脲酶诱导碳酸钙沉淀固化黄土界面强度优化试验研究

Research on Optimization of Interface Strength of Urease-induced Calcium Carbonate Precipitation and Solidification of Loess

为了研究脲酶诱导碳酸钙沉淀固化黄土界面联结性能,采用正交设计,针对影响碳酸钙沉淀生成的主要因素,开展了原状黄土拼接后的直接剪切试验,在基液浓度充足的条件下,通过极差分析和方差分析相结合的方法,分析了海藻酸钠浓度、氯化钙浓度、脲酶浓度等因素对界面直接剪切强度的主次影响因素顺序及演变规律,基于正交设计得到的最优组合开展了不同基液浓度对最优组合的影响。研究结果表明:影响脲酶诱导碳酸钙沉淀的主次影响顺序为:氯化钙浓度、脲酶浓度、海藻酸钠浓度;试验得出的最佳组合为B_(4)C_(4)A_(4),即氯化钙浓度为2.0 mol·L^(-1),脲酶浓度为40 kU·L^(-1),海藻酸钠浓度为40 g·L^(-1);随着尿素浓度的增加,抗剪强度逐渐增大,且尿素浓度从0.8 mol·L^(-1)升高至1.2 mol·L^(-1)时的增加趋势明显,从1.2 mol·L^(-1)升高至1.6 mol·L^(-1)的增加趋势减缓。工程建议值为1.2-1.4 mol·L^(-1)。

In order to study the interface bonding performance of urease-induced calcium carbonate precipitation and solidification of loess,orthogonal design is used to focus on the main factors that affect the formation of calcium carbonate precipitation,and a direct shear test of undisturbed loess splicing is carried out.Under the condition of sufficient base fluid concentration,by means of the combined method of range analysis and variance analysis,the sequence and evolution of the primary and secondary influence factors of sodium alginate concentration,calcium chloride concentration,urease concentration and other factors on the direct shear strength of the interface are analyzed.Based on the optimal combination obtained by orthogonal design,the influence of different base fluid concentrations on the optimal combination was carried out.The results of the study show that the order of the primary and secondary effects that affect urease-induced calcium carbonate precipitation is:calcium chloride concentration,urease concentration,sodium alginate concentration;the best combination obtained from the experiment is B_(4)C_(4)A_(4),that is,the calcium chloride concentration is 2.0 mol·L^(-1),the concentration of urease is40kU·L^(-1),and the concentration of sodium alginate is 40g·L^(-1);as the urea concentration increases,the shear strength gradually increases,and the increase trend is obvious when the urea concentration increases from 0.8mol·L^(-1)to 1.2mol·L^(-1),the increase trend slows down when from 1.2mol·L^(-1)to1.6mol·L^(-1).Engineering recommended value is 1.2-1.4mol·L^(-1).