我国隧道工程中有害气体引发的工程灾害频发，主要涉及中毒窒息、燃烧爆炸及化学腐蚀等问题。针对煤层瓦斯目前已建立相对完整的勘察评价体系，而非煤瓦斯尚缺少较为准确合理的风险等级评价方法，严重制约非煤瓦斯隧道工程建设高质量发展。通过现场检测、原位试验、理论分析和实测计算等方法，研究非煤瓦斯气体在勘察和施工阶段的风险等级评价方法。研究结果表明： 1)在勘察阶段，一般非煤瓦斯区段可采用在勘察钻孔内开展“中途检测+终孔检测+封孔检测”的常规方法进行瓦斯等级判定，在高瓦斯区段需结合聚气试验和逸散试验，通过聚气速率(νg)和逸散曲线进一步判定瓦斯等级和瓦斯类型； 2)在施工阶段，开挖工作面绝对瓦斯涌出量(Q绝)可通过实测风管压入通风量和优化后的断面瓦斯检测点准确实测； 3)开挖工作面前方瓦斯富集体绝对瓦斯涌出量(Q绝)应结合超前地质预报工作，创新采用“TSP+超前钻孔+检测试验”方法进行实测； 4)非煤地层隧道瓦斯等级评价方法已在成渝中线高铁、市域(郊)铁路成都至眉山线成功应用并指导现场安全施工。
Engineering disasters caused by harmful gases in
tunnels across China are frequent, primarily involving poisoning and
asphyxiation, combustion, and chemical corrosion. While a relatively
comprehensive survey and evaluation system has been established presently for
coal seam gas, it is not well suited for noncoal strata. This inadequacy
substantially hinders the high-quality development of noncoal gas
tunnel construction. To address this issue, field detection, in-situ testing, theoretical analysis, and onsite measurement and
calculation methods are employed to develop a gas risk level evaluation system
for harmful gases in noncoal tunnels during survey and construction phases. The
main findings are as follows: (1) During the survey phase, the conventional
method of midway detection + final hole detection + hole sealing detection can
be used to determine the gas grade in general noncoal gas sections through
boreholes. In high gas concentration zones, gas accumulation and escape testing
enable the determination of gas grade and type based on the gas accumulation
rate (νg) and the
escape curve. (2) During the construction phase, the absolute gas emission (Qabsolute) from
the excavation face can be accurately measured using recorded air duct pressure
ventilation data and an optimized layout of gas detection points. (3) The Qabsolute of the gas pocket in front of the excavation face can be evaluated
using an innovative method of tunnel seismic prediction + advance drilling +
detection test, integrated with forward geological prediction work. (4) This
gas grade evaluation method for noncoal stratum tunnels has been successfully
applied in projects such as the Chengdu-Chongqing high-speed railway and the Chengdu-Meishan urban
(suburban) railway line.
