Physico-mechanical characteristics of tropical granite boulders in weathered heterogeneous zones for geotechnical design purposes

The presence of isolated or clustered granite boulders in tropical weathered masses commonly formed a very thick heterogeneous zone in weathering Zone 3 to 5. The boulders with various characteristics are always misinterpreted during the geotechnical design process due to being poorly understood and studied. This study aims to determine the physico-mechanical characteristics of boulders in different weathering zones for design purposes. The parameters studied include boulder types, porosity, density, durability, point load and uniaxial compressive strength. Results revealed boulders in weathering Zone 3, 4 and 5 can be classified into Type A, B and C, respectively. These boulders have significant differences in physical and mechanical properties. The boulders in Zone 4 and 5 consists of corestone, ringlets and saprolites and the boulders in Zone 3 have no ringlets. Corestones have the highest durability, point load and compressibility strength with a median of 94.5%, 7.80 MPa and 187.07 MPa, respectively. The ringlets possess the highest porosity range of 23.3%–31.3% compared with saprolite. Saprolite in Zone 5 has the lowest durability, point load and compressive strength with respectively less than 7%, 0.22 MPa and 1 MPa. The various characteristics of the boulders in different weathering zones could influence the geotechnical design model

Effect of moisture content on the strength of various weathering grades of granite

This paper presents the variation in strength reduction for various weathering grades of granite due to increase of moisture. This problem often associates with the wet tropical region where thick weathering profile and heavy rainfall are expected. Both field and laboratory studies were carried out in order to assess the rock material properties. The field study involved weathering identification and observations at site. Laboratory tests were carried out to determine the strength, weathering grade, petrology of rock material and moisture content of the materials. A total of 300 samples from various weathering grades were tested at a wide range of moisture content varying from oven-dried to saturated condition. The results revealed that the absorption of water is highly dependent on the weathering grade. The petrological analysis revealed that the content of clayey mineral increase with the weathering grade through the decay of feldspar and ferromagnesian minerals. The point load index reduced up to 137.99% with the increase of only 21.40% of moisture content for highly weathered granite (grade IV). However, in a lower weathering grade (Grade II), a strength reduction of only 21.41% was noted with increase of moisture of 0.27%, although samples have been immersed in water for 60 minute. From the field and laboratory test, reductions of rock material strength from various weathering grade with regards of moisture content are suggested

An excavatability classification system for surface excavation in sedimentary rocks

This paper describes the development of an excavatability classification system for surface excavation of weathered sedimentary rock based on practical excavations and statistical analysis. Extensive field and laboratory studies were undertaken on three sedimentary rock sites with a range of weathering and strength conditions in the Iskandar region, South Johore, Malaysia. Rock mass descriptions were made in the field and rock material tests were carried out in the laboratory. Statistical analysis was used to study the correlation between the rock parameters and the productivity of excavation. A classification rating system based on the analysis results is proposed. The proposed classification system incorporates rock parameters such as point load strength (Is50), Schmidt Rebound hammer value (R), uniaxial compressive strength (UCS), density of rock (γ), indirect tensile strength (ITS), second-cycle of slake durability index (Id2), joint number (Jn), joint spacing (Js), joint length (JL), joint direction (Jd), existence of iron pan (IP), moisture content (Mc) and existence of bedding. The proposed model was then verified against further excavations on another sedimentary rock site. It was found that the productivities recorded correlated well with the proposed system when tested on a fourth site

Performance evaluation of existing surface excavation assessment methods on weathered sedimentary rock

This paper is intended as a contribution to the discussion of the overview of existing excavatability assessments and their reliability in assessing the state of tropically weathered rocks, specifically in Nusajaya, Johor, Malaysia. For this purpose, case studies were conducted on sedimentary rock masses of the Jurong formation, located in Nusajaya, Johor. The existing available rock mass excavatability assessments were first critically reviewed. Three case studies were then conducted in order to assess the performance of surface excavatability in these sedimentary rock masses by practical excavation tests on site. Comparisons were then made between the assessments of those assessors and that obtained through the practical excavation test. The conclusions made in the paper about the results of the study show many divergent opinions among the assessors. It emphasizes the limitations of existing available assessments in predicting the excavatability of tropically weathered rock masses. Further complication may arise in sedimentary rock masses where different layers of rock are interbedding, producing different weathering profiles. In view of these, a simpler graphical method, which considers only two parameters, namely point load strength and spacing of surface discontinuities, was introduced to overcome the problems, thus might be misjudged during early excavation assessment. This subjectivity becomes more important as the heterogeneity of a rock mass increases with increasing interbedding and inherent anisotropy of the rock material, giving rise to quite different evaluations, even for a rock with the same state of weathering. Most of the existing excavatability assessment methods are found to be less reliable because nature, lithology and weathering state at various rock mass layers is not being taken into account. A more practical and appropriate excavatability assessment method is thus required to economically assess the tropically weathered sedimentary rock during the preliminary stage

Assessment of weathering effects on rock mass structure

This paper presents an assessment of weathering effect to the rock mass structure by studying the joint characteristics of tropically weathered granite. Joint survey was performed by scanline method and the results were analyzed statistically by stereographic projection plots. The overall trend of mean joint spacing followed a sharp decrement from fresh to moderately weathered zone and then a slight increment to highly and completely weathered zones, whereas the overall trend of mean joint trace length showed a gradual decrement over progress of weathering. In addition, the degree of joints inclination and weathering zones revealed an increasing trend in the percentage of horizontal joints from fresh to completely weathered rocks, while no specific relation was found between the numbers of major joint set and different weathering zones. The results of this study may contribute to understanding the behavior and better classification of weathered granitic rock mass as a heterogeneous mass in engineering works

Waste management and recycling practices of the urban poor: a case study in Kuala Lumpur City, Malaysia

This study assesses waste management and recycling practices of the urban poor households residing as squatters and in low cost flats of Kuala Lumpur city, Malaysia. To attain the objective, the study employed some statistical techniques such as t-tests of equality of means, one-way analysis of variance, chisquared ‘likelihood ratio’ tests, and simple descriptive statistics. The statistical techniques were used to determine and analyse the factors that significantly influence the environmental behaviour of the urban poor concerning solid waste management, particularly their recycling practices. The findings of the study show that the urban poor and low-income communities have been proved to behave in ways that are consistent with and conducive to environmentally friendly solid waste management. This study provides evidence that the urban poor and low-income communities are the main recyclers, re-users, and source-reducers of their household solid waste. The study, however, suggests that policies should be formulated to focus on promoting knowledge, education, and the skills of the urban poor and, in addition, to empower them as a means of improving their quality of life.Md. Wahid Murad, Chamhuri Siwa

The effects of ABC, ICA, and PSO optimization techniques on prediction of ripping production

As blasting has some environmental constraints, ripping has got more prevalent as a method of breaking ground in both civil and mining engineering applications. A rippability model of a higher applicability is, therefore, needed to appropriately predict the ripping production (Q) prior to carrying out such tests. For the purpose of predicting the results of ripping production that were attained in three sites located in Johor state, Malaysia, the present study applied three hybrid intelligent techniques, i.e., neuro-bee, neuro-imperialism, and neuro-swarm, to predict Q. In fact, the effects of artificial bee colony (ABC), imperialism competitive algorithm (ICA), and particle swarm optimization (PSO) on weights and biases of neural networks were examined in the current research to receive better prediction/evaluation of ripping production. To do this, totally, 74 ripping tests were taken into consideration in the investigated regions and their influential parameters were assessed. Many parametric studies on ABC, ICA, and PSO parameters were conducted, and then, a comparison was done on the obtained results of the predictive hybrid models using several performance indices. As confirmed by the comparative results, the neuro-bee model proposed in this study estimated Q with a higher accuracy than the other hybrid models. The root-mean-square error (RMSE) values of 0.060, 0.076, and 0.094 were obtained for testing the data sets of neuro-bee, neuro-imperialism, and neuro-swarm techniques, respectively. This clearly shows that the newly developed hybrid model was superior to its rival in terms of predicting the ripping production. Furthermore, results of sensitivity analysis showed that weathering zone is the most influential factor on ripping production as compared to other inputs

Utilizing regression models to find functions for determining ripping production based on laboratory tests

The selection of suitable overburden loosening method has a crucial importance in several applications of geotechnical engineering. Factors such as rock properties and environmental constrains play a significant role in the selection of the needed equipment for overburden loosening. This paper presents several new models/equations for prediction of ripping production (Q) using rock material properties. To this end, three sites in Malaysia were selected and a total of 52 direct ripping tests were conducted in Johor state on sandstone and shale rock types. In addition, using the collected block samples, point load test, Brazilian test, slake-durability test, p-wave velocity test and uniaxial compressive strength test were also carried out in the laboratory. Numerous equations have been proposed to predict Q considering simple regression, linear multiple regression (LMR), and non-linear multiple regression (NLMR) models. Simple regression analysis indicated that the relationships between rock material properties and Q were meaningful and acceptable. Furthermore, both LMR and NLMR equations indicated similar performance capacity in predicting Q. Nevertheless; the use of NLMR equations resulted in prediction performance with higher accuracy in estimating Q compared to LMR equations