| Recently, increasing extreme weather and hazards lead to frequent blocking events of debris flows, which can also be found in region that covered by Maritime glacier. Blocking events for debris flows threaten local facilities of human-being, development in economic, causing an urgent in proper hazard mitigation measures.This thesis is presented in Min River after Wenchuan earthquake and Palongzangbu watershed in Tibet plateau. Firstly, blocking criteria of debris flow is investigated and analyzed with the blocking case in Min River by field investigation, model tests and theory analysis. Then, with the developed blocking criteria of debris flow in Min River, estimated height of backwater and distribution of local, moraine platform, risk assessment of blocking river, national road (No 318) routine design were carried out. Finally, seismic water wave is poorly-understood in investigations of factors affecting moraine lake outburst while its numbers is increasing for climate change and glacier-retreat. Shaking tank experiments were carried out to investigate the correlation between seismic water wave and moraine lake outburst with the moraine lake case in Panglongzagnbu watershed.(1) Historical data of dammed lake of Min River in Wenchuan regions and Palongzagnbu River in Lulang were collected accompanied with field investigations.Considering resistance from water when debris flow move from tributary to channel, we developed a formula indicating flow behavior of debris flow in main stream referring to that of Takahashi and Yoshida (1979). Then, we can obtain the runout distance of debris flow in a channel.Model tests and field investigations revealed that the material volume for damming river included two parts:material in channel and that of in a straight section of tributary at the junction.Relationship between debris flow volume and damming coefficient is y=76x-30 according to field investigations according to field investigations, models tests and normalized analysis. Both of field investigations and model tests coincide with each other, indicating that this formula can be generally applied while b can be obtained by one of the debris flow tributary. This formula can be used in practice with some measuring data about damming lake by debris flows.Material in debris flow mainly control the stability of debris flow dam suffering from erosion of torrent in channel. We concluded that debris flow dam in this situation can be kept well on condition that the coarse grains accouter for 50% of debris flow deposits according to percolation and renormalization group theory. Then, the debris flow deposits in Gaojia watershed is studied by large shear tests and used for verification.(3) Distribution map of debris flow with varied hydrodynamic conditions is obtained by filed investigations accompanied with historical data in Palongzagnbu watershed. After that, we calculate the potential risk of debris flow in this region according to developed criteria damming condition, and obtain the risk assessment of damming river due to debris flows.In wider river section of cannon, we take high line position against catastrophic flooding hazards for water rise resulted from disaster chain. Geomorphological map piedmont region of Palongzagnbu watershed is obtained by analyzing aerial map in order to figure out the distribution of moraine platform. Furthermore, results of large shear tests on moraine deposits indicate that these materials exhibit engineering condition and can be directly used to road construction. Finally, the moraine platform locate above debris flow fan, which meet the demand that line layout exceed the flooding water level once debris flow block river.We carried out model shaking tank tests to investigation the earthquake and seismic water wave with Wolong wave (Main frequency>1Hz, high frequency), Mexicali wave ((Main frequency<1Hz, low frequency), Synthetic seismic waves of Tongmai (high frequency), and white noise. These model tests were also conducted under still water level ranging from 10cm to 35cm at an interval of 5 cm. Then, DCCA method is used aiming to verify the reliability of model tests by comparing the seismic water wave data in swimming pool and shaking tank experiments. Finally, we developed the empirical-statistical relationship between PGA and maximum height of seismic water wave. Finally, using the PGA of Tongmai seismic wave, we present the application of the empirical equations on Midui Glacier Lake and calculate the critical hydrological conditions which may cause this moraine lake outburst... |
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