| The loess area in northwest China has a very special geological and structuralbackground. The landslide hazard occurs frequently in this area, most of which belongs to thehigh intensity earthquake zone. With the south central region of Gansu province being theresearch object, this dissertation studies the geological conditions and features of the loesslandslide areas. Through a lot of field geological investigation, indoor and outdoorexperiments, theoretical calculation and numerical simulation, a systematic study of thefeatures, stability under earthquake action and control technology of the loess landslides wasmade. And the research results are as follows:1. The features and formation mechanism of the typical loess landslides in the researcharea was studied and the research results indicate that the Sanjiadi landslide falls into the giantloess mudstone old landslide. And the unfavorable geological structure of the slope and thelong-term erosion of the front edge of the slope by the Chenligou mud-rock flow are the maincause of the old landslide.5.12Wenchuan earthquake induced massive of the front edge ofthe landslide and the crack occurred.2. The direct shear test, the tri-axial and the dynamic tri-axial test were conducted withregard to the static and dynamic performance of the slip soil and test results showed that thedynamic cohesion and dynamic inner friction angle of the slip soil of Jiuzhou and Sanjiadilandslide reduced with the increase in the water content, the dynamic modulus of elasticitydecreased with the increase in the dynamic strain, and the damp ratio increased slowly withthe increase in the dynamic strain, varying within a small range. The cohesion and the peakintensity and residual strength of the inner friction angle of the slip soil of the Jiuzhoulandslide and Sanjiadi landslide reduced with the increase of the water content;3. A fuzzy comprehension evaluation model for the stability of the loess landslide underearthquake action was established to evaluate its stability. Considering the randomness andfuzziness of the factors affecting the stability of the loess landslide, the stability reliabilityanalysis model and the randomness and fuzziness reliability analysis model for the loesslandslide under earthquake action were established to calculate the stability of the Sanjiapolandslide. The stability coefficient of the Sanjiadi landslide under earthquake action was calculated by use of the pseudo-static method. which indicated that the Sanjiapo landslideunder earthquake action was in an unstable state.4. A numerical simulation analysis was made of the stability both before and after theearthquake action of the Sanjiapo landslide by use of the FLAC3Dsoftware. The resultsshowed that the Sanjiadi landslide was basically in a stable state, during the earthquake it wasin an unstable state and under the earthquake action there was an significant increase in thehorizontal displacement and the shear strain increment of the front of the slope.5. The orthogonal experiment theory and the improve grey correlation method wereadopted to analyze the sensitivity of the major factors affecting the stability of the Sanjiapolandslide. The results showed that the horizontal earthquake action, as an effect factor, wassecond only to the inner friction angle of the slip soil and the decrease in the stabilitycoefficient tend to increase with the increase in the earthquake intensity.6. The major control measures for the loess landslide were analyzed and the main factorsaffecting the decision-making of the comprehensive control scheme for the loess landslidewere studied. Based on the optimization method, an optimal model for the comprehensivecontrol scheme for the loess landslide was set up. By use of the model, the comprehensivecontrol scheme for the Sanjiadi landslide was selected and the study decided on the optimalcontrol scheme, which is: backpressure project and the gully channel debris flow controlproject and drainage project. Besides, a refined and detailed design of the scheme was made. |
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