Research on Grouting Materials for Underground Construction Projects

The engineering practice shows that the application of grouting technology to treat underground engineering has strong applicability and is one of the most commonly used technical means at present. Based on the underground engineering, this paper introduces the research achievements of grouting materials in recent years, including cement-based grouting materials, mixed grouting materials, anti-scouring grouting materials, and ultra-fine cement grouting materials. Current demand of grouting materials in underground engineering, there exists large dosage of cement, high content, high cost, serious environmental pollution problems, such as looking for alternatives or mixed with other raw materials for preparation of cementation material become the development trend, compared with the cement grouting material, chemical grouting material with higher performance, but in smaller projects within the scope of application. How to reduce the production cost of chemical grouting materials, simplify the production process, overcome the existing toxicity, reduce environmental pollution and improve the durability of solidified body has become the bottleneck of its popularization and application. Some achievements have been made in the modification of cement or chemical materials by nanometer components, but there is still a long way to go before the large-scale application of grouting engineering.

Promoting Precipitation Technique using Bio-Chemical Grouting for Soil Liquefaction Prevention

The applicability of bio-chemical grouting as the environmentally friendly and economically method for liquefaction remediation was evaluated. Several combinations of organic and in-organic precipitations methods were conducted to obtain the optimum grouting solution. Organic precipitation method employs a bio-agent of urease enzyme to dissociate urea into ammonium and carbonate ions. The produced carbonate ions are precipitated as calcite crystals in the presence of calcium ions. Meanwhile, the in-organic methods were performed using chemical compounds only, without the bio-agent. Unconfined compressive strength (UCS) tests were performed to evaluate the applicability of the grouting solutions for improving the soil strength. Grouting solution is injected into the prepared sand samples. The sand samples with a relative density of 50% were treated with one and two PV for 3-day curing times. The experimental results showed that the organic precipitation method produced the high precipitated amount and resulted in the significant improvement in the strength of the treated sand. The presence of the precipitated materials within the grains of soil generated the strength of 272 kPa. The results of this study have elucidated that the organic precipitation method composed of calcium chloride, magnesium sulfate, urea and enzyme of urease may be an alternative soil-improvement technique to prevent the liquefaction susceptibility.