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• The stress-induced damage of cemented paste backfill (CPB) is defined. • The influence of damage and initial pH on the metal leaching behavior is presented. • The pH and conductivity of the leachate increase with the increasing damage of CPB. • The release process of metallic elements in CPB is divided into three stages. • The release rate of metallic elements is described by Kinetic equations. Cemented paste backfill (CPB) is generally considered environmentally friendly when used in mining operations. However, the combination of geological stresses and groundwater seepage in an underground environment may cause the metallic elements contained in CPB to escape confined areas and potentially pollute the external environment. In this paper, geological stress-induced damage to CPB and the initial pH levels of the surrounding environment are assessed to determine their influences on the metal leaching behavior of CPB. Research methods used in the analysis include component characterization, static leaching tests, and kinetic theory analysis. The research results show that: as damage to CPB increased, both the pH and conductivity of the leachate increased, while the concentration of metallic elements in the leachate also increased except for aluminum (Al). Different metallic elements showed various leaching behaviors as the initial pH of the leaching solution increased. The release process of metallic elements from CPB can be segmented into three separate stages: the surface release stage, the internal release stage, and the adsorption and precipitation stage. Kinetic equations are obtained to describe the release rate of metallic elements. The leaching process is a dynamic equilibrium system formed by the release, absorption, and precipitation of metallic elements in the leachate. This research provides data for the evaluation of environmental effects on CPB. [ABSTRACT FROM AUTHOR]

• Microbial Mixed Backfill (MMB) is presented. • The influence of various factors on the mechanical properties of MMB is studied. • Different crystal morphologies of CaCO 3 observed in MMB samples. • The larger number and denser distribution of CaCO 3 crystals, the higher strength. • The strength of MMB is attributed to both the CaCO 3 and salt materials. Cemented backfill mining is an important technology utilized in sustainable mining practices and is fundamental in a wide variety of underground settings. However, the cement-based binder commonly used in cemented backfill materials comes at high costs, is highly alkaline, has high energy consumption, and has high carbon dioxide emissions. As an environmentally friendly technology, microbial induced carbonate precipitation (MICP) technology can produce a variety of cementitious mineral crystals to consolidate otherwise loose materials. In this paper, the MICP technology is used to replace the traditional cement-based binder frequently used in backfill mining, and the microbial mixed backfill (MMB) method is presented. The influences of various factors on the mechanical properties of MMB are also studied. It is found that the strength of MMB samples increases at first, and then decreases, when the cementation solution concentration and the volume ratio of bacterial solution to cementation solution are increased. Solids content is also an important factor that directly affects the strength of MMB samples. However, there was no obvious relationship discovered between strength variation and the total enzyme activity. In addition, different crystal morphologies of calcium carbonate, including calcite and vaterite, are observed in MMB samples. The greater the number and the denser the distribution of calcium carbonate crystals produced in the MICP reaction, the higher the strength of the MMB samples. The strength of MMB is attributed to both the amount of precipitated calcium carbonate by MICP, and the dosage of salt materials contained in the cementation solution. This research can provide basic scientific support for the application of microbial backfilling in the mining field. [ABSTRACT FROM AUTHOR]