Agus Setyo Muntohar

UTILIZATION OF UNCONTROLLED BURNT RICE HUSK ASH IN SOIL IMPROVEMENT

In recent years, meshless methods have been developed as alternative numerical approaches in efforts to eliminate known drawbacks of the Finite Element Method (FEM). The main objective in developing meshless methods was to eliminate, or at least reduce, the difficulty of meshing and remeshing of complex structural elements. The nature of various approximation functions employed by meshless methods allows the definition of problem domains by simply adding or deleting nodes where desired. Nodal connectivity to form an element as in FEM method is not needed, only nodal coordinates and their domain of influence (DOI) are necessary to descretize the problem domain. Meshless methods may also reduce other problems associated with the FEM, such as solution degradation due to locking and severe element distortion [1].Issues related to pricing strategy in the Indonesian construction industry are covered, including problems of current pricing strategy in construction, exploration of pricing strategies with a marketbased approach, and survey findings of the top Indonesian contractors regarding their current pricing practices and the applicability of market-based pricing strategy models developed by Mochtar and Arditi. Comparisons with similar survey findings of the top U.S. contractors are conducted whenever possible. In conclusion, the belief that current pricing strategy in construction is predominantly cost-based is confirmed by the survey findings; indeed, in setting the markup, most contractors rely on subjective assessment of the competition. Using simulated bidding scenarios, it is discovered that Indonesian contractors tend to be more market-based as they know more about the owners characteristics, competitors characteristics, and market demand. Consequently, the implementation of bidding procedure proposed by Mochtar and Arditi is supported. To maximize the benefits of market-based pricing strategies, the bidding procedure change should be explored by all parties involved in the Indonesian construction industry.

Engineering Properties of Silty Soil Stabilized with Lime and Rice Husk Ash and Reinforced with Waste Plastic Fiber

AbstractAlthough abundant plastic waste contaminating the environment may be utilized as reinforcing materials, a potential pozzolanic material (rice husk ash blended with lime) possesses superior properties in stabilizing soils. Engineering behavior of the stabilized clayey/silty soil reinforced with randomly distributed discrete plastic waste fibers is investigated in this paper. The results indicate that the proposed method is very effective to improve the engineering properties of the clayey/silt soil in terms of compressive, tensile, and shear strength, which further enhanced the stability and durability of the soil. Based on the compressive strength, California bearing ratio (CBR), shear strength, and failure characteristics, the optimum amount of fiber mixed in soil/lime/rice husk ash mixtures ranges from 0.4–0.8% of the dry mass.

Influence of Plastic Waste Fibers on the Strength of Lime-Rice Husk Ash Stabilized Clay Soil

Duflow surface water hydrodynamic model has been applied using a case study from Nyando catchment in the western part of Kenya in Africa to simulate various extreme flood behaviours and their retardation levels by using selected structural measures as flood mitigation techniques. The objective of this case study was to establish a design flood recommendable for mitigation, and to identify the most cost effective flood mitigation structure. Various design flows are simulated against the different proposed structures hence, the optimal structure can be recommended when economical, social and environmental constraints are considered in the decision making process. The proposed four flood mitigation structures flood plain extension, embankment (dykes), channel by-pass, and green-storage were simulated for 20-year recurrence interval flood to determine their individual responses in storing excess water. The result shows that building a green-storage is the best and optimal structure for flood mitigation.

SWELLING AND COMPRESSIBILITY CHARACTERISTICS OF SOIL - BENTONITE MIXTURES

The using of Roller Compacted Concrete (RCC) is one of many alternatives that can be used to decrease dam construction cost. Many Roller Compacted Concrete (RCC) composition has been developed to achieve maximum compressive strength. Due to the economical consideration and the possibility of the execution, drop hammer system has been used for this research. Compression test is done after the age of the sample reaches seven, 28, 60, and 90 days. The result shows that 60/40 composition of gravel/sand has higher average compressive strength on all age of sample. The highest compressive strength the achieve is 17.78 MPa for 90 days sample.The slake-durability test is regarded as a simple test for assessing weathering of rocks. This simple test has been accepted as a standard test by the Rock Mechanics Society. However, mechanisms into slaking processes have not been fully understood yet as many factors involved in the processes. The current research explored mechanisms performed by the test by conducting a series of slakedurability tests for four types of soft rocks taken from Coober Pedy, South Australia. Results show that the slake-durability index (Id2) of weathered soft rocks was influenced by the degree of weathering. Distinctly weathered rocks had lower indeces compared to partly weathered rocks. Shapes also influenced the Id2 of these soft rocks. Different shapes displayed different mechanisms in the slaking processes. Samples that had irregular shapes tended to have a lower Id2 compared to samples that had rounded shapes. Thus, the slake-durability test might have simple procedures, but it could have complicated mechanisms in slaking processes that contribute to the result of the test.A method commonly used to stabilize expansive soils is mixing the soil with foreign materials. The main obstacle raised from soil stabilization in the field is the difficulty in mixing process. This paper presents the strength distribution in soft soil due to the addition of single columns of quicklime and carbide wasteproduct from gas industry that contains Calcium Oxide (CaO) up to 60%. The results show that the addition of columns filled with carbide waste product and quicklime increase the shear strength of surrounding soil. The spreading of the strength tends to follow a unique pattern, that the increase of soil shear strength at a certain normalized-distance, S (in column diameter D) from the column axis is constant. A significant increase of strength occurs in the area closer to the column, and it decreases with the distance from the column.

THE INFLUENCE OF MOLDING WATER CONTENT AND LIME CONTENT ON THE STRENGTH OF STABILIZED SOIL WITH LIME AND RICE HUSK ASH

The strength gain of stabilized soils is not only influenced by the type and proportion of the stabilizers and its curing time, but also by the water content needed to maintain the reaction. The reaction of lime – RHA with soil is pozzolanic. Hence, the process will be subjected greatly by the amount of water to react with admixtures and the proportion of the stabilizer. This paper presents the result of a laboratory study on the unconfined compressive strength (UCS) of soils stabilized with lime and RHA, compacted at the OMC, and at the dry and wet side of OMC. The amount of lime required for stabilization (LRS) is determined by Eades and Grims Method. The results showed that the water content determines the UCS characteristics of unstabilized and stabilized soils. The UCS of stabilized soils decreased with increasing molding water content, but it is still higher than of the un-stabilized soils. In general, higher lime content results to a higher UCS. The maximum strength of the stabilized soil is attained at lime/RHA ratio of 1/2. The UCS of the stabilized soil increased significantly about 7 – 9 times to the un-stabilized UCS.

A Numerical Method of the Flexible Pavement Supported by SSC on Expansive Soil

Many road and highway have been constructed over the expansive soil in Java island without proper soil improvement for the subgrade. The behavior of the column on the expansive soil needs for study numerically and large scale. In this study, a numerical analysis is performed to study the effect of swelling on the deformation of the soil stabilized column supported flexible pavement. The main focus of the research is to obtain the deformation due to swelling and vehicle loading. The methodology including comparison the differential settlement of the soil stabilized column supported flexible pavement and unsupported flexible pavement as control model. The numerical analysis was modeled using finite element method. The simulations result that the column installation to support flexible pavement reduced the heaving and differential settlement of the pavement effectively. In case the overlay was performed for rehabilitation and maintenance of the pavement, the mini-columns can be installed before the overlay works. However, the conclusions of the study were limited to the result of numerical modeling that depended on the applied material model and volumetric swelling.

Lessons Learned from the Recent Natural Disasters in Indonesia

Indonesia was at risk from this earthquake because the region was in the megathrust region. Two deadly earthquakes struck the region early and late in September 2009. A 7.3-Mw magnitude earthquake struck the Tasikmalaya District, West Java Province, at a depth of 30 km on September 2, 2009. Additionally, a magnitude 7.6 earthquake hit Padang on September 30, 2009, the epicenter of which was about 60 km northwest of Padang at a depth greater than 120 km. Massive geotechnical hazards were reported in those quakes. The bursting of the Situ Gintung dam on March 27, 2009 washed away housing and the settlement downstream of the dam. Some lessons can be learned from those disasters. This chapter aims to review the disasters’ geotechnical aspects. The recent disasters in Indonesia pointed out poor preparedness in disaster management. Households, governments, and schools have to enhance their awareness and understanding of collateral hazards. An integrated disaster early warning system (EWS) must be improved for high-risk regions to reduce damage and loss.