植物源脲酶诱导碳酸钙固化砂土试验研究
Experimental study on sand solidification using plant-derived urease-induced calcium carbonate precipitation
-
摘要: 植物源脲酶诱导碳酸钙沉积胶结砂土是岩土工程领域的一种新型技术,相比目前广泛应用的微生物固化砂土技术具有很多优点。直接从大豆中提取脲酶,首先研究了温度及pH值对大豆脲酶活性的影响,然后控制胶凝液浓度、pH值、温度和反应时间进行了脲酶诱导碳酸钙沉积试验,在此基础上,采用循环灌注脲酶液和胶凝液的方法固化3种不同颗粒粒径范围的砂土,通过超声波测试、无侧限抗压强度测试及碳酸钙含量测试检测固化效果。结果表明:大豆脲酶最适pH值为8,15℃~75℃范围内脲酶活性随温度升高而增大。大豆脲酶诱导的沉淀产物为方解石型碳酸钙,随胶凝液浓度增大,碳酸钙产率先增大后减小,胶凝液浓度为0.75 mol/L时,碳酸钙产率最大。胶凝液浓度一定时,pH值为8情况下碳酸钙产率最大,且产率随反应时间增加而增大。10℃~40℃范围内温度对碳酸钙产率影响较小。固化试样的抗压强度与碳酸钙含量呈正相关,随砂土颗粒粒径增大,试样的抗压强度先增大后减小,0.25~0.5 mm砂土固化效果最好。Abstract: The plant-derived urease-induced calcium carbonate precipitation cemented sand is a new technology in the field of geotechnical engineering, which has many advantages over the currently widely-used technology of solidifying sand by microorganism. Urease is extracted from soybeans directly. At first, the effects of temperature and pH on soybean urease activity are studied. Then the tests on the urease-induced calcium carbonate precipitation are carried out by controlling gel solution concentration, pH, temperature and reaction time. Based on this, three kinds of sand with different particle sizes are solidified by injecting urease solution and gel solution circularly. The solidification effect is evaluated by ultrasonic tests, unconfined compressive strength tests and calcium carbonate production tests. The results show that the optimal pH of soybean urease is 8, and urease activity increases with the increase of temperature in the range of 15℃~75℃. The precipitation product induced by soybean urease is calcite. With the increase of gel solution concentration, the production rate of calcium carbonate increases first and then decreases, and when the gel solution concentration is 0.75 mol/L, the production rate of calcium carbonate is the highest. When the gel concentration is constant, the production rate of calcium carbonate is the highest at the pH of 8, and the production rate increases with the increase of reaction time. The temperature within 10℃~40℃ has little effect on the production rate of calcium carbonate. The compressive strength of solidified samples is positively correlated with the content of calcium carbonate. With the increase of the particle sizes of sand, the compressive strength of samples increases first and then decreases, and the sand with particle size of 0.25~0.5 mm has the best solidification effect.