Bulletin of the Geological Society of Malaysia, Volume 45, May 2002, pp. 265 – 270
1Department of Geotechnic, Faculty of Civil Engineering, UTM 81310 Skudai, Johor, Malaysia
2Department of Environment, Faculty of Civil Engineering, UTM 81310 Skudai, Johor, Malaysia
Abstract: Unstabilised and stabilised clayey sand soil with 6% of lime were cured in 190 mm and 100 mm diameter of cylindrical plexy-glass mould for 4 weeks to study the effect of lime on permeability and microstructure of the soil. The permeability of soils were measured for every 1 pore volume (PV) solution by falling the head method during the leaching test. The leaching test was conducted until 7 PV solutions. Scanning Electron Microscopic (SEM) was used to study the microstructures of both soils before and after leaching tests. The initial permeability of stabilized soil is typically lower compared to the unstabilised soil after curing for 4 weeks. The permeability of unstabilised soil samples was 7.02 x 10-9 m/s and the stabilised soil was 2.40 x 10-9 m/s. The unstabilised samples show the immediate decrease of permeability to 1.85 x 10-9 m/s with leaching 2 PV leaching solutions, whereas the stabilized samples show the immediate decrease of permeability to 1.86 x 10-10 m/s after 1 PV leaching solution. Further increase in PV values almost maintained the permeability of stabilized and unstabilised soils with average values of 1.42 x 10-10 m/s and 2.33 x 10-9 m/s respectively. The phenomenon of decrease of permeability is due to the clogging of fine particles in pore space and formation of cementitious minerals. The scanning electron micrographs showed the structure of layered kaolinite, angular shape of quartz and high pore space in the unstabilised soil. After leaching at 7 PV solutions, the unstabilized soil at the top layer indicated packed microstructure and good reorientation of clay particles. Whereas, the structures at the bottom layer showed a more packed structure, flocculated and with low pore space. The scanning electron micrographs showed the formation of cementitious mineral in stabilized soil. After leaching with 7 PV solutions, the dissolution of cementitious minerals occurred and formed new channel. However, the dense cementitious minerals at the bottom layer were flocculated, link with one another and clogged up the fine particles in pore spaces. The test result indicates that addition of lime could modify the microstructure and reduce the permeability of the soil.
Abstrak: Tanah pasir berlempung yang tak distabilkan dan tanah yang distabilkan dengan 6% kapur dalam bekas selinder pleksi-kaca berukuran 190 mm dan diameter 100 m telah diawet selama empat minggu, bertujuan menentukan kesan kapur ke atas ketelapan dan struktur mikro tanah tersebut. Ketelapan tanah yang ditentukan dengan kaedah turus menurun ditentukan pada setiap 1 isipadu pori (PV) larutan semasa ujian larut lesap. Ujian larut lesap dijalankan sehingga 7 PV larutan. Kajian mikroskopik pengimbas elektron (SEM) pula telah digunakan untuk mengkaji struktur rnikro kedua-dua tanah sebelum dan selepas ujian larut lesap. Ketelapan awal tanah yang distabilkan adalah rendah berbanding tanah yang tak distabilkan selepas di awet selama 4 minggu. Ketelapan bagi tanah tak distabilkan ialah 7.02 x 10-9 m/s dan tanah yang distabilkan ialah 2.40 x 10-9 m/s. Sampel tidak distabilkan menunjukkan pengurangan dengan pantas nilai ketelapan menjadi 1.85 x 10-9 m/s setelah dilarut lesapkan dengan 2 PV larutan. Manakala sampel yang distabilkan pula menunjukkan pengurangan ketelapan dengan pantas kepada 1.86 x 10-10 m/s setelah larut lesap 1 PV larutan. Peningkatan nilai PV seterusnya menunjukkan nilai ketelapan dikekalkan pada 1.42 x 10-10 m/s dan 2.33 x 10-9 m/s masing-masing bagi tanah distabilkan dan tanah tak distabilkan. Fenomena pengurangan nilai ketelapan adalah disebabkan oleh halangan butiran halus dan pembentukan mineral bersimen. Mikrograf pengimbas elektron menunjukkan struktur berlapis kaolinit, butiran bersudut kuarza dan ruang pori yang tinggi dalam sampel tanah yang tak distabilkan. Sampel tanah tak distabilkan selepas 7 PV pada lapisan atas menunjukkan struktur mikro yang padat dan butiran lempung yang teratur dengan baik. Manakala struktur lapisan bawah pula menunjukkan struktur yang lebih padat, mengalami flokulasi dan dengan sedikit ruang pori. Mikrograf pengimbas elektron menunjukkan tanah yang distabilkan menghasilkan mineral bersimen. Setelah dilarut lesapkan dengan 7 PV mineral bersimen mengalami pelarutan dan membentuk alur baru. Walaubagaimanapun bahagian bawah lapisan tanah menunjukkan mineral bersimen yang lebih tumpat mengalami flokulasi, bersambungan antara satu sama lain dan halangan butiran halus dalam.ruang-ruang pori. Keputusan kajian tersebut menunjukkan penambahan kapur boleh mengubah struktur mikro dan mengurangkan ketelapan tanah.
https://doi.org/10.7186/bgsm45200240
