Combined Impacts of Antecedent Earthquakes and Droughts on Disastrous Debris Flows

This paper describes a study on the combined impacts of antecedent earthquakes and droughts on disastrous debris flows.This is a novel attempt in quantifying such impacts using the effective peak acceleration(EPA)(to represent earthquakes) and standardized precipitation index(SPI)(to represent droughts).The study is based on the analysis of 116 disastrous debris flow events occurred in China's Mainland in the last 100 years covering a wide spectrum of climate types and landforms.It has been found that the combined impacts from earthquakes and droughts on disastrous debris flows do exist and vary from low to very high according to different climate conditions and terrains.The impacts from earthquakes increase with the increased terrain relief,and the impacts from droughts are strongest in semi-humid climate condition(with reduced impacts in humid and semi-arid /arid climate conditions).Hypothetical explanations on the study discoveries have been proposed.This study reveals the possible reasons for the disastrous debris flow distributions around the world and has significant implications in paleo-climate-seismicanalysis and disastrous debris flow risk management.

Centrifuge model test of an irrigation-induced loess landslide in the Heifangtai loess platform, Northwest China

The Heifangtai platform in Northwest China is famous for irrigation-induced loess landslides.This study conducted a centrifuge model test with reference to an irrigation-induced loess landslide that occurred in Heifangtai in 2011.The loess slope model was constructed by whittling a cubic loess block obtaining from the landslide site.The irrigation water was simulated by applying continuous infiltration from back of the slope.The deformation,earth pressure,and pore pressure were investigated during test by a series of transducers.For this particular study,the results showed that the failure processes were characterized by retrogressive landslides and cracks.The time dependent reductions of cohesion and internal friction angle at basal layer with increasing pore-water pressure were responsible for these failures.The foot part of slope is very important for slope instability and hazard prevention in the study area,where concentration of earth pressure and generation of high pore-water pressures would form before failures.The measurements of earth pressure and pore-water pressure might be effective for early warning in the study area.

Fuzzy-support vector machine geotechnical risk analysis method based on Bayesian network

Machine learning method has been widely used in various geotechnical engineering risk analysis in recent years. However, the overfitting problem often occurs due to the small number of samples obtained in history. This paper proposes the FuzzySVM(support vector machine) geotechnical engineering risk analysis method based on the Bayesian network. The proposed method utilizes the fuzzy set theory to build a Bayesian network to reflect prior knowledge, and utilizes the SVM to build a Bayesian network to reflect historical samples. Then a Bayesian network for evaluation is built in Bayesian estimation method by combining prior knowledge with historical samples. Taking seismic damage evaluation of slopes as an example, the steps of the method are stated in detail. The proposed method is used to evaluate the seismic damage of 96 slopes along roads in the area affected by the Wenchuan earthquake. The evaluation results show that the method can solve the overfitting problem, which often occurs if the machine learning methods are used to evaluate risk of geotechnical engineering, and the performance of the method is much better than that of the previous machine learning methods. Moreover,the proposed method can also effectively evaluate various geotechnical engineering risks in the absence of some influencing factors.

Impact of viscosity modifier on asphalt properties used for bus rapid transit lanes in Chengdu

In order to find the effect of different viscosity modifier dosages on asphalt binder＇s performance in bus rapid transit lanes in the city of Chengdu, three different viscosity modifiers were analyzed： TAFPACK-super （TPS）, high-viscosity additive （HVA） and road-science- technology （RST）, and four different asphalt binders were investigated through laboratory experiments. The percent- ages of the viscosity modifiers used were： TPS （0%, 8%, 10%, 12%, 14% and 16%） and RST and HVA （8% and 12%） depending on the type of asphalt binder. Technical indicators of modifier asphalt were tested through con- ventional and unconventional binder tests. It has been found out that only a percentage greater than or equal to 14% TPS is reasonable to achieve the requirement set by 20,000 Pa. s for the 60℃ dynamic viscosity on local #70 grade asphalt. The results indicate that conventional bin- ders did not meet the requirements of the 60℃ dynamic viscosity when 12% of TPS or HVA modifiers were used. In addition, the B-type styrene-butadienne-styrene （SBS） modified asphalt binder has better viscosity balance than the A-type SBS modified when 8% of each of the three different kinds of viscosity modifiers is used. Therefore, the B-type modified SBS thus appears to be a suitable choice in asphalt mixtures for bus rapid transit lane with the 60℃ dynamic viscosity.