木钙源EICP溶液固化路基黄土性能研究

Properties of Subgrade Loess Solidified by Calcium Lignosulfonate-EICP Solution

黄土地区有砟货用铁路路基遇水强度下降,严重影响线路的正常运营。针对该工程问题,采用植物源脲酶诱导碳酸钙沉积技术固化路基黄土,在胶凝液中开展了以环保型木钙代替传统钙源进行技术改进的系统研究。结果表明:首先,木钙源EICP溶液能同时显著提高黄土的无侧限抗压强度和抗剪强度。其中,无侧限抗压强度提高至0.232 MPa,提高了20.8%;抗剪强度指标C值提高至69.06 kPa,提高了31.2%;Φ值提高至26.8°,提高了52.3%。其次,木钙源EICP溶液的抗剪切效果明显优于传统氯化钙源和乙酸钙源的EICP溶液,并且各组分存在最优浓度。其中,1000 U/g活性脲酶的最优浓度为3 g/L,尿素的最优浓度为1 mol/L,木钙的最优浓度为1 mol/L。随着各组分掺量的增加,黄土的抗剪强度呈现先增大后减小的规律。最后,通过XRD、SEM等微观试验结果分析得出木钙源EICP溶液改良黄土强度的作用机理,发现其中脲酶诱导产生的碳酸钙晶体既胶结了黄土骨架颗粒,也填充了粒间孔隙,同时提高了土颗粒间的摩擦强度和粘结强度,最终改善土体的力学性能。

The mechanical loss of subgrade loess contacting with water impacts gravelythe line's circulation.Facing to the loess subgrade engineering issue,attempts to improve the loess strength using the EICP technology,a process of calcium carbonate precipitation induced by plant-extracted urease.Especially,replacing the traditional calcium source with environmentally friendly calcium lignosulfonate in the cementation process of the EICP technology improvement was studied systematically.The results show that firstly EICP solution of calcium lignosulfonate can significantly improve both the lateral unlimited compressive strength and shear strength of loess,wherein the compressive one increases to 0.232 MPa,increased by 20.8%,the C value of shear strength index increases to 69.06 kPa,increased by 31.2%,and theΦvalue increases to 26.8°,increased by 52.3%.Secondly,the shear improvement effect of the loess with EICP solution of calcium lignosulfonate is obviously better than that of the loess with EICP solution of calcium chloride and the one of calcium acetate.The optimal concentration of each component of calcium lignosulfonate-EICP solution is 3 g/L for 1000 U/g active urease,1 mol/L for urea and 1 mol/L for calcium lignosulfonate.Moreover,with the increase of the dosage of calcium lignosulfonate-EICP solution,the shear strength of the loess primarily increases but then decreases.Finally,microscopic test results(XRD and SEM)demonstrate that the mechanism of the loess solidified by calcium lignosulfonate-EICP solution is mainly linked to the new calcium carbonate deposits.The deposits were induced both on the surface of the loess skeleton particles and in pore filling.As a result,the friction strength between the loess skeleton particles rise up,as well as the bonding connection strength reinforced,so that the mechanical properties of loess are improved in the end.