隧道围岩压力拱研究进展

从压力拱定义来看压力拱是能保证岩体的稳定性的,那么充分发挥压力拱的拱效应,就可以提高隧道工程经济性和安全性。因此,压力拱的研究一直是个热点和难点。通过收集整理、归纳总结及综合分析已有的相关研究“成果”得出：随着试验手段的多样化和现代技术的发展,压力拱及相关概念的研究取得了一定的成果,但对其判断标准、形成条件依然未陈述清楚,并且缺少统一的标准;压力拱的自稳性和动态压力拱是否具有一般性的规律,是否在一定条件才成立？仍有待证实;压力拱研究中的数值分析和物理模型试验各有优缺点,因此,二者需要相互“合作”,彼此补充和验证。从当前情况看,试验设备、试验材料及加载方法仍达不到清洁高效、简洁适应、智能环保的要求,仍需深入研究。     

桩间三维土拱效应颗粒流数值模拟及其演化规律

抗滑桩桩间形成的土拱是水平土拱和竖向摩擦拱的共同体现,具有明显的三维特征。利用颗粒流分析软件PFC^3D建立数值模型,在桩后不同高度处及同一水平面不同位置设置一系列测量球,监测桩后土体应力变化情况。结合颗粒位移变化情况对抗滑桩桩间三维土拱效应的形成演化进行分析,并对土拱厚度的演化规律做了深入研究,提出结合相对位移和最大主应力等值线综合确定土拱厚度的新方法。分析表明：桩后土拱由桩间临空面靠近桩底开始并不断向土体内部和上部发展,土拱的破坏过程由桩底向桩顶扩展;土拱厚度随深度变化表现为沿桩底向桩顶先增加后减小的趋势;土拱厚度随时间的变化表现为随着加载时间增加,土拱厚度先增加后减小直至土拱破坏。     

矩形和直墙拱断面围岩巷道破坏的数值模拟研究

通过对岩石破坏特性和机理的分析,得出岩石破坏的剪切强度与参数的数学关系。在此基础上建立围岩巷道的数值模型,模拟围岩巷道在矩形和直墙拱等断面条件下的破坏过程,得出巷道在不同侧压系数条件下的围岩破坏特征。结果表明:同一断面形状,当侧压系数较小时,破坏裂纹首先出现在两帮,随着荷载的增大,破坏裂纹由底部向顶部转移;另外基于矩形和直墙拱形断面巷道的数值模拟,得出了围岩巷道的破坏是一个渐进的过程,并伴随应力场而不断转移,且在相同侧压系数和外荷载条件下,矩形巷道破坏较为严重。分析矩形巷道和直墙拱巷道变形破坏过程,为合理寻求巷道设计和支护方法提供依据。     

煤层断层构造演化应力场分布特征数值模拟研究

采用有限元数值模拟软件ADINA,模拟了一次构造作用下煤层断层构造的形成过程以及煤层断层形成后受现代构造应力场作用下煤层的破坏情况及地应力的分布规律.模拟结果表明,一次构造作用下煤层断层构造的形成过程中,在接近断层面的下盘煤层底部和接近断层面的上盘顶部,煤体容易遭到破坏;断层构造形成后在不同的铅直应力和水平应力组合情况下,正逆断层的下盘断层面附近区域均存在应力集中现象,逆断层的应力场方向主要由最大应力的方向决定,而正断层仅在水平应力与铅直应力比较接近时,应力场方向主要由铅直应力决定.     

筒仓卸料时的压力计算

把筒仓卸料过程中贮料的动量变化引入分析中,并提出了“承压拱”、“卸料压力增大系数”等概念,研究了卸料时的压力增大规律,给出了计算卸料和卸料起拱时压力增大的公式,计算结果与有关实测结果吻合较好。     

深浅仓卸料压力离散元数值模拟研究

筒仓卸料时贮料作用在仓壁上的动压力出现骤然增大及震荡分布的现象,采用室内模型试验法和离散单元法,通过改变筒仓高径比来研究贮料在静态储粮状态和卸料过程中的力学行为,从宏观流态和细观颗粒层次研究贮料颗粒物质的力学行为及二者的本质联系。采用锥形漏斗筒仓,贮料为小麦,装料高4.4 m,直径1.5 m,漏斗高0.7 m,在室内模型试验验证的基础上,利用离散元PFC2D软件分别建立6个不同高径比的深浅模型仓,对筒仓卸料过程进行数值模拟,对静压力、动压力以及超压系数进行对比分析,并从宏观流态和细观动力拱两方面来探究筒仓侧壁动压力增大的原因。结果表明:试验最大动压力发生在筒仓下部约1/3处,模拟最大动压力发生在筒仓下部约1/4处;相同高度、较大直径的筒仓最大动压力随直径增大呈整体上升趋势,但非线性;流态不同、动力拱发生时间不同是深浅仓动压力不同的重要原因。     

偏压连拱隧道合理开挖方法的数值模拟研究

针对铜黄高速公路汤屯段大田双连拱隧道进口段埋深浅、地质条件复杂、存在偏压以及隧道结构受力复杂等特点,采用FLAC3D对隧道合理开挖方法进行了三维数值模拟研究.通过与隧道典型断面的拱顶下沉、支护结构受力、地表沉降的现场监测数据对比分析得出科学结论,能够动态地指导偏压双连拱隧道全过程施工,确保施工安全.     

扬压力作用下反拱水垫塘缝隙动水压力研究

以国内某高坝工程为参照,对水垫塘排水和底板锚固措施都失效后,底板缝隙动水压力随扬压力、底板缝宽以及不同止水破坏程度这3个关键因素的变化规律进行了理论分析和试验研究。研究表明,止水正常时,由于底板表面动水压力脉动、底板振动,使缝隙动水压力大于扬压力;止水破坏后在小扬压力范围内,缝隙动水压力增大,但增幅随扬压力增大而减小、也随底板缝宽增加、或止水破坏程度增加而减小;止水破坏后在大扬压力范围,缝隙动水压力减小,但减幅随扬压力增大而增大,也随底板缝宽增加、或止水破坏程度增加而减小。分析了水工规范中底板块安全系数的不妥之处,建议用缝隙动水压力代替扬压力准确计算底板块安全系数。工程中应尽可能做好排水措施,确保水垫塘排水设施正常运行。     

热采井不同注汽速率的储层压力场数值模拟

在注蒸汽热采井中,注汽速率是影响油藏压力场分布的重要因素.基于油藏温度场与渗流场耦合理论,通过数值模拟的手段研究了热采井不同注汽速率对油藏压力场的影响.研究表明:注汽速率越大对储层压力的影响范围越大,而当注汽速率达到一定值后,储层压力场的影响范围增幅较小.该研究结果为油田现场选择合理的注汽速率提供了理论依据.     

深部硐室围岩分区破裂化现象数值模拟研究

围绕深部岩体工程的分区破裂化现象,通过数值模拟方法研究了深部硐室围岩分区破裂化现象产生的力学机理及其应力的变化规律。针对深部圆形硐室围岩,分别对应力状态PyPx、Py=Px、PyPx进行数值模拟,发现了深部围岩产生的应力集中现象。当应力集中的应力值超过岩石的强度时,就会产生分区破裂化现象。     

Pore pressure fluctuations of overlying aquifer during residual coal mining and water-soil stress coupling analysis

Three test models and a simulation model were constructed based on the prevailing conditions of the Taiping coalmine in order to analyze pore pressure fluctuations of an overlying aquifer during residual coal mining. As well, the relation between pore pressure and soil stress was evaluated. The model tests show the vibrations of pore pressure and soil stress as a result of mining activities. The simulation model tells of the response characteristics of pore pressure after mining and its distribution in the sand aquifer. The comparative analysis reveals that pore pressure and soil stress vibration are activated by unexpected events occurring in mines, such as collapsing roofs. An increased pore pressure zone always lies above the wall in front or behind the working face of a mine. Both pore pressure and vertical stress result in increasing and decreasing processes during movements of the working face of a mine. The vibration of pore pressure always precedes soil stress in the same area and ends with a sharp decline. Changes in pore pressure of sand aquifer are limited to the area of stress changes. Obvious changes are largely located in a very small frame over the mining face.     

Stress field evolution law of mining environment reconstructing structure with change of filling height

For improving global stability of mining environment reconstructing structure, the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code. Three kinds of filling schemes were designed and calculated, in which the filling heights were 2, 4, and 7 m, separately. The results show that there are some rules in the stress field with the increase of the filling height as follows: (1) the maximum value of tension stress of the roof decreases gradually, and stress conditions are improved gradually; (2) the tension stress status in the vertical pillar is transformed into the compressive stress status, and the carrying capacity is improved gradually; however, when the filling height is beyond 2.8 m, the carrying capacity of the vertical pillar grows very slowly, so, there is little significance to continue to fill the low-grade backfill; (3) the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill, and the maximum value of tension stress of the bottom pillar firstly increases and then decreases. Considering the economic factor, security and other factors, the low-grade backfill has the most reasonable height (2.8 m) in the scope of all filling height.     

登封地区煤炭开采历史沿革

登封地区不仅是旅游胜地,还有丰富的煤炭资源.登封的煤炭开发和利用,始于公元前的春秋战国时期,具有悠久的发展历史.研究这里的煤炭开采史,对于丰富河南地区煤炭开采历史的研究成果具有一定意义.     

Numerical simulation of dewatering thick unconsolidated aquifers for safety of underground coal mining

With an increase of mining the upper limits under unconsolidated aquifers, dewatering of the bottom aquifer of the Quaternary system has become a major method to avoid water and sand inrushes. In the 8th District of the Taiping Coal Mine in south-western Shandong province, the bottom aquifer of the Quaternary system is moderate to excellent in water-yielding capacity. The base rock above the coal seam is very thin in the concealed coal field of the Carboniferous and Permian systems. Therefore, a comprehensive dewatering plan from both the ground surface and the panel was proposed to lower the groundwater level in order to ensure mining safety. According to the hydrogeologic conditions of the 8th District, we established a numerical model so that we could simulate the groundwater flow in the dewatering process. We obtained the simulation parameters from previous data using backward modeling, such as the average coefficient of permeability of 12 m/d and the elastic storage coefficient of 0.002. From the same model, we predicted the movement of groundwater and water level variables and obtained the visible effect of the dewatering project. Despite the overburden failure during mining, no water and/or sand inrush occurred because the groundwater level in the bottom aquifer was lowered to a safe water level.     

群体烟囱风压分布规律的数值模拟

针对火力发电厂烟囱群之间的风干扰效应,应用数值风洞方法完成了任意风向角下烟囱静态风压分布的测定,并求解了风压分布系数。结果表明,相对于单个烟囱,由于烟囱群的风干涉效应导致烟囱群中风压分布异常复杂,具体表现为受扰烟囱风压极值的改变及正负风压分布区的偏移变化,为进一步研究烟囱群风荷载相互干扰对体型系数的影响及改变打下了基础.     

煤层开采过程中上覆岩层裂隙演化规律研究

以淮南煤矿典型工作面为例,采用离散元数值软件UDEC(universal distinct element code)对工作面回采过程中上下煤岩体内应力场的变化及直接顶冒落过程进行了模拟,分析了上覆煤岩体裂隙产生、发展的形成过程,得到了上覆煤岩裂隙演化规律。研究结果表明,倾向方向工作面回采后,上覆煤岩体内产生冒落、裂隙带和离层带,在工作面内上角位置产生O型圈裂隙带,裂隙发育最大高度为45m。煤层走向回采方向得到了初期来压步距约50m,周期来压步距约20m,上覆煤岩体裂隙在采空区上方约呈45°角发展,并随工作面的前进由下向上、由后往前依次演变。该结果对于煤与瓦斯共采中瓦斯抽放钻孔方位的布置具有工程指导意义。     

Predicting the height of water-flow fractured zone during coal mining under the Xiaolangdi Reservoir

It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40% of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model,which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.     

Underground pressure characteristics analysis in back-gully mining of shallow coal seam under a bedrock gully slope

We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope, by means of physical simulation, numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface. The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully, whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully. The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable, multilateral block hinged structure, due to slipping. The subsidence of multilateral blocks is considerable when the block fragmentation is small, resulting in enormous changes in the underground pressure. With an increase in the mass of the block body, the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf, resulting in a decrease of the underground pressure.