1. Introduction
Plate-shaped clay particles can be assembled in many ways. The ability of some clay particles to attract and hold water molecules on their surfaces and absorb them is of great interest. It is well known that water molecules exhibit a phenomenon known as polarization, in which each molecule has a distinct charge on its opposite sides, one positive and the other negative [
1]. These polar water molecules adhere to each of the plate-shaped particles, forming a film of charged fluid on them. The swell or heave noticed in the swelling soil when the water content of this soil is increased is caused by the clay particles repelling one another as a result of the “double layer phenomenon”, which emerges when distinct nearby particles are taken into account. Greater clay-particle-specific surfaces and higher charge densities make clay soils better suited to take water into their structure. The liquid limit and plastic limit indices are used to determine how well a cohesive soil can keep water molecules inside its structure. Montmorillonite clays have the greatest tendency to swell when compared to other clay minerals, whereas kaolinite has relatively low swelling potential [
2].
She et al. [
3] used a model test to study the swelling behavior of expansive soil at various elevations under fully saturated conditions of water injection from the top to the bottom. The results showed that there was a clear distinction in swelling between the expanding soil layers at various elevations during the saturation process and the electric charge effect, which comprises two variables, The primary causes of the swelling disparity between diverse expansive soil layers were (i) the transformation impact and (ii) the electrical environment. The expansive soil’s ability to expand may be lessened in the first scenario due to the cation exchange that occurs between expansive soil and aggregation bivalent cations. Additionally, the water film that has formed around the aggregates prevents additional water molecules from adhering into the montmorillonite interface, which halts the expansion of the swelling soil.
A swelling soil was treated by Fattah et al. [
4], including a different range of additives, such as cement, steel fibers, gasoline and cement-based grout. Results were better when cement grout was injected or when the expansive soil was treated with 5% cement or steel fibers, although 4% gasoline oil is enough to show this material’s best uses. The treatment does not affect the angle of internal friction, but the addition of these components caused a small variation in the adherence of the additive to the particles of the soil, which has a small impact on the cohesion between the particles.
A soil treated with waste fly ash was studied by Baloochi et al. [
5]. The findings of this study, demonstrated that adding different percentages of waste fly ash causes stabilized soil to expand, but that the expansion can be slowed down by waiting for around 30 min before combining the material with water and compacting it.
Al-Soudany [
6] used clayey soil mixed with 30, 50 and 70% of bentonite and stabilized the mixing soil with 3, 5 and 7% of nano-silica fume, and the findings showed that the Atterberg limits, specific gravity, maximum dry unit weight and optimum water content improved when increasing the nano-silica fume percentage.
When built on expansive soils, roads and other structures that are considered as light structures are significantly impacted. After a few years, the capacity of these soils to heave causes damage to these structures due to the swelling pressure, which causes cracking and swelling, with rapid lifting of the subgrade beneath the road and foundations causing cracks in the floor, walls and road that result from water seeping into the soil [
7]. By utilizing the technique of stabilization of soil, which is a general term for any physical, chemical, or biological method, or any combination of these methods, used to enhance or change the specific characteristics of natural soil to make it usable for the intended engineering work, the risk posed by such soils can be reduced [
8].
The moisture content of the soil changes as a result of precipitation or evapotranspiration in tandem with the climatic or seasonal changes in the region, known as the active zone or seasonal zone, which is sufficiently close to the ground surface. With the depth of the active zone, the major portion of the soil zone that experiences swelling phenomena increases [
9]. The geography, climate, soil type and soil structure all have an impact on the depth of the active zone (depth of desiccation), which typically ranges between 1 and 4 m [
10].
To analyze the features and behavior of this type of soil under circumstances that are comparable to those observed in the field, a variety of methodologies have been utilized to quantify the potential magnitude of swell in clay. Das [
11] presented a simple laboratory test that is used to determine the magnitude of swelling pressure in soils, which is the “oedometer test”. According to ASTM D 4546 [
12], the sample is added to the oedometer cell with a modest surcharge of 6.9 kN/m
2, and water is then added to cause the soil sample to expand, which allows the volume to be measured until equilibrium is attained. It is possible to express the amount of free swell as a ratio:
where:
SW(free): free swell as a percentage;
ΔH: change in height of swell due to saturation;
H: original height of the specimen.
According to Negi et al. [
13], if fine-grained clay soil passes through a 75 mm screen at least 25% of the time, has more than 0.3% sulfate, has a plasticity index above 10 and contains more than 1% organic material, stabilization is required. Before it may be used as a sub-base, sub-grade or base for the construction of highways, bridges and many structures, expansive soil needs to be stabilized. The main goals of stabilizing the soil are to make the natural soil more rigid and hard and to lessen its flexibility and tendency for shrinkage and swelling [
14]. According to Firoozi et al. [
14], stabilized expansive clay soil has a higher bearing capacity when a heavy load is placed on it.
For expansive soils to have a lower likelihood of expanding, soil stability is essential [
15]. Chemical stabilization seeks to offer additives that decrease and increase for both the liquid limit and plastic limit, respectively, as well as decreasing the plasticity index as a result of the liquid and plastic limits. As a result, the stabilized soil becomes more compressible, which improves the workability of the soil, the water content and the maximum dry density.
The shear strength of soils treated with cement is increased, but the liquid limit, plasticity index and swelling potential are all reduced [
16]. Since only a tiny amount of cement is needed, stabilizing granular soils using cement has proven to be more effective and cost-effective. According to research, it is difficult to treat soils with a plastic index (PI) > 30 with cement; for this reason, lime is added before mixing to maintain the soil’s workability. This study also demonstrated that when the cement concentration is increased from 0 to 12%, the unconfined compressive strength (UCS) improves, and the soil flexibility decreases, changing from 57.81% to 27.57%.
With the use of the F1 ionic stabilizer, the basic physical parameters and shear strength parameters of this reinforced expanding clay were examined from an engineering standpoint [
17]. The expansive clay soil’s water sensitivity, compaction properties and shear strength were all greatly enhanced by the F1 ionic soil stabilizer. The adequate water and F1 ionic soil stabilizer mixture was determined at 0.5 L/m
3. According to the findings, adding F1 ionic stabilized to expansive clay soil raised the plastic limit by around 46%, increased the maximum dry unit weight by around 6%, decreased the liquid limit by around 10% and increased both the ideal moisture content and plastic limit. In terms of cohesiveness and the angle of internal friction, the shear strength parameters were both raised by around 64 and 30%, respectively.
According to Liu et al. [
18] who suggested a combined seepage–erosion water inrush model, a grouting thickness of 6 m is appropriate for various types of soils. These studies illustrate why the amount of water surge should be used as an evaluation metric for grouting effectiveness. For the grouting materials’ slurry to permeate the soil, they must have a particular level of grout ability [
19]. Technical problems including poor hole formation and challenging slurry diffusion must be addressed by the grouting procedure. For different flowing water circumstances that may arise during grouting, Liu et al. [
18] recommended the selection criteria for injection materials and grouting volume per meter.
Wu et al. [
20] studied the effect of grouting for a tunnel in a case study. The findings demonstrated that minimizing the amount of water surge is mostly achieved by the displacement of the support structure and the thickness of the curtain grouting. The tunnel’s ability to stop water rapidly is essentially unaffected by a grouting thicknesses greater than 5 m.
The objective of this study is to stabilize an expansive soil with (5, 7 and 9%) lime, cement, and silica fume to reduce the free swelling and swell pressure. A grouting technique is used through a small-scale model to improve the bearing carrying capacity, as a technique that can be used in the field. The methodology adopted in this paper presents a practical method of utilizing cement, lime, and silica fume as grout to swell soil, so as to enhance its properties. Thus, the suggested method of applying a stabilizer through grouting can be considered as a new method.