Fundamental investigation of compensation grouting using transparent soil

本研究将通过对透明土中注浆运移和水力压裂过程的实时可视化，对补偿注浆进行实验研究。本文的研究成果对补偿灌浆的设计和施工具有直接的指导意义。补偿灌浆是一种较新的灌浆技术，是在高压下注入低粘度浆液来补偿邻近地下施工造成的地面损失。它已成功地应用于许多城市地区，特别是在隧道施工中。然而，由于补偿注浆涉及土体条件和注浆变量等一系列复杂参数，其机理尚不清楚。土内注浆涉及土骨架、流体流动和浆液运移之间复杂的相互作用。一般认为，补偿注浆包括压实注浆和断裂注浆两种注浆方式。补偿注浆的应用很大程度上依赖于实践经验和经验主义。制定高效经济的注浆方案需要对注浆机理及其控制参数有深入的了解。进行了一些实验室研究，对注浆有了基本的了解。然而，对裂缝的初始化、几何形态以及浆液在土体中的运移研究较少。在注入过程中也没有进行土壤位移测量。这项拟议的研究将使用透明土壤来解决这些问题，并提供对土体内灌浆运输和破裂的全面了解。为了实现这些目标，将开发一种最先进的光学测量系统，能够对注浆参数进行实时数据采集和图像捕获。该光学系统由一个激光照射透明土壤内部的目标截面和两个配置良好的摄像机组成，用于同时捕捉照射截面的图像。利用立体粒子图像速度技术计算三维土体变形。注浆过程中土体变形的信息有助于解决补偿注浆中的注浆效率问题，实现有效的沉降控制。数字图像边缘检测将用于描绘浆液体的几何形状，识别裂缝的初始化，并观察裂缝的方向和几何形状。本研究将进行一系列的比例模型试验，主要在实验室的1-g条件下进行。将检查控制参数的影响，包括土壤条件，覆盖层压力，浆液成分，注入速度和注入压力。将进行一些离心模拟试验，以补充1-g模型试验，以便更好地模拟现场的应力梯度条件。还将进行数值模拟，以系统地研究各种影响因素的影响。该研究将首次实时可视化浆液在多孔介质中的扩展和注浆过程中水力裂缝的初始化。该研究项目对改变或改进土木、环境和石油工程领域的许多现有技术具有重要意义。这项拟议的研究对于培养高智商人士在加拿大的职业发展也至关重要。

This proposed research will experimentally investigate compensation grouting through the real-time visualization of the transport of grout and hydraulic fracturing by using transparent soil. The findings from this research program are expected to directly benefit design and construction of compensation grouting in practice.Compensation grouting is a relatively new technique which injects a low viscosity grout at high pressure to compensate for ground loss due to adjacent underground construction. It has been successfully applied in many urban areas, particularly during tunnelling. However, the mechanisms of compensation grouting are not well understood as it involves a set of complex parameters due to different soil conditions as well as grouting variables. The injection of grout inside soil involves complex interactions between the soil skeleton, fluid flow, and grout transport. It is generally understood that compensation grouting consists of two grouting modes: compaction grouting and fracture grouting. The application of compensation grouting heavily relies on practical experience and empiricism. The development of an efficient and economical grouting program requires a thorough understanding of the grouting mechanisms and its controlling parameters. A few laboratory studies have been conducted that have obtained a basic understanding of grouting. However, there is limited research on the initialization and geometry of fractures, and the grout transport in soils. There are also no soil displacement measurements made during injection. This proposed research will use transparent soil to address these issues and provide a full understanding of grout transport and fracturing inside a soil mass. In order to achieve these goals, a state-of-the-art optical measurement system will be developed to be able to conduct real-time data acquisition of the grouting parameters and image capture. The optical system consists of a laser to illuminate a targeted cross section inside the transparent soil and two well-configured cameras to simultaneously capture the images of the illuminated section. Three-dimensional soil deformation will be calculated by using a stereo particle image velocity technique. The information on soil deformation during grout injection will help to address the issue of grout efficiency in compensation grouting for efficient settlement control. Digital image edge detection will be used to delineate the geometry of the grout body, identify the initialization of fractures, and observe the direction and geometries of fractures. A series of scaled model tests will be carried out in this study, mainly under 1-g conditions in the laboratory. The influence of the controlling parameters will be examined, including soil conditions, overburden pressure, grout composition, injection rate, and injection pressure. A few centrifugal modeling tests will be conducted to complement the 1-g model tests to better simulate stress gradient conditions in the field. Numerical simulation will also be conducted to provide a systematic investigation of the influence of various influencing factors.This proposed research will be the first of its kind to visualize the propagation of grout in a porous medium and the initialization of hydraulic fractures during grout injection in real time. This research program has significant implications of changing or improving many existing technologies used in civil, environmental, and petroleum engineering fields. The proposed research is also vital in training HPQs for their career development in Canada.