建筑结构的保温与防潮

采暖建筑在建造和使用过程中,会因受到水及水蒸汽间歇浸渗而受潮,建筑受潮,对其使用寿命及保温性能均具有不良影响,承重结构受潮,将降低其机械强度;保温层受潮,不仅降低其抗压强度,还可能引起破坏性变形,内饰面受潮,将增大室内环境湿度,并破坏其外观质量。冬季室内环境的污染与潮湿有直接关系,无论是建筑生霉,还是其它生物性污染都是如此。显然,防潮是建筑保温的重要环节。防潮应从多方面入手,如屋面防水,墙角防潮湿,装配式建筑接缝及各种节点防水等。但围护结构内部及表面冷凝是防潮的关键问题,同时也比较容易处理。

Numerical Analysis of Finite Deformation of Overbroken Rock Mass in Gob Area Based on Euler Model of Control Volume

The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The beating pressure of the gob can directly affect the safety of mining fields, formarion of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA＇2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area： （1） a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the beating pressure is nearly zero; （2） an overcompacted region, 10-20 m away from unbroken walls, where the beating pressure results in the maximum value of the gob area; （3） a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the beating pressures show basically no differences. Such a characteristic can exolain the easy-seeoaged “O”-ring phenomena around mining fields very well.

Numerical analysis of deformation and failure characteristics of deep roadway surrounding rock under static-dynamic coupling stress

In actual production,deep coal mine roadways are often under typical static-dynamic coupling stress(SDCS)conditions with high ground stress and strong dynamic disturbances.With the increasing number of disasters and accidents induced by SDCS conditions,the safe and efficient production of coal mines is seriously threatened.Therefore,it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS.In this paper,the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations,and the deformation and failure characteristics are obtained.According to the simulation results,the horizontal stress,vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock.Among these factors,the influence of the dynamic disturbance is the most substantial.Under the same stress conditions,the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor.The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses.The results indicate that for the roadway under high-stress conditions,the in-situ stress test must be strengthened first.After determining the magnitude of the in-situ stress,the location of the roadway should be reasonably arranged in the design to optimize the mining sequence.For roadways that are strongly disturbed by dynamic loads,rock supports(rebar/cable bolts,steel set etc.)that are capable of maintaining their effectiveness without failure after certain dynamic loads are required.The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS,and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

Failure mechanism and stability control technology of rock surrounding a roadway in complex stress conditions

To solve the problem of supporting three downhill coal structures in the Yongan Coal Mine of Shanxi Jincheng, we studied the regular development of stress and plastic zones and characteristics of deformation of rock surrounding roadway groups after a period of roadway driving, mining one side as well as mining both sides, we used FLAC 3D for our numerical and theoretical analyses. Field test were carried out, where we revealed the deformation mechanism of roadways and its coal pillars in complex stress conditions. We proposed a roadway stability control technology using backwall grouting with high-water rapid hardening material and combined support with bolt and cable anchoring after mining both sides. Our field practices showed that deformation of rock surrounding roadways can be controlled with this technology.

Deformation failure and countermeasures of deep tertiary extremely soft rock roadway in Liuhai coal mine

In view of failure phenomena with nonlinear large deformation including extensive damage,whole section destruction in short time,high rate of repair,most destruction forms occurred in the tertiary roadway of soft rocks engineering in Liuhai mine,according to the methods of geological survey,theoretical analysis,numerical calculation and in-situ test,the composite failure mechanism of molecular expansion,tectonic stress,gravity stress and engineering deviatoric stress,faults and random joint in this area is analyzed deeply,then an coupling support of double-layer-truss is proposed.The research results show that the first wave of deformation energy was released by bolt-mesh-cable fixed into the roof,floor and two sides of the roadway.While the second wave of deformation energy was released through the interface function between double-layer-truss and the surrounding rock.The double-layer-truss that characterized by high strength,good integrity can absorb high deformation energy of surrounding rocks,which led to the uniform distribution of the stress.Engineering practice shows this technology has been successfully applied to control the deformation failure of the tertiary extremely soft rock roadway.

Three dimensional efficient meshfree simulation of large deformation failure evolution in soil medium

An efficient Galerkin meshfree formulation for three dimensional simulation of large deformation failure evolution in soils is presented. This formulation utilizes the stabilized conforming nodal integration, where for the purpose of stability and efficiency a Lagrangian smoothing strain at nodal point is constructed and thereafter the internal energy is evaluated nodally. This formulation ensures the linear exactness, efficiency and spatial stability in a unified manner and it makes the conventional Galerkin meshfree method affordable for three dimensional simulation. The three dimensional implementation of stabilized conforming nodal integration is discussed in details. To model the failure evolution in soil medium a coupled elasto-plastic damage model is used and an objective stress integration algorithm in combination of elasto-damage predictor and plastic corrector method is employed for stress update. Two typical numerical examples are shown to demonstrate the effectiveness of the present method for modeling large deformation soil failure.