Yundong Zhou

Enzyme-induced carbonate precipitation has been studied for wind erosion control in arid areas. A comparative study was conducted between the pure urease- and crude soybean urease-induced carbonate precipitation methods with the same enzyme activity for enhancing the wind erosion resistance of desert sand. Tube tests were carried out to monitor the amount of organic matter and CaCO₃ precipitates at different reaction times. Two groups of sand specimens received several cycles of treatment with soybean urease (SU) and pure urease (PU), respectively, with urea or without urea. The treated specimens were exposed to wind-blown sand flow to evaluate erosion resistance. The results showed that SU induced more organic precipitation under the salting-out effect, which was 9.88 times higher than that from PU. Under the one-cycle treatment, SU-treated specimens with higher contents of CaCO₃ and organic matter exhibited lower erosion mass. Under the multiple-cycle treatment, the high viscosity of SU and rapid precipitation of organic matter resulted in the inhomogeneous distribution of CaCO₃ (more precipitation at the top). Once the top of SU-treated specimens was eroded, the sand below the top layer was lost rapidly, causing the erosion mass of PU-treated specimens to be 95% lower than that of SU-treated specimens.

Biocementation, based on microbially induced calcite precipitation (MICP), is a novel soil improvement method, which can form a cemented layer on the surface of desert sand to resist wind-induced erosion. In this work, the surface penetration resistance test and wind tunnel test were conducted to evaluate the various influential factors for the resistance of biocemented desert sand to wind-induced erosion, including the treatment factors, such as treatment temperature and biocement solution concentration, and durability factors such as the development of time, freezing–thawing cycles, and drying–wetting cycles. The test results demonstrated that the erosion resistance of biocemented desert sand was improved by the increase of treatment temperature and the concentration of biocement solution, which was manifested in the increase of surface penetration resistance of biocemented samples. In addition, the resistance of biocemented desert sand to wind-induced erosion decreased with the increased number of drying–wetting cycles, to lesser extents, with the development of time and the increased number of freezing–thawing cycles.

Rigid pile composite foundation is often used as an effective ground treatment method in the construction of highways. The PCC (cast-in-place thin-wall concrete piles) composite foundation is more and more frequently used in highway ground treatment. The research conducted on this type of foundation is very little. This paper highlights the use of PCC in Yan-Tong highway. The design, construction and quality test of this method are introduced. Test results show that the pile quality is good and its bearing capacity is relatively high.