Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Effects of soil fillers, vegetation lateral variation and basin ‘dome’ shape on tropical lowland peat stabilization. Mohamad Tarmizi Mohamad Zulkifley1*, Roslan Hasyim3, John Kuna Raj1, Ng Tham Fatt1, Wan Hasiah Abdullah1, Azman Abdul Ghani1, Mustaffa Kamal Shuib1, Muhammad Aqeel Ashraf1, Ahmad Farid Abu Bakar1, Jasmi Hafiz Abdul Aziz1, Nur Iskandar Taib1, Meor Hakif Amir Hassan1, Nur Islami Rahman1, Ismail Yusoff1 & S. Paramananthan2 1Department 2Param of Geology, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia Agricultural Soil Surveys (M) Sdn Bhd, A4-3 Jalan 17/13, 46400 Petaling Jaya, Selangor, Malaysia 3 Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia *Corresponding author: email address [email protected], [email protected], tel: +6016-5773114 Extended Abstract : Field mapping involving observation, identification, characterization, classification (von Post) to map and identify the natural extent and occurrence of tropical lowland peat deposits was carried in the Kota Samarahan-Asajaya study area in West Sarawak (Malaysia). Field identification and classification indicates that there is a lateral variation of peat humification levels (von Post) in the form of dominantly occurring fibric, fibric to hemic, sapric and hemic to sapric peat, occurring from margin and towards the centre of the tropical lowland peat dome or basin (Engineering Geology Working Group, 2007). Cement-peat stabilization (Alwi, 2008; Wong, 2010; Wong et al., 2008; 2009 and 2011) can be achieved or enhanced with the addition of mineral soil fillers (silt, clays and fine sands) obtained from Quaternary floodplain deposits and residual soil (weathered schist). Unconfined Compressive Strength (UCS) of the stabilized cement-mineral soil filler-peat mix is observed to increase with the further addition of selected mineral soil filler (msf) in increasing quantities. Results indicate that there is a lateral variation of stabilized peat strength (UCS) occurring on the top 0 to 0.5 metres layer, from margin towards the near-centre, of the tropical lowland peat dome. This study indicates that these stabilized strength variations are at the maximum near the dome/basin margin/periphery, followed by a decrease to a low (intermediate) at the mid-section area and progressively increases back again further towards basin centre of the peat dome. Almost all the stabilized cement-filler-peat mix specimens with added msf (silt, clay and fine sands) that were tested, exhibited brittle or shear failures with no barrelling except for the specimen with peat obtained from KS.TP.08 which exhibited dominantly more shear failure than barrelling failure. In conclusion, topogenic, clayey, high-ash or shallow peats (with more naturally occurring in-situ msf content) occurring near or at the margin/periphery of the peat dome/basin have relatively higher UCS compared to the deeper intermediate topogenic to ombrogenic, low-ash peats (with relatively lesser or no natural msf content) occurring at midsection or towards the basin centre. Furthermore, stabilized peat specimens from topogenic, marginal, shallow, transitional peat areas also exhibited relatively better, uniform and consistant cylindrical shape, less deformation, are denser, are harder, has lesser cracks, lesser holes, less indentations and lesser joints/discontinuities at the tamped layer planes. These observations may probably reflect the enhanced field conditions of the stabilized peat columns if msf were applied in the cement-filler-peat stabilization process and targetted at the marginal/fringe, topogenic, shallow peat areas of the peat basin/dome. Variations of UCS of stabilized tropical lowland peats occurring with varying distance from periphery towards the centre of the peat dome in the current scope of this study, is probably caused by a combination of factors due to variations of mineral soil or ash content in the peat and the indirect effect of horizontal zonation or, lateral variation of dominant species of plant assemblages (due to peat swamp forest successive vegetation zonations occurring from periphery towards centre of the tropical lowland peat dome). These factors are further associated to the shape of the peat basin or ‘dome’ shape (Anderson, 1964; Anderson and Muller, 1975). The observed stabilized strength zonations are: (a) Fibric or fibric to hemic, topogenic, clayey, shallow, transitional peats that usually occur near the basin margin or near the peat-soil lithological boundary with relatively higher natural, mineral soil (naturally deposited silt/clay/sand) or ash content that act as “natural fillers”, that may probably have contributed to relatively higher UCS of cement-msf stabilized peat when compared to peats occurring at locations intermediate and towards the centre of the peat dome; (b) Sapric, intermediate topogenic to ombrogenic peats that occur at intermediate locations between basin margin and towards the centre of peat basin with lesser “natural msf” or ash content that may likely produce cement-msf stabilized peat with a relatively lower UCS; (c) Ombrogenic, sapric peat (from decomposed hardwood fragments of tree logs, broken branches, bark and roots contributed by dominant, hardwood, plant species (e.g. Shorea type)) that occur in these vegetation zones (phasic community II to IV) towards and near the centre of the peat swamp forest, may produce cement-msf stabilized peat with a relatively higher UCS compared to stabilized peats occurring at the mid-section area (phasic community I) . Hence, lateral or horizontal vegetation succession (phasic community zonation) which is indirectly due to the tropical lowland peat basin “dome” shape and unconfined compressive strength of the stabilized cement-mineral soil filler (msf)-peat mix may probably be associated in tropical lowland peat basins/domes. Keywords: tropical lowland peat dome or basin; mineral soil filler; cement-soil filler-peat stabilization; topogenic to ombrogenic; unconfined compressive strength; lateral vegetation succession Acknowledgements: The authors greatly appreciate financial assistance from University of Malaya IPPP research grant no PV018/2011A. References: Alwi, A., 2008. Ground improvement of Malaysian peat soils using stabilized peat-column techniques. Ph.D thesis, University of Malaya, Kuala Lumpur(Malaysia). 260 pp. Anderson, J.A.R., and Muller, J., 1975. Palynological study of a Holocene peat and Miocene coal deposit from NW Borneo. In: Review of Palaeobotany and Palynogy 19(1975), 291-35. Elsevier Scientific Publishing Company, Amsterdam, Netherlands. Anderson, J.A.R., 1964. The structure and development of the peat swamps of Sarawak and Brunei. Journal of Tropical Geography 18, 7-16. Engineering Geology Working Group, 2007. Guideline for Engineering Geological Investigation in Peat and Soft Soils. Minerals and Geoscience Department of Malaysia. Wong, L.S., 2010. Stabilization of peat by by chemical binders and siliceous sand. PhD thesis. University of Malaya, Kuala Lumpur (Malaysia). 260 pp. Wong, L.S., Hashim, R. and Ali, F., 2009. Unconfined compressive strength of cemented peat. Australian Journal of Basic and Applied Sciences 3(4), 3850-3856. Wong, L.S., Hashim, R. and Ali, F., 2011. Unconfined compressive strength characteristics of stabilized peat. Scientific Research and Essays 6(9), 1915-1921. Wong, L.S., Hashim, R. and Ali, F., 2008. Engineering Behaviour of Stabilized Peat Soil. European Journal of Scientific Research 21(4), 581-591.