Abstract
The silty clay in the lower reaches of the Yellow River is characterized by loose structure, low strength, and strong capillary effect. Based on the technology of ancient glutinous rice mortar and microbial-induced calcium carbonate precipitation (MICP), experiments on optimal mass ratio of cementitious liquid to bacterial liquid and optimal concentration of cementitious liquid for MICP and improved MICP technology were carried out by measuring the production of CaCO3, and direct shear test and unconfined compressive strength test of plain silt, glutinous mixing silt, and improved silt with MICP and modified MICP were conducted. The microstructure of the reaction products of MICP and improved MICP technology were also evaluated based on scanning electron microscopy (SEM). Research results showed that the mechanical properties of silt with glutinous rice slurry were effectively improved. With the increase in the concentration of glutinous rice slurry, the strength and internal friction angle of soil samples first increased and then decreased, and the cohesion presented a linear increasing trend. When the concentration of cementitious liquid was 0.5 M and the mass ratio of cementitious liquid to bacterial liquid was 2 : 1, the amount of CaCO3 formed was the most, and the conversion rate of Ca2+ was more than 80%. The improved MICP could increase the conversion rate of Ca2+ (93.44%). An improved MICP showed that glutinous rice slurry could improve bacterial activity, increase the urease content in the bacterial solution, and promote the production of CaCO3. Silt cohesion and internal friction angle of the silt were improved by the improved MICP technology, and the strengthening effect of mechanical properties of modified MICP-reinforced soil is better than that of the MICP-reinforced soil; conventional MICP technology could also improve the soil cohesion, but the improvement in the internal friction angle was not obvious. The SEM results indicated that compared with the reaction product of MICP technology, the structure of the product of improved MICP technology is more compact, resulting in a marked reinforcement of MICP performance with glutinous rice slurry. This study provides new insights into enhancing the mechanical behaviour of MICP-treated silt in the Yellow River Basin with glutinous rice slurry.
Highlights
Soil stabilization or soil strengthening is the process whereby soils are made stronger and more durable
Puyang City soil is mostly silt soil formed by the Yellow River flood and alluvial with poor water stability, strong water capillary effect, high strength when dry, but significantly reduced when wet [31]. e bearing capacity characteristic value of foundation soil before and after improvement is calculated with regard to the code for design of building foundation [32]. e basic physical properties of the soil used in this study are shown in Table 1. e basic physical property indexes of the research soil were measured according to the standard for the geotechnical testing method (GB/T 501232019) [33]. e grain size distribution of the site soil is presented in Figure 1, which are analysed through the particle grading test
Based on the technology of the glutinous rice mortar and the principle of biomineralization, experiments on improved silt with glutinous rice slurry, improved microbial-induced calcium carbonate precipitation (MICP) with glutinous rice slurry, and improved silt with modified MICP were carried out, and the improvement of mechanical properties of silt by modified MICP was studied. e main conclusions are summarized as follows: (1) e mechanical properties and microstructure of Yellow River silt with glutinous rice slurry were studied
Summary
Soil stabilization or soil strengthening is the process whereby soils are made stronger and more durable. Biological, or chemical methods can be used. Cement has been widely used in foundation treatment for a long time [1]. The demand for alternative materials to cement is increasing because of its contribution to CO2, SO2, and NOx emission during production processes [2]. E environmental problems related to chemical or traditional soil additives were summarized by Al-Bared et al [3]. More studies were provided on stabilizing soils using. Advances in Materials Science and Engineering environmentally friendly materials. Ere are humongous amounts of bacteria in soil, which generate various biochemical products such as biofilms, various gases (e.g., N2, CO2, NO, H2, and H2S), biopolymers, or biominerals Several innovative and sustainable green soil improvement techniques were introduced for geotechnical applications [4]. ere are humongous amounts of bacteria in soil, which generate various biochemical products such as biofilms, various gases (e.g., N2, CO2, NO, H2, and H2S), biopolymers, or biominerals
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