考虑紊动射流与土体相互作用的大深度高压旋喷成桩机理研究

Jet-grouting technology has been widely used in the construction; however, there exists a problem that it is difficult to create jet grouting column under large depth with high stress level, which causes engineering hazards and puzzles the geotechnical engineers. In this proposal, in order to elucidate the mechanism of column forming under large depth with high stress level and to establish the related construction theory to control diameter of jet grouted column under large depth, laboratory test, turbulent theory, and numerical analysis with smoothed particle hydrodynamics (SPH) method are employed to solve the following key scientific problems: i) to revel the effect of stress level in soil on the erosion resistance ability of soil and to establish the theoretical relationship between critical velocity of jet flow for soil erosion and the stress level; ii) to investigate the ability of the hydraulic jet to erode the soil with the content of fine particles, based on which it is aimed to establish the relationship between critical velocity of soil erosion and the content of fine particles; iii) to establish a theoretical model to predict diameter of jet grouted column based on the jetting parameters, soil parameters (strength and content of fine particles of soil) and stress level in soil strata. This research project can not only break thorough the limitation for predict the diameter of jet grouted column based on the qualitative analysis but also clarify the construction procedure of jet-grouting in the strata under large depth with high stress level. Research results can provide the scientific basis and theoretical support to guide the development and application of new technology of jet-grouting in large depth.

旋喷技术在地下工程中得到了广泛应用，但在大深度高应力水平条件下的成桩直径经常达不到预期效果，从而造成工程事故。本项目以上海地区的大深度天然沉积地层为研究对象，拟探明大深度高应力条件下高压旋喷施工的成桩机理，建立大深度下高应力水平地层的旋喷桩施工控制理论，通过室内试验、紊流力学理论、光滑粒子流体动力学(SPH)数值模拟相结合的研究手段，解决如下关键科学问题：①揭示土体中应力水平对射流临界速度与抵抗射流冲刷破损效应的影响规律，确定射流临界速度与应力水平的关系；②探讨土层中细颗粒含量对土体抵抗射流冲刷破损效应的影响规律，建立细颗粒含量与射流临界速度的定量关系；③建立不仅可以考虑施工参数与基本土性参数(抗压强度与细颗粒含量)而且可以考虑土层应力水平的旋喷桩成桩直径计算的理论模型。研究成果预期可以突破传统的旋喷技术中停留于定性认识的瓶颈，为大深度旋喷施工新技术的开发提供科学依据与理论支撑。

本项目以上海地区的天然沉积地层为研究对象，通过室内试验、现场试验、紊流力学理论、光滑粒子流体动力学(SPH)数值模拟的研究手段，探明大深度高应力条件下高压旋喷施工的成桩机理，建立大深度下高应力水平地层的旋喷桩施工控制理论，解决了如下关键科学问题：①通过室内试验确定了喷嘴直径对高速射流性能的影响；②基于半无限平面内圆孔受均布力作用的Verruijt解答，提出了计算高压旋喷施工引起土体变形的新方法；③建立可以考虑施工参数、土性参数，以及土层应力水平的旋喷桩成桩直径计算的理论模型。④运用SPH数值模拟分析了流体对固体的作用，揭示旋喷施工过程中射流对土体冲刷破损的作用机理。研究成果为大深度旋喷施工新技术的开发提供科学依据与理论支撑，研究成果提出的旋喷桩直径计算方法，为设计施工提供参数，对大直径旋喷桩的安全施工具有重要指导意义。本项目共发表SCI论文20篇，授权专利3项，培养研究生3人等多项成果。