Causes of Failure in Deep Excavations
Causes of failure in deep excavation are divided into two subtopics which include:- Causes of failure in open deep excavation
- Causes of failure in braced deep excavation
Fig: Failure of deep excavation
Causes of Failure in Open Deep Excavation
Site investigation is conducted insufficiently which lead to overestimated design assumptions of soil, rock strength, and groundwater condition. The ramification of this error would be inadequate dewatering, possibly excessive deformation of soil. These will undermine the safety of excavation and eventually could lead to failure. Poor understanding of the designer regarding settlement susceptibility of neighboring buildings and services. This would increase the load on the soil support structure and cause failure. Another factor is the misunderstanding of both designer and constructor about the influence of time and weathering on soil strength. This could lead to excessive deformation of soil and soil support structure and subsequent failure of the excavation.Causes of Failure in Braced Deep Excavation
- Site investigation is conducted insufficiently which lead to optimistic design assumptions of soil and rock homogeneity, groundwater condition, and soil and rock fabric strength.
- Poor quality of structural detailing
- Poor communication between the designer and constructor
- Insufficient understanding of the designer about the limitations of specific techniques used to support excavation wall for example anchoring and diaphragm wall.
- Misunderstanding of the designer about the effect of deflections of soil support structure and retained soil deformations.
- Variations in loading from natural conditions for instance waves, groundwater, tidal, and temperature. These will lead to excavation failure unless the constructor has adequate knowledge about the result of these variations.
- Poor workmanship in the temporary works of the project site
- Finally, overloading of soil support structure as a result of loads of temporary plants.