基于DEM和CFD法的超高压喷射注浆提高地基承载力的机理研究

Study on the mechanism of ultra-high pressure jet grouting to improve the bearing capacity of foundation based on DEM and CFD method

摘要

超高压喷射注浆是提高地基承载力的主要方法之一，为探明超高压喷射注浆扩散机理，使用将颗粒流(DEM)和计算流体动力学(CFD)相结合的模拟方法，通过实验室三轴试验和数值模拟试验确定颗粒各项宏观及微观参数，并进行相似模型试验验证了该模拟方法的有效性。基于此，开展20~60 MPa不同喷射压力下超高压喷射注浆数值试验，监测其喷射范围、孔隙率、流体压力变化。结果表明：超高压喷射注浆加固过程可分为切割裹挟、压迫紧缩、大范围涡流切削置换三个阶段。随着喷射压力的提高，喷射距离近似线性增加，但不同压力下空腔宽度可能相同；喷射过程中空腔周围土体孔隙率的峰值与形成的空腔形状密切相关；在喷射开始的极短时间(0.05内)土体就已出现多级劈裂现象，流体压力呈阶梯状显著变化；随着压力提高，喷射形成的旋涡切削搅拌土体会提前发生，且存在一个临界压力值为30 MPa,研究结果可为实际工程提供一定参考。

Abstract

Ultra-high-pressure injection grouting is one of the main method to improve the bearing capacity of foundations, in order to investigate the diffusion mechanism of ultra-high-pressure injection grouting, the simulation method combining particle flow(DEM) and computational fluid dynamics(CFD) is used, and the macroscopic and microscopic parameters of the particles are determined by triaxial tests in the laboratory and numerical simulation tests, and the simulation method is verified by similar model tests. The validity of the simulation method was verified by similar model tests. Based on this, the numerical test of UHP injection grouting was carried out under different injection pressures of 20~60 MPa to monitor the changes of injection range, porosity and fluid pressure. The result show that the UHP jet grouting reinforcement process can be divided into three stages: cutting and wrapping, compression and tightening, and large-scale vortex cutting and replacement. With the increase of injection pressure, the injection distance increases approximately linearly, but the width of the cavity may be the same under different pressures; the peak value of the porosity of the soil around the cavity in the injection process is closely related to the shape of the cavity formed; in a very short period of time at the beginning of the injection(within 0.05) the soil body has appeared to have a multi-stage splitting phenomenon, and the fluid pressure is a significant change in the form of a stair-step; with the increase of the pressure, the vortex cutting and stirring of the soil body formed by the jetting will With the increase of pressure, the vortex cutting mixing soil formed by jetting will occur in advance, and there may be a critical pressure value(30 MPa), which can provide a certain reference for the actual project.

关键词

超高压喷射流 / 数值模拟 / 流固耦合 / 颗粒流 / 地下工程

Key words

ultrahigh-pressure jet flow / numerical simulation / fluid-solid coupling / particle flow / underground engineering

Author summay

刘长宝(1981—), 男, 正高级工程师, 硕士, 主要从事城市交通工程方面研究。E-mail: [e-mail]

基金资助

国家重点研发计划资助项目(2021YFB2300805)