Experimental study on the reinforcement mechanism and wave thumping resistance of EICP reinforced sand slopes

Sand slope is an important part of coastal zone and islands,which is severely affected by wave erosion and causes problems such as degradation of coastal zone and reduction of island area.Enzyme-induced calcium carbonate precipitation(EICP)technology is a new reinforcement technology with environmental friendly and excellent effect,which has been widely studied in the field of geotechnical engineering in recent years.In this research,we focus on the coastal or reef sand slopes in marine environments.The EICP reinforcement of representative sand slope units and large scale flume wave thumping experimental study are conducted indoors.By analyzing the physical and mechanical properties,erosion resistance,and microstructure of EICP-reinforced sand slopes,the mechanism of EICP reinforced sand slopes is revealed,the feasibility of EICP reinforced sand slopes is confirmed,and a feasible solution for EICP reinforced sand slopes is finally obtained.Results show that:(1)EICP reinforcement effectively enhances the surface strength and erosion resistance of sand slopes.Higher calcium carbonate content in the sand slopes corresponds to greater surface strength and improved erosion resistance.When the calcium carbonate content is similar,using low-concentration reinforcement twice is more advantageous than using high-concentration reinforcement once due to its superior uniformity.(2)The intensity of waves,the angle of the sand slope,and the severity of erosion damage are interrelated.Higher wave intensity,steeper sand slope angles,and more serious erosion damage require stronger reinforcement measures.(3)Scanning Electron Microscope(SEM)image analysis reveals that the reinforcing effect of sand slopes primarily depends on the amount of calcium carbonate crystals cemented between sand particles.A higher content of calcium carbonate crystals leads to better erosion resistance in the sand slope.

Fracture sealing based on microbially induced carbonate precipitation and its engineering applications:A review

In this review,the development and application of microbially induced carbonate precipitation(MICP)technology for the sealing of underground engineering fractures are discussed in detail.The importance of sealing micro-fractures in an environmentally friendly and efficient manner is emphasized,and the potential of the MICP method in controlling pore and fracture seepage is highlighted.The fundamental mechanisms,key influencing factors,numerical models,and applications of the MICP in the fields of geological CO_(2) storage and oil resources development are comprehensively summarized in the paper.At the same time,the limitations of the existing research and the future research directions are discussed,especially in terms of improving the processing efficiency,environmental impacts,and cost considerations.Overall,the development of MICP technology provides a new environmentally friendly reinforcement method for geotechnical engineering and is expected to play a key role in the future development of underground space engineering.

Stability analysis of tunnel under coal seam goaf:Numerical and physical modeling

The goaf formed by coal seam mining would dramatically reduce the strength and stiffness of the ground in and around the goaf,which is not conducive to tunnel excavation near the mined-out area.By establishing the Finite differential method and Discrete element method coupling numerical analysis method and conducting similar model test,the influence of dip angle,thickness and distance of coal seam goaf on the stability of unsupported tunnel excavation is studied.The results show that when the tunnel under the goaf is exca-vated,the circumferential stress increment increases first and then decreases along the radial direction of the tunnel,the radial stress increment gradually decreases to zero along the radial direction of the tunnel,the displacement is approximately distributed in a trough shape,and the maximum displacement is at the top of the tunnel.The area of the stress loosening zone(SLZ)is negatively correlated with the dip angle and the distance of the goaf,and positively correlated with the thickness.The SLZ near the goaf is larger,and the peak value of the asymmetry is about 1.35.When the thickness of the mined-out area is 1.8–2.1 m,the SLZ and displacement around the tunnel increase sharply and then become stable.When the dip angle of the mined-out area is greater than 30°or the distance exceeds 1.3 times tunnel diameter(D),the asymmetry converges.The research results of this paper are of great importance to the design and construction of tunnel support and the formulation of excavation schemes.