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1中文译文关于二柱掩护式支架与顶板之间相互作用的研究二柱掩护式支架如图 1 所示。为了评定支架的适应性，通常有两个特性要考虑：顶板控制影响显然，掩护式支架更容易阻止冒落矸石掉在工作面上，但是它更难阻止冒落矸石掉在遮蓬区。根据来自阳泉和翟梨的资料显示,下落时间导致停止生产，归因于下落顶板在遮蓬区大约是 4060的下落时间在工作区。顶板沿着朝向倒塌。就是说，在一个装有二柱掩护式支架的面上更多关注的是顶板及时控制问题，特别是面向遮蓬区。在顶板压力作用下对支护结构的作用近期来自煤矿的报道证明，二柱掩护式支架已经在顶板压力作用下破坏，特别是遮蓬和稳定柱面连接处。明显的是这种支架的支护空间被认为对一些顶板条件不够，并且必须改进。二柱掩护式支架加载条件分析作用在二柱掩护式遮蓬上的压力：顶板压力，来自立柱的力，撞击，遮蓬和洞穴保护的销轴，顶梁和顶板的破碎表面。假设表面破碎和作用在掩护梁上的力不考虑，可以得到下面的公式： 2(cosin)bhxpbZPLzgg上式中符号的意思表达在图 4a 中。假设 cos(in)/AhbiBLzg然后我们可以得到下面的公式。 ()AxpZzB可以看出，当 P 增大到屈服载荷 P+，力因此在撞击中形成象在图 4b 中曲线 Z 所描述的。事实上撞击的推拉力有一个屈服载荷。例如，对于掩护式支架 W.S.1.7，屈服力是推力 67.7t 和拉力 62.4t。因此，撞击力的曲线如图 4b 所示。那么总的载荷 Ps整个的支架给出如下： 1(cos/in)(sicos)/sPhbZhLzbWgg假设 W=0,那么 sPAB2因此，根据顶板作用在顶梁上的压力的位置和支架支护的表现，我们可以遮蓬划分为 3 个工作区，即，IIBC 区，立柱的载荷 P 等于 P+，BC 区，立柱载荷 P 等于P+和-CD 区，和撞击的载荷力等于Z（撞击的屈服力是拉力） 。支撑立柱承受力的特性和每个遮蓬区上的冲击显示如下：区 ZZ；()zBxPZApg区 PP + ()xzBg()sApPx区 ZZ -()BzZAxpg()sP显然，作用在和区遮蓬上的反作用力是由冲击的屈服载荷产生的。例如，如果 Z 等于 0，在和区支护本身的反作用力将失去和反作用力丢失和只有当来自相应区域的一些附加力存在时反作用力将产生。在或区，存在由顶板产生的平衡力。如果冲击的屈服载荷产生了，显然，区的距离将变的更宽，并且或区上的反作用力将由此增加。这些如图 5 所示。顶板压力和支护反作用力的相互作用众所周知，作用在支护顶梁上的顶板压力可以分成两个部分，它们是：由及时顶梁产生的 Q1，由主顶梁产生的 Q2，显示在图 6 中。作为通用法则，作为一个不连续的媒体被考虑和存在一个沿着洞穴的自由面。载荷 Q1固定作用在支护上，载荷分布在遮蓬区可以认为是均布的。来自主顶梁的载荷 Q2被作为一个集中载荷考虑，作用在及时顶梁和支护保护。基于顶板测量显示，发现主顶梁过度层可以作为由大量的岩石连续互锁形成的一种结构。当煤高度提高，每一石块滑向另一石块。主顶梁在图 7 中显示。显然，来自主顶梁的载荷作用位置首先依靠石块在主顶梁上的稳定条件。Q 2可以作用在掩护区的前部和尾部。其次，依靠及时顶梁下落的位置。Q 2。如果条件反向，3那么力作用在前部遮蓬的位置。结果，顶梁压力 Q 作用在遮蓬上因此可以从 Q1和 Q2连接起来。当顶梁压力 Q 作用在 I 区和 QPs，将首先减轻冲击的影响。那么遮蓬前部将向下转和平衡力 Q3将在遮蓬尾部产生。显然，在这种情况下，在遮蓬尾部以上的顶板保持完整或者不能剪断。联合作用（Q+Q 3）的作用点移向区直到联合作用（Q+Q 3）等于支护的反作用力 Ps。在相反条件下，平衡作用 Q3将在区产生。从这我们能看出这类支架的反作用力因此能形成在当平衡力 Q3产生和作用在遮蓬的条件下。就是说，及时顶梁不能完全剪断。根据以上提到的分析，现在考虑在下列不同的条件下：顶梁未知和支护阻力 Ps的反作用力等于 P+（立柱的屈服载荷） 。那么支护的反作用力可以按下式表达：QQ 3P s假设 PsP +，那么 ()1AzBpxg那么 X 在连接作用的位置（QQ 3）的作用将变为xP（1A）z/B假设顶板作用力 Q 作用在 x1的位置，平衡作用力 x3（原因是在于连接点） ，然后可以得到下式：Qx1Q 3x3（QQ 3）（p（1A）z/B）和 Q3等于： 13 3()/xzBxgQ顶板压力 Q 的支护反作用力等于： 31()/)pAzPxQ采用 来代表支护作用，这有下面因素的联系：几何参数的支持，也就是参数+/Pp，A，B，和 z；顶板压力的作用位置 x1；及时支护的平衡力作用位置 x3。很明显，越近，x 1的值靠近区，支护效率就越高。有时，x 3的值作为遮蓬和及时顶梁之间相互关系的顺序。当 Q 作用位置 平衡力 Q3等于 0，支护效率 ，等于 1。(-)/pAzB +Q/P图 8 显示，当变量顶板压力 Q 作用在 3 个不同的位置，遮蓬区的位置 x1和区不同顺序 x3，为了反抗顶梁压力（Q） ，相应的平衡力 Q3，和在区必须给出的不同的值。例如，当顶板压力作用在遮蓬尖端和等于 80t 如果 x337cm,那么没有遮蓬作用力4在遮蓬尾部形成。因为顶板下落发生在面向遮蓬区变得不规则，因此为了遮蓬转动遮蓬有 3 种操作条件：向下（10 ）和从 0 到 10 不同的角度。根据翟梨煤矿收集的统计数据，遮蓬旋转的操作条件，15 ，对应 11。由于，顶板对顶板的作用位置是不同的，顶梁和掩护梁的角度是变化的。通过表1，我们可以看到方向变化的百分数占 44.8，意味着顶板压力 Q 首先作用在区和平衡力 Q3形成在区；最后，合力（QQ 3）作用位置将转向区。在表 1 中负变量百分数占 19.4。相似的结果也可以从翟梨煤矿的 No.322 工作面区域测量得出，在表 2 和图 9 中的显示。显然，顶板压力作用在区或遮蓬的区，如果合力作用（QQ 3）位置移动到区。支架的操作条件是正常的。但是如果合力作用位置移到区，和继续向前或向后移动，支架将工作在非正常条件下。英文原文A STUDY OF THE INTERACTIONBETWEEN THE 2-LEG SHIELD SUPPORTAND THE ROOF STRATAINTRODUCTIONThe 2-leg shield powered support is shown in Fig.1.It is known that in order to asses the adaptability of a powered support normally there are two principles to be considered:Fig.1 2-leg shield support 5EFFECTIVENESS OF ROOF CONTROL Obviously, shield support is much easier to prevent the broken rocks from falling into the working space, but it is much harder to prevent the broken rocks from falling into the face-to-canopy area. On the basis of the statistical data obtained from the Collieries Yang-Quan and Zhai-Li, the down-time leads to stop production due to falling roof in the face-to-canopy area is about 40-60% of the total down-time in the working face. Collapse of roof strata along the faceline is shown in Fig.2. That is to say, in a face installed with 2-leg shield powered support much more attention must be paid to the problem of immediate roof control, especially in the face-to-canopy area.EFFECT ON SUPPORT STRUCTURE UNDER THE ACTION OF ROOF PRESSURE Recent reports from some collieries reveal that 2-leg shield support has been broken under the action of roof pressure, especially at the joint of the canopy and the stabilizing cylinder as shown in Fig.3. It is evident that the supporting capacity of this type of support could not be considered as adequate to some such kind of roof conditions and must be improved.Fig.2 Collapse of a longwall face at the faceline6Fig.3 Damage at the joint of the stabilizing cylinder and the canopy ANALYSIS OF LOADING CONDITION OF 2-LEG SHIELD SUPPOIRT The forces acting on the canopy of 2-leg shield support are: the roof pressure, the forces from the support legs, ram, hinge pin of the canopy and the caving shield, the surface friction between the canopy and the roof strata.Assuming that the surface friction and the force acting on the caving shield are not taken into account, the following formula can be obtained:2(cosin)bhxpbZPLzggThe meanings of all the symbols used in this formula are illustrated in Fig.4a.Assuming that cos(in)/Ahbgi/BLzthen we can obtain the following formula.()AxpZzgIt can be seen that When P is increased to the yield load P+, the force thus in the ram would be distributed as shown in curve Z in the Fig.4b. In fact the ram has a yield load in push and pull. For example, for the shield support W.S.1.7,the yield load in push is equal to 67.7t and in pull 62.4t. So the curve of the force from the ram would be redistributed in the face as curve Z+, and the curve of force for the support legs would be redistributed as carve P shown in Fig.4b. Then the total load Ps for the whole support can be given as follows:, Assuming that W=0, then:1(cos/in)(icos)/sPhbZhLzbWggsAZBThus, according to the position where the roof pressure acts on the canopy and refer the support performance to the load of the ram Z is equal to +Z, (the yield load of the leg ) and -CD zone, on which the load of ram is equal to Z (the yield load of the ram in pull ).The load bearing characteristics of the support legs and the each zone of the canopy are 7shown as follows:Fig.4 Three working zones of support canopy zone Z=Z+.()zBxPZApg zone P=P+.()xpZPzBg()sAzBpPxg zone Z=-Z-()BxzPZApg()szxObviously, the resistances of zone and zone on the canopy are produced by the 8yield load of the ram. For example, if Z is equal to zero, the resistance of the support itself in zones and would loss and the resistance can be produced only when there exists some additional forces from the corresponding zones. In zone or . There exists a balance force produced by the roof strata. If the yield load of the ram is increased, obviously, the interval of the zone would become much wider, and the resistance on the zones and will be increased accordingly. There are shown in Fig.5.Fig.5 Resistance Curve of different yield load of ramINTERACTION BETWEEN ROOF PRESSURE AND SUPPORT RESISTANCEIt is well- known that the roof pressure acting on the canopy of the support can be divided into two components, they are: Q1 produced by the immediate roof and Q2 by the main roof, as shown in Fig.6.As a general rule, the immediate roof can be considered as a discontinuous media (like a loose body) and there is a free face along the caving line. Load Q1 acts steadily on the supports. Load distribution on the canopy may be considered as uniform. Load Q2 from the main roof may be considered as a concentratedload which acts on the immediate roof and then acts on the canopy of the support. Based on the displacement measurement of roof strata it has been found that the main roof of the overlying strata can be considered as a structure formed by layers of rock blocks interlocking with one another, when the coal face advances, each block becomes to move forming a turning block. The displacement of the main roof is shown in Fig.7.Obviously, the acting position of the load from the main roof firstly depends on the stability condition of the blocks in the main roof. Q2 can act either in front or in the rear of the canopy. Secondly, it depends on the position where the immediate roof falls. If the front 9section of the immediate roof is fractured and falls into the working space, then the force from the main roof would act on the canopy. If the condition is opposite to this, then the force would act on the position in front of the canopy.Consequently, the roof pressure Q acting on the canopy can thus can be combined from those of Q1 and Q2.Fig.6 Roof Pressure Produced by the main roof and the immediate roof Fig.7 Displacement of the main roof When the pressure Q acts on zone and QPs, the relief valve of the ram would firstly open ,then the front part of the canopy would turn downwards and the balance force Q3 would be produced in the rear part of the canopy must be kept intact or must not cave equal to the resistance force (Ps) of the support. In the opposite condition the balance force Q3 would be produced in zone .10From this we can see that the resistance of this type support can thus be formed in the condition when the balance force Q3 occurs on the canopy. That is to say, the immediate roof must not cave at all.According to the analysis mentioned above, now consider that is under the different conditions: The roof is unbroken and the resistance of the support Ps is equal to P+ (the yield load of the legs). Then the resistance of the support can be expressed as follows:QQ 3P sAssume Ps P+, so that ()1AzBpxgThen the acting position where the roof pressure Q acts would become xP（1 A）z/BAssume that the acting position where the roof pressure Q acts is at x1, and the balance force Q3 is x3 (the origin is in the hinge pin point), then the following formula is obtained:Qx1 Q3x3（ QQ 3） （p（1A）z/B）The roof pressure Q which the support can resist is equal to:13 3()/xpzBAxgThe roof pressure Q which the support can resist is equal to:31()/)pzBxPgQTake to stand for the efficiency of the support, obviously, this has relation with the +/Pfollowing factors: the geometrical parameters of the support, i.e. parameters of the balance force (reaction) of the immediate roof x3. It is obvious that the nearer the value x1 approaches to zone , the higher the efficiency of the support would be. Something the value x3 can be represented as an index to stand for the interactive relation between the canopy and the immediate roof. When Q acts in the position , the balance force is equal (1-)/pAzB3Q11to zero, and the efficiency of support , is equal to 1.+Q/PFig.8 shows that when a variable roof pressure (Q) acts in three different positions (x1) in the zone of the canopy and with different index x3 in zone , in order to resist the roof pressure (Q), a corresponding balance reaction force Q3 with different values must be given in zone . For example, when the roof pressure is acting on the tip of the canopy and is equal to 80t if x337cm. then there would be no such balance force formed in the rear part of the canopy.Because roof fall occurs in the face-to-canopy area where the roof would become irregular, thus the canopy would have three kinds of operating condition for the canopy to swing: downwards (10) and at an angle from 0 to 10. According to statistical data collected from Zhai-Li Colliery, the percentage of the operating of the operating conditions of the canopy swinging canopy in 15, for 11%.Due to the fact that the acting position of the roof pressure on the canopy is different, the angle between the canopy and the caving shield may be variable. Table1 shows the variation accounts for 44.8%, which means that the canopy and the caving shield may be variable. Table1 shows the variation of this angle in each operation cycle.From Table1, we can see that the percentage of positive variation accounts for 44.8%, which means that the roof pressure (Q) firstly acts on zone and than the balance force (reaction) (Q3) is formed on zone ;finally, the acting position of the combined force (Q+Q3) would move towards zone . In Table1 the percentage of negative variation accounts for 19.4%.Similar results have also been obtained from field measurements in working face No.332 of Zhai-Li Colliery as shown in Table2 and Fig.9.Obviously, whether the roof pressure acts on zone or of the canopy, if the acting position of the combined force (Q+Q3) moves towards zone ,the operating condition of the support would be normal. But if the acting position of the combined force moves over zone 12 and continuously moves forwards or backwards, the support would then work in abnormal conditions.Fig.8 Balance force Curves for different index X3 in zone
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