Based on the actual engineering conditions of a mine in Northeast China, this study conducts rainfall model tests on open-pit mine slopes using a self-designed model box, coupled with numerical simulations to investigate slope stability under rainfall infiltration. The physical test results reveal that during rainfall infiltration, the displacement in the Y-direction is more pronounced than that in the X-direction, with such displacements predominantly concentrated on the slope surface. Pore water pressure exhibits a continuous increase as rainfall infiltration proceeds. In the late stage of rainfall, the maximum principal strain is initially concentrated at the slope toe and subsequently propagates toward the middle of the slope. The rainfall infiltration sequence follows a pattern of slope top-slope surface-lower part of the slope mass. Multiple stress mutations occur at various stages of rainfall, inducing further extension of internal cracks within the model and widening of surface cracks due to rainfall erosion. Numerical simulation results indicate that the Y-direction strain convergence on the left slope surface presents an arc-shaped distribution, with an overall increasing trend in strain magnitude. Displacements are mainly concentrated in and around the underground stope, while pore water pressure gradually rises with increasing slope depth. The numerical simulation results are in substantial agreement with those from the physical model tests. The findings of this study provide a scientific reference for the prevention and control of open-pit slope instability induced by underground mining under rainfall conditions.

In view of the multi-field coupling effects such as rainfall infiltration, reservoir water level (RWL) seepage, and fissure seepage, the risk of slope disaster increases sharply. This study takes an open-pit mine in China as the research object. Based on the improved Green–Ampt model as the key objective, the rainfall infiltration model was improved by combining the dynamic changes of the wet front depth in the slope. The proposed model integrates Darcy's law and the mass conservation principle and establishes the coupling mechanism between seepage and stress fields. Numerical verification was performed using comprehensive performance indicators, including the Nash efficiency coefficient, root mean square error, relative standard deviation, mean absolute error, volume error, and relative error. The comparative analysis with the existing models shows that the improved model has higher accuracy and reliability in predicting slope stability under rainfall-induced seepage. The results emphasize the key role of RWL seepage and rainwater pressure in weakening the mechanical properties of the slope through the wetting softening effect. This work provides theoretical support and practical guidance for predicting slope instability caused by rainfall.

There are many factors affecting the stability of open-pit mine slopes, among which slopes with soft interlayers have become an important factor inducing deformation and instability due to their poor mechanical properties. In this paper, for the destabilization of a slope with soft interlayer under rainfall infiltration in an open-pit mine in Zhejiang Province of China during the rainy season, a sudden change of displacement at the monitoring point and the formation of a continuous plastic deformation of the slope are proposed as the criteria for slope destabilization through the establishment of a rainwater seepage-stress coupling model combined with the strength reduction method, and by using COMSOL Multiphysics finite element numerical simulation software to establish a three-dimensional numerical model based on the actual mining slope conditions. The safety principle is introduced through the strength reduction method to analyze the stability of the slope with soft interlayer under the coupling effect of seepage and stress. The safety coefficients of the slope with soft interlayer are calculated by using Numerical methods under the coupling effect of seepage and stress. The influence of rainfall intensity and duration on the stability or safety factor of the slope with soft interlayers was studied through analysis of stress, saturation, displacement, and pore pressure evolution. The mechanism of rainfall affecting slope stability was investigated, and the findings were validated using an engineering case study of a slope with a soft interlayer. The findings show that rainfall intensity is the main factor affecting slope stability in the open-pit mine slope with soft interlayer. The higher the rainfall intensity, the faster the shallow soil forms a saturation zone, whereas soft interlayers speed up the process and endanger slope stability. The slope prevention and control technology of the prestressed anchor cable (rod) framework was proposed based on the slope management construction conditions of the mine, and the effectiveness of the measure was verified through on-site industrial tests. The research findings provide a reference for preventing and controlling slope with soft interlayers in open-pit mines under similar conditions.

In order to accurately predict the evolution law of the morphological distribution of the goaf and the changes in surface subsidence after mining of the shallow ore body, the No. 6 copper ore body was used as the research object. According to the actual situation of the site, the numerical simulation software COMSOL Multiphysics is used to analyze the shape evolution of the goaf, establish the prediction model for the shape evolution of the goaf and surface subsidence, and make predictions on the scene. The rationality of the prediction model is verified by comparing it with the actual measured surface subsidence results. The results indicate that: (1) As mining progresses, stress concentrations gradually form on both sides of the different sections of goaf, the top plate breaks up and loses its bearing capacity, and stress are transferred to the bottom plate of the deposit and form a stress reduction zone. (2) As mining progresses, the subsidence of the surrounding rock at the top of the goaf increases with the increasing mining area and is transmitted to the upper part of the goaf, eventually leading to surface subsidence and the formation of a concentric sink basin, with the maximum displacement occurring at the centre of the circle corresponding to goaf. (3) By determining the safety of the overlying buildings in goaf, it is concluded that the extraction of the shallow ore body will have little impact on the damage to the surface buildings.

Cemented tailings backfill (CTB) is a mixture of tailings, binder and water. The freshly prepared CTB slurry is commonly transported into underground mined-out areas via pipeline. The flowability of fresh CTB slurry is significantly affected by the coupled thermal (T), hydraulic (H), rheological (R) and chemical (C) processes. Therefore, this paper develops a THRC coupling model, which considers the evolutions of thermal conduction, fluid flow, rheology, and binder hydration to predict the fluidity of fresh CTB slurry. Rheological testing experiments are conducted to verify the availability of the developed model. The validated model is used to further investigate the effect of time and temperature factors on the hydraulic behavior of the hydrating CTB slurry. The obtained outcomes can make contributions to a better regulation of the time and temperature factors in the preparation and transportation of fresh CTB slurry. (C) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

To study the stability of the concrete structure during the whole process of fire, the temperature variation law of steel structure in fire was researched.The temperature variation principle of steel structure in fire was studied, and the values of critical parameters of the prediction model were reselected.Then the relative experiment designs were introduced.Five scenarios were set to research the temperature variation of steel structure and smoke.The predicted value and experiment results were compared to verify the accuracy of the model.The results manifests indicated that the modified prediction model is able to predict temperature change of the steel structure in fire accurately, especially the law of temperature variation at the declining phase.

通过对储煤场煤堆火灾危险性进行分析,并结合大涡场模拟软件FDS对不同防火间距的储煤场煤堆火灾数值模拟.通过研究发现,封闭式储煤场内煤堆发生火灾时,着火建筑内不同高度处的热辐射通量由低至高逐渐增强,且符合指数函数关系,并推断出火场内热辐射主要来自着火煤堆和火灾产生的高温烟气.提出此类建筑内煤堆在分堆堆放的同时还应控制煤堆高度以保证火灾时安全的建议.