Research purposes: Shenyang-Baihe high-speed railway passes the Changbai Mountain area with the thick pozzolanic silty clay, whose material composition, strength and deterioration properties and mechanism are unknown. However, the bearing deformation calculation, analysis and control of the foundation of high-speed railway urgently need to be investigated. Therefore, the material composition test, strength deterioration test and scanning electron microscopy test were performed to obtain the basic physical properties and material composition of the pozzolanic silty clay and to reveal the evolution law of the shear strength with the soaking time and its mechanism.
Research conclusions: (1) Pozzolanic silty clay in the state of hard plastic contains the large fine-grained particle and has the characteristics of large void ratio and medium to high compressibility. (2) It consists of illite(29.5%), quartz, mica and feldspar, etc., and its composition barely changes with depth. (3) The shear strength decreases exponentially with increase of the soaking time and this deterioration process consists of three stages of the rapid attenuation (0~4 d), slow attenuation (4~8 d) and basic stability (8~16 d). The final degradation coefficients of internal friction angle and cohesion stress are 0.28 and 0.81, respectively. (4) The high content of illite with strong ability to adsorb water results into thickening the layer of water, accordingly enlarging the void ratio and making particle morphology more complex and irregular with the increase of soaking time. (5) The research results deepen the understanding of the physical and mechanical properties of pozzolanic silty clay and the strength deterioration characteristics for water immersion. It can provide valuable calculation parameters and technical support for the foundation design of high-speed railway constructed on the pozzolanic silty clay stratum.
Key words
pozzolanic silty clay /
material composition /
strength deterioration /
micro-structure /
deterioration mechanism
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