Effects of using Concrete Pre-Supporting Systems with NATM in construction of Underground Stations

Mostafa Zaki Abd Elrehim, Ahmed Talaat Abd-Ellaah

Abstract


The soil in Egypt and especially in Cairo city is mostly soft soil varying between clayand sand layers. Excavation of large span (more than 10 meter) underground station insuch soil layers can cause large displacements (more than 30 mm) which may resultin harmful effects for the nearby buildings which are often located within distancefrom the center line of station equal to 1.5 times of total width of station. Therefore,the excavation process of large span underground stations needs a supporting systemto enable redistribution of the loads and stresses around the excavation opening to thesurrounding soil mass to avoid undesirable excessive displacements. This paper showshow the concrete pre-supporting system can be used to control the stability of theunderground space and the ground settlement. Numerical modeling is used to simulateall the construction stages and to analyze the ground behavior. Analysis results fromdifferent models show that pre-supporting systems can be used successfully to reducethe ground surface settlement and to enhance ground stability.

Keywords


NATM; pre-supporting system; soft soil; tunnels; underground stations.

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