Cement based eco-grouting composite for pre-reinforcement of shallow underground excavation in vegetation protection area

Abstract

The search for eco-friendly grouting materials with excellent workability performance to strike a balance between environmental protection and manipulability is a popular topic in underground engineering. This paper presented a practical and efficient strategy for producing a composite grouting material with microbial polysaccharide gum (CGMG) for pre-reinforcement of shallow underground excavation in a vegetation protection area. The CGMG grout is formulated based on excellent synergistic interactions among cement, water, xanthan gum and sodium aluminate, and an optimal weight proportion of 1, 1.5, 0.01 and 0.004 for cement, water, sodium aluminate and xanthan gum is proposed by orthogonal experimental design. The obtained CGMG shows a fluffy mass structure and high stability (bleeding rate less than 5%), satisfactory early compressive strength (1.5 MPa), and a pumping period of more than 30 min. In particular, the pot experiment results shows that the germination, root growth characteristics, root activity and chlorophyll content were similar in the study group (plant soil injected with CGMG as the growing media) and the control group (plant soil as the growing media) at different growing stages. Moreover, the effectiveness and eco-friendly characteristics of the CGMG were verified by a field grouting application for shallow tunnel excavation in a vegetation protection area. This work provides a new option for grouting in ecologically sensitive areas.