Grouting As A Soil Improvement Technique
One of the well-known substances to add to soil is cement, which is usually added through the process of grouting. Grouting is attained by injecting fluid-like material (concrete, usually) into soil. The injection uses specially formulated cement-like liquid that either fills soil openings (such as pores, fissures, and voids) or pushes the cement at a high flow rate and pressure into the soil to create a new soil-cement mixture with increased strength. The main purpose of using this technique is to take easily dispersible clay soils and inject them with binding agents that help solidify them and prevent unforeseen movements due to excess seepage. Calcium chloride and sodium silicate are some other general examples of grouting material used to bind with soft soils and help strengthen them. These materials in particular present some noticeable advantages to the building process, such as being nontoxic, cost-effective, and presenting no harm of contamination. When using these kinds of materials during field applications, it is important to note specific times to inject said materials into the soil. For example, the suitable time to inject sodium silicate solutions into a soil can be set by selecting the time between the first turning point and the second turning point on the relational curve of the total amount of water volume drained and the soil’s time of treatment. Shortly after injecting the sodium silicate solution into the soil, it will become completely cemented, thereby drastically reducing the permeability of the soil.
The main type of grouting usually implemented for ground improvement involves the use of jet-propulsion to help open up groundwork, which is more commonly referred to as jet grouting. However, this is not the only way to get grout into soil. The other types of grouting methods that can be used on construction sites are pressure grouting, compaction grouting, and fracture grouting. Pressure grouting is practically the same as jet grouting as it involves injecting grout materials under a controlled pressure at strategic locations within the soil through high-velocity jets. This hydraulic process allows the soil to be cut, eroded, replaced, and mixed with the new cement in a way that efficiently forms uniform, high-strength columns. Pressure grouting has become one of the more essential ground improvement procedures used in the field, despite it requiring lots of expertise and personal judgements in order to execute it properly.
Compaction grouting is often used to implement displacement grouting, meaning it keeps ground settlement caused by projects like underground construction or deep excavation under control by making sure the soil stays dense. This technique provides the best help for stabilizing voids beneath the ground, such as sinkholes, by displacing and reinforcing these loose soils by means of injecting low-slump, low mobility aggregate grout. Like jet grouting, compaction grouting can be executed above water tables as well as below them, meaning the voids can be filled regardless if there is groundwater or saturated soils hidden beneath the soil layer being grouted.
Fracture grouting is a more uncommon technique as it is used to correct a problem that already exists rather than be used to prevent stabilization problems from happening in the first place. In scope with how this can be used in a project, this method of grouting is best used for re-leveling structures that already exist on a building site or are located above tunnels. To this, the injector is typically drilled into the ground at an angle to where the resulting grout can be pumped directly underneath the structure in need of leveling. This is the biggest difference that sets this method apart from the other methods as those methods usually benefit from being drilled directly vertical to the ground. Once the hole has been drilled, the slurry type of cement is then injected under pressure into the soil. As this slurry grout expands over time, the resulting hydro-fracture pressure of the treated soil increases. This increase in pressure then causes fractures to form inside the soil, and those fractures help the cemented soil to expand. The resulting expanded soil causes the ground above the soil to push upward, leaving newly elevated groundwork as the end result.
