【作者】 吴晓东；

【导师】 纪洪广；

【作者基本信息】 北京科技大学 ， 安全科学与工程， 2022， 博士

【摘要】 超大断面分岔隧道是公路隧道地下结构宽大化的建设趋势,作为联结大断面隧道和小净距隧道的重要区段,其多变的隧道结构和繁杂的开挖工序给钻爆法安全施工带来了挑战。为防止超大断面、小净距隧道爆破开挖引起的安全事故,系统研究分岔隧道开挖方法和控制爆破技术,具有重要的理论意义和应用价值。本文以2018年我国三大标志性隧道工程之一的深圳莲塘隧道分岔部428.5m2超大断面和0.5m超小净距区段为背景,围绕形成超大断面的安全开挖方法、小净距隧道后行洞开挖时空分区、分岔区段不同类型断面精准控制爆破技术三大目标,采用数值模拟、现场监测、理论分析、现场试验等方法,对超大断面分岔隧道安全控制爆破技术展开较为系统的研究。在分岔隧道超大断面区段形成方法研究中,针对超大断面隧道区段跨度、高度较大带来的爆破安全问题,提出了一种小断面提前爬坡形成超大断面的变截面开挖方法,包括从小断面隧道提前爬坡、横向扩挖、反向掘支等阶段,采用MIDAS GTS程序分析不同开挖方案的围岩受力与变形特性,现场位移和支护结构压力监测验证了推荐方法的正确性。解决了超大断面形成过程的爆破技术问题。在现场大断面隧道爆破中采用电子雷管起爆技术,研究并形成了电子雷管爆破参数设计方法。该方法基于Anderson理论延时爆破振动合成理论,采用现场单孔爆破实验实测波形作为计算振源,设计不同药量和延时时差编入程序,计算得到多种孔间延时振动合成曲线,选取安全振速下最大药量的孔间延时作为优化参数。将此方法应用于莲塘隧道大断面爆破,爆前计算预测的微差爆破振动峰值与实测值高度吻合,相比常规爆破振动峰值下降69.1%,确保了超大断面施工安全。针对小净距隧道区段后行洞爆破导致中夹岩片帮、垮塌等安全问题,构建了小净距隧道爆破开挖时空分区方法和分区微振爆破组合技术。基于等代圆法和Schwarz交替法分析了围岩受力特性,计算得到莲塘隧道缓震层最优厚度为3m,形成了后行洞预留缓震层的四部开挖断面分区,制定了小净距后行洞不同分区的开挖爆破振动控制指标,建立了不同分区安全爆破开挖技术。在后行洞时空分区基础上,针对不同分区的爆破技术进行了针对性研究,具体为:(1)破解了后行洞首爆开挖区(Ⅰ区)开挖兼顾控制振动和成本的安全爆破技术难题。首爆区爆破开挖采用了电子雷管与导爆管雷管孔内外延时混合起爆技术,为消除混合起爆网路串段、拒爆和断路的安全隐患,构建了孔内外延时混合起爆网路时间序列计算模型,推导出基于安全起爆的关键参数计算公式。工程实践表明,混合起爆网路相比电子雷管网路可节约60.3%的电子雷管数量,振动控制效果显著,减少了后行洞首爆区爆破开挖对中夹岩柱的损伤。(2)对于与中夹岩柱直接相连的后行洞Ⅱ区(缓震层)高要求减振降损的安全爆破技术问题,基于LS-DYNA程序分析了缓震层爆破荷载作用于中夹岩柱的损伤机理;根据中夹岩柱厚度渐变特点,提出了微震控制爆破组合技术。莲塘隧道试验数据显示,先行洞迎爆侧振动峰值较常规爆破降低了73.8%,爆后0.5m中夹岩柱完整性良好,验证了该方法的安全性。本文提出的研究方法与技术,提供了超大断面分岔隧道安全开挖方法和爆破技术应用的一种方案,在实践中解决了莲塘隧道工程的安全隐患和技术难题,保障了大断面区段围岩稳定性和小净距区段中夹岩柱的完整性,为400m2以上超大断面分岔隧道实现高效、安全爆破开挖提供了理论支撑与实践指导。更多还原

【Abstract】 Bifurcation tunnel with super-large cross-section is the construction trend of widening underground structure of highway tunnel.As an important section connecting large cross-section tunnel and small clearance tunnel,the variable tunnel structure and complicated excavation process of super large cross-section branching-out tunnels bring challenges to the safe construction of drill and blast method.To prevent safety accidents caused by blasting excavation,it has great theoretical significance and application value to systematically study excavation methods and controlled blasting techniques of the branching-out tunnel.This paper takes the 428.5 m2 oversized section and 0.5 m ultra-small clearance section of the branching-out tunnel of the Shenzhen Liantang Tunnel,one of the three landmark tunnel projects in China in 2018,as the background,it focuses on the three major objectives of forming a safe excavation method for the oversized section,spatial and temporal partitioning of the excavation of the small clearances tunnel back tunnel,and precise control blasting technology for different types of sections in the branching-out tunnel.In this paper,numerical simulation,field monitoring,theoretical analysis,field experiment and other methods are used to study the safety controlled-blasting techniques of the bifurcation tunnel with superlarge cross-section.For the formation method of the super-large cross-section in the bifurcation tunnel,the safe excavation method of advance climbing,lateral expansion and reverse boring support from small section tunnel is proposed for the blasting safety problems brought by the large span and height of oversized section tunnel.MIDAS GTS program is used to analyze the stress and deformation characteristics of surrounding rock of different excavation schemes,and the correctness of the recommended method is verified by field displacement and pressure monitoring of supporting structure.The technical problems of blasting implementation of super-large crosssection excavation method are solved.The electronic detonator initiation technology is used in large section tunnel blasting,and the design method of electronic detonator blasting parameters is studied and formed.This method is based on Anderson’s theory of delayed blasting vibration synthesis.The measured waveform of single-hole blasting experiment is marked as the calculation vibration source.Different charge number and delay interval are designed and programmed into the program,and various delay vibration synthesis curves between holes are calculated.The delay time between holes of the maximum charge amount at safe vibration speed is selected as the optimization parameter.The method is applied to blasting of the large-section in Liantang tunnel.The peak particle vibration(PPV)calculated and predicted before blasting is highly consistent with the measured value,and the PPV of blasting is reduced by 69.1%compared with that of conventional blasting,which ensures the safety of super-large-section construction.To solve the safety problem caused by the blast-induced vibration in the following section in the small clearance tunnel,which include rock slump and collapse,the four-part excavation method of reserved seismic mitigation layer was proposed in the following tunnel.The equivalent circle method and Schwarz alternating method are used to study the influence of different cushioning layer thickness on the stress of surrounding rock,and the optimal thickness of cushioning layer of Liantang tunnel is calculated to be 3m.According to this,different zoning geometric sizes are divided,and the excavation scheme of space-time zoning for the back tunnel with small clear distance is established.On the basis of the abovementioned space-time partition excavation scheme of the following tunnel,the blasting technology of different partitions is studied pertinently,specifically as follows:(1).The technical problem of safe blasting,which takes into account vibration control and cost control,is solved in the first excavation area(Area I)of the following tunnel.To eliminate the potential safety hazards of serial section,misfire and open circuit of the mixed initiation network,the time parameter calculation model of the mixed initiation network during the extension in the hole is constructed.The formula of key time parameters is derived based on safe initiation constraints.The field experiments showed that the mixed initiation network can save 60.3%of the number of electronic detonators compared with the electronic detonator initiation network,and reduce the PPV by 81.5%compared with the conventional blasting,which reduced the damage of the middle interval rock by the blasting for Area Ⅰ of the following tunnel.(2).For the controlled-blasting of cushioning layer in the key blasting area(Area Ⅱ)closely connected with the middle interval rock,the damage mechanism of blasting load on the middle interval rock in cushioning layer was analyzed by the LS-DYNA program.Base on the gradual change of the thickness of the middle interval rock,the combined technology with multi-parameter controlled-blasting was put forward.The field monitoring results of blast-induced vibration showed that the PPV of the advance tunnel nearby the middle interval rock was reduced by 73.8%compared with the conventional blasting,and the middle interval rock with 0.5 m thickness is intact after blasting,which verifies the safety of the combined technology with multi-parameter controlled-blasting.The research method and blasting technique proposed in the paper provides a scheme for the safe excavation of the branching-out tunnel with super-large crosssection.The potential safety hazards and technical problems of Liantang tunnel project have been solved in field practice.Meanwhile,the stability of surrounding rock in super-large cross-section and the middle interval rock in small clear distance section have been guaranteed.It provided to the theoretical support and practical guidance for efficient and safe blasting excavation of branching-out tunnels with super-large cross-section above 400 m2.更多还原