Improvement of Organic Soil Shear Strength through Calcite Precipitation Method Using Soybeans as Bio-Catalyst

Heriansyah Putra,Minson Simatupang,Dede Heri Yuli Yanto,Sutoyo Sutoyo,Erizal Erizal

doi:10.3390/cryst11091044

Heriansyah Putra, Minson Simatupang + Show 3 more

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https://doi.org/10.3390/cryst11091044

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Abstract

Organic soil has a high content of water and compressibility. Besides that, it has a low specific gravity, density, and shear strength. This study evaluates the applicability of the soybean crude urease for calcite precipitation (SCU-CP) method and its effectiveness in organic soil as a soil-amelioration technique. Various soybean concentrations were mixed with a reagent composed of urea and calcium chloride to produce the treatment solution. Its effect on the hydrolysis rate, pH, and amount of precipitated calcite was evaluated through test-tube experiments. SEM-EDS tests were performed to observe the mineralogy and morphology of the untreated and treated samples. The treatment solution composed of the reagent and various concentrations of soybeans was applied to organic soil. The increasing strength of the organic soil was evaluated using direct shear (DS) and unconfined compression (UCS) tests. The test-tube results show that a hydrolysis rate of 1600 u/g was obtained when using 50 g/L of soybeans with a precipitation ratio of 100%. The mechanical tests show a significant enhancement in the parameters of the organic soil’s shear strength. A shear strength improvement of 50% was achieved in this study. A UCS of 148 kPa and cohesion of 50 kPa was obtained in the treated samples of organic soil. This research elucidates that the SCU-CP is an effective technique for improving organic soil’s shear strength.

Highlights

Organic soil has high compressibility, high saturation, low density, and low shear strength, resulting in massive and long-term deformation [1,2]
The soybean crude urease for calcite precipitation (SCU-calcite precipitation (CP)) method was evaluated for its effectiveness as a soil-enhancement technique
The hydrolysis-rated results confirm that the urease activity was linearly related to the increase in soybean concentration

Summary

Introduction

Organic soil has high compressibility, high saturation, low density, and low shear strength, resulting in massive and long-term deformation [1,2]. These characteristics bring about certain problems and limitations for the development of civil structures, especially in the geotechnical field. The EICP method has been stated to be able to significantly ameliorate both the shear and the unconfined compressive strength of the soil. They range from 50 kPa to 1.6 MPa [19,20,23,24,25].

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