scholarly journals Geotechnical Engineering Properties of Soils Solidified by Microbially Induced CaCO3 Precipitation (MICP)

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Jia Liu ◽  
Gang Li ◽  
Xi’an Li
Keyword(s):  
Ground Improvement ◽  
Geotechnical Engineering ◽  
Solution Concentration ◽  
Engineering Properties ◽  
Soil Restoration ◽  
Calcium Carbonate Precipitation ◽  
Liquefaction Resistance ◽  
Sand Liquefaction ◽  
Other Substances ◽  
Research Findings

Microbially induced calcium carbonate precipitation (MICP) uses the metabolic function of microbes to carry out biochemical reactions with other substances in the environment. Through the controlled growth of inorganic minerals, soil particles are cemented and soil pores are filled to solidify the soil and reduce its permeability. Thus, the application of this technology was foreseen in geotechnical engineering and environment (building antiseepage, contaminated soil restoration, slope soil erosion, and sand liquefaction). In this review article, based on current research findings, the urea hydrolysis and the cementation mechanism of MICP are briefly described. The influences of factors such as enzyme activity, cementation solution concentration, pH, temperature, grouting method, and particle size on MICP-treated soil are discussed. The engineering properties of MICP-treated soils are evaluated, for instance, the strength, stiffness, liquefaction resistance, permeability, and durability. The applications of MICP technology in ground improvement, geotechnical seepage control, foundation erosion resistance, and fixation of heavy metals are summarized. Finally, future directions of the development of MICP technology are elucidated to provide a reference and guidance for the promotion of MICP technology in the geotechnical engineering field.

scholarly journals Microbial healing of nature-like rough sandstone fractures for rock weathering mitigation

2022 ◽  
Author(s):  
Zhi-Hao Dong ◽  
Xiaohua Pan ◽  
Chao-Sheng Tang ◽  
Bin Shi
Keyword(s):  
Fracture Healing ◽  
Injection Pressure ◽  
Solution Concentration ◽  
Fracture Aperture ◽  
Rock Weathering ◽  
Calcium Carbonate Precipitation ◽  
High Fracture ◽  
Injection Strategy ◽  
Healing Efficiency ◽  
Fracture Transmissivity

Abstract Rock weathering fractures in nature are complex and fracture healing is an effective strategy for rock weathering mitigation. This study is a first attempt to apply microbially induced calcium carbonate precipitation (MICP) technology in the healing of nature-weathering-like rough fractures (NWLRF). Sandstone was studied as an example due to it is a wide-spread construction, sculpture and monuments material all over the world. In order to achieve a high healing efficiency, a repeated mixture injection strategy was proposed. Based on a series of laboratory MICP injection experiments on four types of NWLRF, we systematically explored the fundamental micro-healing mechanism and the influence of factors including fracture aperture, characteristics of branch fractures, and cementation solution concentration. Experimental results demonstrated that MICP healing with the repeated mixture injection strategy had the ability to efficiently heal the penetrated NWLRF well with length in centimeter-scale and aperture in millimeter-scale, but cannot heal the non-penetrated branch fractures under low injection pressure. The repeated mixture injection strategy furtherly achieved a high apparent fracture healing ratio and a significant reduction of transmissivity. The apparent fracture healing ratios of all main fractures were higher than 80% and the maximum was 99.1%. Fracture transmissivity was reduced by at least three orders of magnitude from about 1×10-4 m2/s to less than 1×10-7 m2/s, and the highest reduction reached to four orders. For the aspect of the effects, larger cementation solution concentration, finer aperture and the existing of penetrated branch fracture were beneficial to improve the healing effect. Moreover, the MICP healing mechanism with high fracture healing ratio and significant reduction of transmissivity on sandstone NWLRF was also analyzed. The research results have important theoretical significance and technical guidance value for the disaster prevention and mitigation of rock weathering.

scholarly journals Feasibility Study of Native Ureolytic Bacteria for Biocementation Towards Coastal Erosion Protection by MICP Method

2019 ◽  
Vol 9 (20) ◽  
pp. 4462 ◽  
Author(s):  
Md Imran ◽  
Shuya Kimura ◽  
Kazunori Nakashima ◽  
Niki Evelpidou ◽  
Satoru Kawasaki
Keyword(s):  
Coastal Erosion ◽  
Urease Activity ◽  
Ground Improvement ◽  
Soil Improvement ◽  
Engineering Properties ◽  
Culture Solution ◽  
Precipitation Trend ◽  
Mediterranean Countries ◽  
Erosion Protection ◽  
Ureolytic Bacteria

In recent years, traditional material for coastal erosion protection has become very expensive and not sustainable and eco-friendly for the long term. As an alternative countermeasure, this study focused on a sustainable biological ground improvement technique that can be utilized as an option for improving the mechanical and geotechnical engineering properties of soil by the microbially induced carbonate precipitation (MICP) technique considering native ureolytic bacteria. To protect coastal erosion, an innovative and sustainable strategy was proposed in this study by means of combing geotube and the MICP method. For a successful sand solidification, the urease activity, environmental factors, urease distribution, and calcite precipitation trend, among others, have been investigated using the isolated native strains. Our results revealed that urease activity of the identified strains denoted as G1 (Micrococcus sp.), G2 (Pseudoalteromonas sp.), and G3 (Virgibacillus sp.) relied on environment-specific parameters and, additionally, urease was not discharged in the culture solution but would discharge in and/or on the bacterial cell, and the fluid of the cells showed urease activity. Moreover, we successfully obtained solidified sand bearing UCS (Unconfined Compressive Strength) up to 1.8 MPa. We also proposed a novel sustainable approach for field implementation in a combination of geotube and MICP for coastal erosion protection that is cheaper, energy-saving, eco-friendly, and sustainable for Mediterranean countries, as well as for bio-mediated soil improvement.

Confining stress and static shear effects in cyclic liquefaction

2001 ◽  
Vol 38 (3) ◽  
pp. 580-591 ◽  
Author(s):  
Y P Vaid ◽  
J D Stedman ◽  
S Sivathayalan
Keyword(s):  
Initial Density ◽  
Confining Pressure ◽  
Empirical Method ◽  
Shear Stresses ◽  
Confining Stress ◽  
Liquefaction Resistance ◽  
Sand Liquefaction ◽  
Cyclic Resistance ◽  
Cyclic Resistance Ratio ◽  
Static Shear

Liquefaction resistance of a sand under cyclic loading is assessed and the effects of the levels of confining pressure and static shear on resistance to liquefaction are investigated. Site-specific values of the resistance under specified levels of confining and static shear stresses are measured in the laboratory. The measured values are compared with those which would be predicted by the application of empirical multiplying factors Kσ and Kα to the reference resistance at 100 kPa effective confining stress with no static shear. It is shown that Kσ and Kα are not independent, as assumed in current practice. The combined factor Kσ × Kα resulting from the empirical method is shown to underestimate the cyclic resistance ratio regardless of the initial density and confining and static shear levels. The degree of conservatism is most dramatic at looser density states.Key words: sand, liquefaction, static, cyclic, static shear, confining stress.

scholarly journals Vertical ground motion and its effects on liquefaction resistance of fully saturated sand deposits

2016 ◽  
Vol 472 (2192) ◽  
pp. 20160434 ◽  
Author(s):  
Vasiliki Tsaparli ◽  
Stavroula Kontoe ◽  
David M. G. Taborda ◽  
David M. Potts
Keyword(s):  
Vertical Component ◽  
Vertical Motion ◽  
Soil Liquefaction ◽  
Elastic Response ◽  
Saturated Sand ◽  
Liquefaction Resistance ◽  
Sand Liquefaction ◽  
Variable Permeability ◽  
Lower Amplitude ◽  
Input Motion

Soil liquefaction has been extensively investigated over the years with the aim to understand its fundamental mechanism and successfully remediate it. Despite the multi-directional nature of earthquakes, the vertical seismic component is largely neglected, as it is traditionally considered to be of much lower amplitude than the components in the horizontal plane. The 2010–2011 Canterbury earthquake sequence in New Zealand is a prime example that vertical accelerations can be of significant magnitude, with peak amplitudes well exceeding their horizontal counterparts. As research on this topic is very limited, there is an emerging need for a more thorough investigation of the vertical motion and its effect on soil liquefaction. As such, throughout this study, uni- and bidirectional finite-element analyses are carried out focusing on the influence of the input vertical motion on sand liquefaction. The effects of the frequency content of the input motion, of the depth of the deposit and of the hydraulic regime, using variable permeability, are investigated and exhaustively discussed. The results indicate that the usual assumption of linear elastic response when compressional waves propagate in a fully saturated sand deposit does not always hold true. Most importantly post-liquefaction settlements appear to be increased when the vertical component is included in the analysis.

Nanotechnology in Geotechnical Engineering

2011 ◽  
Vol 261-263 ◽  
pp. 524-528 ◽  
Author(s):  
Marzieh Kadivar ◽  
Kazem Barkhordari ◽  
Mehdi Kadivar
Keyword(s):  
Geotechnical Engineering ◽  
Engineering Properties ◽  
Index Properties ◽  
Recent Advances ◽  
Electron Microscopes ◽  
Geotechnical Studies ◽  
Properties Of Soil

The present paper reviews the application of nanotechnology in geotechnical engineering, in which the concept of nanotechnology as well as the new concept of nanosol is explained. We have also given explanation for nanometer additives used in the introduced soil, different forms of nanoparticles, their specific properties, and effects of these nanoparticles on engineering properties of soil including index properties and strength, and analyzed the reasons through which these effects are caused. Furthermore, influence of recent advances in nanoinstruments and electron microscopes as well as their application in geotechnical studies.

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