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Realizing quantitative evaluation of disaster reduction benefits of debris flow retaining dams has important theoretical and practical significance for optimizing engineering design and protecting the safety of people's lives. and property. The paper uses numerical simulation methods to obtain the mud depth, flow velocity, and range of debris flow under different operating conditions, establishes two risk evaluation index systems based on the area of high risk level and the total risk degree, proposes a quantitative evaluation method for the disaster reduction benefits of retaining dams, and conducts an empirical study using the Chutougou debris flow as an example. According to the evaluation method for disaster reduction benefits of retaining dams, it is possible to analyze the disaster reduction benefits of the proposed and existing projects and their combinations, determine whether they have achieved the disaster reduction goals, and compare and quantify the importance of different projects in disaster reduction, which can provide a basis and reference for the construction and improvement of debris flow retaining dams. The disaster reduction benefits per unit height can reflect the value of risk reduction per meter of retaining dam heightening, and can be applied to the determination of optimal engineering combination scheme of debris flow retaining dams. The change rule of the total risk degree and the disaster reduction benefits of the area with high risk level is consistent, indicating that both risk assessment methods can reflect the disaster reduction benefits of the combination of retaining dams and their changes. [ABSTRACT FROM AUTHOR]

Large-diameter pile group foundations have the characteristics of high bearing capacity, and have broad application prospects in large-scale engineering foundations in soft soil areas. Based on the field test data of vertical bearing capacity of a bridge group pile foundation, the ABAQUS numerical calculation platform is used to calculate and fit the soil parameters. Based on the soil parameters obtained from the fitting, the bearing characteristics of the piles under the horizontal load are calculated and analyzed, and the bearing characteristics of the group pile foundation under vertical and horizontal loads are also studied. The results show that when the maximum vertical load acts on the cap-pile group foundation, the maximum displacement of the cap is 84.83 mm, and according to the displacement control principle, the upper limit of the pile group effect is 83%, and the lower limit is about 62.8%. Under the vertical load, there are differences in the settlement value of each pile in the pile group, the center piles are the largest, followed by the side piles, the corner piles have the smallest settlement. With the load gradually increased, the displacement differences of the corner piles, the side piles and the center piles show a trend of first increasing and then decreasing. When the maximum vertical load is applied to the group pile foundation, the horizontal influence range of foundation horizontal displacement is about 1.5 times of the side length of cap, and the maximum influence depth is about 1.5 times of the side length of cap. The soil between piles shows tension shear stress in the range of 0.5 times of side length of cap below the ground surface. This paper analyzes the bearing characteristics of pile groups under horizontal and vertical loads and its conclusions can be used for reference for relevant engineering design. [ABSTRACT FROM AUTHOR]

The dangerous rock mass is widely distributed in southwest China, and is easy to formate collapse for many times. In order to study the collapse disasters reported in the terrain, the accumulation of subsequent collapse rockfalls characteristics, this paper, by using multiphase collapse simulation method, can reflect the changing situation and the threat range of the deposit after many times collapse according to certain probability, and supplement the deficiency of the conventional calculation result of once collapse of stones. It provides a scientific basis for the prevention and control of geological disaster in the study area in the following period. This paper takes the Xujiadabang collapse in Sinan County, Guizhou Province as an example. The multi-stage numerical simulation of unstable rock collapse is studied based on laboratory tests and numerical simulation, combined with GIS technology and 3D collapse software. The numerical simulation results of four stages of collapse by using the characteristic parameters obtained from physical experiments are in good agreement with the field investigation results. It is found that almost all of the large size rockfalls and most of the small size rockfalls are deposited in the area with a slope less than 35°. More than 90% of the rockfall deposits in the 30 m buffer zone on the abandoned road surface, that is, 100 m away from the residential area. The percentage of rockfall deposits in the direction of the abandoned road toward the cliff shows an upward trend. The nearest large particle size rockfall is mainly 60 m away from the residential area, and the possibility of threatening the residential area is low. A small number of small particle size rockfalls will fall to the residential area. The research ideas and technical methods in this paper have reference values and significance for the study of multi-stage dangerous rockfall. [ABSTRACT FROM AUTHOR]

Loess is a kind of Quaternary loose deposits. There are many primary and secondary pores and cracks in the loess, which provide preferential channels for water to enter the soil and form preferential infiltration phenomenon. This water movement mode is called preferential flow. The existence of preferential infiltration and preferential flow is one of the main causes of landslide and other loess geological disasters, so it is necessary to study the phenomenon of preferential infiltration. Based on the discussion of the classification of loess dominant structural planes by previous scholars, this paper puts forward the classification method of loess preferential channels, then discusses the preferential flow classification of domestic and foreign scholars and the main research methods, and analyzes their advantages and disadvantages. This paper summarizes the main infiltration models of the current preferential flow and the characteristics of the governing equations representing the models, analyzes and discusses the deficiency of present research and the development direction in the future at the end. [ABSTRACT FROM AUTHOR]

The wind damage of thin⁃film greenhouse buildings is serious due to the frequent strong wind or typhoon in tropical islands. However, there is little research on the wind⁃resistant design of thin⁃film greenhouse buildings in islands in China. It is of great theoretical and engineering significance to research near⁃surface wind field and the wind effect of thin⁃film greenhouse buildings. This paper states the background and significance of wind⁃resistant research on thin⁃film greenhouse buildings in tropical islands, introduces the current research status of near⁃surface wind field characteristics, and summarizes the wind resistance of agricultural greenhouse buildings and membrane structures from different hands of field measurement, wind tunnel test, and numerical simulation. Based on the deficiencies of current research, according to distributed optical fiber sensing technology, field measurement, wind tunnel aeroelastic test, fluid⁃structure interaction numerical simulation and theoretical analysis, etc., it is proposed to develop the research on wind effect, wind⁃induced damage mechanism, wind⁃resistant measures and design theory of thin⁃film greenhouse buildings in tropical island [ABSTRACT FROM AUTHOR]

Segment failure and leakage phenomena often appear in the construction process of TBM, which directly affect the safe operation of metro. In view of this, this paper based on Chongqing Metro Loop Project, conducted on⁃site monitoring of segment forces during segment assembly, and explored the surrounding rock load of tunnel segments in the actual construction environment. The evolution law of segment⁃stratum interaction during single shield TBM tunnel construction was found out through on⁃site monitoring.Using ANSYS three⁃dimensional finite element analysis software, a numerical model considering the interaction of shield segment⁃bolt, segment⁃surrounding rock and segment⁃shield tail was established, the force of the segment under the action of surrounding rock in the construction process was analyzed, the deformation of the segment under the action of normal propulsion load and additional torque was compared, and the eccentric jack effect on the mechanical behavior of segment was obtained. The analytical results indicate that, the pressure behind the segment of single shield TBM tunnel is the combined action of pea gravel, slurry and surrounding rock. The surrounding rock pressure behind segment of single shield TBM construction in sandstone stratum in Chongqing area is slightly higher than the theoretical calculation value, and the actual surrounding rock pressure at the top, bottom and waist of segment is 150～160kPa, 165～200kPa and 45～52kPa, respectively. Excessive additional torques may cause partial segment breakage. [ABSTRACT FROM AUTHOR]

In view of the spatial scale of threat and potential risks caused by debris flow under four extreme rainfall conditions, risk assessments of debris flow hazard in Maiduo Gully, Chaya County, Tibet were carried out, using a single building as an evaluation unit. Assessments include the risk division, vulnerability analysis and risk assessment of debris flow. This paper describes a whole workflow of a refined risk assessment. Firstly, based on a three dimensional geological model acquired from UAV, the FLO⁃2D software was used to simulate the process of debris flow outbreaking in Maiduo Gully under four extreme rainfall conditions(10%,5%,2%,1%),and the risk zones were divided. Then, analyzed the vulnerability of buildings and population in the affected area according to on site data. After that, took a single building as the evaluation unit, risks and vulnerability were normalized, and to eventually get the risk zones of building and population in study area, overlay analysis was applied on ArcGIS Desktop. These evaluation results are able to provide scientific reference to the works of local geological disasters and risk control, and the evaluation workflow can be used as a reference for future refined quantitative risk assessments of debris flow hazard as well. [ABSTRACT FROM AUTHOR]

In order to improve the deformation energy dissipation and self centering capacity of concrete frame joint an improved design method of beam column joint with super elastic SMA bar and steel end plate was proposed to improve the capacities. A finite element numerical model of concrete beam column joints with super elastic SMA bars and steel end plates was established based on Open Sees finite element analysis platform, and the hysteretic and skeleton curves of the joints obtained from experiments and numerical simulation under low cycle reciprocating loading were compared to verify the effectiveness of the numerical model, while the effects of SMA bar diameter, yield strength and other parameters on the hysteretic energy consumption, stiffness degradation, residual deformation and other mechanical properties of the designed joints in this paper were further analyzed. The results show that the parameters such as the diameter and yield strength of SMA bars have great influence on the carrying capacity and self centering energy consumption of the new joint. On the premise of suitable reinforcement, the larger diameter of SMA reinforcement we design, the higher bearing capacity and self centering performance of the joint will have. Within a certain range, the increase of the yield strength of SMA bars has little effect on the overall stiffness of the joint, but has a greater effect on the residual deformation. [ABSTRACT FROM AUTHOR]

In this paper, the finite element method is introduced to solve the spectral amplification factor for dimensionless frequency in detail. According to the comparison between the calculated results and the analytical solutions, the feasibility of this method is verified. The feasibility of the method in this paper is verified by the comparison between the calculated results of the homogeneous half-space semi-circular Canyon Topograph and the analytical solution. At the same time, it is pointed out that in the process of obtaining the spectral amplification factor corresponding to the dimensionless frequency by using the finite element numerical simulation method, the input type of the seismic wave has no effect on the result, and the selection of the calculation model size and medium parameters is also flexible, which can be convenient to study on the surface amplification effect of different frequencies of complex topography under the seismic waves. [ABSTRACT FROM AUTHOR]

The influence of the mutual disturbance of twin tunnels shield construction on the distribution characteristic and evolution rules of the stratum deformation are significant. On the basis of the case study of the twin parallel shield tunnels of subway, considering the critical distance and the interaction effects of twin shield construction. Adopting numerical simulation method to analyze the evolution rules of stratum deformation caused by twin shield construction and combining with the actual measurement date, and the prediction model of stratum deformation caused by twin shield tunnels construction was put forward consider the critical distance. The results show that the stratum vertical deformation curve is developed into an asymmetrically "W" shape from the "V" shape when the twin tunnels excavated successively. The range of settlement trough is increased from 6D to lOD, and the more obvious is the "W" shape settlement curve characteristic with the stratum depth increasing. The stratum horizontal deformation curve is the asymmetric distribution, and the soil deformation is greatly influenced by construction disturbance in the middle of twin tunnels. The shape of surface settlement curve successively transformed from deep "V" shape, shallow "V" shape, "U" shape, shallow "W" shape, deep "W" shape and then to two independent "V" shape with the critical distance of twin tunnels, and using Lcr = 2CKH can be considered as the criterion of critical distance for the twin parallel shield tunnels. The prediction model proposed in this paper can better reflect the influence rules of critical distance state and mutual disturbance on stratum deformation caused by twin tunnels shield construction. The research provides reference for similar subway tunnel shield construction deformation prediction and refinement control. [ABSTRACT FROM AUTHOR]

The loading of the trailing edge and the excavation of the leading edge will adversely affect the stability of the slope. For the engineering activities of excavation at the trailing edge of the slope to form a water storage system, a comprehensive assessment of the impact on the stability of the slope is required. This paper combines the saturated and unsaturated two-dimensional seepage field continuity equation and the stress field balance equation to establish a fluid-solid coupling calculation model. The slope water storage system excavation and the water level changes in the water storage system at the trailing edge of the slope are calculated. The leakage caused by the different storage heights results in slope stability coefficients of various working conditions such as the increase of groundwater level in the slope of the trailing edge. The calculation results show that the slope stability has a certain relationship with the excavation and storage height of the water storage system, but the impact on the stability coefficient is relatively small, and the leakage of the water storage system will significantly reduce the stability of the slope stability. Therefore, by controlling the height of the water level in the water storage system and anti-seepage treatment, it can be considered to reduce the adverse effect of the slope water storage system on the slope stability. [ABSTRACT FROM AUTHOR]

In order to study the movement speed and deposition thickness of the rain-induced debris flow in mid-low mountain, a new approach was proposed in this paper of the debris flow in Pingshi temple, Xiushui county, Jiangxi province. Field investigation and flume test were to be used to provide the debris flow runout parameter, then Voellmy theory and RAMMS3 D were used to simulate the debris flow evolution process. The results show that the maximum velocity and the maximum sedimentary thickness of this debris flow were 5.69 m/s and 12.63 m respectively. The movement velocity and the sedimentary thickness at the key positions of the mudslides similarly to field investigation results. Field investigation and flume test could provide topography, dry friction coefficient and the viscous coefficient for numerical simulation. RAMMS3 D numerical simulation can accurately simulate the movement and deformation process of debris flow and determine the affected area of debris flow. [ABSTRACT FROM AUTHOR]