Subsidence is a term used to describe the downward movement of the ground beneath a building, which can be caused by the extraction of moisture from the soil. This can lead to the sinking of the foundation, which ultimately puts the entire structure at risk of collapsing.
Subsidence is typically observed in clay soils, which shrink as moisture is withdrawn due to factors such as trees or other vegetation. As the soil dries out, it can cause the foundation to shift downwards, leading to a range of issues for the building.
It is crucial to identify the signs of subsidence as early as possible to address the problem before it worsens. One of the most common indicators of subsidence is the appearance of cracks, particularly during dry months, which may close up again during wetter periods. Additionally, a decrease in the moisture levels of the soil beneath the foundation, cracks in slabs without intersections, and outward movement of exterior walls at the top may also signal subsidence.
What are the Signs of Soil Subsidence?
The superstructure exhibits wider cracks during the dry season and narrow cracks during the wet months. These cracks are present both internally and externally on brick walls, running diagonally and wider at the top. They are particularly noticeable near windows and doors and have a width greater than 3 mm. The upper soil layer beneath the foundation has recently become drier. Concrete slabs do not have intersecting cracks, and the external walls tend to move outward at the top. A deteriorating concrete driveway can be observed. Over time, the foundation has become increasingly distorted, with a bowl shape and a low point at the center. This distortion is more pronounced in the dry season. The exterior foundation grade beam is in direct contact with the surrounding soil during the drier months, and the plasticity index of the soil is greater than 25. Soil readings from a pocket penetrometer near the grade are high, indicating a dense soil structure with a value of approximately 4 TSF. The soil below the grade beam is difficult to probe, with a depth of more than 2.5 cm to 5 cm and is dry when excavated. Large tree roots are visible at grade, extending towards the structure.
FAQs
What is soil subsidence?
Subsidence occurs when the ground beneath a building sinks downwards due to the withdrawal of moisture. This downward movement of the ground can cause significant damage to the building, resulting in cracks in the walls and foundations, and other structural issues. The withdrawal of moisture can happen due to a variety of reasons, including changes in the water table, the removal of trees or vegetation, or even changes in the weather patterns. If left untreated, subsidence can lead to serious safety risks for those living or working in the affected building. Therefore, it is essential to monitor and address any signs of subsidence as soon as they are detected.
What are the effects of soil subsidence on a structure?
Soil subsidence is a phenomenon that can result in the sinking of a building’s foundation. When the ground beneath a building becomes unstable, it can cause the foundation to sink, which can then compromise the overall stability of the structure. This can be a serious problem for buildings of all types, as it can lead to structural damage and even collapse in extreme cases. Therefore, it’s essential to address soil subsidence issues promptly to prevent further damage to the building and ensure the safety of its occupants.
What are the types of soils in which subsidence is highly likely to occur?
Subsidence is a phenomenon that often takes place in clay soil. This occurs due to the drying out of the soil, which can be brought about by trees or other types of vegetation. When the soil becomes too dry, it loses its structural integrity, causing it to compress and settle. This can result in the ground sinking, which can cause a range of problems such as foundation damage, structural issues with buildings, and other similar issues. The drying out of the soil can occur due to a variety of factors, but it is often linked to the presence of trees or other types of vegetation.
What are the signs of soil subsidence?
Subsidence is a phenomenon that can be identified by several telltale signs. One such sign is the appearance of cracks in the ground during dry months, which tend to close up during wetter months. This is often due to the shrinking and expanding of the soil as it dries and becomes wet again.
Another sign of subsidence is a decrease in moisture levels in the upper layer of soil beneath the foundation of a building. This can be caused by the soil compressing under the weight of the building, which in turn can lead to structural damage.
Cracks that appear in slabs without any intersections can also be indicative of subsidence. These types of cracks are often wider at one end and taper off towards the other, indicating that the movement of the soil has caused the slab to shift.
Finally, the outward movement of exterior walls at the top is another common sign of subsidence. This occurs when the foundation of the building sinks or shifts, causing the walls to move outwards at the top. If left untreated, this can cause serious structural damage to the building over time.