Developmental research of sustainable technologies to minimise problematic road embankment settlements

Challenging, problematic and non-uniform ground conditions are a night mare to geotechnical engineers tasked with the design and construction of buildings and transport infrastructure. These often suffer undesirable structural settlements. Designing within the current understanding of geotechnics; settlement in peat and organic soils need to be recognised to include the known “primary and secondary consolidation characteristics” and the lesser known “tertiary consolidation phase”. These eventually contribute cumulatively to the consequential uneven and hazardous “bumpy road” surfaces. Undulating flexible road pavements result primarily from the transference of the heavy self-weight of the embankment fill to yielding and non-uniform subgrade. The adoption of conventional design/repair methods such as pile, vertical drain, soil replacement and soil stabilisation are expensive and inappropriate in very soft ground conditions. These then lead to unjustifiably high and repetitive maintenance costs. There being no one quick fix solution for all; pragmatic research must necessarily identify the best/progressively improved practical and sustainable solution. A viable solution is to develop criteria and explore the concept of a “masonry arch bridge structure/lintel-column structure” and adopting sustainable materials through pragmatic searching for appropriate recyclable waste materials. This will lead to the basis for a sustainable, innovative, strong, stiff, permeable composite mat structure that can be used on soft and/or yielding ground conditions. Conceptual lightweight fill technology including the popularly used expanded polystyrene (EPS) and the innovative composite mats recently being developed by the research team are outlined

Categorization of slope failure in southern Malaysia using total estimated hazard (TEHD) method

Slope is a measure of steepness or the degree of inclination of a feature relative to the horizontal plane. One of the phenomenon or incidents of a slope was called as slope failure or landslide. Slope failure was a major natural disaster that had affected the country in terms of injuries, deaths, property damage, destruction of services, public inconvenience and economic as well as financial losses. Slope failure cases were very serious geologic hazard disaster that happened in many countries around the world. The aim of this paper is to determine the category of slope failure in the state of Johor based on Landslide Hazard Zonation (LHZ). Data were calculated by using Total Estimated Hazard (TEHD) value method which considered six factors effecting the slope failure, including lithology; slope steepness, topography, land use class, annual rainfall and type of soil. Data on the factors were collected from Malaysia Public Works Department (JKR) inspection form, website, and secondary data resource. After that weight for each factor were identified by referring to Landslide Hazard Evaluation Factor (LHEF) rating scheme. Then determination of LHZ was done according to TEHD values which have five hazard zones; (1) very low; (2) low; (3) medium; (4) high; and (5) very high. The results of this study found that out of total fifty two cases there were three medium hazard (MH), twenty seven high hazard (HH) and twenty two very high hazard (VHH). Comparison between actual data from JKR and total 52 locations of slope failure in Johor showed that 94% accuracy, TEHD equation could calculate potential slope failure hazards in Johor very well

Sustainability study of the application of geosynthetic clay liners in hostile and aggressive environments

This paper discusses the sustainable performance of geosynthetic clay liners (GCLs) which are popularly specified as “leachate retaining” or as “water proofing” membranes in the geo-environmental construction industry. Geosynthetic clay liners (GCLs) are composite matting comprising of bentonite clay with two covering geosynthetics. These are innovative labour saving construction material, developed over the last three decades. The paper outlines the variety of Geosynthetic Clay Liners (GCLs) can be classified essentially into two distinctly different forms viz; (a) air dry (< 8% m/c) with granular or powdered bentonite or (b) bentonite cake factory prehydrated to a moisture content (~40% m/c) beyond its shrinkage limit and vacuum extruded as a clay cake to enhance its sustainable performance. The dominant mineral in bentonite clay is the three-layered (2:1) clay mineral montmorillonite. High quality bentonites need to be used in the GCL manufacture. Sodium montmorillonite has the desired characteristic of high swelling capacity, high cation exchange capacity and the consequently very low hydraulic conductivity, providing the basis for the hydraulic sealing medium in GCLs. These encapsulate the active montmorillonite clay minerals which depend on the water and chemical balance between the sealing element and the surrounding geo environment. Quantitative mineralogical analyses and an assessment of the adsorbed cation regime, diffusion coefficients and clay leachate compatibility must necessarily be an integral part of the site appraisal to ensure acceptable long term sustainability and performance. Factors influencing the desired performance of bentonite in the GCLs placed in difficult construction and hostile chemical environments are discussed in this paper. Accordingly, the performance specifications for GCLs are identified and the appropriateness of enhancing the cation exchange capacity with polymer treatment and the need for factory prehydration of the untreated sodium bentonite is emphasised. The advantage of factory prehydrating the polymer treated bentonite to fluid content beyond its shrinkage limit and subsequently factory processing it to develop laminated clay is to develop a GCL that has enviable sealing characteristics with a greater resistance to geochemical attack and cracking. Since clay liners are buried in the ground as base liners, capping layer or as structural water proofing membrane, they can easily avoid strict quality and performance monitoring being “out of sight, out of mind!”. It is very necessary that barrier design for leachate containment must necessarily be in accordance with legislative requirement Assessment of long term hydraulic conductivities and clay-leachate compatibility assessment is deemed necessary. The derogatory factors affecting the sustainable performance of the bentonite in GCLs placed in difficult construction and hostile chemical environments are discussed. Sustainability concepts incorporated in waste management practice must aim to achieve 100% recycling and fully implement the handling of solid waste in developing countries with relatively lower labour costs

Comparative Study of Stress-Strain Characteristic of Peat Soil

Abstract. This paper shows the stress-strain behavior of peat from the perspective of geotechnical engineering based on laboratory test. Stress happens when a load applied to a certain specimen and deformed the specimen while strain is the response from applied stress on a specimen. Peat is known as an ultimate soft soil in engineering terms because it has low shear strength and compressibility. This research is concerned about the stress-strain behavior of hemic peat. The undisturbed samples were collected at Parit Sulong and Parit Nipah, Batu Pahat, Johore, Malaysia. Normal stresses are 12.5kPa, 25kPa, 50kPa and 100kPa. The shear rate to determine the stress-strain on peat is 0.1mm/min. It is a drained condition test. Both results from each method that obtained were compared based on the relationships of stress-strain. Parit Sulong has higher stress-strain than Parit Nipah. If shear stress increased, shear strain also increased. The result shows that, direct simple shear test of stress-strain that tested on hemic is more relevant than a direct shear box because DSS shear the entire specimen of peat while DSB only shear at the center of the specimen. Geotechnical engineers can use the direct simple shear method to understand efficiently about the stress-strain behaviour of peat

Young's modulus of peat soil under cyclic loading

Peat soil classified as high organic content with diverse range of fibers, distinctive intrinsic properties with low shear strength. The behaviour of peat soils under dynamic loading conditions has been studied. Therefore, a series laboratory of cyclic triaxial test on peat soil carried out to determine the effect of cyclic loading to the peat soil behavior after subjecting to cyclic loading is presented. In this study, the frequencies applied for the dynamic testing on the peat soil samples were focused and simulated on traffic vehicle loading frequencies, earthquakes and machine operations. Peat soil sample used from Parit Nipat, Malaysia (PNpt) with natural moisture content, m = 603% and liquid limit of wl = 231%. A series of undrained cyclic triaxial test were performed on undisturbed peat soil sample under isotropically consolidated specimens. In addition, the strain of amplitude applied is 0.1% to investigate the effectiveness of large strain amplitude response by allowing the generation of cyclic pore pressure and developed stress-strain cycle during cyclic loading. Correspondingly, the undrained Young's modulus of the undrained shear strength subjected to cyclic loading in this study in the range of 60 to 70 for hemic peat soil. The specimen loaded into specific frequency causes in reduction of Young's modulus related to stiffness and more pronounced in softening behaviour. The hysteresis-loops profile with regard to E parameters from 1st cycle to 100th cycles of Young's modulus, E (MPa) for PNpt degrades precisely to an applied effective stress, 0.4 MPa (25 kPa) and 0.4 MPa (50 kPa). Cyclic loading frequencies resulted in decreases of the Young's Modulus of peat soil that related to stiffness and more pronounced in softening behaviour. The result indicates that a reduction effect in the stress-strain cycle occurs in a peat soil from the initial stage of cyclic loading towards the end of 100th cycles due to the repeated loading application

Geotechnical characteristics of peat

Peat soil is encountered in many areas and generally originates from plant/animal remains and is considered partly as decomposed biomass. Due to this composition, the structure of this soil is very different when compared with inorganic soils like clay, sand and gravel. Peat has a high compressibility, low shear strength, high moisture content and low bearing capacity. The behaviour and composition of peats in different geographical areas are different from one another, accentuating the need in soil engineering for a useful geological classification of peat soils. This paper focuses on presenting a comparative overview of the characteristic geotechnical properties for these soils. It also examines and discusses the effects of composition on the basic properties and behaviour of each soil, supported by case studies from Malaysia.Soft Soil

Determining the peat soil dynamic properties using geophysical methods

The small strain dynamic properties of peat soil are a fundamental parameter related to the mechanical behaviour of a structure constructed on peat ground. These parameters are used in evaluation of the dynamic behaviour and seismic design in geotechnical structures. Determination of dynamic properties of peat soil is often done using laboratory-based tests that risk overestimation and underestimation due to sample disturbance. Since geophysical methods are proven to be able to obtain small strain dynamic properties with similar magnitude as the laboratory tests, it has become popular and is increasingly used in practice. Two geophysical methods known as multichannel analysis of surface waves (MASW) and seismic refraction were performed in this study to estimate the small strain maximum shear modulus (Gmax) and maximum elastic modulus (Emax). The results showed the value of Gmax and Emax were ranging from 1.01 to 6.83 MPa and from 3.88 to 10.9 MPa respectively. Correlations were also established to assist in estimating Gmax and Emax on peat soil with bulk density. There appears to be a particularly good link between the Gmax, Emax and bulk density. Overall, the small strain dynamic properties determined shows significant increment with depth which could be governed primarily by the effective stress. Other parameters such as water content, bulk density, organic content and degree of decomposition also could significantly influence the dynamic properties of peat soil

Comparative study of British and Malaysian peat soils pertainting to geotechnical characteristics

Peat soils occur in many countries and are described differently at times from both a qualitative and quantitative perspective. Peats are formed naturally through the decomposition of plant and animal matter under anaerobic conditions that take place over long periods of time. While the estimated and reported extent of Malaysian peat was approximately 2.6 million hectares respectively [12], there is an estimated 1.6 million hectares (minimum) of peat land available in British [6]. In British, peat soils are classified as Bog and Fen Peat. However in Malaysia, peat soil is described and generally termed as basin and valley peat [4]. The behaviour and composition of these peats are different from each other, accentuating the need for a useful engineering geological classification of peat soils. These soils are known for their low shear strength and high compressibility characteristics leading to unstable ground conditions. This paper focuses on comparative study an overview of the characteristic geotechnical properties for these soils. It also examines and discusses the effect of basic properties and behaviour of composition of each soil with case studies that had been done by one of the authors at Western Johore, Malaysia.Soft Soil

Settlement behavior of treated hemic peat at Parit Nipah, Johor

Peat is classified as soft material which consists of decaying wood and plant remains. Peat has been considered as a challenging material for engineers due to its high natural moisture content, large void ratio, and high compressibility. Its rapid initial settlement followed by large long-term settlement always caused problems for any form of construction on peat. Numerous ground stabilization method for peat have been developed in recent years. Polyurethane grouting is one of the ground stabilization method that is gaining recognition as a fast and effective way to stabilize ground. Polyurethane is a lightweight material with high compressive strength. This study investigated the settlement of polyurethane treated peat under static embankment through full scale testing at Research on Peat Station (REPEATS), Parit Nipah, Johor. The peat in Parit Nipah is categorized as hemic peat with thickness of 4.0m. Four static embankments were constructed representing different depth of peat stabilization by polyurethane grouting. The settlement of the embankments was monitored on daily basis. Results indicated that the injection of polyurethane grout into the peat able to reduce the settlement of peat under static embankment loading. This study also shows the potential of polyurethane grouting to mitigate long term settlement of peat

Microstructural analysis of fired clay masonry brick under aggressive environment

The microstructural changes in fired clay masonry brick, exposed to various aggressive environments were studied. Test samples were subjected to sodium sulphate, sodium chloride and a combination of chloride-sulphate. Beside, for the durability of specimens exposed to chloride and sulphate attack, 5, 10, and 15% solutions were used. Micrographs of the internal structure were taken at the age of 180 days. Energy-dispersive X-ray spectroscopy (EDX) analyses were performed on scanning electron microscope (SEM) images. SEM/EDX studies revealed that halite is the main deterioration product for the samples exposed to sodium chloride where thenardite formations were dominant products of deterioration in the case of sulphate attack. However, the combination of sodium sulphate-chloride produced a double compound in the specimens