Design of Roof Cover Structures by Help of Numerical Models Defined in Formian

Numerical models defined by means of a suitably assumed set of parameters make it possible to select the optimal structural solution for the given or assumed conditions. The paper presents examples of applications of numerical models defined in the programming language Formian during the shaping processes of various types of spatial structural systems designed for roof covers. These types of numerical models can be relatively easily adapted to the requirements, which can be frequently changed during the investment process, what makes possible a considerable reducing of costs and time of design of the space structures having even the very complex shapes. The advantageous features of application of numerical models defined in Formian are presented in models determined for selected forms of the roof covers designed also by means of a simple type of a space frame. In the paper, there are some presented visualizations made on bases of these models defining mainly for structural systems developed recently by the author for certain types of the dome covers. The proposed structural systems are built by means of the successive spatial hoops or they are created as unique forms of the geodesic dome structures.

Experimental investigation on friction and squeezing of roof structure key blocks corner upon long-wall face

The coefficients of friction and squeezing of the key blocks comer in the roof structure of underground coalface are key factors to roof structure stability quantitative analysis. In this paper, through the special test of three-type corner friction and squeez- ing of real rock specimens, and physical simulation test on the roof key blocks of roof structure as well as the finite element calcula- tion of the corner stress distribution and failure mechanism, the characteristics of friction and squeezing of the roof key blocks comer are revealed. It is found that the friction angle of the roof key blocks corner is the residual friction angle, and the frictional angle of the roof key blocks is 22-32° (average 27°), so the friction coefficient is determined as 0.5. It also found the squeezing strength is less than the uniaxial strength, and the squeezing coefficient of the roof blocks corner is determined as 0.4. Based on the results, the ground control theory can be updated from qualitative analysis to quantitative analysis.

Research and application of mechanical models for the whole process of 110 mining method roof structural movement

For the 110 mining method,it is challenging to accurately calculate the support resistance of the roadway due to the lack of understanding of the dynamic movement of the overlying strata in this method.The consequential excessive support results in a significant increase in the cost of roadway support.The authors explored the overlying strata movement and roadway deformation of the gob-entry retaining in the 110 mining method to solve this problem.First,the typical stages of the roof-cutting gob-side entry were defined.Second,the mechanical model and calculation formula of the support resistance on the roof were explored.Then,using numerical simulation software,the starting ranges of the specific supports at different stages were verified and the feasibility of the support scheme was examined.Finally,combined with the field measurement data,the stress and the deformation of the gob roadway at different stages under the influence of two mining processes in the 110 mining method were obtained.The numerical simulation results obtained are consistent with the field test results,providing a theoretical basis for precision support at different stages by the 110 mining method.

Stability influence factors analysis and construction of a deep beam anchorage structure in roadway roof

Deep beam anchorage structures based on spatial distribution analysis of the cable prestressed field have been proposed for roadway roof support, Stability and other factors that influence deep beam structures are studied in this paper using mechanical calculations, numerical analysis and field measurements, A mechanical model of deep beam structure subjected to multiple loading is established, including analysis of roof support in the return airway of S1203 working face in the Yuwu coal mine, China, The expression of maximum shear stress in the deep beam structure is deduced according to the stress superposition criterion, It is found that the primary factors affecting deep beam structure stability are deep beam thickness, cable pre-tension and cable spacing, The variation of maximum shear stress distribution and prestressed field diffusion effects according to various factors are analyzed using Matlah and FLAC3DTM software, and practical support parameters of the S1203 return airway roof are determined, According to the observations of rock pressure, there is no evidence of roof separation, and the maximum values of roof subsidence and convergence of wall rock are 72 and 48 mm, respectively, The results show that the proposed roof support design with a deep beam structure is feasible and achieves effective control of the roadway roof,

Mode of overlying rock roofing structure in large mining height coal face and analysis of support resistance

The mining space of large mining height coal face is large,the range of movement and caving of rock strata is large and the stability of supports at coal face is low and damage rate of supports is high,which significantly affects the safe and efficient production of coal mines.By similar simulation experiment and theoretical analysis,the mode of fractured roofing structure of large mining height coal face and the method of determination of reasonable support resistance of the support was evaluated.Analysis shows that the structural mode of "combined cantilever beam – non-hinged roofing – hinged roofing" of the large mining height coal face appears at the roofing of large mining height coal face.The supporting factor of caved gangue at the gob is introduced,the calculating equations of the fractured step distance of roofing were derived and conventional calculating method of caved height of roofing was corrected and the method of determination of the length and height of each structural area of the roofing was provided.With reference to the excavating conditions at Jinhuagong coal mine in Datong minefield,the dimensions of structural areas of the roofing of the coal face were determined and analyzed,and reasonable support resistance of the height coal face was acquired.By selecting Model ZZ13000/28/60 support and with procedures of advanced pre-cracking blasting,the safe production of large mining height coal face was assured.

Influence of backfilling rate on the stability of the"backfilling bodyimmediate roof"cooperative bearing structure

To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.

The relation between modes of lithologic association and interlayer-gliding structures in coal mine

As a case study of the Panji No.1 Coal Mine in Anhui Province, based on thesite measured and statistical data, summarized the lithologic associations, characteristicsand distribution laws of interlayer-gliding structures and tectonic coal in the No.11-2 coalseams.The results show that 9 modes of lithologic association can form interlayer-glidingstructures.It is more easy for rock slip to occur when the lithologic associations are mainroof + coal seam + immediate floor type, compound roof+immediate roof + coal seam +immediate floor type and immediate roof + coal seam + immediate floor type.Lithologicassociations of roof and floor are the precondition to the formation of interlayer-glidingstructures.

Roof structure theory and support resistance determination of longwall face in shallow seam

This paper presents the structure models founded in shallow seam, the roof asymmetry arch with three articulations in roof first weighting and the step voussoir beam in roof periodic weighting. These structure models are differ from classic theory, it establishes the new roof control theory of instability structure roof, especially in shallow seam. Based on the new roof structure theory, the support working state of "given sliding load" is put forward, and the factor of load transmitting is introduced to determine the load on roof structure. Therefore, the proper and accurate calculating methods of support resistance are established. Based on this, the dynamic structure theory in shallow seam could be predicted.

Effect of a single weak lithological structure on the height of a collapsing roof in a deep soft rock roadway

Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding rocks. This thesis analyzes the effect of two single and weak lithological structures of both sides and the roof on the height of a collapsing roof in a deep soft rock road- way. Using the two-dimensional UDEC3.1 software, a numerical structures of both sides of a roadway and of two weak lithological simulation was carried out on the models of weak lithological structures of roof of different depths. We reconstruct the overall processes from a break-away layer, bending, subsidence and the cracking of a collapsing roof. We also illustrate the distribution characteristics of displacement fields in the surrounding rock after the roof collapse in a deep soft rock roadway. The results of our numerical simulations indicate that the form of a roof collapse is side-expanding when the roadway is a weak structure at both sides The height of the roof collapse is related to the lithological combination of the roof when the roadway is a weak structure of the roof.

Using of Key Stratum Theory to Study the Structural Development of Roof Aquifer

During the underground mining of coal resources,overlying rocks on the roof of excavated tunnels will be destroyed due to ground pressure,and as a result,part of them will break and fall into the tunnels.How to determine the distribution of fractured areas and fissures presents a major problem for preserving the overlying aquifer.

Experimental Study on Roof Structure Characteristics and Its Failure Pattern in Coal Roadway

Based on the investigation and statistics of logs of 211 bole holes and strata data from 79 roadways in 13 coal mines located in Xishan, Jincheng, Lu’an, Fenxi, and Huozhou in China, the roadways’ roof structures were classified as multi-thin-layer, thin-thick combined layer, integrated thick layer, thick-coal layer, and cracked layer according to the geometric features and spatial strength distribution of surrounding rock. Then eight sub-categories were defined as different situations. And seven simulation modeling tests were carried out. The strata structures of these models were different from each other. At last, the relationship between roof structure and its failure pattern was discussed.

Physical Modeling of Influence of Rock Mass Structure on Roof Stability

Based on the developing degree of structure planes in coal roof, whole, blocky and heavily fractured structure models are built up. Through simulation test of similar materials, the distribution of deformation, failure and underground pressure induced by coal mining in coal roof with different rock mass structures are analyzed. The test results indicate that the distances of first and periodic weighting of main roof and the height of caving and fracture zone decrease with the increment of fractures in roof rock mass. From whole to blocky and heavily fractured structures, abutment pressure ahead of working face reduces and the peak value of abutment pressure migrates to inside of roof rock mass.

Lessons from the seismic behavior of a steel grid roof structure heavily damaged in Lushan earthquake

The seismic behavior of a school gymnasium, whose steel grid roof was heavily damaged during the Mw6.6 Lushan earthquake in 2013, is simulated through nonlinear dynamic analysis. The simulated damage is compared with field observations to validate the numerical model, based on which a parametric study was performed to provide insight into the failure process and damage patterns of steel grids. The results suggest that the grid damage is strongly related to roofsubstructure interactions. These include not only the substructure's amplification of the vibration, but the uncoordinated displacement of the substructure's columns which support the grid also play an equally important role. In particular, the latter effect may significantly alter the internal force distribution in the steel grid and lead to unexpected buckling of members that are proportioned as tension-only members. While such interactions are generally not accounted for in the design practice for grid structures in China, similar seismic damage may be expected for other existing grid roofs in future earthquakes. As is also demonstrated in this study, seismic isolation of the roof is a promising solution to protect grid roof structures by mitigating the detrimental effects of roof-substructure interactions.

Practical Aspects of the Design and Construction of a Small Cable Roof Structure

Cable roof structures?have?only become widespread in large span structures in the latter part of the twentieth century. However,?they?still represent a relatively new form of roof construction, especially as in the present case of a small span innovative structural solution. The contribution of this text to the structural engineering community lies in the increased interest in building simple cable roof structures. Since its completion in September 1996, this small cable roof structure has been recognized as an interesting architectural and structural example. The text describes aspects of the design and construction of a small cable roof that was designed as a roof for an open-air theater stage for the city of Sao Jose do Rio Pardo, Sao Paulo, Brazil. A cable network, in the shape of a hyperbolic paraboloid surface, is anchored in a reinforced concrete edge ring. The projection of the ring’s axis onto the ground plane is an ellipse. Workers with specialized training were employed in the various stages of the construction, which was completed in September 1996.

Basic Structural Forms of Main Roof

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Proposal of Stainless Steel Roof Structure and Tiles for Gymnasiums

This work proposed an architectural alternative project of a stainless steel roof structure that uses roof tiles also in stainless steel with emphasis on roofs for multi-sport gymnasiums.In the development of the work,two existing multi-sports gymnasiums are taken as a reference,but with ASTM(American Society for Testing and Materials)A36 steel roof structure.The proposed cover system uses cables and light gauge profiles,in commercial stainless steel,which reduces the weight and of course the final price of the roof structure.A structure that presents technical feasibility is obtained and analyzed by checking its behavior with respect to the efforts and displacements generated by the combinations of the acting loads,following the safety recommendations of the applicable standard.It is verified that using the stainless steel structure proposed in this work would cost 42%of the reference structure if this were in AISI(American Iron and Steel Institute)304 stainless steel.And this cost tends to be minimized due to greater durability and consequent reduction in maintenance costs of this type of steel.

天窗系统与金属屋面板连接构造设计

对天窗系统与金属屋面板连接构造进行了研究分析与设计。通过对已有天窗连接构造进行分析和总结,基于厦门国际博览中心金属屋面工程提出了一种新的天窗与金属屋面连接构造的设计思路和施工方案,采用了优化后的连接方式和材料,提高了屋面板连接的强度和稳定性,并兼顾了施工的便利性。实际结果表明,提出的天窗连接构造具有较好的受力性能和施工性能,能够满足实际应用要求。

基于力学模型构建的留巷切顶高度确定与围岩控制技术

以顺和煤矿2401运输巷道沿空留巷为工程背景,分析巷道围岩结构特征,基于巷道局部空间结构稳定性,分别构建了沿空留巷未切顶与切顶力学结构模型,并以巷道不同切顶高度进行物理相似模拟试验。结果表明:巷旁采空区切落的矸石增加对关键块的支撑力,同时弱化关键块对直接顶悬壁端部挤压,巷旁支护阻力减少35.78%;随着切顶高度增加,巷道顶板采空区侧端部悬臂由F型缓慢过渡到大I型,同时大保护结构具有向上平移趋势,相比于未切顶1巷,4 cm切顶2巷、8 cm切顶3巷与16 cm切顶4巷叠加应力峰值分别下降9.38%,28.13%,25.00%。结合巷道顶板岩性,最终确定切顶高度为8.2 m,留巷段采用三列单体液压支柱作巷旁支护,长短锚索超前补强,巷道围岩稳定,较好满足使用要求。

底板动压巷道压裂弱结构体应力转移控制技术

为了满足煤矿安全生产的需要,许多巷道都会布置在煤层底板中,如部分运输大巷、排水巷道、瓦斯抽采巷道等。采动应力容易造成底板巷道围岩应力升高,加剧底板巷道围岩变形,造成支护永久失效、顶板下沉、巷道底鼓、两帮收敛等破坏。针对此,提出了在应力传递路径上实施水力压裂,在指定的区域制造出一定空间形态的水压裂缝网,形成压裂弱结构体,实现区域范围内的应力转移,从而降低巷道区域范围内的应力,控制巷道的围岩稳定性的控制技术,并通过理论分析及现场工程验证等方式,揭示了底板动压巷道压裂弱结构体应力转移的力学机制,建立了相应的力学模型,对压裂弱结构体的合理位置、范围等影响因素进行了求解。得出:(1)压裂弱结构体使局部应力场发生明显变化,出现应力升高区和应力降低区,应力降低区主要分布在弱结构体与采动应力连线的方向上,主要集中在一个拱形的范围内;由于膨胀效应,在与应力来源垂直的方向上产生应力集中,出现应力升高区。(2)最大主应力变化幅度与压裂弱结构体的长轴长L、短轴长H、到巷道的距离P、与巷道连线的水平夹角β、压裂层的强度C及内摩擦角α、压裂的损伤变量D等有关。其中到巷道的距离P对卸压效果影响最大,损伤变量D对卸压效果影响最小。(3)采用提出的计算方法设计了淮北矿业集团袁店一矿的103运输集中巷的卸压方案,工程应用结果表明,底板动压巷道变形速率明显减缓,验证了底板强动压巷道压裂弱结构体应力转移模型的合理性。

弹−塑性基础边界两侧采空(留煤柱)基本顶板结构初次破断特征

为了研究两侧采空留煤柱工程条件下基本顶板结构的断裂位态及工程指导意义,构建考虑实体煤弹塑性变形与两侧煤柱宽度及支撑能力弱化的基本顶板结构双塑化基础边界力学模型,基于有限差分算法与主弯矩破断准则系统计算了在非对称煤柱区和长边实体煤区的断裂线形态、区位属性及整体位态特征,并从7个层面、横纵向4对区域与传统模型对比,阐明新模型所得新结论及工程意义。结论如下:(1)两侧非对称煤柱参数对长边实体煤区域的基本顶主弯矩及破断位置影响小,但分别显著影响煤柱区的主弯矩大小、位置及断裂形态。两侧煤柱区(较强/宽煤柱区+较弱/窄煤柱区)基本顶断裂线形态有3类演化模式,随基本顶厚度及弹模增大而煤柱宽度、支撑能力及悬顶跨度减小,其变化规律为:非对称的“连续单弧形+连续单弧形”→“连续单弧形+开口间断双短弧形”→非对称的“开口间断双短弧形+开口间断双短弧形”。(2)长边实体煤区基本顶的断裂线主要有3类区位属性,随基本顶厚度及弹模增大而实体煤的塑性区宽度、塑化程度及悬顶跨度减小,其演变规律为:断裂线在塑性煤体区(C-S式)→弹塑性煤体分界区(C-TS式)→弹性煤体区(C-T式);(3)考虑断裂线区位属性,随基本顶厚度和弹模增大而煤柱宽度、支撑能力及悬顶跨度减小的基本顶全区域破断模式及演变规律为:C-S式的■→C-TS式的■→C-T式的■→C-T式的■→C-T式的■。针对研究两侧采空(煤柱)基本顶板结构破断的3类力学模型,从7个层面对比了3类模型的重要区别,从横向4个区域(开采区域的前方与后方、两侧煤柱区)与纵向4个区域(非对称遗留煤柱下伏、下伏开采空间出/进煤柱/体)阐明了其重要工程作用。