ABSTRACT:

The technique of a soil nailed wall in a soft soil area for deep excavation was developed in this paper. Soil nailed walls are generally used to reinforce clay, residual soil, sand and angular soil etc. In recent years, they have been adopted for deep excavations by reinforcing soft soil such as muck and mucky clay. The design method of a soil nailed wall on excavations in a soft soil area is presented. The mechanism of the structure and retaining effect is analyzed. A case history for a depth of excavation is 5.0m is presented. If the capacity of foundation pit basal soil is low, vertical strengthening needs to be introduced. These retaining structures can be used for the excavation in depths of 3m-7m soft soil areas.

INTRODUCTION

Fuzhou is a soft soil area that is located on the southeast coast of China. During this decade, many new high-rise buildings have been constructed. Generally 1 or 2 levels of basements are common for high-rise buildings, and excavation depth is 3.5m–10m. The retaining and protecting for excavations of deep foundation pit therefore becomes more important. The technique of a soil nailed wall (also named combined shotcrete-anchorage-netting reinforcement technique in local area) is the slope retaining technique that the soil nail is the main force structure and is installed across the potential failure surface. It consists of in-situ stabilized soil body, a shotcrete facing and necessary waterproof system. The retained soil mass is drilled and a steel bar or steel pipe is put into the drill hole and grouting is used 1 or 2 times. Steel mesh is then installed and concrete facing is sprayed to make the soil nail and shotcrete facing a bond. It was previously considered not suitable for use on soft soil ground.

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