ELMINA RIDGE LANDSLIDE

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Quote : 

SHAH ALAM: Two Bangladeshi construction workers died after being buried in a landslide in an incident at a concrete drain construction site in Elmina Ridge, Section U15 here today.

In the incident at about 10 am, the victims were working on the construction of a 0.3 m deep drain in the housing area.

Upon inspection, firemen found that the victims were buried by earth and concrete of the U box culvert while they were doing drainage construction work.

Meanwhile, Shah Alam district police chief ACP Mohd Iqbal Ibrahim said his investigation found that at the time of the incident, there were three workers who were installing concrete drains at the location involved.

He said the ground at the side of the drain suddenly collapsed causing the concrete wall of the drain to break and fall on one of the workers and the other was buried by the falling earth.

Photo Source : Bernama

MY PERSONAL OPINION

Let's first look into the typical construction methodology (excerpt from a method statement)

TYPICAL RISK, DANGERS AND HAZARDS DURING U-BOX CULVER INSTALLATION

1) Trench Collapse

The sides of the trench may collapse, especially if the soil is unstable or the trench is deep.

1.1  Preventive Measures

Use trench shoring, trench boxes, or sloping to prevent collapse. Workers should avoid working in trenches without proper protective systems.

2) Heavy Equipment Hazards

Risks associated with the operation of heavy machinery like cranes, excavators, and trucks. These include crushing, falling objects, and equipment malfunction.

Note : Please be aware that limited working space between heavy equipment, such as a crane, and the excavation area can impact the soil load and potentially lead to a collapse.

2.1 Preventive Measures

Ensure proper training and certification of operators, maintain equipment, and establish clear communication and signaling protocols.

Ensure the placement of heavy equipment such as cranes are placed at the appropriate position during excavation. The working space between the crane and the excavation area must be adequate.

3) Falls

Workers can fall into the trench or off equipment.

3.1 Preventive Measures

Install guardrails, barriers, or fencing around open trenches, and ensure workers use harnesses or fall protection gear when necessary.

4) Water Accumulation

Water can accumulate in the trench, leading to slippery conditions or creating a drowning hazard.

4.1 Preventive Measures

Ensure proper drainage and dewatering systems are in place before excavation begins.

5) Exposure to Hazardous Materials

Workers may be exposed to hazardous materials such as contaminated soil or underground utilities.

5.1 Preventive Measures

Conduct a site survey for potential hazards and use appropriate personal protective equipment (PPE).

6) Utility Interference

Risk of damaging underground utilities (like gas, water, or electrical lines) during excavation.

6.2 Preventive Measures

Conduct a utility survey and mark utility locations before excavation. Follow local regulations for safe digging.

INCLEMENT WEATHER

During the rainy season, the ground becomes saturated with water, which can reduce soil stability. This makes the soil more prone to collapsing, especially if the trench walls are not properly supported or shored. Saturated soil can be heavier and less cohesive, increasing the risk of a trench collapse, which poses a safety hazard and can delay the installation process.

Water Accumulation in Trenches

Rainwater can accumulate in the open trenches, creating additional challenges for the installation of the culvert. Waterlogged trenches may require dewatering before installation can proceed, which can add time, effort, and cost to the project.

Difficulties in Compaction and Backfilling

Proper compaction of the backfill material is essential for ensuring the structural stability and longevity of the culvert. However, wet conditions make it difficult to achieve the required compaction levels. Wet or muddy soil may not compact well, potentially leading to settlement issues in the future.

Logistical Challenges

Heavy rain can disrupt transportation of materials and equipment, affect worker safety, and make the construction site more challenging to navigate.

Damage to Installed Structures

Rain can cause erosion around the newly installed culvert if drainage and runoff are not adequately managed, potentially undermining the structure before it is fully set.

DO IT DURING DRY SEASON

Benefits

Reduced Water Interference During the dry season, there is minimal or no water flow in the drainage channel, making it easier to excavate, place, and align the culvert without the risk of flooding or waterlogging.

Improved Safety

Lower water levels reduce the risk of trench collapse and other water-related hazards, such as slippery conditions or equipment getting stuck in mud.

Better Soil Conditions

Dry soil is generally more stable, making excavation and backfilling easier and more effective. It also reduces the risk of soil erosion or settling, which could compromise the culvert's installation.

Efficient Construction

Work can proceed faster in dry conditions since there are fewer weather-related delays, allowing for a more efficient and timely installation.

Typical Safety Slope for Trench Walls

To prevent trench collapse, especially in deeper trenches or in unstable soil conditions, the trench walls should be sloped or benched according to safety standards. The appropriate angle of the slope depends on soil type:

Stable soil

A slope of 1:1 (45 degrees) is typically used.

Less stable soil: A slope of 1.5:1 or even 2:1 (about 33 to 27 degrees) may be necessary.