THE INFLUENCE OF INJECTION CONDITIONS AND SOIL TYPES ON SOIL IMPROVEMENT BY MICROBIAL FUNCTIONS Y. Inagaki 1 , M. Tsukamoto 2 , H. Mori 3 , T. Sasaki 4 , K. Soga 5 , Ph. D, A. Al. Qabany 6 ,and T. Hata 7 , Ph. D 1 Soil Mechanics and Dynamics Research Team, Material and Geotechnical Engineering Group, Public Works Research Institute, Japan, 1-6 Minamihara, Tsukuba, Ibaraki 305-8516, Japan; PH＋81-29-879-6771; FAX +81-29-879-6735; email: y-inaga@pwri.go.jp 2 As above; email: m-tsuka44@pwri.go.jp 3 As above; email: hi-mori@pwri.go.jp 4 As above; email: t-sasaki@pwri.go.jp 5 University of Cambridge Department of Engineering Geotechnical Research Group, Trumpingon Street, Cambridge CB2 1PZ UK; PH +44(0)1223766683; FAX +44(0)1223339713; email: ks207@cam.ac.uk 6 As above; email: aaaa2@cam.ac.uk 7 Nagano National College of Technology, Department of Civil Engineering, 716 Tokuma, Nagano City, Nagano Prefecture, 381-8550, Japan; PH＋81-26-295-7096; FAX +81-26-295-7096; email: t_hata@eu.nagano-nct.ac.jp ABSTRACT: Research has begun on Microbial Carbonate Precipitation (MCP), which shows promise as a soil improvement method because of its low carbon dioxide emission compared to cement stabilized agents. MCP produces calcium carbonate from carbonates and calcium in soil voids through ureolysis by “Bacillus Pasteurii”. This study focuses on how the amount of calcium carbonate precipitation is affected by the injection conditions of the microorganism and nutrient salt, such as the number of injections and the soil type. Experiments were conducted to simulate soil improvement by bio-grouting soil in a syringe. The results indicate that the amount of precipitation is affected by injection conditions and soil type, suggesting that, in order for soil improvement by MCP to be effective, it is necessary to set injection conditions that are in accordance with the soil conditions. KEY WORDS: soil improvement, microbial functions, nutrient salt, Microbial Carbonate Precipitation INTRODUCTION As, for example, Victoria S. Wiffen and others suggest, one method of ground improvement is soil solidification through the precipitation of calcium carbonate that results from the reaction between the carbon dioxide generated from microbial metabolism and calcium sources in the voids of the soil (Microbial 4021 Geo-Frontiers 2011 © ASCE 2011 Geo-Frontiers 2011 Downloaded from ascelibrary.org by Iowa State University on 01/01/15. Copyright ASCE. For personal use only; all rights reserved.