Gongcheng Kexue Yu Jishu/Advanced Engineering Science

Gas-containing coal is a two-phase dielectric composite material with porous characteristics and solid-gas coupling characteristics. In order to accurately simulate the physical and mechanical properties of gas-containing coal, based on similarity criteria and similarity scales of main control parameters, with more than 80 sets of material matching tests and mechanical parameter tests, a similar material for coal-gas two-phase medium was developed. The similarity between similar materials and raw coal was compared, and based on the new material, a three-dimensional simulation test of coal and gas outburst was performed. The main conclusions were as follows. 1) The elastoplastic parameters and adsorption parameters of new material prepared by pulverized coal and sodium humate aqueous solution as aggregate and binder is similar to raw coal. Similar materials with different elastic-plastic parameters can be prepared by adjusting the material ratio. The adsorption of similar materials is consistent with that of raw coal. 2) The expansion energy of the binary mixture of CO2 and N2 is between CO2 and N2. The proportional coefficient of expansion energy and CO2 volume fraction are quadratic functions. The expansion energy of the mixture with 45% CO2 volume fraction is consistent with that of CH4. The binary mixture of CO2 and N2 can be used as similar gas to CH4, and it is safer than CH4. 3) The new material is highly similar to the physical and mechanical parameters of raw coal containing gas, which realizes the simulation of gas-solid coupling characteristics. 4) A three-dimensional physical simulation experiment reproduces the phenomenon of outburst caused by uncovering coal, and the morphology of outburst holes and the quality of outburst pulverized coal that are close to the field are obtained, which verifies the rationality of similar materials, and also provides a scientific means for further study of the law of outburst and monitoring the precursor information of outburst.

The macro mechanical properties of slope are determined by the meso parameters of soil particles and their motion. Although the stress and deformation characteristics of slope at the macro level can basically be obtained by the finite element method based on continuum model, it is difficult to reveal the deformation and instability mechanism of slope in the micro scale, and there are obvious limitations. The three-dimensional DEM-CFD model of fluid solid interaction of coal measure soil slope was established by coupling DEM and CFD. The meso mechanism of coal measures soil slope failure under rainfall was analyzed. The results show that the failure mode of coal measure soil slope simulated by DEM-CFD is mainly of rain erosion, and the slope sliding surface is predicted to be of approximate straight-line section, which is very close to the range of rain erosion of slope in outdoor model test. This shows that the numerical method is suitable to analyze the stability of coal measure soil slope. Micro parameters such as force chain, coordination number and porosity of soil particles in slope will change during the rainfall. For example, the porosity of particles on the top of slope changed from 0.35 in initial state to 0.8 in unstable state. The change of these micro parameters is directly related to the macro mechanical performance of the slope soil. In this paper, the law of the failure evolution of the coal measure soil slope under the rainfall was explained through the analysis of the micro parameters change of the particles. The research results of this paper not only provides theoretical basis for the protection design and construction of the coal measure soil slope in this area, but also provides a new way of analyzing the macro mechanical laws in geotechnical engineering from the micro perspective.

With the development of computer technology, grid division technology is becoming more mature. Considering the frequent occurrence of floods due to climate change, the broad extents of calculation domains, the wide range of actual terrain, and the study area usually has narrow and long gullies and wide flooding areas, this paper proposes a structured non-uniform grid model with hierarchical topological relationships combined with a high-resolution model based on GPU acceleration to simulate the surface water flow process. High-quality grids affect the calculation accuracy and efficiency of the model. The principle of grid division is designed based on the gradient change of terrain elevation, and key terrain features are detected in the computational domain that requires high-resolution grids to reliably solve shallow water equations. Moreover, local area grids can be statically encrypted, so that the sensitive area of the water level calculation can be captured more accurately, while reducing the number of calculation grids and reducing the calculation cost. The numerical model adopts Godunov-type finite volume method for spatial discretization, uses the second-order TVD-MUSCL format to improve the temporal and spatial accuracy of the model, and uses GPU parallel technology to greatly increase the running speed of the model without reducing the calculation accuracy. The performance of high-resolution models on non-uniform grids is demonstrated by the more accurate simulation of flood inundation time and inundation area through ideal and practical cases. The results show that the numerical model based on the non-uniform grid has good stability, compared with the uniform grid, its running speed is about 2-3 times under the premise of ensuring the simulation accuracy and the efficiency is further improved on the basis of GPU acceleration. The new model is suitable for simulating large-scale flood evolution and urban inundation processes in complex areas, which has good potential in actual large-scale flood simulation.

Urban and rural mixed organic waste, including perishable waste and partial agricultural waste, are high yield, complex composition, high water content and nutrient content. Aerobic fermentation is one of the key technologies for the utilization of this resource, but the application is limited in China due to the low conversion efficiency and unknown risk of by-products. Therefore, in view of the bottleneck problem of aerobic fermentation of organic waste in China, the resource utilization technologies of urban and rural mixed organic waste were compared and analyzed, the advantages of aerobic fermentation in the treatment of organic solid waste was clarified, the transformation mode of organic matter in the process of aerobic fermentation was deeply analyzed, and the main problems faced by aerobic fermentation in the treatment of organic waste was revealed. Accordingly, the main factors affecting the efficient stabilization and resource utilization of aerobic fermentation products was further identified. The concept of rapid stabilization and resource utilization of urban and rural mixed organic waste, named as detecting the regulation principle of microbial metabolic network during organic waste aerobic fermentation, was proposed. Meanwhile, intelligent integrated rapid stabilization technology and equipment (intelligent screen display-online monitoring-feedback control) was also developed overcome the technology of directional humification and pollution enhancement in microbial factory, the technology of deep processing-quality evaluation- attribute complementary of resource products to utilize resource products by their characteristics was constructed. In order to provide technical support for the resource treatment of urban and rural mixed organic waste in China, researches and demonstration projects will be carried out to meet the major needs of national science and technology, such as in-situ reduction of organic waste by aerobic fermentation, pollution control in the process, and resource utilization of the end products.

When Levy type rigid bracing dome is impacted by unexpected load, its structure may collapse continuously, resulting in property loss and casualties, therefore, it is necessary to analyze its progressive collapse performance. According to characteristics of rigid bracing dome, the threshold coefficients of members and its calculation formula were given, and the discriminant criteria and types of progressive collapse were proposed. Damage coefficient based on response difference was proposed, and importance coefficient of members was given. Member importance of levy type rigid bracing dome were analyzed and sorted based on importance coefficient of members. Based on the discriminant criteria of progressive collapse and the results of importance analysis of members, the method and process of progressive collapse analysis were proposed. Progressive collapse performance of structure was analyzed. The influence of both rise span ratio and initial prestress on the progressive collapse performance was discussed. The method of progressive collapse resistance against rigid bracing dome was proposed. The research showed that the progressive collapse types of levy type rigid bracing dome could be divided into non collapse, local collapse and overall collapse. The outer ring bar obtains the largest importance coefficient, followed by the inner ring bar. The smaller rise span ratio is or the larger the initial prestress, the smaller importance of the member will be. When the outer ring member, inner ring member or node is damaged, the structure will collapse continuously, while other members will not collapse. Strengthening the joints and ring members can improve resistance of structure against progressive collapse.