Infiltration Characteristics of Unsaturated Residual Soils of Various Weathering Grades

Kertas kerja ini memperihalkan kajian yang telah dibuat di lapangan mengenai ciri–ciri penyerapan air ke dalam tanah baki pelbagai gred yang tak tepu. Dua tapak ujian dikaji, iaitu tapak A dan tapak B. Tapak–tapak ini mewakili tanah baki daripada batuan yang lazimnya terdapat di Malaysia, iaitu tanah baki granit dan tanah baki sedimen (batu kapur). Kadar penyerapan air didapati bergantung kepada darjah luluhawa tanah. Untuk tanah baki granit, tanah bergred IV didapati mempunyai kadar penyerapan air yang tertinggi. Kadar penyerapan ini didapati bertambah daripada tanah bergred VI ke gred IV, yang kemudianya menurun daripada gred IV ke gred III. Kadar penyerapan air juga didapati bertambah dengan bertambahnya keliangan dan nisbah lompang tanah, dan menurun dengan meningkatnya ketumpatan tanah. Bagi tanah sedimen (batu kapur) pula, tanah bergred III didapati mempunyai kadar penyerapan yang tertinggi. Kadar penyerapan air di dapati meningkat daripada tanah bergred V ke gred III. This paper presents the results of a field study on the infiltration characteristics of unsaturated residual soils of various weathering grades. Two field sites were studied, namely site A and site B. These sites respectively represent two of the most commonly occurring residual soils or rocks in Malaysia, that is the granitic residual soil and sedimentary (sandstone) residual soil. The water infiltration rate is found to vary depending on the soil weathering grades. For the case of granitic residual soils, soil of weathering grade IV was found to have the highest infiltration rate. Water infiltration is found to increase from grade VI to grade IV, and decrease from grade IV to grade III. Water infiltration is also found to increase with the increase in the soil porosity and void ratio, and decrease with the increase in the soil density. While for case of sedimentary (sandstone) residual soil, the soil of weathering grade III was found to have the highest infiltration rate. Water infiltration is found to increase from grade V to grade III.