Before the construction of a building can commence, workers are required to carry out excavation work below ground level. This involves digging foundations, installing utilities, and spending weeks working in potentially hazardous conditions, as they are constantly exposed to the risk of cave-ins and collapses. The shifting of soil and debris within the excavation site can lead to trench or ground collapse, which pose significant dangers. These collapses occur when the walls of the trench fail, resulting in the sudden collapse of thousands of pounds of dirt or soil into the excavation.

Ground collapses represent one of the most perilous types of accidents that can occur on construction sites. Apart from the immediate danger of being trapped, such incidents can lead to additional hazards for construction workers, including burst pipes and exposure to hazardous substances, as well as property damage.

Various factors can contribute to ground collapses on construction sites, including:

Inadequate protection systems: Proper procedures and protection systems should be implemented before excavating a trench to safeguard workers from collapses. Occupational Safety and Health requirements recommend the use of appropriate protective measures to prevent workers from being crushed during a collapse.

Stress loading the soil: Additional stress placed on trench walls, such as heavy construction equipment located too close to the walls, can contribute to collapses. It is crucial to maintain a safe distance between equipment and trench walls to prevent such dangerous conditions.

Failure to inspect the trench: Regular inspections of trench / excavation walls are necessary to evaluate soil classification, water content, and any changes caused by weather conditions or environmental factors like any movement of the soil. Failure to conduct proper inspections before each shift and after inclement weather conditions can put construction workers at risk.

Vibration: Trench walls are at risk of collapsing when subjected to nearby sources of vibration, such as traffic or construction equipment. Implementing appropriate protection systems can help mitigate this risk.

Different types of trench cave-ins can occur depending on soil conditions and weaknesses:

  • Layered Soil Failure: Occurs when one side of the soil is strong near the surface and weak below, while the other side is weak near the surface and strong below.
  • Soft Zone Failure: A ridge of weak soil between two strong layers creates instability and leads to collapse.
  • Sloughing/Air Drying: Dry or windy conditions can cause once-stable trench walls to become weak and prone to sloughing.
  • Soft Pockets: Small pockets of soft, sandy soil within stable ground can eventually give way, leading to a collapse.
  • Wedge Failure: High traffic or vibration can cause cracks to form on the ground, resulting in an angular slide of soil into the trench.
  • Rotational Failure: A soft pocket causes fractures and a circular collapse at the bottom of the trench.

Understanding the different soil conditions and weaknesses is crucial for designing effective solutions and implementing appropriate safety measures. Regular testing of soil consistency by a competent person is essential to identify potential risks.

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At Cairnmead, we understand that achieving simplicity necessitates time, expertise, and experience. We have the ability to navigate intricate details and condense them into a clear and understandable solution. Regardless of the complexity of the problem at hand, we prioritize delivering a simple and effective end result.

Contact us to find out more:

Christof Lourens

CEO Cairnmead Industrial Consultants (Pty) Ltd

Tel: 012 346 5752 | Email: christof@cairnmead.co.za

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