No abstract

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.

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.

Shear strength behavior of expansive soil reinforced by randomly placed fiber depends on the added materials’ content. This research investigated the effect of the waste coconut fibers content on the stress-strain relationship, the shear strength parameters, and the mixture’s elastic modulus. In this study, the coconut fiber content was varied from 0.25% to 1% with 0% fiber as control. The clay samples were tested after mixing by unconsolidated-undrained triaxial test. In general, according to the test result, the inclusion of randomly placed waste coconut fiber has enhanced the peak deviatoric stress, the shear strength parameters, and the elastic modulus. At 0.6% fiber content, the shear strength and the samples’ elastic modulus have increased to 79.46% and 153%, respectively, compared with those not reinforced with coconut fiber.

This study explored the investigation into enhancing soil strength characteristics using eggshell powder (ESP) as a lime substitution on soil-lime stabilization. The ESP was naturally available while using this material, which could reduce cost and other environmental effects. The influence of varying percentages of eggshell powder as a lime substitution in changes of the strength and durability is observed based on the unconfined compression test conducted on two soil and two lime types (hydrated lime and quicklime). Influence factors were studied, including soil and lime types, ESP content, curing time, and durability against wetting-drying (w-d) cycles. The unconfined compressive strength (UCS) and the durability values of ESP-stabilized soils decreased, while ESP content increased. However, this value was higher than the unstabilized ones. The ESP substitution on soil-lime stabilization marginally affected the strength and durability of soil-lime stabilization. The UCS increased with the increasing curing period for all specimens. Soils with more clay particles reacted better to both hydrated lime and quicklime. Additionally, strength development occurred in soil-quicklime mixtures more than in soil-hydrated limes. Based on a durability test, it was known that the maximum ESP substitution was 50% from the Optimum Lime Content (OLC); beyond that content, the strength of soil might dramatically be degraded.