Collapsible soil can pose a problem for structures due to its tendency to experience significant settlement. Although it can withstand pressure with minimal settlement, its behavior changes drastically when it becomes wet, resulting in sudden and substantial volume reduction. Therefore, it is imperative for engineers to find an appropriate solution to address the issues related to collapsible soil.
In cases where the thickness of collapsible soil is low, removing it entirely can be a viable option. However, if the soil layer is thick, treating it to reduce its settlement potential becomes necessary. One method that can be used to address the thickness is compaction. This technique involves the use of heavy machinery to compress the soil, making it denser and less prone to significant settlement.
How to Deal with Collapsible Soil Before Building Construction?
1. Soil Replacement
When dealing with a thin collapsible soil layer, the optimal solution is to remove it entirely. This can be followed by compacting the construction site during the grading process. The removed material can either be replaced in several compacted layers or substituted with strong filler materials.
One possible material for replacing collapsible soil is sand or crushed stone. By using these materials, the bearing capacity of the construction site is increased, and the likelihood of settlement is significantly reduced. This approach is especially well-suited for road pavement construction.
2. Chemical Stabilization
Chemical stabilization is a method used to modify soil properties to minimize the risk of settlement. This technique involves the use of chemical additives such as cement, lime, or other substances that can interact with the soil, making it less likely to collapse. When it comes to treating collapsible soil, fly ash can be added to cement or lime to improve soil stability even further.
One option for stabilizing soil is to flood trenches with solutions of sodium silicate and calcium chloride. However, it is crucial that the material solution reaches the desired depth, or else it will not be effective in stabilizing the soil.
3. Pre-wetting
One possible solution for addressing the settlement of a collapsible soil layer is to apply flooding or force water through it. This process involves introducing water into the soil, which causes it to densify and reach equilibrium conditions as the water flows through it. To implement this technique, it is necessary to flood or force water through wells into the building footprint and wet the soil layer.
Before employing this approach, it is crucial to conduct a subsurface investigation to evaluate its effectiveness. In addition, prewetting should be combined with preloading or dynamic compaction to achieve the desired results. However, it is crucial to avoid flooding or forcing water into collapsible soil if there are structures around the construction site. Such action may cause damage to buildings adjacent to the construction site.
4. Select Suitable Foundation
Collapsible soils can pose significant challenges for construction projects. However, appropriate foundations can often provide effective solutions to deal with these issues. One possible solution is to use a deep foundation that can bypass the collapsible soil layer and transfer the load of the superstructure to a harder soil layer below.
Another effective approach is to use a mat or raft foundation that can withstand the large settlement that is expected to occur in the collapsible soil. By distributing the load of the superstructure over a larger area, these types of foundations can help to minimize the potential for differential settlement and ensure that the structure remains stable over time.
Overall, while collapsible soils can present significant challenges for construction projects, there are a variety of foundation options available that can help to mitigate these issues and ensure the long-term stability of the structure. By selecting the appropriate foundation based on the specific characteristics of the soil and the demands of the project, engineers can ensure that the structure is built to last.
FAQs
What is Collapsible Soil?
Collapsible soil is a type of soil that possesses a remarkable ability to resist pressure while experiencing minimal settlement. However, when this soil becomes wet, it undergoes a sudden and significant reduction in volume, which can create serious problems for structures built upon it. The primary issue with collapsible soil is the extensive settlement that it experiences, which can cause significant damage to buildings and other structures. As a result, this type of soil must be carefully managed and mitigated to ensure the safety and stability of any structures constructed upon it.
What are the problems with collapsible soil?
When collapsible soil becomes wet, it experiences significant settlement. This settlement can cause serious damage to the foundation of a structure. The damage can be severe enough to require extensive repairs. This is a common problem in areas with collapsible soil and can lead to costly repairs and potential safety hazards. It is important for engineers and builders to take this into consideration when designing and constructing buildings in these areas. Proper precautions must be taken to prevent damage and ensure the safety and stability of the structure.
How is collapsible soil treated?
Collapsible soil bearing capacity can be improved using various techniques. One such technique involves removing some of the soil to strengthen the remaining layers. Another approach is chemical stabilization, which involves adding substances to the soil to increase its strength and stability. Pre-wetting is yet another method that can be employed to improve the bearing capacity of collapsible soil.
Another strategy for mitigating the challenges posed by collapsible soil is to choose a foundation that is suitable for this type of soil. The foundation should be designed in such a way that it can bypass the problems associated with collapsible soil. This may include selecting a foundation that is more flexible or resilient than standard foundations. Ultimately, the key to successfully enhancing collapsible soil bearing capacity is to carefully evaluate the soil’s properties and select the most appropriate method for improving its strength and stability.
What type of foundation is suitable for collapsible soil?
When it comes to building on collapsible soil, the most appropriate type of foundation to use is deep foundation. This is particularly true in cases where multi-story buildings are being constructed. Deep foundation provides a much stronger and more stable base for the building, ensuring that it is less susceptible to collapsing or sinking due to the unstable nature of the soil.
When the soil is prone to collapsing, it means that it has a low bearing capacity, which makes it difficult to support heavy structures. Deep foundation, however, is designed to bypass the weaker topsoil and reach deeper into the more stable layers of the ground. This type of foundation can be achieved through various methods such as piling, drilled shafts, and other types of deep foundation systems.
By using deep foundation, the weight of the building is transferred from the weaker topsoil to the deeper, stronger layers of the soil. This helps to minimize the risk of structural failure or settlement, which is essential when constructing multi-story buildings. Ultimately, deep foundation is the most suitable choice for building on collapsible soil, as it provides a strong and stable base for the building that can withstand the forces of nature and the test of time.
When is soil replacement suitable for collapsible soil treatment?
When constructing roads, the soil replacement method is often employed. This method involves the removal of a particular layer of soil, which is then substituted with sturdy fill materials. This is done to ensure that the road is built on a strong and stable foundation, which will help to prevent any potential issues that may arise from weak or unstable soil. By replacing the weaker soil with more durable fill materials, the road is better equipped to handle the weight and pressure of heavy vehicles, as well as the various weather conditions that it may be subjected to over time. Overall, the soil replacement method is an effective way to ensure that roads are built to last and can withstand the demands of everyday use.