model surface.  Physical properties of the soil model were also investigated: water content, specific gravity, gradation, and atterberg limit. Meanwhile, mechanical properties were also investigated in a compaction test, unconfined test, and direct shear test.  The obtained soil parameters were then used for numerical modeling with PLAXIS 2D and 3D DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY RESEARCH METHODOLOGY

RESULTS AND DISCUSSION  Soils Properties Soil index properties represent 43.4% water content, 2.7 specific gravity, 57.5% of the soil passing sieve No. 200, 46% Liquid Limit, 32% Plastic Limit, Plasticity Index of 14% and Shrinkage Limit of 16%. The density of the soil is 16.6 kN/m 3. Proctor standard test confirmed the optimum water content is 36% with the dry density of 13.3 kN/m 3. Direct shear test revealed that shear angle is 11.31° and cohesion is 19 kPa. Unconfined pressure test showed that q u is 225 kPa at a strain of 2.0 % and modulus elastisity of 5556 kPa. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

RESULTS AND DISCUSSION  Grouted Sand Column The water content is 28.32% and specific gravity is Sieve analysis showed 40% fine grain and 60% coarse grain. The dry density is 17 kN/m 3 and optimum water content is 10.25%. Unconfined pressure test revealed that q u is 300 kPa, with a 0.5 % strain and modulus elasticity of 7500 kPa. Direct shear showed that shear angle is 38.66° and cohesion is 18 kPa. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

RESULTS AND DISCUSSION  Experimental model test showed that the soil model without reinforcement of sand column possess a settlement of mm at ultimate load of 20.0 kN. The percentage of the settlement was found to be % of the soil model height. The reinforced soil model with a 30 cm sand column yielded a mm settlement with ultimate load of 60.0 kN or the settlement is 5.02%.  The result of reinforced soil model with 200 mm sand column showed that the settlement is mm at ultimate load at 47.5 kN. The settlement was accounted for 9.04 % of the total height of soil model. The reinforced soil model with a 400 mm sand column possess a 9.98 mm settlement or 1.99 % settlement and the ultimate load is 65 kN DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

RESULTS AND DISCUSSION  Experimental Results bearing plate 100 mm bearing plate 200 mm DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY  Numerical Analysis

It can be seen that the heaving of approximately 10cm is recorded with the application 20 kN Load. Typical Experimental Results for Radial Measurements (without column reinforcement) – Plate bearing 10cm DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

With the same amount of applied load, the recorded heaving is much lower with the column reinforcement. This indicates that column reinforcement managed to reduce the effect of heaving. Albeit the efficacy, the larger heaving is recorded if the load is increased twice. Typical Experimental Results for Radial Measurements (with grouted column reinforcement) – Plate bearing of 10 cm DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

NUMERICAL ANALYSIS (RECAP) DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

RESULTS AND DISCUSSION  Numerical results using PLAXIS 2D with soil without sand column reinforcement revealed that large settlement is yielded at mm with ultimate load of 20 kN and mm for 3D analysis. For a 200 mm bearing plate, the settlements are mm and mm with ultimate load of 40 kN.  For numerical analysis of reinforced sandy clay with a 200 mm sand column depth and bearing plate of 100 mm, the settlements are mm and mm.  In the case of a 300 mm sand column penetration, the settlements are mm and mm with ultimate load of 60 kN. In the reinforced sandy clay with a 400 mm sand column, a 100 mm bearing plate yielded the settlements of 9.62 mm (2D-FEM), and mm (3D-FEM) with ultimate load of 65 kN. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

RESULTS AND DISCUSSION  The settlements were mm (2D-FEM) and mm (3D-FEM), for the ultimate load of 65 kN with 300 mm bearing plate. Whereas the settlements of 7.57 mm (2D-FEM) and 7.56 mm (3D-FEM) at ultimate load of 70 kN with 400 mm bearing plate  It can be justified that the results of experimental model provide a well agreement with numerical modeling findings. Sand column increases the bearing capacity of the soil, and reduces the settlement due to the load applied. The deeper sand column grouted into the soil, the smaller settlement yielded and larger ultimate load can be supported.  However, the results based on PLAXIS 3D reveals more excessive settlement compared to that of using PLAXIS 2D. This is expected as PLAXIS 2D may underestimate the calculated settlement. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

CONCLUSIONS  Sandy clay without sand column reinforcement cannot support large ultimate load and prone to yield excessive settlement  The reinforcement of sand column could enhance the ultimate load of sandy clay with lower settlement yielded  The deeper sand column grouted into the sand clay soil, the lower settlement yielded and the larger ultimate load supported  The results based on numerical analysis using PLAXIS 2D have well agreement with the results obtained from experimental tests. Results of PLAXIS 3D reveals more excessive settlement compared to that of using PLAXIS 2D. Even though the results from PLAXIS 2D can be accepted, PLAXIS 3D provides more realistic settlement calculation thus the results are more representative. DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY

DEPARTMENT OF CIVIL ENGINEERING FACULTY OF ENGINEERING HASANUDDIN UNIVERSITY