Sains Malaysiana 48(11)(2019): 2521–2528

http://dx.doi.org/10.17576/jsm-2019-4811-22

Modelling Viscous Behaviour of Clayey Geomaterials using Single Mechanical-Analogue Model

(Pemodelan Sifat Kelikatan Bahan Geologi Berlumpur menggunakan Model Analog Mekanik Tunggal)

NOR SHAHIDAH MOHD NAZER*

Centre for Earth Sciences and Environment, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

Received: 4 April 2019/Accepted: 15 August 2019

ABSTRACT

The design of sustainable early warning systems for landslide prone areas requires deep understanding of the kinematic of landslides with emphasis on the evolution of its movement. This is controlled by many factors, and creep is a major one. Creep is perceptively slow land sliding process where the movement is nearly imperceptible and occurring at a rate of millimetres (mm) per year. This article reports the results of investigations of the viscous shear behaviour of clayey geo-materials, in particular creep and relaxation, which were carried out using a direct shear box. The viscous behaviour was investigated by either measuring the decay in shear stress at constant relative horizontal displacement (stress relaxation test) or by measuring the evolution of relative horizontal displacements at constant shear stress (creep test). Initially, 3 elements model of spring and dashpots combination was proposed to simulate the viscous behaviour of clayey geo-materials. However, because the loading system of direct shear box is not stiff and is showing some creep/relaxation interplay during viscous test, effect from the compliance system of the shear box must be carefully considered when formulating mechanical models for saturated and unsaturated slope kinematics. Another elastic element was added to the 3 elements model to address the issue of deforming loading system. The proposed modified model capable of simulating creep and stress relaxation response using a single set of parameters and thus, allowing creep response to be inferred from stress relaxation response by means of direct shear test in lab.

Keywords: Clayey geomaterials; mechanical-analogue model; modelling; viscous

ABSTRAK

Penciptaan Sistem Amaran Awal untuk kawasan dedahan tanah runtuh memerlukan pemahaman mendalam terhadap kinematik tanah runtuh dengan penekanan terhadap evolusi pergerakannya. Ianya dikawal oleh banyak faktor, dan rayapan adalah yang paling utama. Rayapan adalah proses pergerakan tanah secara perlahan kerana pergerakan adalah hampir tidak dapat dikesan dan berlaku pada kadar milimeter (mm) setiap tahun. Kertas ini melaporkan hasil kajian sifat kelikatan ricihan bahan geo-lempung, khususnya rayapan dan santaian, dilakukan menggunakan kotak ricih terus. Sifat kelikatan dikaji melalui pengukuran pereputan tekanan ricih pada anjakan mendatar seragam relatif (ujian santaian tekanan) atau melalui pengukuran evolusi anjakan mendatar relatif pada tekanan ricihan seragam (ujian rayapan). Asalannya, model 3 unsur yang terdiri daripada gabungan spring dan peredam telah dicadangkan untuk mensimulasi sifat kelikatan bahan geo-lempung. Walau bagaimanapun, memandangkan sistem bebanan kotak ricih terus tidak pegun dan menunjukkan sedikit saling rayapan/santaian semasa ujian kelikatan, kesan daripada sistem pematuhan kotak ricih terus mestilah diambil kira dengan waspada sewaktu merumuskan model mekanik bagi kinematik cerun tepu dan tidak tepu. Unsur elastik tambahan telah ditambah kepada model 3 unsur untuk mengatasi masalah kebolehubahan bentuk sistem bebanan. Model terubah suai yang dicadangkan berkebolehan mensimulasi tindak balas rayapan dan tekanan santaian menggunakan set parameter tunggal dan maka dengan itu, membolehkan tindak balas rayapan dijana daripada tekanan santaian melalui ujian kotak ricih terus di makmal.

Kata kunci: Bahan geologi berlumpur; kelikatan; model analog mekanikal; pemodelan

REFERENCES

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*Corresponding author; email: shahidahnazer@ukm.edu.my