Innocent Chatikobo
Engineering and Construction Matters
Introduction
Settlement of buildings and structures refers to the gradual sinking or downward movement of a building or structure into the ground over time. This occurs when the weight of the building or structure causes the soil beneath it to compress or settle. A school of thought suggests that a building or structure makes such movements for three rainy seasons
Settlement and soil movement can occur due to various natural and human – induced factors. Some of the common causes are:
- Natural causes
Soil consolidation: Soil settlement occurs when soil particles are compressed, causing the soil to densify and settle. Poor soil quality, density, or moisture content can lead to crack development
Water table changes: Changes in the water table can cause soil settlement or movement. High water table and poor drainage can lead to settlement
Tectonic activity: Earthquakes, volcanic activity, and other tectonic events can cause soil movement and settlement.
Weathering and erosion : Weathering and erosion can cause soil particles to be transported away, leading to settlement or movement.
Thermal expansion and contraction : Temperature changes can cause soil to expand and contract, leading to settlement or movement.
- Human induced causes
Construction and excavation : Building construction, excavation, and tunneling can cause soil disturbance and settlement. Poor foundation design and construction can lead to settlement
Vibrations: Vibrations from traffic, construction, or industrial activities can cause soil settlement or movement.
Water leakages: Leaks from pipes, reservoirs, or other water sources can cause soil erosion and settlement.
Soil compaction: Over-compaction of soil during construction or other human activities can cause settlement or movement. The weight of the building is also a factor, heavy buildings or structures can cause the soil to settle.
- Appearance of vegetations
Vegetations and root growth: Tree roots and other vegetation can cause soil disturbance and settlement.
Types of Settlement
Immediate Settlement: Occurs immediately after construction, as the soil adjusts to the weight of the building.
Consolidation Settlement: Occurs over time, as the soil consolidates and becomes more dense.
Creep Settlement: Occurs due to the gradual deformation of the soil under constant load.
Effects of Settlement
Structural Damage: Settlement can cause cracks in walls, floors, and foundations.
Uneven Floors: Settlement can lead to uneven floors and surfaces.
Door and Window Issues: Settlement can cause doors and windows to become misaligned or difficult to open.
Water Damage: Settlement can lead to water damage and flooding.
Measures to overcome, prevent and mitigate settlement and soil movement
To minimise the risk of wall cracks due to settlement and soil movement, consider the following measures:
Soil investigation: Conduct thorough soil investigations before construction to determine soil type, density and moisture content. Differential soil properties lead to uneven soil movements hence cracking occurs.
Foundation design: Design the foundation properly to accommodate expected soil settlement and movement, ensuring that it can support the weight of the building. Repair or replace damaged foundation elements.
Reinforced foundation: Use reinforced foundations, such as pile foundations or raft foundations, to resist soil movement if Necessary. Installation of piles transfers the weight of the building to a more stable soil layer. If the Bearing capacity is Average Strip can be used.
Soil compaction: Compact the soil properly to improve its density and reduce settlement during any aspect in construction, especially while backfilling.
Soil stabilisation : Use soil stabilisation techniques, such as grouting or chemical stabilisation, to fill voids and improve soil strength.
Drainage system: Install drainage systems to prevent water accumulation and reduce soil erosion.
Regular inspection: Regularly inspect walls and foundations for signs of cracking or movement.ý
Monitoring soil conditions: Monitor soil conditions, such as moisture content and settlement, to anticipate potential issues.
Trees planting: Avoid planting trees near buildings, as their roots can cause soil disturbance and movements.
Underpinning: Install new foundation elements to support the existing foundation.
Innocent Chatikobo is an Engineer by profession with AtroServe Engineering Zimbabwe. He has extensive knowledge and experience in Structural Engineering and Construction. For your comments, views, questions and feedback he can be contacted on the following platforms Cell: +263 777 950 224; +263 712 376 037; +263 782 502 732, Email: [email protected] <mailto:[email protected]> Like the Facebook page: AtroServe Engineering Zimbabwe. Follow the Whatsapp Channel: AtroServe Engineering Zimbabwe
