SOIL INVESTIGATION USING DILATOMETER TESTS (DMT) FOR THE METRO-DF TUNNEL EXCAVATIONS IN BRASÍLIA'S SOUTH WING (ASA SUL)

Abstract

This paper presents a detailed analysis of the results obtained through Flat Dilatometer Tests (DMT) in Brasília porous clay during the excavation of the Federal District Subway (Metrô-DF) tunnel in the Asa Sul section. The primary objective is to investigate the geotechnical causes for the high differential surface settlements observed during construction, which significantly exceeded initial design predictions. The methodology was based on the re-examination and interpretation of intermediate and derived DMT parameters from five representative borings, correlating the Material Index (Id), Dilatometer Modulus (Ed), Oedometer Modulus (M), and Earth Pressure Coefficient at Rest (K0) with the classification criteria proposed by Marchetti (1980) and Marchetti & Crapps (1981). Results indicated a distinct variation in soil composition with depth: the upper layer (0 to 2 meters) consists of a mixed composition of silt and sand, whereas the underlying layer (2 to 10 meters) exhibits a predominance of clay and silt. It is concluded that the presence of this shallow layer with lower cohesion and heterogeneous composition acts as a likely contributing cause to the higher surface settlements recorded during the works.