Construction in Urban Areas

1. Introduction

With the increase in infrastructure and the subsequent decrease in available land, especially in the more over populated areas such as the CBD, there has been a greater call for construction to move below ground. This has a number of advantages for the property owner such as providing parking or simply increasing the floor area of an existing building, but with this comes a number of challenges. It is a huge task to perform such large excavations without damaging of effecting the structural integrity of the building in question as well as the surrounding buildings.

However construction in urban areas encounter numerous difficulties, not only the potential damage to surrounding buildings, the lack of space above ground for machinery and workforce poses a major threat especially when excavations need to be executed.

Support systems need to be implemented to add to the strength of the soil and prevent the collapse of the excavated surface, various methods used for this include: braced walls, sheet pile walls, contiguous or secant pile walls, RCC retaining walls and diaphragm walls. For the purpose of this assignment focus will be put on diaphragm walls and the various steps taken in the construction of these walls as well as the equipment used in this process, as well as analysis of the bentonite slurry used in the implementation of diaphragm walls.

Definition

Robert Ratay (2012, p 8.4) described the term diaphragm wall as a reinforced concrete wall constructed below ground level, using the slurry method of trench stabilization. Once fully completed and lateral bracing installed making the wall a retaining or foundation wall depending of the requirements of the building.

History

Ratay (2012. P 8.4) further adds to t...

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...limited space around site. This could therefore form a major issue for contractors in developed areas such as the CBD. In developed urban areas it is essential for the contracting team to do a large amount of research on the surrounding buildings and roads to fully understand the limitations.

As highlighted in the introduction of this report one of the most common reasons for basement construction is the limitation of above ground space, this is why it is essential to be well aware of the surrounding buildings. The contractor should only go ahead with plans if he is confident that he is able to overcome these possible threats.

Taking into account all the above information I believe that diaphragm slurry walls will continue to be used for years to come and even increase in the frequency of use due to the increased over population in some areas around the world.