| This paper chooses the loess of Q3 in Qingyang area as my research object. The physical properties,characteristics of chemical properties, dynamic strength characteristics and internal structural changeable characteristic of loess are studied under the construction loads through the particle analysis test,the XRF test,the dynamic triaxial test and the particle flow simulation test.Here lists the main work completed and the result obtained.(1) Conducted field geological reconnaissance in Qingyang area and laboratory test by adopting soil samples. The particle analysis test identifies that the Q3 loess in Qingyang belongs to Sandy loess, and the sand content reaches 51.4%. The XRF test indicates that mineral composition of Q3 loess is mainly about detrital mineral, secondly is clay mineral and carbonate mineral. The chemical composition is mainly about Si O2 and secondly is about Al2O3 and Ca O and so on, which is similar to the chemical composition of crust.(2) Dynamic triaxial test completed 4 samples of undisturbed loess and 9 samples of remolded loess. It also analyzed dynamic strength and residual strain characteristics of undisturbed samples under different water content and different dry density, confining pressure of remolded samples.The overall variation is the dynamic modulus, dynamic strength of undisturbed sample decreased with the increase of the moisture, the residual strain increased with the water content increased in the same condition. By comparison,the undisturbed loess samples of natural water content have the lager maximum dynamic modulus(315.3MPa),dynamic strength(325k Pa,use Yield criteria) and the smaller residual strain. Dynamic modulus and dynamic strength of remolded samples increased with the increasing of confining pressure,residual strain decreased with the increase of dry density. Neither remolded samples nor undisturbed samples has obvious rule.(3) The dynamic modulus and strength of Q3 loess in Qingyang is larger than of the loess in other areas compared with related study. It shows the structure of loess in Qingyang is very strong. In addition, the content of sand grain is higher than other areas and exhibits the stronger elastic characteristic under the dynamic pressure.(4) I simulated the dynamic response of the loess samples under the static load, cyclic load,impact load by adopting Numerical simulation of particle flow. I also described variation characteristics of internal structure of the samples resulted from the loads through monitoring the coordination number of sample particles, the porosity of related areas and the change of the unbalance force in system. It showed that the porosity decreased gradually but tend to stable later which is lager than the initial values of coordination number, which explained the structure of the specimen is damaged at first and then be condensed to a more closely structure. The porosityof the cyclic loading decreased in general, the particle coordination number short-lived decreased and then showed the same waveform characteristic with the wave of loading pressure;Coordination number increased slowly and appeared crest at a moment, which showed that samples got a certain damage, and then compressed by shaking under cyclic loading. It could be destroyed at a moment and then compressed again. The coordination number of particles fell sharply with impact of loading, although with recovery, the coordination number is not up to the initial values. It proved that the structures of samples got damaged suddenly, and the porosity is stepped down, which showed the samples were still compressed even though the structure is destroyed. |
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