不同方向爆炸荷载作用下地下洞室抗爆效果研究

基于抗爆模型试验结果,利用数值分析方法,研究不同方向爆炸荷载作用下地下洞室的抗爆效果。通过对比分析地下洞室爆炸压应力时程曲线和动态裂纹分布形态,发现数值分析和试验的应力波曲线和锚固洞室围岩动态裂纹分布比较相似,这说明数值分析的结果比较合理。锚固洞室在相同当量爆炸荷载作用下,顶爆产生的位移最小,其次拱部侧爆,最大是直墙侧爆,并且直墙侧爆产生最大位移的位置是侧墙墙底,而不是离爆源最近的洞壁位置。在爆炸荷载作用,由于锚杆加固作用,在锚杆间发生受拉"劈裂",同时还在锚固区内以及锚固区末端发生"层裂"现象。在相同当量顶爆、拱部侧爆和直墙侧爆作用下,毛洞和锚固洞室的位移和动态裂纹分布形态相似,经过锚杆加固的洞室抗爆能力都得到提高。     

在爆炸荷载条件下锚固洞室破坏形态 对比试验研究

通过物理模型试验,研究洞室在平面装药和集中装药爆炸荷载作用下不同加固方案的对比抗爆效果.简要介绍新研制的岩土工程抗爆结构模型试验装置、模型试验相似条件、平面装药和集中装药爆炸模拟方法,着重给出在爆炸荷载条件下几类锚固洞室模型的破坏形态试验结果.模型试验结果表明,对相同试验条件下的洞室,在平面装药爆炸试验中洞室拱部材料均发生脱落,在集中装药爆炸试验中洞室拱脚均产生剪切错动裂缝;全长黏结式锚索加固的洞室比自由式锚索加固的洞室抗爆效果好;只增加锚杆长度对阻止围岩裂缝的发展不起控制作用,必须在锚杆间距达到一定密度时才可以阻止围岩裂缝进入锚固区;在拱脚局部加长的密锚杆支护可以有效地阻止或者阻断围岩裂缝的发展,或者迫使裂缝绕过锚固区,从而提高锚固洞室的抗爆能力.研究结果对改进地下抗爆结构加固措施,提高其抗爆能力具有重要参考价值.     

锚固洞室在顶爆作用下破坏形式及破坏过程研究

利用抗爆模型试验和数值分析方法,研究锚固洞室在顶爆作用下的破坏形式及破坏过程。根据锚固洞室破坏模型试验,发现锚固洞室主要有:受拉破坏、剪切破坏、受压破坏和压剪破坏4种破坏形态。通过分析试验解剖图和应力波传播规律发现:爆炸应力波作用下,锚固洞室首先在拱顶锚固区发生"层裂"现象,在自由面附近有类似半椭圆拱岩石介质脱落;同时两侧容易形成"八"字型剪切裂纹,随着爆炸荷载强度增加,如果锚杆加固较弱会在洞顶产生局部坍塌,一旦锚杆加固较强就会发生从爆心至洞室整体坍塌。最后利用数值分析方法分析了洞室受力情况和塑性区发展过程,进一步探讨了锚固洞室在顶爆作用下破坏形式和破坏过程。     

端部加密锚固洞室在重复顶爆作用下的应力波传播及衰减规律

利用实验室抗爆模型试验装置,研究了端部加密和普通长密锚杆锚固洞室在重复顶爆作用下的应力波传播及衰减规律。端部加密锚固洞室和普通长密锚固洞室每一炮的拱顶压力峰值随着比例距离的增加呈幂函数逐渐衰减,并拟合出相应的幂函数曲线,前两炮拟合的应力波衰减指数均小于未受扰动岩石的衰减指数。两个洞室在爆炸应力波作用下,锚固区附近的岩石先被密实,然后不断损伤破坏。在相同的爆炸条件作用下,随着比例距离增加,两个洞室在相同比例距离时的压力差值逐渐减小;相同比例距离端部加密锚固洞室峰值压力比普通长密锚杆加固洞室峰值压力先大后小;端部加密锚杆加固洞室与普通长密锚杆加固洞室离加固范围最近测点的压应力峰值衰减规律比较相近,并且压应力峰值大小也比较相近。     

一种新型复合锚固结构抗爆性能的试验研究

对一种新型复合锚固结构的抗爆性能进行了试验研究。这种新型复合锚固结构是“注浆锚杆-构造措施”型,用于地下空间的加固支护。“构造措施”是指在锚杆里端规律设置一段表面经过处理的空孔。试验研究表明:①复合锚固结构洞室的临界破坏荷载显著高于单一锚固结构洞室,其安全性和稳定性更高,其构造措施段具有一定的抗爆吸能作用;②复合锚固结构用于岩石洞室的抗爆加固是完全可行的;③就本次试验条件而言,在累次爆炸加载作用下,单一锚固结构洞室的破坏程度是复合锚固结构洞室的2.5倍;④加固区具有足够的深度、强度、刚度和稳定性是复合锚固结构优化设计实现的前提。     

外交叉锚固洞室抗爆性能数值模拟

目前,国内外针对洞室锚固结构抗爆性能的研究主要集中于爆炸波在岩土介质中的传播特性、对围岩的破坏作用、锚喷支护内加固效果分析等方面,很少涉及对外加固效果的研究。笔者为研究薄被覆层条件下外锚固结构对地下洞室抗爆性能的效果,在模型试验的基础上,利用FLAC3D建立无锚固和外交叉锚固两种三维整体式有限元模型,模拟洞室在爆炸荷载作用下的响应。结果表明:洞室加固前后侧墙破坏区域基本相同,但加固后其拱顶的位移、破坏长度和破坏面积明显减小;加固后洞室周围应力集中区域缩小,主应力明显降低,各部分动应变趋向均匀;加固后洞室压应力与反射拉应力出现的时刻延后,应力波传播速度减缓。研究结果和该有限元预测方法可为地下洞室抗爆设计提供参考。     

喷锚支护洞室抗爆现场试验锚杆应变研究

如何提高地下洞室的抗爆能力对国防和民用地下结构设施有着重要的工程意义,而锚杆锚固支护是常见的洞室加固方法。结合现场爆炸试验,介绍了三种锚杆锚固洞室,分析在不同形式锚杆锚固体系的作用下,位于洞室各个位置的锚杆内部应变情况,对比分析了第五炮次作用下锚杆的应变时程曲线,以及到达最大应变的时刻和最大应变所在锚杆位置,其中,短密锚杆锚固作用下锚杆应变数值较小,长密锚杆次之,常规锚杆应变较大;另外,本次试验还对比分析了两种锚杆垫板锚固效果,从抗爆效果上看,碗形垫板具有更好的锚固效果。本文总结出较好的锚杆锚固形式,为工程实践提供一定的借鉴。     

爆炸波作用下锚杆间距对围岩加固效果影响的模型试验研究

为比较锚杆间距对洞室围岩加固效果以及抗爆性能的影响程度大小,通过实验室地质力学模型试验,研究在集中装药爆炸应力波作用下,2种长度相同而间距不同的锚杆对洞室围岩的不同加固效果.比较和分析因锚杆间距不同所造成的洞室围岩中测点的应力、洞壁表面应变、洞室顶底板相对位移、顶底板及侧墙加速度和洞室围岩宏观破坏形态的差别.试验结果表明,与较大间距锚杆加固的洞室相比较,较小间距锚杆加固的洞室围岩中应力较大,洞壁表面应变、顶底板相对位移、顶底板加速度较小,加固区域内围岩无破坏裂纹,说明对洞室围岩的加固宜采用较小间距锚杆.将部分试验数据同相应的数值分析结果进行比较发现,两者的拱顶应力峰值和顶底板相对位移峰值较为一致,证明模型试验结果是可靠的,对防护工程设计及坑道围岩加固具有一定参考价值.     

外部连接全长黏结式锚杆和弹力式锚杆 抗爆加固效果模型试验研究

 利用实验室抗爆模型试验装置,研究在平面装药爆炸应力波的作用下,外部连接全长黏结式锚杆和弹力式锚杆对洞室围岩的不同加固效果。通过分析自由场爆压时程曲线,发现该试验仪器测试效果较好,并分析和比较2种锚杆加固所造成的洞室围岩拱顶位移、洞壁应变和拱顶、底板及侧墙加速度的差别。试验结果表明：经过外部连接全长黏结式锚杆加固的洞室比弹力式锚杆加固的洞室拱顶位移峰值减少明显;在平面波的作用下,3个洞室洞壁各个位置都是产生压应变,最大应变出现在拱脚处;拱顶加速度是振动最激烈的地方,底板加速度在变形不大时加固洞室增加较大,必要时应该采取减震措施;对比2个加固洞室的最大应变峰值和加速度,发现外部连接全长黏结式锚杆相对较小,说明对洞室围岩的加固宜采用外部连接全长黏结式锚杆。     

地下洞室锚固抗爆技术研究之现状

锚固抗爆技术是提高地下洞室抗爆性能的重要技术手段。综述了国内外地下洞室锚固抗爆技术的研究现状,包括全长粘结锚杆抗爆技术、预应力锚索抗爆技术、锚索+锚杆复合抗爆技术、屈服锚杆抗爆技术及端部消波锚杆抗爆技术;在此基础上,分析了锚固抗爆技术研究中存在的问题,指出了今后应重点开展的研究工作。     

端部消波和加密锚杆支护洞室抗爆能力模型试验研究

 利用抗爆模型试验装置,研究在集中装药爆炸应力波的作用下,端部消波和加密锚杆支护洞室的抗爆能力;分析和比较3个洞室的拱顶垂直压应力、顶底板相对位移、洞壁应变、顶底板加速度及洞室围岩宏观破坏分布形态的差别。试验结果表明：在爆炸应力波的作用下,当洞室没有发生严重破坏时,端部消波和加密锚杆支护洞室顶底板相对位移和拱脚处最大应变都有减小;拱顶加速度整体上都有不同程度的降低;3个洞室都在拱脚处两侧产生断裂缝,但端部消波和加密锚杆支护洞室在拱顶方向断裂缝明显减少,其拱顶破坏程度得到减轻。说明端部消波和加密锚杆支护洞室能够提高锚固洞室抗爆能力。     

Principles of rockbolting design

This article introduces the principles of underground rockbolting design.The items discussed include underground loading conditions,natural pressure zone around an underground opening,design methodologies,selection of rockbolt types,determination of bolt length and spacing,factor of safety,and compatibility between support elements.Different types of rockbolting used in engineering practise are also presented.The traditional principle of selecting strong rockbolts is valid only in conditions of low in situ stresses in the rock mass.Energy-absorbing rockbolts are preferred in the case of high in situ stresses.A natural pressure arch is formed in the rock at a certain distance behind the tunnel wall.Rockbolts should be long enough to reach the natural pressure arch when the failure zone is small.The bolt length should be at least 1 m beyond the failure zone.In the case of a vast failure zone,tightly spaced short rockbolts are installed to establish an artificial pressure arch within the failure zone and long cables are anchored on the natural pressure arch.In this case,the rockbolts are usually less than 3 m long in mine drifts,but can be up to 7 m in large-scale rock caverns.Bolt spacing is more important than bolt length in the case of establishing an artificial pressure arch.In addition to the factor of safety,the maximum allowable displacement in the tunnel and the ultimate displacement capacity of rockbolts must be also taken into account in the design.Finally,rockbolts should be compatible with other support elements in the same support system in terms of displacement and energy absorption capacities.     

拱顶端部加密锚杆支护洞室抗爆加固效果模型试验研究

采用抗爆模型试验方法,研究了在集中装药爆炸应力波的作用下,拱顶端部加密锚杆支护洞室抗爆效果。通过分析压力时程曲线,证明测试数据规律性合理,数据可靠。分析和比较了拱顶端部加密锚杆支护洞室与不加密锚杆支护洞室所造成的洞室围岩拱顶位移、洞壁应变、顶底板加速度和洞室宏观破坏形态,得出拱顶端部加密锚杆支护洞室抗爆加固效果不佳。     

Shear resistance contribution of support systems in double shear test

Rockbolt and surface support systems such as shotcrete and thin spray-on liners (TSLs) are widely used as underground support elements to resist the convergence and maintain the stability of excavations. In order to evaluate the bearing capacity of combined reinforced rockbolt and surface support systems in preventing sliding along discontinuities, double shear tests (DST) was carried out using fully grouted rockbolts installed in three separate blocks. These blocks were covered with a 5 mm layer of TSL followed by a 50 mm layer of shotcrete. Two rockbolts were installed at an inclined angle of 45°, and 20 kN lateral constraining force was applied to clamp together the three blocks. Three different support combinations were tested: 50 mm shotcrete only, 5 mm TSL only, and combined shotcrete and TSL, with and without rockbolts. It was confirmed that the shotcrete plays a mechanical role in resisting the shear load, and TSLs increase the bond strength between shotcrete and substrate replicating the side wall of an excavation. The contribution of rockbolt and surface support system in resisting joint movement was also compared. The failure mechanism of rock substrate, rockbolt and surface support system was also analysed.     

A theoretical approach for analysis of the interaction between grouted rockbolts and rock masses

Rock-support interaction concepts, which are applied to support systems such as concrete linings and ungrouted rockbolts, cannot be applied to grouted rockbolts, because of the nature of the structural interaction of the rock mass and grouted rockbolts. In this paper, with consideration of a non-linear strength criterion for rock mass and on the basis of two material behavior models and rock-support interaction concepts, corresponding relationships are derived. In this method, the equation of the ground response curve which has been reinforced with grouted rockbolts is also derived for a circular underground excavation under hydrostatic stress field. Because of algebraic complexity, it is not possible to obtain closed-form solutions; therefore a computer program was prepared for solving the problem on the basis of numerical methods.     

Analytical approach for the design of active grouted rockbolts in tunnel stability based on convergence-confinement method

Assuming that grouted rockbolts increase internal pressure within a broken rock mass, a new procedure for computation of ground response curves for a tunnel reinforced with active grouted rockbolts is presented, while the effect of distance of bolted section to tunnel face has been also considered. This analytical solution for a circular underground excavation under hydrostatic stress field, and with consideration of a non-linear strength criterion for rock mass and on the basis of two material behavior models has been developed. In this work, the equation of the ground response curve for a tunnel which has been reinforced with passive grouted rockbolts is also derived. The proposed model allows one to take, the effect of the distance of the bolted section to the tunnel face, the effect of increasing rockbolts spacing, the influence of increasing pretension load in calculating of the ground response curve, and the effect of increasing the cross-section area of rockbolts, into account. The results show that decreasing rockbolts spacing increase the support system stiffness rather than preloading of them.     

拱脚局部加长锚杆锚固洞室抗爆模型试验研究

 根据Froude相似理论,开展拱脚局部加长锚杆和等长锚杆加固洞室抗爆对比模型试验,分析各洞室受力变形特性和围岩破坏形态。研究结果表明：与等长锚杆相比,在爆心离洞室很近的极端情况下,拱脚局部加长锚杆起到“密闭”爆炸荷载的作用,增大洞室拱部的爆炸荷载,带来洞室拱顶底板相对位移的快速增长;在爆心离洞室较远的一般情况下,拱脚局部加长锚杆具有承担或转移较多爆炸荷载的作用,不仅能明显减小洞室附近的爆炸压力、洞室拱顶底板相对位移、拱脚压应变峰值和残余值,而且还能明显减少和减轻围岩裂缝数量和开裂程度,有效阻断裂缝的发展和延伸,有利于提高洞室的抗爆能力。