Summary: To further enhance the engineering properties and performance of soil, a novel engineering material called soil stabilizer is commonly used during the construction process. The following article will introduce the specific applications and mechanisms of soil stabilizer in construction, compare it with traditional binding materials to highlight its economic advantages, and then present practical application cases to demonstrate its usage.
1. Overview of Soil Stabilizers
In the past, soil stabilization in construction projects often relied on materials like lime and cement. However, with the rapid development of the transportation industry, the drawbacks of these stabilization materials have become increasingly apparent, struggling to meet the demands of actual construction. Soil stabilized with lime has poor strength and is prone to cracking and softening, requiring a high lime-to-soil ratio. Excessive lime addition weakens the soil's strength, failing to meet the requirements for soil integrity in road projects. Soil stabilized with cement is susceptible to significant thermal contraction, frequent cracking, and lacks adequate frost and water resistance. Soil stabilizers, as a new material, offer superior compressive strength and water-repellent properties, adaptable to various soil types, including sandy soils. Additionally, they are environmentally friendly, capable of meeting the requirements of different road construction grades. Compared to traditional stabilization materials, they provide enhanced performance and greater economic benefits.
2. Soil Stabilizer Mechanism
Soil Stabilizer is a new type of engineering material characterized by its environmental protection and energy-saving properties. It is a composite of various inorganic and organic materials. When mixed with soil, it undergoes both physical and chemical reactions, altering the soil's properties. It converts free water in the soil into crystalline water, fixing it in place. It reduces the surface current of soil aggregates, weakens the double-layer of charges adsorbed on aggregates, enhances ionic concentration, and thereby aggregates particles. This leads to an expansion in volume, filling the soil pores. Through the action of compaction work, the stabilized soil becomes more stable and compact, with a higher density.
Soil Stabilizer Construction Application
3.1 Processing the lower sub-layer
To ensure that the subgrade meets the design requirements for cross slope, flatness, and strength, a check of the subgrade must be conducted prior to the placement of soil materials, and any uneven areas should be leveled.
3.2 Soil Sampling
Prior to construction, analyze the soil sample's composition and type, then determine the appropriate soil stabilizer and mix ratio based on the analysis results.
3.3 Test Section
On the construction site, a test section of 100-150 meters is selected to determine the soil spreading coefficient, appropriate moisture content, and dosage of stabilizer, among other data.
3.4 Material Preparation
Ensure that the soil collected is free of humus, branches, debris, etc., and that the collected soil has been sifted to remove any soil, sand, or stones exceeding the standard size. Additionally, ensure that the pile of soil is level and even.
3.5 Survey and layout, soil preparation and leveling
Based on the design plans, stakes are placed every 20 meters along the centerline and edge lines. The width of the subgrade edge should be 30 centimeters wider than the roadbed width. The required earthwork for the construction section is brought into the roadbed, roughly leveled using a bulldozer according to the measured height and width, and the thickness of the laid material is checked.
3.6 Spraying curing agent, material storage
Based on the data from the test section, calculate the water补给 amount for the test section, apply the curing agent, mix evenly, and then store the material for 6-10 hours. This method prevents excessive moisture in localized areas.
3.7 Integer
The grader is used to initially shape the road section, followed by rolling the area with a tire roller or tractor to identify uneven spots. A tooth rake is then used to loosen the low-lying areas to a depth of about 10 centimeters below the surface. The prepared solidifier mixture is filled into these locations to even them out, and the grader is used for a second shaping process.
3.8 Crushing
Upon proper moisture content, the compaction is typically performed using a three-wheeled roller (12 tons) and is done in 6 to 8 passes. Afterward, a check is conducted to ensure no distinct tire marks are present on the road. The mixed crushed stone is then spread onto the surface, with a thickness of approximately 3 centimeters, ensuring even distribution. Subsequent to this, the area is compacted again to ensure the stones are embedded into the base layer and no visible surface marks are left.
3.9 Maintenance
Following the aforementioned compaction, traffic was immediately halted post-density test, and maintenance commenced for a week. The road surface was then covered with grass bags for care, or watered for maintenance. If opting for watering, ensure at least two waterings per day.
4. Economic Advantages Analysis of Soil Stabilizer
4.1 Energy-saving and Environmental Protection
As social and economic development progresses, the scale of road construction has rapidly increased, leading to a surge in demand for raw materials such as sand and stone. The high demand for these materials has resulted in mountain destruction, deforestation, and environmental pollution. Particularly, the production of lime and cement consumes a significant amount of energy. However, the use of soil stabilizers can reduce the consumption of traditional binding materials, which is crucial for energy conservation and environmental protection, aligning with China's sustainable development strategy and advancing the construction of a resource-saving society. Moreover, the materials used for clay stabilizers are locally sourced, eliminating the need for transporting waste soil. This not only prevents environmental pollution but also avoids disruptions to traffic.
4.2 The construction process is relatively simple, reducing both construction and maintenance costs.
Soil stabilizers can modify abundant, cost-effective natural soil, converting it into subgrade and sub-subgrade materials for road construction. By utilizing existing road subgrade materials and sourcing locally, the construction process can be streamlined, with machinery similar to traditional road subgrade construction equipment, thus reducing labor demands. Compared to previously used subgrade materials, this method can achieve a cost savings of up to 15%. Additionally, the treated subgrade, whether in terms of strength or compactness, sees improvements. The surface's resistance to natural conditions is enhanced, extending its lifespan and reducing the frequency of maintenance, ultimately saving costs.
4.3 Project Timeline Shortened
The subgrade and sub-subgrade of roadbeds typically use cement-stabilized gravel or lime-stabilized soil, which increases the mining and transportation processes and is limited by the supply radius. In contrast, high-concentration soil stabilizers require less quantity, have lower transportation costs, and offer a wider supply radius; they are also non-combustible. Consequently, the use of stabilizers can shorten the construction period by 50%.
4.4 Excellent performance indicators
Through on-site testing, the subgrade or sub-subgrade treated with a stabilizer has seen a 40% increase in lateral confinement compressive strength. It remains intact when submerged in water at room temperature, demonstrating excellent waterproofing properties and suitability for use in winter regions. It boasts high compressive strength, good water stability, excellent durability, and frost resistance, significantly enhancing the lifespan of roads.
5. Case Study of Road Construction Project
A municipal road, spanning 1,128.782 meters in length with a width of 12 meters and designed for a speed of 40 km/h, has a low point at the K0+502.5 location where it passes beneath an airport highway. Due to the limited road elevation at this point, it serves as the lowest section of the entire road. With significant runoff in the area, the road has been submerged during the rainy season, leading to cracks, damage, and subsidence of the subgrade. The road underwent reconstruction in 2019, where soil stabilizer technology replaced 6% lime soil in the subgrade construction. Field measurements showed a design deflection value of 38mm, with an actual measurement of 27.2mm, both meeting the design specifications.
6. Conclusion
As economic levels advance and the transportation industry flourishes, the number of roadways opening increases, necessitating higher vehicle carrying capacities. Against this backdrop, the demands for civil engineering escalate, with an increased focus on road strength and compaction. Traditional solidification materials are no longer sufficient to meet these demands, but soil stabilizers can meet the standards and possess significant potential for development. Extensive experiments have already confirmed that soil stabilizers can alter the mechanical properties of soil, offering clear economic advantages. The application of soil stabilizers has already commenced in domestic highway and port construction projects.
