Heat Analysis and Fire Prevention of Timber Buildings in Southwest China Based on Fractal and Seepage Theory

In traditional settlements in Southwest China, there are many timber historical buildings and residential buildings, which feature a low fire resistance rating. The preservation and inheritance of these timber buildings are mainly threatened by fire. However, the existing research has not explored the deep correlation between the spatial structure of settlements and fire. To make up for the gap, this paper aims to find the ideas and measures that effectively prevent the fire from occurring in timber buildings of traditional settlements in Southwest China, based on fractal and seepage theory. Firstly, the fractal features were extracted from the spatial structure of these settlements. Then, the authors identified the factors affecting the spread of fire in buildings, and analyzed the mechanism of fire propagation between the timber buildings of traditional settlements. On this basis, a fire prevention scheme was proposed, which integrates the “targeted control of overall structure” with “comprehensive synergy between multiple local elements”. The research results provide a reference for applying fractal and seepage theory in the fire prevention of other buildings with special structures.

Comparison and analysis of pile-soil separate calculation and composite foundation calculation method for gravel pile reinforcement

This paper uses Indraratna seepage theory, Han pile-soil seepage theory and composite foundation theory to establish three plane strain models. Through finite element calculations, the changes in pore pressure and settlement are compared, and the following laws are found: (1) The model established by the composite foundation theory cannot reflect the objective laws of seepage and deformation; (2) In the case of multiple piles, there is no difference in settlement between Han pile-soil seepage theory considering the bearing characteristics of gravel piles and Indraratna seepage theory without considering the bearing characteristics of gravel piles. (3) The settlement value obtained by the principle of composite foundation is much smaller than the settlement value obtained by the separate calculation of pile and soil.

Application of seepage theory methods for solving the tasks of flow planning in transport networks with consideration of their structural dynamics

This article reviews the theoretical-graph approach towards transport and logistic systems, which allows describing key details and processes that take place therein. The question of searching for an effective solution of transport and logistics tasks and dependence of such solutions to throughput of the system and the value of the seepage coefficient. This article offers to use seepage theory as an applied instrument for describing and solving transport and logistics tasks. The indicated approach is innovative and original, which may be very promising in the context of global transport planning and management. The essence of this method, based on adaptation of seepage theory for solution of the typical transport and logistics tasks, is reduced to operation of surface run-off and origin on the graph. The model for assessment of the global throughput of transport and logistics system is developed on the basis of the methods of seepage and multidrain flow models. The author offers a model calculation of the impact of holdups upon transport and logistics systems and the tasks solved thereof. A theoretical-graph model, which reflects the structure of transport and logistics system, describes the objects and processes common to transport and logistics tasks. The toolset of graph theory allows solving the specific transport and logistics tasks, as well examining the structural properties of the system, building predictive models, as well as developing new approaches towards solving of these tasks. The characteristics of graph are correlated with the actual network, system and task, as well as with the characteristics of transport or logistics flows examined for the purpose of optimization of topological structure of the system and solution of other tasks.

Study on rainfall infiltration in high groundwater channels

In order to solve the adverse effect that the lining of high groundwater level channels is prone to damage when subjected to heavy rainfall, the response law of internal structural state of high groundwater level channels under different rainfall conditions was studied. Based on the non-seepage seepage theory, the seepage pressure (total water head) in the tunnel under four different rainfall types is analyzed and studied. The results show that the most unfavorable rainfall types for the lining structure safety are the frontal rainfall and uniform type rainfall. Therefore we should pay more attention to the front type and uniform type rainfall from the perspective of seepage. The research results can provide reference for slope and seepage control design of high groundwater level channels.

Seismic Stability of Loess Tunnel with Rainfall Seepage

Rainfall seepage changes the mechanical properties of loess masses. Considering fluid-solid coupling, the calculation model of a loess tunnel is established according to the finite element method (FEM). Based on porous media seepage theory and rainfall infiltration depth theory and considering the infiltrated depth of the loess surface for different rainfall intensities over a certain period, the stability of a loess tunnel under different rainfall amounts and loess cover thicknesses is studied using the dynamic finite element static strength reduction method. The results show that under the same rainfall intensity, the safety factor increases with the depth of the tunnel; the safety factor of the loess tunnel with the same loess cover thickness decreases with increasing infiltration depth. The plastic strain is mainly distributed on both sides of the vault and the arch feet. The stability of the loess tunnel is directly related to the loess cover thickness and rainfall seepage.

Slope stability analysis under rainfall conditions considering unsaturated characteristics of materials

As one of the important facilities in mines, the dump has become one of the major hidden dangers of mine safety management due to its large volume and loose structure. In this paper, based on unsaturated seepage theory of soil and practical engineering slope cases, the slope stability calculation model based on Bishop limit equilibrium method is established. This paper analyzes and calculates the evolution law of slope stability under extreme rainfall, obtains the law of slope stability safety coefficient changing with rainfall under unsaturated characteristics, and puts forward the corresponding countermeasures.

Solution and type curves for the seepage model of the water-bearing coalbed with leakage recharge

To analyze the effects of the leakage recharge of the aquifer on the initial dewatering of coalbed methane wells, the mathematical seepage model of water in the coalbed considering the aquifer leakage was established by using the leakage coefficient according to the unsteady seepage theory. The model was solved after Laplace transform and the Stehfest numerical reverse inversion was used to obtain the solution in right space. Then, the log-log type curves of pressure and pressure derivative were created with new combinations of parameters. Based on the natural seepage mechanism, the influence of aquifer leakage on curve shape was judged. It is found that the radial flow ends earlier as the leakage coefficient increases. Moreover, it was proposed to obtain reservoir permeability, skin factor, and leakage coefficient by using type curve matching. The type curves are useful for quantitatively evaluating the level of leakage, thereby guiding the adjustment of the following production system for CBM wells. Curvas de solución y tipo para el modelo de filtración de capas carboníferas acuíferas con recarga de fugasResumenEste estudio estableció el modelo matemático de filtración de agua en una capa carbonífera al estimar la salida acuífera con el uso del coeficiente de fuga, de acuerdo con la teoría de filtración inestable, para analizar los efectos en la recarga de pérdida de fluidos de un acuífero en el drenado inicial para pozos de gas metano. El modelo se resolvió tras usar la transformación Laplace y la inversión numérica Stehfest para encontrar la respuesta en el lugar indicado. Luego, se creó la representación algorítmica de la presión y la presión derivativa con nuevas combinaciones de parámetros. Se evaluó la influencia de la pérdida de fluido del acuífero en la forma de la curva con base al mecanismo físico de filtración. Se estableció que el flujo radial finaliza antes de que el coeficiente de pérdida de fluido se incremente. Además, se propone el uso de la curva tipo correspondiente para obtener la permeabilidad del reservorio, el factor de daño y el coeficiente de pérdida de fluido. Las curvas tipo son útiles para evaluar cuantitativamente el nivel de la pérdida de fluido, y de esta manera guiar el ajuste de un sistema de producción consecuente para pozos de gas metano de carbón.

The Research Progress of Threshold Pressure Gradient

Fluid seepage needs to overcome threshold pressure gradient in low permeability reservoir and heavy oil reservoir. A conclusion about the research progress of threshold pressure gradient was made by summarizing the literatures, which includes: the existence and experimental study of threshold pressure gradient, research of seepage theory considering threshold pressure gradient and applications. These can supply reference for the researching and engineering staffs engaged in related work.

Research on Mechanism of Concrete Creep

Under sustained loads with a fixed value, the deformation of concrete will continue to increase as time increases; this phenomenon is called creep of concrete. Currently, there are several theories to explain the phenomenon of concrete creep, viscoelasticity theory, seepage theory, viscous flow theory, plastic flow theory, micro-fractures theory and internal forces balance theory. Above models mostly studied linear creep of concrete under low stress status. This paper mainly research on concrete creep mechanism, and pointed out the advantages and limitations of the various theories, which has a guiding significance for theoretical research.