Effect of Particle Breakage on Shear Strength Parameters of Schist Soils

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Effect of Particle Breakage on Shear Strength Parameters of Schist Soils

ارائه دهنده: Provider: saeid sharifnia

اساتید راهنما: Supervisors: Abbas Qadimi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Vahid Reza Ouhadi and mohammad maleki

زمان و تاریخ ارائه: Time and date of presentation: 2024

مکان ارائه: Place of presentation: 43

چکیده: Abstract: Schist soils that are left behind from weathering or crushing of schist rock show a behavior similar to granular soils. As a result of additional stress caused by factors such as increasing the height of the building or the dam under construction or hammering the piles, the force applied to the soil particles at the level of the foundation of the building and the dam or around the tips of the piles leads to the breaking of the soil grains, although weathering and Or repeated freezing and thawing can also lead to the breaking of soil particles. The breaking of particles changes the natural grain size of the soil, which leads to a change in its behavior. Furthermore, particle fracture challenges classical soil mechanics, which assumes that soil deformation is mainly caused by changes in void space between soil particles and particle motion relative to each other. For this reason, investigating particle fracture in soil behavior has become an important research topic in geotechnical engineering. During the past years, particle breakage has been widely investigated under different conditions, especially under the effect of added stress (Lade et al., 1996; Xiao and Liu, 2017; Yu, 2021). In this research, first, three different types of schist soils, which are the result of mechanical crushing of schist masses, were collected from different parts of Hamadan city. Then, by examining the basic physical properties of these soils, the fracture of their particles under one-dimensional pressure was investigated in order to study the fracture process of the particles by changing the granulation curves during the application of stress. Hardin's relative fracture index values were calculated for the states before and after loading. Observations showed that the fracture of schist soil particles, similar to other granular soils, increases with increasing pressure and axial strain. More significant particle breakage is seen in denser samples. Fracture shaft for all types of schist soils studied at each constant strain rate increased by 29 and 46 units in the dry state and at least 22 and 39 units after the saturation period. This index has changed in each fixed initial specific gravity with the increase of strain, in the dry state at least 9 and at most 23 and after the saturation period at least 15 and at most 33 units. Before applying the stress, all the soils were of SP (Poorly graded sand with gravel) class, and after applying the stress, in the most critical state, they were transformed into ML (Sandy silt), SM (Silty sand) and SM (Silty sand) respectively. Also, a series of direct cutting tests were performed on the original samples and samples that were subjected to different one-dimensional pressures. Fracture of particles changes the shear strength of shaly soils by significantly reducing the angle of internal friction.

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