Considering the significant sources of uncertainty associated with a rock mass improvement by grouting and in order to facilitate its design under observational methods, we present different tools for decision making based on the results and experience obtained from several projects. From basic information regarding the evolution of permeability and grout consumption during treatment, this proposal presents recommendations to optimize: injection pressure, maximum volumes injected, hole pattern, grout mix properties, among other parameters and procedures.

1 Introduction

The improvement process of rock masses by grouting involves a considerable number of variables affecting the results; these include the geological and hydrogeological features of the rock mass, in addition to issues arising from the grouting process (grouting mixture, maximum pressure, rate of grouting, drilling technology, geometrical arrangement of treatments, etc.).

Grouting treatments generated from limited information or performed with prescriptive specifications, frequently require modifications during construction which makes more appropriate the application of observational design methodologies. Considering this, we propose diverse tools that can facilitate the decision making to optimize the design and implementation of treatments, based on the evolution of grout consumption and permeability as well as the continuous ground zonation according to their hydrogeological features..

2 Background

The proposed methodology was generated from the evaluation of results and experiences obtained from several projects in Mexico where grouting treatments were performed during previous studies, construction and operation of hydropower and geothermal power projects. Rock mass treated was mostly of igneous and sedimentary origin with a wide range of qualities (Fig. 1).

Three different grouting methods were applied in reviewed projects, its main features and application percentages are illustrated in Table 1 and Figure 1 respectively; cement-based mixtures were used for all methods.

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