单管旋喷工法成桩半径实用计算方法
Practical calculation method for column radius by single fluid jet grout system

为解决在采用单管旋喷工法对软土地基加固时，对成桩半径的合理预测问题，通过对单管旋喷工法施工过程的理论分析，以单位长度高压旋喷桩为研究对象，综合考虑水泥浆射流性质、高压射流喷射能量和土体抵抗力，提出一种预测单管旋喷桩成桩半径的实用计算方法。该方法针对细粒土和粗粒土情况，选取岩土工程勘察报告中常用的静力触探试验获得的锥尖阻力qc和标准贯入试验获得的标贯击数NSPT代表土体抵抗力；建立成桩半径与喷嘴处高压射流喷射能量En和土体抵抗力（锥尖阻力qc和标贯击数NSPT）的定量关系；同时分析成桩半径随高压射流喷射能量En、锥尖阻力qc和标贯击数NSPT的变化情况；最后总结了该方法的计算步骤，并通过与现场实测数据的对比分析，验证了该方法的合理性。研究结果表明：成桩半径随锥尖阻力qc（细粒土）和标贯击数NSPT（粗粒土）的增大迅速减小，即土体抵抗冲刷破坏的能力越强，成桩半径越小；喷嘴处高压射流喷射能量En越大，代表高压射流对土体的破坏力越强，则成桩半径越大；在喷射参数相同的情况下，单管旋喷工法在粗粒土中的成桩半径一般要高于细粒土中的成桩半径。
In order to solve the problem that how to reasonably predict jet grout column radius when using single fluid system to reinforce soft ground, by theoretical analysis on the construction of single fluid system, taking the jet grout column with unit length as the research subject, a practical method for predicting jet grout column radius was proposed based on the consideration of the effect of jetting fluid property, jetting energy and resistance of soil to erosion. For the case of fine-grained soils and coarse-grained soils, the results of cone penetration tests qc and the results of standard penetration tests NSPT that frequently used in geotechnical investigation reports were chosen to represent the resistance of soil to erosion. The quantitative relationship among column radius, energy at the nozzle En, and the resistance of soil to erosion (the result of cone penetration test qc and the result of standard penetration test NSPT) was established in this method. Then the variation of column radius with energy at the nozzle En, the result of cone penetration test qc and the result of standard penetration test NSPT were analyzed. The calculation procedure of this method was summarized, and the analysis results of the calculated and measured data in field verified the applicability of this method. The results show that column radius rapidly decreases with the increase of the result of cone penetration test qc and the result of standard penetration test NSPT, namely, the higher the resistance of soil to erosion, the smaller the column radius. The higher the energy at the nozzle En, the larger the column radius. Column radius formed in coarse-grained soils is larger than that formed in fine-grained soils when the jetting parameters are identical