ABSTRACT ABSTRACT
In the field of grouting, practitioners frequently advocate procedures that are often unique and contradictory. As a result there has been considerable debate as to what constitutes optimum grouting practice. A knowledge of both the rheological properties and the flow characteristics of grouts is essential to the development of a rational understanding of the grouting process. Flow models and viscosity experiments have been conducted using cement grouts comprising High Early Strength Portland and Microfine cements. The addition of superplasticizers was found to enhance the flowability of the grouts as well as to reduce the effective groutability ratio. Steady state flow equations and design charts for predicting the radial penetration of cement grouts have been developed.
INTRODUCTION
In the context of ground engineeringsthe term grouting is used to describe the process of the pressure injection of setting fluids into the pores, cavities and fissures of a soil or rock mass. The process of grouting can be used both as a preventive and as a remedial measure in engineering construction. The important questions in grouting relate to the extent and degree of grouting to be undertaken. Due to variations in the geological environment, the successful application of a particular grout mix, procedure and equipment in one case may not guarantee the same performance in another seemingly similar condition. As a result, practitioners in the field of grouting frequently advocate a variety of grouting practices which are unique but are often contradictory. Case histories are frequently presented to substantiate each proposition. As a result, engineers who are less familiar with grouting operations may find it very difficult to design an optimal grouting procedure. Some of the important factors that determine the success of a grout operation are the consistency or the water: cement ratio of the grout mix, the grain size distribution of the cement as related to the joint aperture and the type and dosage of admixtures used to improve the flow properties of the grout. These factors influence the stability and penetrability of a grout, which in turn determines the extent of propagation, the strength, the permeability and the durability of the hardened grout. A knowledge of the above factors would aid the practitioner in choosing the necessary pumping pressures, grout pump type, as well as the layout of the grout holes.
SCOPE OF STUDY
The primary objectives of this study were to develop a fundamental understanding of the flow characteristics of cement grout through rock discontinuities, to develop simple procedures for measuring these flow characteristics and to apply these findings to the development of grouting design charts. The various aspects are as follows:
To characterize two types of cement grout through rheological studies which included viscosity and sedimentation tests.
To determine the influence of two types of superplasticisers on these rheological proper- ties and to determine the optimum dosage of each superplasticizer for each cement grout.
From the physical properties of the grouts and from observations made in flow tests, the factors affecting the minimum groutability ratio were defined.
Design charts were developed for predicting the radial penetration of cement grouts.