Geostatistical Modelling and Simulation Scenarios as Optimizing Tools for Curtain Grouting Design and Construction at a Dam Foundation

Abstract

Foundation treatment is a crucial stage in dam construction. An intense construction stage dedicated to ground improvement and quality control is often implemented. Foundation permeability is the parameter to be monitored and optimized during the construction stage. This work describes the application of geostatistics to permeability data obtained by the Lugeon test during curtain grouting at a dam foundation. The usual construction methodology consists in applying a sequentially phased drilling strategy materialized by drilling and grouting a first line of primary boreholes followed by a secondary collinear line of in-between boreholes. The studied site is located at the Sabor river mouth, northeastern part of Portugal. Groundwater flows in a fractured medium. The main objective of this study is assessing the advantage of a geostatistical modelling approach in identifying the zones in which the project design criteria may demand for a first- and a secondary-stage grouting treatment defined by a threshold permeability of 1 Lugeon unit, Lu. After a preliminary statistical, spatial continuity characterization and error study, estimation and probability maps are compared based on ordinary and indicator kriging and indicator simulation. The obtained models are compared with the information of the acquired construction phase data. Obtained models are finally compared with the initial geological-geotechnical information indicating that the described approach can be used as an optimizing tool for curtain grouting design at a dam foundation.