Sains Malaysiana 45(1)(2016): 141–156

New Progress in the Study of Intergranular Suction and Shear Strength of Unsaturated Soil

(Kemajuan Baharu dalam Kajian Sedutan Bebutir dan Kekuatan Ricih daripada

 Tanah Tak Tepu)

LIANSHENG TANG¹*, HAITAO SANG^2,3, LIQUN JIANG¹ & YINLEI SUN¹

¹School of Earth Sciences and Geological Engineering, Sun Yat-Sen University, Guangzhou, Guangdong 510275 China

²School of Engineering, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China

³Guangdong Province Key Laboratory of Geological Processes and Mineral Resources Guangzhou, Guangdong 510275, China

Diserahkan: 11 Julai 2014/Diterima: 15 November 2014

ABSTRACT

The suction between soil particles is the basis and core problem in the study of unsaturated soil. However, is the suction between soil particles just the matrix suction (which has been widely used since the discipline of unsaturated soil mechanics was established). In fact, the concept of matrix suction is from soil science and reflects the water-absorbing capacity of the soil. Matrix suction characterizes the interaction between soil particles and pore water rather than the interactions between soil particles, which were not in conformity with the principle of effective stress of soils. The suction of unsaturated soil, in essence, is the intergranular suction composed of absorbed suction and structural suction. In this paper, first, the basic concepts of absorbed suction and structural suction were briefly introduced. Then, with soil mechanics, powder science, crystal chemistry, granular material mechanics and other related disciplines of knowledge for reference, the quantitative calculation formulas were theoretically deduced for the absorbed suction for equal-sized and unequal-sized unsaturated soil particles with arbitrary packing and the variable structural suction for equal-sized unsaturated soil particles with arbitrary packing and unequal-sized unsaturated soil particles with close tetrahedral packing. The factors that influence these equations were discussed. Then, the shear strength theory of unsaturated soil was established based on the theory of intergranular suction through the analysis of the effective stress principle of unsaturated soil. This study demonstrates that the shear strength of unsaturated soil consists of three parts: The effective cohesive force, the additional strength caused by external loads and the strength caused by intergranular suction. The contribution of the three parts to the shear strength of unsaturated soil depends on the following influence factors: Soil type, confining pressure, water content and density. Therefore, these factors must be comprehensively considered when determining the strength of an unsaturated soil.

Keywords: Absorbed suction; intergranular suction; shear strength; structural suction; unsaturated soil

ABSTRAK

Sedutan antara zarah tanah adalah asas dan teras masalah dalam kajian tanah tidak tepu. Walau bagaimanapun, adakah sedutan di antara zarah tanah hanya sedutan matrik (yang telah digunakan secara meluas sejak disiplin mekanik tanah tak tepu ditubuhkan). Malah, konsep matriks sedutan adalah daripada sains tanah dan mencerminkan keupayaan menyerap air daripada tanah. Matriks sedutan menyifatkan interaksi antara zarah tanah dan air liang daripada interaksi antara zarah tanah yang tidak selaras dengan prinsip tegasan berkesan tanah. Sedutan tanah tak tepu, pada dasarnya, adalah sedutan bebutir terdiri daripada sedutan diserap dan sedutan struktur. Dalam kertas ini, pertama, konsep asas sedutan diserap dan sedutan struktur telah diperkenalkan secara ringkas. Kemudian, dengan mekanik tanah, sains serbuk, kimia kristal, mekanik bahan berbutir dan disiplin lain yang berkaitan pengetahuan untuk rujukan, formula pengiraan secara teori kuantitatif telah disimpulkan untuk sedutan diserap untuk sama bersaiz dan tidak sama rata bersaiz zarah tanah tepu dengan sewenang-wenangnya dan pembungkusan sedutan struktur tanah tak tepu yang berubah-ubah dan yang sama bersaiz zarah dengan pembungkusan sembarangan dan saiz zarah tanah tepu tidak sama rata dengan pembungkusan tertrahedron tertutup. Faktor yang mempengaruhi persamaan ini telah dibincangkan. Kemudian, teori kekuatan ricih tanah tidak tepu ditubuhkan berdasarkan teori sedutan bebutir melalui analisis prinsip tegasan berkesan tanah tidak tepu. Kajian ini menunjukkan bahawa kekuatan ricih tanah tidak tepu mengandungi tiga bahagian: Daya padu efektif, kekuatan tambahan disebabkan oleh beban luaran dan kekuatan yang disebabkan oleh sedutan bebutir. Sumbangan daripada tiga bahagian untuk kekuatan ricih tanah tidak tepu bergantung kepada faktor pengaruh berikut: Jenis tanah, tekanan mengurung, kandungan air dan ketumpatan. Oleh itu, faktor-faktor ini perlu dipertimbangkan secara menyeluruh apabila menentukan kekuatan tanah yang tidak tepu.

Kata kunci: Kekuatan ricih; sedutan bebutir; sedutan struktur; serap sedutan; tanah tak tepu

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*Pengarang untuk surat-menyurat; email: eestls@mail.sysu.edu.cn