Indonesia is the largest coconut producing country in the world. However, the resulting coir waste is still rarely used for structural materials. This research studied the effect of random inclusion of coir fiber on the shear strength of clay with high plasticity. The carried test in this study is a direct shear strength test. The fiber content variations used are 0%, 0.25%, 0.50%, 0.75%, and 1% of the dry weight of the mixture with a fiber length of between 30 mm to 50 mm. The results show that the reinforcement of coir fiber can increase the cohesion and friction angle. The maximum increase in cohesion value was obtained at fiber content of 0.75%, which was 39.66%. The increase in the value of the friction angle was obtained at 1% fiber content, which was 46.67%. The optimum coir fiber content was achieved at the fiber content of 0.75%. With this content, the value of the shear strength reaches its maximum with an increase of 39.4% at a normal stress of 8.071 kPa.
Abstract. Nailed slab system has been developed as an alternative rigid pavement on unstable soils such as soft soil and expansive soil. Nailed slab system is a rigid pavement system, which consists of a thin plate (thickness 12 cm-20 cm) reinforced with micro piles with a diameter of 15 cm-20 cm and a length ranging from 1.5 m -2.0 m. On soft soil, the nailed slab system can increase the modulus of subgrade reaction and shows better performance than conventional rigid pavement systems in their ability to support the load. However, behaviour nailed slab system on expansive soil still needs to be researched. This research aims to study the behaviour of nailed slab system on expansive swelling soil under heavy and loading test. On expansive soil, nailed slab system was subjected to uplift force due to the soil expansion. Small scale experimental models have been done in the laboratory. Nailed slab system models with a variation in the length of piles have been made. The test results showed upward displacement on nailed slab system were smaller than the slab without pile; pile was functioned as heavy reducer. The upward displacement observed on the unreinforced slab was 57.40 mm and 39.85 mm on a slab reinforced with 25 cm length of pile, decreased the upward displacement of 30.57%. The longer pile produces, the smaller vertical displacement. The Modulus of subgrade reaction on the slab reinforced with 25 cm piles length was two times greater than the unreinforced slab. Soil expansion causes decreased modulus of subgrade reaction, with reinforcing and increasing pile's length (L) the difference in its modulus of subgrade reaction due to soil expansion decrease.
In foundation design on an expansive soil, the most critical step is to quantify accurately the magnitude of heave and swelling pressure due to change in moisture content. The one-dimensional oedometer has been widely accepted method to determine the heave and swelling pressure of expansive soil. Its simplicity, suitability, and the availability were the reasons for the frequent use of oedometer swell testing technique, but many procedures were identified to measure the swelling properties. Each testing procedures were not unique and resulted different swelling properties and heave prediction. Then, this paper provides an overview of various existing heave prediction by oedometer methods and evaluate common practices of this methods. The techniques were reviewed systematically and summarized. The study summarized a state-of-the-art heave prediction based on the oedometer methods. Various equations forms to predict heave based on the oedometer method have been presented, but the fundamental principles were the same to propose the equation of heave prediction. The differences in these methods were related to the procedures in which the heave index parameter were determined. The three main procedures of oedometer test, i.e. consolidation swell (CS), constant volume CV, and swell overburden (SO), have been summarized. Most of the heave prediction uses the parameter from CS and CV methods. Several reports have shown that the closest estimates of field heave were predicted based on CV method.
Expansive soils are clay that swells and shrinks with changing moisture content. The pavement that constructed on these soils is subjected to large uplifting forces caused by swelling. Hence, there is an imperative need to counteract the problem posed by these soils by devising innovative pavement technique. An attempt to develop a simple, easy to install and cost-effective alternative pavement system, nailed slab system was developed, wherein slab pavement will be connected to a reinforced concrete mini piles.This research examines the emerging role of mini piles in the context of reducing soil uplift movement and the nailed slab system (pile supporting slab pavement) a system for minimizing slab movement due to swelling in expansive soil by conducting small-scale experimental modeling in laboratories. The heave prediction also doing by using the correlation between change in moisture content and vertical strain from oedometer test data. The results of this study indicate that reinforcing the soil by using the mini piles can reduce heave of soil, and the nailed slab system experiencing smaller upward movement than an unsupported slab. The connection between the pile and the slab has a significant effect on the system's ability to withstand the upward movement of expansive soil. When pile and the slab were monolithically connected, the system shows the better performance than those the slabs with the free head pile. Thereafter a heave prediction analysis provided the amount of heave that slightly overestimates, but still good enough for a rough estimation.
This research aims to determine the optimum bitumen content for sandy soil stabilization (sandy soil obtained from Glagah beach, Kulon Progo). Variation in bitumen content being used was 0% to 5% by weight of dry soil. Against, a mixture of bitumen and sandy soil proctor compaction tests was performed to obtain optimum moisture content (OMC) mixture which then was tested its California Bearing Ratio (CBR). The addition of bitumen content in soil stabilization with bitumen causing a continuing lack of OMC (Optimum Moisture Content) and increased MDD (Maximum Dry Density) on the compaction process. The maximum CBR value, 20%, was obtained at 2% bitumen content. . There was an increase of 150% CBR value when compared with the original soil without stabilization. CBR tends to decrease with further increase of the bitumen content up to 5% which may due to the mixture being more plastic.
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