Iniciação e propagação de fraturas induzidas por injeções em solos argilosos com canalículos: aplicação ao tratamento do solo residual de fundação da barragem de terra da UHE Balbina

Abstract

Due to the pecularities of the residual soil at the Earth Dam Foundation at Balbina Power Plant, in which zones of high values of permability (K ≥ 10-³ cm/s) were found to be intimately connected with the existence of Small Channels, it was decided to treat the foundation with a soil-cement grout courtain which, by means of induced hydraulic fracturing, would permit the grout to penetrate and obstruct the intercepted canalicules, reducing the average permeability to values prescribed in the project (K ≤ 10-4 cm/s). This work presents a synthesis of the theories concerning the Mechanism of Hydraulic Fracturing, both for the initiation and the propagation phases of fracture development, aiming at the understanding of the whole phenomena, known the involved parameters and their influence on the process. Experimental data obtained at Balbina applied to the theoretical solutions permitted to estimate the dimension of fractures and thus the area of influence of the grout per injected volume, so defining the ideal spacing between holes. A determination of the rheological parameters of the grout obtained fro Pressure Loss tests in pipes and a study on the penetrability of the grout into canalicules were also put forward.