Bujang Kim Huat

Geotechnics of Organic Soils and Peat

Peat and organic soils commonly occur as extremely soft, wet, unconsolidated surficial deposits that are an integral part of wetland systems. These types of soils can give rise to geotechnical problems in the area of sampling, settlement, stability, in situ testing, stabilisation and construction. There is therefore a tendency to either avoid building on these soils, or, when this is not possible, to simply remove or replace soils, which in some instances can lead to possibly uneconomical design and construction alternatives. However, in many countries of the world, these soils cover a substantial land area and pressure on land use is resulting in ever more frequent utilisation of such marginal grounds.

Influence of Cement – Sodium Silicate Grout Admixed with Calcium Chloride and Kaolinite on Sapric Peat

Abstract Sapric peat is extremely soft, unconsolidated and has high organic content. It is most decomposed peat with less fiber content among all peats. This paper investigates the effectiveness of using different ratios of cement–sodium silicate system grout compounds with kaolinite in mechanical property (shear strength) and micro–structural properties (SEM and EDX) of sapric peat samples after 3 and 30 days of curing. The study showed that the kaolinite was effective in increasing the shear strength and reducing the moisture content of the treated peat. Calcium chloride seemed to have different effects on the grouts strength. It caused to increased shear strength of samples until the net charge of the sample changed to zero and then it decreased with further increase in calcium chloride. By increasing sodium silicate (within 3%), cement and soaking time on treated peat, it was observed that they are able to increase the shear strength and density with a corresponding decrease in moisture content, porou...

Reinforcement Benefits of Nanomodified Coir Fiber in Lime-Treated Marine Clay

AbstractIn this study, reinforcing effect of nanomodified coir fibers with ferric hydroxide, Fe(OH)3, and aluminum hydroxide, Al(OH)3, on shear strength of limed marine clay soil was investigated. Accordingly, triaxial compression strength (TCS) testing was carried out to determine the shear strength parameters of the reinforced soil. Also, wetting/drying cycle testing was conducted to assess the durability of samples. The results from the experimental investigation show that the lime and nanomodified fibers improved the shear strength and durability through the intended modification on natural coir fiber. Moreover, an increase in the effective stress internal friction angle and the cohesion intercept were observed. To confirm the morphology alteration in fibers, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) tests were performed. Nanomodification of fibers increased their tensile strength and caused a better interaction with the limed matrix by an enhanced interfacial adhesion. The ...

Effect of Coir Fibers on the Tensile and Flexural Strength of Soft Marine Clay

The effects of the mechanical properties of the coir fiber which reinforces soft marine clay were investigated by a series of laboratory tests regarding unconfined-compression, indirect tensile properties, and three point bending. In this study, fiber content was found as the main factor that affected the strength of the soil specimens. The results indicated that for the unconfined compression test at the maximum dry density and optimum moisture content, compressive strength increased with fiber content up to 1%. A similar trend was also found in the tensile strength, flexural strength, and young’s modulus of the soil. The strength and ductility increased sharply until the threshold of 1.5% fiber content. Furthermore, the improvement in the mechanical behavior of the soil mixtures indicates that the use of fibers mixed with soft marine clay as potential building materials for land-based structures.

Structural geologic control with the limestone bedrock associated with piling problems using remote sensing and GIS: a modified geomorphological method

Geotechnical engineering and unpredictable piling problems of highly urbanized areas underlain by intensive geological fracture zones require a better understanding of their spatial pattern and developments. Unlike traditional techniques which use geophysical survey and visual interpretation of optical satellite images, this study presents a modified approach to revealing the buried geological fractures in karst terrain, which incorporates Wood’s algorithm. The algorithm binary maps were modified by applying additional Soble filter with 10% threshold and equalization enhancement. These modifications have proven good discrimination for morphological linear and curvilinear derived from DEM. Results of the modified method were compared to the existing geological map and validated by conducting field observations. The analysis of the results and corresponding geological and topographical maps showed the effectiveness of the method to recognize the pattern of buried geological fractures. The results obtained demonstrated that maps of the modified method can be used as a reference map prior to any site investigation.

Settlement Problems in Peat Due to Their High Compressibility and Possible Solution Using Cement Columns

Tropical peat soils are considered as extremely soft, wet, unconsolidated deposits. These kinds of soils are geotechnically problematic due to their high compressibility or high settlement and low shear strength. Cement columns may be used to improve the settlement problem of these soils. This paper describes the results of the effects of cement columns on the compressibility of fibrous tropical peat soils. Coefficient of consolidation, compression index, coefficient of secondary compression, and coefficient of volume compressibility were obtained by a Rowe cell test for both, untreated peat soil and peat soil treated with cement column. The results indicate that installing cement columns and increasing cement ratio could reduce the compressibility of peat soils and decrease its settlement dramatically.

Effect of Stabilizer Reagents on Zeta Potential of Kaolinite and Its Relevance to Electrokinetic Treatment

The influence of the dispersion of pH and concentration of chemicals on zeta potential of kaolinite were investigated. Adding the cationic species led to an increase of the zeta potential, contrary to measuring done in water. The results proved that even a very low concentration of the cationic species (0.001 mol/L) causes a remarkable change of the zeta potential. The zeta potential of the kaolinite soils varied from 204.6 to −41.9 mV, according to the chemical reagents and electrolyte concentration. Moreover, the negative charge in kaolinite soils is highly pH dependent and surface charge of pure kaolinite is dropped to zero, (pHpzc) at pH 3.2–3.5. The greater electrolyte concentration resulted in the thicker diffuse double layer and higher pH at the iso-electric point. While, for some reagents there was no isoelectric point that to be observed, increase the pH at isoelectric point and Na2CO3 as well as CH3COONa led to decrease in pH at iso electric point of suspension kaolinite. Results revealed that presence of low molecular weight CaCl2, , H3PO4, Na2Sio2, CH3COONa, and Na2CO3 led to a increase in diffuse double layer thickness in order of CaCl2, , Na2CO3 and H3PO4, and Na2SiO4, and electrolyte concentration has important effect on such incrasing. Based on results of ζ and pH observed from using different cationic species, those pHpzc which are more close to the soil pH (ζ is dropped to zero) are more succeptible to be chosen as best reagent to stabilizing soil.

Application of Geophysical Techniques for 3D Geohazard Mapping to Delineate Cavities and Potential Sinkholes in the Northern Part of Kuala Lumpur, Malaysia

This work describes the application of the electrical resistivity (ER) method to delineating subsurface structures and cavities in Kuala Lumpur Limestone within the Batu Cave area of Selangor Darul Ehsan, Malaysia. In all, 17 ER profiles were measured by using a Wenner electrode configuration with 2 m spacing. The field survey was accompanied by laboratory work, which involves taking resistivity measurements of rock, soil, and water samples taken from the field to obtain the formation factor. The relationship between resistivity and the formation factor and porosity for all the samples was established. The porosity values were plotted and contoured. A 2-dimensional and 3-dimensional representation of the subsurface topography of the area was prepared through use of commercial computer software. The results show the presence of cavities and sinkholes in some parts of the study area. This work could help engineers and environmental managers by providing the information necessary to produce a sustainable management plan in order to prevent catastrophic collapses of structures and other related geohazard problems.

Review of available approaches for ultimate bearing capacity of two-layered soils

Abstract This paper presents the state of the art report on available approaches to predicting the ultimate bearing capacity of two-layered soils. The article discusses three most popular methods, including the classical method, application of the finite element method and artificial neural network. Various approaches based on these three powerful tools are studied and their methodologies are discussed.

Utilization of Alkali-Activated Olivine in Soil Stabilization and the Effect of Carbonation on Unconfined Compressive Strength and Microstructure

This paper reports for the first time the stabilization of soil using olivine and the application of novel techniques utilizing alkaline activation and carbonation. A rigorous study addressed the effect of carbon dioxide pressure and alkali concentration (10-M sodium hydroxide soil additions from 5 to 20%) between 7 and 90 days. Microstructural and compositional changes were evaluated using microscopic, spectroscopic, and diffraction techniques. Results demonstrate the advantages of using olivine in the presence of NaOH and the associated increases in soil shear strength of up to 40% over 90 days. Samples subjected to carbonation for a further 7 days led to additional increases in soil strength of up to 60%. Microstructural investigations before and after carbonation attributed the strength development to the formation of Mg(OH)2, hydrated magnesium carbonates, and M─S─H, A─S─H gel phases. The impact of this work is far reaching and provides a new soil stabilization approach. Key advantages include significant improvements in soil strength with a lower carbon footprint compared with lime or cement stabilization.