Hong Kai Chen

Excitation Action Triggered by Perilous Rock Avalanche to the Stability of Perilous Rock

The mechanism failure of massive perilous rock should consider the interaction among perilous rock masses. Study on the stability of adjacent perilous rock from the excitation wave, which is produced by the perilous rock mass at the collapse instantaneousness, has important significance. Focusing on the falling-type perilous rock, physical model of perilous rock with excitation wave is considered and the stress characteristics for the excitation wave of perilous rock avalanche on dominant fissure with normal incidence is analyzed. Based on the fracture mechanics, a method to calculate the combined stress intensity factors of dominant fissure under falling excitation action of perilous rock is established. As the instance results showed, two cites of nature and rainfall, the stability coefficient are both reduce, specially in the horizontal, stability coefficient reduced by about 10% respectively, while in vertical about 2%. The results provided some scientific progresses disasters prevention and mitigation of perilous rock.

Experimental Study on the Process of Geomorphic Evolution of Debris Flow on Slope

To reveal the process of geomorphic evolution of debris flow on slope, the qualitative-semi-quantitative model experiment was built from experimental model, characteristics of soil and rainfall scheme. The results indicate that the essence of geomorphic evolution of debris flow on slope is the interaction of soil and water. And the change of geomorphology is reflected by the elevation of topsoil. In antecedent rainfall, the elevation of topsoil is in increasing trend generally except some parts. During short heavy rainfall, the soil creeps intensively, mixes with water and becomes fluidization gradually. The elevation of topsoil on the top is decreasing generally, while on the button, the elevation is increasing. Moreover, because water infiltrates into slope and interacts with soil needing a period of time, the change of geomorphology falls behind the rainfall process.

The Effect of Coarse Aggregate Gradation Degradation on the Mechanical Behavior of Asphalt Mixture

The objective of this study is to investigate and evaluate the effect of coarse aggregates (aggregate size bigger than 2.36 mm) on the compressive strength and creep behavior of asphalt mixture. The variable that is mainly considered in the study is the gradation degradation of coarse aggregates. A kind of standard aggregate gradation and three kinds of degraded aggregate gradation mixture specimens are used. Uniaxial compression and static creep tests were realized at different loading conditions and temperatures. The test results on asphalt mixture showed that the compressive strength and creep behavior of asphalt mixture are significant affected by the different coarse aggregate gradations.

A New Method to Estimate Routine Based on the Motion Modes of Rockfall

This article divides the motion route into four phases: free fall, initial collision, in-flight and subsequent collision. There could be bounce, slippage or rolling movement in the phases of initial collision and subsequent impact. Based on the theory of movement mechanics, the certain methods on the motion direction, velocity and distance of each movement mode is established and the effected discrimination standard to distinguish the motion phases and modes is put forward.

Study on Wavelet Denoising of Pulse Impact Force of Non-Viscosity Debris Flow

Noise filtering of impact load spectrum is the key to ensure the impact load of debris flow during the control engineering design of debris flow. As the laboratory impacting test indicates, noise effect in pulse impact force spectrum can be denoised using Daubechie(dbN)and Symlet(symN)wavelet methods, both of which contain hard threshold method and soft threshold method. Analyzed the pulse impact force of non-viscosity debris flow testing results by wavelet denoising method, the testing conditions are A-3(whose grain size is range from 0.3cm to 0.8cm), B-3(whose grain size is range from 0.8cm to 1.5cm) and C-3(whose grain size is range from 1.5cm to 3.0cm),all of whose solid phase ratio are 0.16.The analyzing results show that the denosing effect adopting Db5 wavelet function is superior to ones adopting Sym2 wavelet function, meanwhile, the denosing effect adopting hard threshold method is superior to ones adopting soft threshold method. The results also indicate that the bigger the solid phase ratio is, the bigger the Signal Noise Ratio is, the better the wavelet denosing effect is. These results could provide scientific basis for further accurate experimental study to ensure impact load of non-viscosity debris flow.

Experiment of the Rockfall Impact Characteristic onto Gravel Cushion

Rockfall is one of common geological disasters in the mountainous area. The experiment gained the impact waves for cushion soil mass contained 12density, 4 soil-rock ratio, 4 cushion obliquity, 3 moisture content, 3 rockfall quality, 5 height of rock fall. Used the wavelet theory to deal with the experiment waves, analyzed the experiment results: with rock’s mass, the height and density increased, the impact force is increasing, or the impact force is decreasing with the moisture content and cushion inclination increasing. The impact force spreads from the point of rockfall to all directions. The impact force data of the experiment is a little large than others, so this method provides a gist for choosing the prevention and cure measure for rockfall.

Study on the Damage Mechanism of Bridge Pier and Foundation by Turbulent Debris Flow

The debris flow is the uppermost water-destroyed type of highway, which caused large direct economic loss annually in china, especially in mountainous area highway small bridges and culvert damaged seriously. This paper started from the theory of debris flow two-phase flow, it is divide turbulent debris flow into liquid and solid, and with the turbulent debris flow wash against bridge pier increased, the erode depth overpass the burial depth of foundation, base bearing capacity reduced gradually and then result bridge pier instability; in addition for the strong force of impact of debris flow resulted in resistance to capsizing weaken. The damage of bridge and culvert’ foundation mainly duo to the erosion, which lead to the erode depth overpass the burial depth of foundation, furthermore, debris flow force of impact greater then structure resistance and result the structure instability and damaged.

Formation Mechanism Study on Houchuangzi Slope Debris Flow

Taken the Houchuangzi slope debris flow along Kunming- -Songming highway as instance, analyzed the mineral composition of provenance on the slope debris flow adopted the polycrystal X ray diffractometer, which was rich in hydrophilic clay mineralssuch as kaolinite and montmorillnite; analyzed the fornation mechanism of the HouChuangzi slope debris flow by the laboratory model test, compartmentalized the fornation process of the HouChuangzi slope debris flow in to five stages from the aspects of slope debris flow morphology and crack extension mechanism.The results provide certain reference value for further research of the formation mechanical mechanism.

The Time-Frequency Analysis for Energy Dissipation Shed-Tunnel’s Rockfall Impact Signal Based on Wavelet Theory

Shed-tunnel is one of common prevention measures along the highway. Through the wavelet theory we denoised the rockfall impact signal when the rock impact the ordinary shed-tunnel and the energy dissipation shed-tunnel. And then we evaluated the wavelet theory’s denoise effect by the signal-to-noise ratio. The calculation result indicated that the denoise effect is very good. At last, through the autocorrelation analysis and time-frequency analysis for the rockfall impact signal, it was found that the ordinary shed-tunnel’s impact signals didn’t have obvious frequency and the frequency contained many component,but the energy dissipation shed-tunnel’s impact signals had obvious frequency. So the energy dissipation shed-tunnel’s impact signals had a relatively fixed cycle and frequency. The received frequency of rockfall impact by the time-frequency analysis could provide the basis for the design of energy dissipation shed-tunnel’s natural frequency.

Energy Analysis for Energy Dissipation Shed-Tunnel’s Rockfall Impact Signal

Shed-tunnel is one of common prevention measures along the highway. First, denoised the rockfall impact signal when the rock impact the ordinary shed-tunnel and the energy dissipation shed-tunnel by the wavelet theory. The calculation result indicated that the wavelet theory’s denoise effect is very good. Then, pick-up each frequency band’s the rockfall impact signal, and analysed the energy for each frequency band’s impact signal. The result indicated that the energy dissipation shed-tunnel’s impact energy concentrate in the low frequency part. There are only 0.4% impact energy in the high frequency part. Besides, the energy dissipation shed-tunnel’s impact energy in the low frequency part is higher than the the ordinary shed-tunnel, and the energy dissipation shed-tunnel’s impact energy depressed velocity when the impact frequency increase is fast than the ordinary shed-tunnel. So the energy dissipation shed-tunnel’s design must consider the low frequency impact,and could ignore the high frequency impact.