**2. Materials and methodology**

### **2.1 Soil**

Locally available clayey soil was found form the nearby hill slope in the outskirt of Guwahati city of Assam state in India. The particle size distribution curve of the tested soil is presented in **Figure 1**. The soil confined 25%, 54% and 21%, sand, silt and clay size particles, respectively. The soil had 46% liquid limit, 25% plastic limit value. As per Unified Soil Classification System (USCS) according to ASTM D2487 [40], the soil was classified as low plastic clay (CL). The coefficient of uniformity and the coefficient of curvature based on the gradation curve were 12.5 and 3.125, respectively. The optimum moisture content (OMC) and maximum dry unit weight (MDU) values of the soil were 19.4% and 16.8 kN/m3 , respectively as per ASTM D698 [41].

#### **2.2 Reinforcement**

Glass fiber of 20 mm length nd 0.15 mm average diameter was used as reinforcement (**Figure 2**). The glass fiber has specific gravity and water absorption capacity as 2.57 and zero respectively. The modulus of elasticity, tensile strength and elongation at break of the glass fiber were 112.3 GN/m3 , 1.53 GN/m2 , and 1.8%, respectively. As glass fiber has higher stiffness, strength, high ratio of surface area to weight, dimensional stability [42], and is ready available and non-biodegradable [43], it can be more valuable for long-term soil remediation. Glass fiber has also been found to retain its elastic modulus and tensile strength at 70–75% of that of raw fibers even under 450°C temperature [44] and thus will be suitable for the country where environmental temperature becomes high in the range of 50° in summer.

**Figure 1.** *Particle size distribution curve of clayey soil.*

*Experimental Investigation of Glass Fiber Reinforced Clayey Soil for Its Possible Application… DOI: http://dx.doi.org/10.5772/intechopen.102802*

**Figure 2.** *Commercially available glass fiber used in this study.*

### **2.3 Specimen preparation**

Designated weight of dry soil, fiber and water was taken and mixed in a steel tray. At first, the dry soil was mixed only with water, and then fiber was added with moist soil in small increments manually taking proper care. Thereafter, the soil-fiber homogeneous mix was shifted to a poly bags and reserved in a desiccators for 24 hrs to confirm its moisture steadiness. Afterward, the soil-fiber mixture was compacted in a cylindrical mold of 38 mm inner diameter having detachable collars at both ends for UCS and triaxial test sample. The whole amount of moist soil-fiber mix was shifted into the mold from either end, after fixing the collar at the other end. Subsequently, compaction was done from both ends by giving simultaneous equal rotation to the collars till the specimen length of 76 mm was attained. For CBR test, the specimen was compacted in CBR mold using standard proctor compaction energy as per ASTM D 698 [41].

It was decided not to go for fiber content above 1% as with 1% fiber content, homogeneous mixing of fibers was difficult due to formation of soil-fiber lumps. 20 mm fiber of different fiber doses (*f*c = 0.25, 0.5, 0.75, and 1% by parent soil dry weight) were selected to mold the soil-fiber samples.

### **2.4 Testing programme**

The standard compaction tests were performed for unreinforced and glass fiberreinforced soil according to ASTM D698 [41] to obtain the OMC and MDU value of various mixes. Unconfined compressive Strength (UCS) test were performed as per ASTM D 2166/D 2166 M [45] with 1.25 mm/min axial strain rate for all specimens. Consolidated undrained (CU) triaxial tests were performed according to ASTM

D4767 [46] with an axial strain rate of 0.12 mm/min for different soil fiber mixes under varying confining pressure ranging from 100 to 400 kPa. Load, axial deformation and pore pressure during triaxial test were electronically measured and recorded by load cell of a capacity of 10 kN with a sensibility of 0.01kN, LVDT of capacity ±20 mm with a sensibility of 0.01 mm and pore pressure transducers, respectively. The CBR tests were performed as per ASTM D 1883 [47] under both unsoaked and soaked conditions for all soil-fiber mixes.
