Experimental study on the reinforcement performance of unloading-damaged mudstone by microbial grouting

Area of Science:

• Geotechnical Engineering
• Materials Science
• Environmental Engineering

Background:

• Unloading damage during foundation excavation causes structural deterioration and swelling in mudstone.
• This damage significantly reduces mudstone strength and increases its susceptibility to water-induced swelling.
• Effective reinforcement strategies are crucial for the stability of such foundations.

Purpose of the Study:

• To investigate the effectiveness of microbial induced calcite precipitation (MICP) and MICP-volcanic ash grouting for reinforcing unloading-damaged mudstone.
• To systematically analyze the impact of these methods on swelling deformation, mechanical properties, and microscopic reinforcement mechanisms.
• To compare the reinforcement effects of MICP alone versus MICP combined with volcanic ash.

Main Methods:

• Preparation of mudstone specimens with varying degrees of unloading damage using triaxial unloading tests.
• Application of MICP and MICP-volcanic ash grouting as reinforcement treatments.
• Conducting physical-mechanical tests and microstructural analyses (e.g., SEM) to evaluate performance.

Main Results:

• Unloading damage significantly decreases mudstone strength and heightens swelling sensitivity.
• Both MICP and MICP-volcanic ash treatments effectively mitigate swelling and enhance strength.
• MICP-volcanic ash demonstrated superior improvements in residual strength (13.45%-20.61%) and peak strength (5.36%-9.45%) compared to MICP alone.
• Microstructural analysis revealed pore filling, crack sealing, and enhanced cementation by calcium carbonate precipitation.

Conclusions:

• MICP and MICP-volcanic ash grouting are viable green reinforcement techniques for damaged mudstone foundations.
• The addition of volcanic ash amplifies the benefits of MICP by improving microbial retention and pore structure densification.
• These findings provide valuable insights for improving the stability of red-bed mudstone foundations affected by unloading damage.