Supervisor(s): China Earthquake Asministration Sponsor(s): China Association for Disaster Prevention; Institute of Engineering Mechanics, CEA CN：23-1324/X
Journal of Natural Disasters, started in 1992, publishes papers on disaster prediction and prevention, disaster risk assessment, disaster mitigation for agriculture, meteorology and city, disaster mitigation policy and management system. It also focuses on social factors of natural disasters, loss prediction of earthquake all over the world, awareness improvement on disaster prevention, the system engineering on disaster prevention and mitigation, and so on.
Director XIE Lili
Assistant Director Ou Jinping, Li Youshan, Shi Peijun, Han Linhai, Xiao Yan, Zhou Xianyan, Cui Jie
Editorial Board Ma Zongjin, Ma Zhiliang, Wang Lanmin, Wang Zifa, Wang Chunyi, Wang Zhenqing, Shan Chunchang, Shi Peijun, Fu Qiang, Lv D
Landslide–debris flow is a common form of motion for high-level landslides. It has the characteristics of large scale, long runout distance, and high flow velocity. The deposit area of landslides and the intensity of hazard could be reduced by the retaining structure. In this study, we used three-dimensional discrete element simulation software to study the accumulation and kinematic characteristics of debris flow with three different retaining structures. The results indicate that the movement direction of the debris flow particles is deflected, and the velocity distribution of the sliding body changes significantly, in which the maximum speed of the sliding body changes from the slope to the trailing edge. As the length of the retaining structure rises, the normal force increases significantly, while the tangential force grows slightly. The area of the stacking area and the maximum horizontal moving distance continue to decrease, and the area of the safe area continues to increase. Also, this paper introduced the dimensionless number (
N
k) to analyze the effect of particle sorting effect on the kinematic and accumulation characteristics of different particles. For the same intercept width, the
N
k value of
K3 is the smallest, while the
N
k value of
K1 is the largest. The
N
k values of three particles gradually increase with the rise of the barrier structure width. After the resistive structure is added, the percentage of debris flow volume exhibits the distribution of an exponential function, and it decreases gradually with the increase in the moving distance. When there is no resistive structure, the percentage of the particle bulk volume exhibits the distribution of Extreme function. It means that the volume distribution reaches the peak near the middle position, and both sides show a decreasing trend.
Bonding performance of the interface between FRP bars and concrete is the key of mechanics properties in the concrete structure strengthened with FRP bars. The constitutive relations of the interface bonding performance are described by the interface bond–slip model of FRP–concrete, which predict the stripping damage of FRP–concrete and must determine the appropriate bond–slip model. For the establishment of an interface bond–slip model, a four-point bending test of 11 concrete beams was carried out on the basis of a new test method to study the interface characteristics of reinforced concrete beams with embedded CFRP bars. Based on the shear stress model of the interface between resin bolt and anchoring agent in rock, the analytical expression of the axial normal stress of CFRP bar along the anchorage length of CFRP bar in the cross-section was derived, and the elongation of CFRP bar anchorage segment was obtained. In combination with the measured slip of the specified section of CFRP bar and the elongation of exposed CFRP bar, the slip of the interface between CFRP bar and concrete is obtained, and the bond–slip curve of the interface between CFRP bar and concrete is plotted. The test and analysis of the wide-notch beam show that the bonding shear stress and the slip properties are easy to obtain by the testing system. Bar stress is clear and the average interface shear stress of the CFRP is convenient to obtain. The slip and bond–slip curve is accurate and simple, and the interference of strain gauges is eliminated, so it has demonstrative guidance to the research on the interface properties of CFRP–concrete.
There are frequent disasters in the downtown of Tianjin. It is proposed to use engineering and non-engineering methods to mitigate urban shackles. As for engineering measures, we should accelerate the construction of “sponge city” and “ecological rehabilitation and patchwork urbanism” to transform the open space from small, medium, and large scale, build urban water storage and seepage space to contain the drainage from the source, and slow down urban runoff. We should construct a perfect drainage pipe network and delimit reasonable drainage zones, improve urban drainage standards and set up one-way drainage outlets, build river gates and drainage pumping stations, and achieve rapid drainage during heavy rainfall. With respect to non-engineering measures, we should use big data and Internet technologies to build urban waterlogging prediction and service platforms, increase the forecast level of urban water accumulation points and the level of public participation, and realize the participation of all people in the city during heavy rainfall. The management also quickly controls the inflowing water points. Finally, we should rely on the construction of smart cities, strengthen the construction of a comprehensive disaster prevention platform and construct an emergency disaster prevention platform in the city by the intelligent control of various drainage facilities and departments. At the same time, we should enhance the exchange of data among different departments and draft the emergency strategies timely. In these ways, we can finally mitigate the waterlogging in the city.
For the aim of studying the anti-seismic performance of concrete gravity dam under earthquake loads, the Guangzhao concrete gravity dam with 200 meters height in the Southwest China was taken as an example. The three-dimensional finite element model of the dam body–reservoir water–foundation system was established. Dynamic analysis and seismic vulnerability analysis were carried out based on the incremental dynamic analysis (IDA) method. According to the IDA results of the whole dam model, the displacements of the dam crest and the bottom hole were extracted. The IDA curves, the fractile curves, and the seismic vulnerability curves were obtained. It is concluded that when the PGA of the seismic wave was below 0.2 g, the probability of damage to the dam was very low; when the PGA was 0.3 g or less, the basic function guarantee of the dam can be satisfied; when the PGA was below 0.6 g, the basic safety requirement of the dam can be met.
A comprehensive method for landslide stability discriminant is proposed based on the improved catastrophe theory. The 24 landslides in Jiaocheng County, Shanxi Province, were investigated. We chose relative elevation differences, rock and mass types, slope rock weathering degree and fracture development characteristics, plant cover ratio, slope structure type, slope morphology, slope ratio, trailing edge load, leading edge slope, and precipitation as indicators from three aspects of hazard inducing environment, attribute of hazard bearing body, and inducing disaster factor, and then we established a landslide stability discriminant model. The initial membership function values were derived by combining catastrophe theory, fuzzy mathematics, and contribution rate method. Normalization formula was utilized to form recursive calculating to get total catastrophe progression, which then was transformed into a new criterion by the improved catastrophe theory to determine landslide stability. The improved catastrophe theory to evaluate the stability of landslides has a higher accuracy by comparing the improved results with on-site verification results. Therefore, this method can be used to evaluate the stability of landslide and provide the basis for landslide prevention and control.
After fire tests of six reinforced concrete beams, one unbroken concrete beam reinforced with steel bars and two unbroken hybrid-reinforced concrete beams were subjected to static load tests according to the fire resistance time and their condition after fire. In this study, the flexural capacity of the concrete beams reinforced with steel bars and hybrid-reinforced concrete beams after fire were investigated. The influence of the ratio of the steel bars to GFRP bars and the load on the hybrid-reinforced concrete beams was discussed. As a result, firstly, the strength of the GFRP bars was basically wiped out, but the strength of the steel bars can restore to a certain degree after fire. The restoring of the flexural capacity of the concrete beams reinforced with steel bars was better than that of the hybrid-reinforced concrete beams. Secondly, the residual flexural capacity of the hybrid-reinforced concrete beams was significantly influenced by the ratio of the steel bars to the GFRP bars. The higher the ratio was, the better the restoring of the flexural capacity after fire. Based on experiments and the theoretical analysis, a method for calculating the residual flexural capacity of hybrid-reinforced concrete beams was proposed. The results of calculation and experiment showed a good agreement, for which the method can be used for future engineering applications.
Based on the measured wind speed data of a Doppler sodar in the observation point A and an anemometer at the top of the lab building B in Wenzhou, Zhejiang Province, China under typhoon Maria in 2018, according to logarithmic law, exponential law, D-H model theory, and hypothesis testing methods in statistics, we studied the variations of the horizontal and vertical wind profile curves and came to the following conclusion. Firstly, the linear regression analysis of mean wind speed on two measured points at same height with a distance of 6.21 km under different landscape achieved highly correlation. Faster wind speed and shorter periods led to higher correlations. Secondly, the fitting curve of the horizontal wind profile was quite close to the exponential law model in the influence period and tended to be the D-H model in the stable period. The fitting roughness index of wind profile decreased significantly with the growth of the horizontal mean wind speed. Thirdly, the mean value of the boundary layer height obtained from the calculation of the wind profile sample was 1,421 m, which was 3.06 times more than the standard value and 1.78 times more than the calculation value of normal wind. Lastly, the vertical mean speed varied intensely compared to that in the horizontal direction. The fitting roughness index of wind profile increased with the growth of the vertical mean speed.
