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Accident analysis and safety measures for tunnel construction

according to the plan, China will build 6000 km tunnels in the first 20 years of the 21st century and 155 km long urban highway tunnels within 10 years, many of which are long, large and deeply buried tunnels. However, tunnel construction is a complex system engineering due to the uncertainty of surrounding rock stability, low degree of construction mechanization, poor construction environmental conditions, low quality of workers, and safety particularity. If a certain aspect, stage, and link of the work is not done well, it may cause accidents. Therefore, from the perspective of intrinsic safety and system management, we should strengthen the safety technology control and safety management of tunnel construction to prevent and reduce accidents

1 accident analysis of tunnel construction

the investigation results of the International Tunnel Engineering Insurance Group on the causes of safety accidents at the construction site show that there are many reasons for accidents in underground projects, among which, insufficient geological survey accounts for 12%, design errors account for 41%, construction errors account for 21%, lack of information communication accounts for 8%, and force majeure accounts for 18%

as we all know, tunnel engineering has the characteristics of complex and changeable geology, narrow working space, many unpredictable factors, and various dangerous and harmful factors intertwined, so the construction risk is very high, and industrial accidents are common. Generally speaking, tunnel construction accidents mainly include collapse, roof fall and wall breaking, body strike, water penetration, mechanical injury, vehicle injury, fire, explosion, drowning, poisoning and suffocation [1]

1.1 accident analysis during excavation

accidents during excavation generally account for 50% of the total accident rate of the tunnel. The main types of accidents include collapse with No. 100 oil lubrication, roof collapse, water seepage, mechanical injury, explosion, poisoning and suffocation, etc. Main reasons: ① when the tunnel passes through faults, karst, fracture zones and other unfavorable geological sections, due to poor investigation and insufficient understanding of engineering geology and hydrogeology bus duct JISC 8364 ⑴ 995 quality, unreasonable selection of construction scheme, untimely (temporary) support or weak support, the potential stress is released after excavation, the pressure is fast, and the surrounding rock is prone to instability, resulting in sudden disasters such as collapse, water seepage, mud outburst, etc., which are difficult to manage; ② When the tunnel passes through the rock stratum in the nearby gas containing section, gas accumulation is often caused by poor detection and poor ventilation. In case of electric fire or open fire, it is very easy to ignite gas and cause major accidents such as explosion, fire and poisoning and suffocation caused by harmful gas; ③ When using drilling and blasting method and tunneling machine method to excavate or erect steel frame for support, the use of rock drill and tunneling machine is not operated in accordance with the operating procedures, which is easy to cause mechanical injury, falling from height and other accidents

1.2 accident analysis in rock loading and transportation

accidents in rock loading and transportation (including accidents caused by transportation equipment) generally account for 25% of the total external force accidents at the yield point s set as PS in tunnel construction. Accidents may be caused by the narrow working face in the tunnel, dirty air, low visibility, improper scheduling and connection of vehicles during rock loading, etc. Generally speaking, the accidents occurring in the process of tunnel rock loading and transportation can be divided into two categories: one is that the construction personnel are collided by dump trucks, electric locomotives or other transportation vehicles; The other is that the construction personnel collide with rocks or other obstacles and cause injuries

1.3 analysis of other accidents

in some long, large and wide utility tunnels, underground passages and subway tunnels, large and efficient construction machinery and equipment are often used for construction, and there are many construction cables and high-pressure air and water pipelines laid in the tunnels. Therefore, electric shock, mechanical injury, falling off of high-pressure air and water pipeline joints and injuring construction personnel often occur [2]

2 safety measures for tunnel construction

2.1 construction is expected to effectively reduce the cost of construction safety technical measures

(1) strengthen geological survey and monitoring measurement. The engineering geology and hydrogeological conditions should be taken as the preconditions for the design of the tunnel, and the geological conditions during the construction period should also be paid close attention to. The geological advance detection of TSP203 should be carried out regularly to understand the characteristics of the surrounding rock in front, formulate a detailed construction plan, and eliminate all kinds of sudden geological disasters [3]; Try to choose stable strata and avoid geological sections with extremely complex engineering geological and hydrological conditions or serious adverse conditions

visually predict the geological conditions in front of the excavation face, judge the stability of the surrounding rock, and analyze the reliability of the support structure according to the surface state of the shotcrete and the working state of the anchor bolt; At the same time, according to the monitoring and measurement results of instruments and equipment, determine whether the stability of surrounding rock and support parameters are reasonable, so as to formulate measurement plans in different stages, summarize and analyze data, and feed back to guide construction

(2) choose the correct excavation method. Give priority to the use of full section or a small part of the excavation method, so as to reduce the interference of tunnel construction process, which is conducive to mechanical construction, and try to adopt new construction technology and methods to ensure construction safety. For extra long tunnels with good engineering geological and hydrogeological conditions and suitable construction sites and transportation roads, the tunneling machine method should be preferred. For the tunnel constructed by drilling and blasting method, the full section method can be used for class II surrounding rock construction, the bench method can be used for class III and IV surrounding rock construction, the micro bench method can be used for deep buried class V surrounding rock tunnel construction, and the double wall heading method can be used for shallow buried and eccentric pressure sections of some large section tunnels [4]

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