In order to construct a stable foundation, it is important to carefully consider the soil conditions of a given site. Soil investigation is typically carried out to determine the existing ground conditions and soil properties to inform the selection of an appropriate foundation type. However, when the soil is found to be poor in bearing capacity or consists of filled subsoil, the designer must make decisions regarding potential solutions.
The first option for the designer is to relocate the construction project to a site with more suitable soil conditions. If the poor soil depth is not too significant, excavation and replacement with good compacted soils may be feasible. However, this method can carry a risk of differential settlement of foundations and may be uneconomical for depths greater than 4 meters.
Another option is to improve the soil’s bearing capacity through consolidation or compaction via surcharge load. This involves placing heavy loads of aggregates or other materials on the ground surface to speed up the settlement process. However, this approach may delay the construction project as the process can take weeks to years depending on the soil type.
Vibration of the ground surface is another method of soil improvement that involves compacting coarse granular particles to create stone columns within the ground. This technique utilizes a large poker vibrator to rearrange and compress the soil, resulting in an increase in bearing capacity up to 200 to 500kN/m2.
Dynamic compaction is a method of improving soil bearing capacity that involves dropping a heavy weight from a considerable height. This approach is particularly effective in granular soils and may require drainage of water before implementation. The size, weight, and height of the drop are selected based on the specific site conditions, and typically 3-4 drops are made in each location, forming a crater up to 2.5 meters deep and 5 meters in diameter.
Dynamic compaction is a method used to improve the bearing capacity of soil by creating vibrations in the surrounding area through the free-fall of a heavy weight. However, this can cause issues for nearby structures and buildings due to the vibrations produced. Therefore, before using this method, it is crucial to consider the condition of existing buildings in the area.
Another method for consolidating ground is jet grouting, which is suitable for all types of subsoil. This process involves lowering a monitor probe into a pre-bored guide hole with a diameter of 150mm. Jet grouting is a reliable and efficient way of consolidating ground, which makes it a popular choice among engineers and construction professionals. It can be used in a variety of settings to improve the stability of the ground and ensure safe and durable construction projects.
The image displayed in the center of the paragraph shows the process of jet grouting, which is carried out using a probe that has two jets. The upper jet shoots water, which is pressurized with compressed air, to dislodge any loose material and bring it up the guide to the ground level. On the other hand, the lower jet injects cement slurry to fill the void, which solidifies into a hard mass over time.
This process is widely used in construction projects to create strong, stable foundations in soil or rock. The high-pressure water jet dislodges and removes any weak or unsuitable material, and the cement slurry injection fills the void and creates a solid, stable mass that can support the weight of the structure. Jet grouting is particularly effective in difficult soil conditions such as loose sand, gravel, or rock, where conventional foundation methods may not be feasible.