Coal measure stratum tunnel harmful gas surveying and evaluating method

Abstract

The application discloses a coal measure stratum tunnel harmful gas surveying and evaluating method, which comprises the following steps: based on the regional coal rock geological background and the regional geological condition, the tunnel body is segmented according to the engineering geology; test holes are arranged to measure the coal measure stratum magnetization rate and the ton coal gas content, and the relationship between the ton coal gas content and the magnetization rate is fitted as Q0=2.35*10 ‑2 ×e (C / 32.34) -0.05; 3) surveying holes are arranged according to the engineering geology segmentation, the tunnel body coal measure stratum section is inferred according to the occurrence, the rock stratum magnetization rate in the surveying hole is measured through the comprehensive well logging test in the hole; based on the measured magnetization rate in the hole, the ton coal gas content of each test hole of the tunnel is calculated, the ton coal gas content change curve of the coal measure tunnel is drawn, and the gas comprehensive evaluation of the tunnel segmentation is carried out. Through the division of the tunnel body according to the engineering geology segmentation, the relationship between the ton coal gas content and the magnetization rate is fitted, the gas concentration detection and the content calculation are reduced while ensuring the continuous exploration, the surveying period is shortened, and the surveying cost is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to tunnel engineering, in particular to a coal measure stratum tunnel harmful gas survey and evaluation method. BACKGROUND

[0002] The geological conditions along the railway lines in the southwest mountainous area are complex, the structural types are various, the fault structures are developed, and the rock types are complete, including magmatic rock, metamorphic rock and sedimentary rock. A large number of coal measure stratum tunnels emerge in the planning and construction process of railways and highways. For a long time, the harmful gas encountered in the process of tunnel construction has been a big problem for tunnel safety construction and is one of the main types of common diseases in tunnel engineering. From the gas explosion in the Yansuozhai Tunnel of the Dianqian Line of the first railway in New China to the gas explosion at the Dongjiashan Tunnel construction site of the Sichuan Dujiangyan-Wenjiang Expressway, they have brought huge life and property losses. Therefore, it is necessary to strengthen the research on harmful gas in the tunnel survey and design stage.

[0003] At present, the survey of tunnel gas harmful gas mainly relies on data collection, geological mapping and exploration testing. In the data collection stage, regional geology, mineral geology, hydrogeology and harmful gas area survey data are collected. The geological mapping mainly aims at the lithology of the stratum containing gas, the position of the coal measure stratum, oil and gas layer and oil shale layer and the closed structure. The above methods are mostly qualitative or semi-quantitative research, which requires a lot of manpower and material resources, and the survey accuracy is limited. The exploration test mainly relies on drilling combined with geophysical well testing and field testing, and the main purpose is to find out the characteristics of coal, oil shale, oil and gas and harmful gas. This method has high accuracy, but a large number of drill holes need to be arranged and gas concentration and gas emission testing need to be carried out, which leads to a long survey period and a large increase in survey cost. Therefore, there is an urgent need for a coal measure stratum tunnel gas segment survey and evaluation method with high survey accuracy and low cost. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a coal measure stratum tunnel harmful gas survey and evaluation method to effectively reduce the survey period, save the survey cost and improve the survey accuracy.

[0005] The technical solution adopted by the present application to solve the above technical problem is as follows:

[0006] A coal measure stratum tunnel harmful gas survey and evaluation method, comprising the following steps:

[0007] ① Based on the regional coal rock geological background and the tunnel geological conditions, the tunnel body is segmented according to the engineering geology;

[0008] ② On the engineering geology section, arrange test holes to measure the coal measure strata magnetic susceptibility, and carry out coal measure strata ton coal gas content detection in the same test hole, and the relationship between ton coal gas content and magnetic susceptibility is obtained by fitting analysis as shown in formula (1):

[0009]

[0010] In the formula, Q0 is the ton coal gas content of the coal measure strata, and C is the magnetic susceptibility of the coal measure strata;

[0011] ③ On the engineering geology section, arrange several drilling exploration holes, calculate the tunnel body coal measure strata section according to the occurrence, reveal the occurrence, position and thickness of the coal measure strata, and measure the magnetic susceptibility in the exploration hole through comprehensive logging test in the hole;

[0012] ④ Based on the measured magnetic susceptibility in the exploration hole, calculate the ton coal gas content of each exploration hole of the tunnel, draw the ton coal gas content change curve of the coal measure tunnel, and perform gas comprehensive evaluation on the tunnel section according to the following coal measure strata tunnel gas section danger grade discrimination table:

[0013]

[0014] The engineering geology section in step ① is based on the relative difference zone of the magnetic susceptibility of the coal measure strata tunnel coal-bearing layer, carbon-bearing layer, oil-bearing layer, asphaltic rock layer, anticline structure, fault zone, joint dense zone and strong crustal activity area structure activity influence area.

[0015] In step ③, the tunnel body coal measure strata section is inferred according to the occurrence, the occurrence, position and thickness of the coal measure strata are revealed through the drilling exploration hole, and the apparent dip angle of the coal measure strata is According to formula (2):

[0016]

[0017] In the formula, α is the true dip angle of the coal measure strata, ω is the included angle between the true dip direction and the apparent dip direction of the coal measure strata, and β is the included angle between the coal measure strata strike and the tunnel body axis;

[0018] The included angle ω between the true dip direction and the apparent dip direction of the coal measure strata and the included angle β between the coal measure strata strike and the tunnel body axis are related as formula (3):

[0019] ω+β=90° (3)

[0020] The true thickness H of the coal measure strata revealed by the drilling exploration hole is calculated according to formula (4):

[0021]

[0022] In the formula, M is the thickness of the coal measure strata revealed by the drilling exploration hole;

[0023] According to the coal measure stratum true thickness H, apparent dip angle and strike revealed by the drilling exploration hole, the mileage range and length of the tunnel hole body coal measure stratum are calculated, wherein the tunnel hole body section coal measure stratum length L is calculated according to formula (5):

[0024]

[0025] The beneficial effect of the present application is that the tunnel hole body section is divided into several engineering geological sections, drilling is carried out in each engineering geological section, the number of drilling is reduced, the relationship between the coal measure stratum ton coal gas content and the magnetic susceptibility is obtained through fitting analysis, the gas concentration and emission amount test experiment is reduced while ensuring continuous exploration, and the exploration period is effectively shortened, the exploration cost is saved, and the exploration accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a flow chart of a coal measure stratum tunnel harmful gas exploration and evaluation method of the present application;

[0027] Figure 2 is a structural schematic diagram of the coal measure stratum tunnel hole body section based on engineering geological segmentation;

[0028] Figure 3 is a relationship between the coal measure stratum magnetic susceptibility and the ton coal gas content;

[0029] Figure 4 is a structural schematic diagram of the coal measure stratum tunnel apparent dip angle and the coal measure stratum true dip angle;

[0030] Figure 5 is a structural schematic diagram of the tunnel hole body coal measure stratum section calculated according to the coal measure stratum thickness and occurrence revealed by the drilling exploration hole;

[0031] Figure 6 is a ton coal gas content and work area grade result diagram of the coal measure stratum tunnel hole body section based on gas segmented exploration and evaluation of the embodiment.

[0032] wherein the marks and their meanings are shown: 1-tunnel, 2-tunnel hole body, 3-engineering geological section, 4-engineering geological section interface, 5-coal measure stratum, 6-drilling exploration hole, 7-fault. DETAILED DESCRIPTION

[0033] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0034] A technical flow chart of a coal measure stratum tunnel harmful gas survey and evaluation method is shown in FIG. Figure 1 The method comprises steps 1 to 4.

[0035] In step 1, the tunnel body is segmented according to the regional coal rock geological background and the tunnel geological conditions.

[0036] The engineering geological segmentation is based on the relative difference zone of magnetic susceptibility of the coal measure stratum tunnel coal-bearing stratum, carbon-bearing stratum, oil-bearing stratum, asphaltic rock stratum, and the magnetization difference zone of the structural activity influence area of the anticline structure, fault zone, joint dense zone, and intense crustal activity area.

[0037] Figure 2 FIG. is a structural schematic diagram of the coal measure stratum tunnel body segment segmented according to the engineering geology. According to the tunnel coal-bearing stratum, carbon-bearing stratum, oil-bearing stratum, asphaltic rock stratum, and the structural activity influence area of the anticline structure, fault zone, joint dense zone, and intense crustal activity area, a plurality of engineering geological segments are divided based on the engineering geological segmentation interface. Figure 2 In step 2, 19 test holes are arranged on the engineering geological segments, the coal measure stratum magnetic susceptibility and the ton coal gas content in the holes are measured, and the maximum measurement results of the ton coal gas content and the magnetic susceptibility of the test holes are shown in Table 1.

[0038] Table 1

[0039]

[0040]

[0041]

[0042] According to the maximum measurement results of the ton coal gas content and the magnetic susceptibility of the test holes in Table 1.

[0043] Figure 3 FIG. is the relationship between the coal measure stratum magnetic susceptibility and the ton coal gas content, and the relationship between the ton coal gas content and the magnetic susceptibility obtained by fitting analysis is shown in formula (1).

[0044] ​

[0045] In the formula, Q0 is the gas content per ton of coal in the coal measure stratum, and C is the magnetic susceptibility of the coal measure stratum;

[0046] In step ③, a plurality of survey holes are arranged on the engineering geology section, the tunnel hole body coal measure stratum section is calculated according to the occurrence, and the magnetic susceptibility in the survey hole is measured through the comprehensive logging test in the hole. The plurality of drilling survey holes are arranged on the engineering geology section, and the interval of the drilling survey hole is preferably 2-3 times the hole depth, and the hole depth of the survey hole needs to be more than 10-50 m of the tunnel base;

[0047] Figure 4 is a structural diagram of the apparent dip angle of the coal measure stratum tunnel and the true dip angle of the coal measure stratum. See Figure 4 The tunnel hole body coal measure stratum section is calculated according to the occurrence, the occurrence, position, thickness and the like of the coal measure stratum are revealed through the drilling survey hole, the apparent dip angle of the coal measure stratum is is calculated according to formula (2):

[0048]

[0049] In the formula, α is the true dip angle of the coal measure stratum, ω is the included angle between the true dip direction and the apparent dip direction of the coal measure stratum, and β is the included angle between the strike of the coal measure stratum and the axis of the tunnel hole body;

[0050] The included angle ω between the true dip direction and the apparent dip direction of the coal measure stratum and the included angle β between the strike of the coal measure stratum and the axis of the tunnel hole body are related as formula (3):

[0051] ω+β=90° (3)

[0052] The true thickness H of the coal measure stratum revealed by the drilling survey hole is calculated according to formula (4):

[0053]

[0054] In the formula, M is the thickness of the coal measure stratum revealed by the drilling survey hole;

[0055] The true thickness H, apparent dip angle and strike of the coal measure stratum revealed by the drilling survey hole are used to calculate the mileage range and length of the tunnel hole body coal measure stratum, and the length L of the tunnel hole body section coal measure stratum is calculated according to formula (5):

[0056]

[0057] In step ④, the gas content per ton of coal in the tunnel is calculated based on the measured magnetic susceptibility in the survey hole, and the tunnel is segmented for gas comprehensive evaluation according to the following coal measure stratum tunnel gas section danger grade discrimination table:

[0058]

[0059] The drilling exploration hole comprises a vertical exploration hole, a horizontal exploration hole, an upward exploration hole and a downward exploration hole.

[0060] Embodiment:

[0061] Referring to Figure 6 A certain railway tunnel in the southwest mountainous area has a length of about 24069m, and the maximum buried depth of the tunnel is about 1350m.Through the combination of methods such as collection of regional geological data, field geological surveying and mapping, and geophysical exploration, the geological conditions of the tunnel site area are found out, and the tunnel geological longitudinal section is drawn.Based on the engineering geological segmentation basis, the tunnel is mainly bounded by the large engineering geological segmentation interfaces such as coal measures strata and faults, and is divided into 6 engineering geological segments.

[0062] 6 drilling exploration holes are arranged on the engineering geological segments, and the hole depth of the drilling exploration hole needs to exceed the tunnel base by 10-50m.The magnetic susceptibility in the exploration hole is obtained through hole testing, formula (1) is substituted, and the ton coal gas content value of the 6 drilling exploration holes is calculated.According to table 3, the gas risk of the tunnel drilling exploration hole is evaluated, and table 4 is the coal measures strata tunnel drilling exploration hole test data and gas risk grade.

[0063] Table 4

[0064]

[0065] Based on the coal measures strata thickness and occurrence revealed by the drilling exploration hole, formula (2)-(5) are used, and the coal measures strata section of the tunnel body section is calculated.According to tables 4 and 5, the specific section and risk grade of the coal measures strata tunnel gas are known, and the gas section is divided into 7 sections, including 1 high gas section with a total length of 2500m, 3 low gas sections with a total length of 10800m, and 3 micro gas sections with a total length of 10769m.

[0066] Table 5

[0067]

[0068] The tunnel body section is divided into several engineering geological sections, drilling is carried out in each engineering geological section, the number of drillings is reduced, the relationship between the magnetic susceptibility of the coal measures strata and the gas emission is obtained through fitting analysis, the gas concentration and emission test are reduced while ensuring continuous exploration, the exploration and evaluation method can effectively reduce the exploration period, save the exploration cost and improve the exploration accuracy.

[0069] The method can also be used for coal measures strata tunnel gas segmentation exploration and evaluation of hydropower stations, water diversion tunnels, underground caverns, coal mines and the like, and can also be used for coal measures strata tunnel gas segmentation exploration and evaluation of carbon-containing layers, oil-containing layers, asphaltic rock layers and the like.

[0070] It is apparent that the described embodiments are only some, but not all of the embodiments of the present application. The elements and features described in one drawing or one embodiment of the present application can be combined with the elements and features shown in one or more other drawings or embodiments. It should be noted that the representation and description of components and processes that are irrelevant to the present application and known to those of ordinary skill in the art are omitted from the drawings and the description for the purpose of clarity. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor fall within the scope of protection of the present application.

[0071] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment includes only one independent technical solution, and the description of the specification is only for the purpose of clarity. Those of ordinary skill in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those of ordinary skill in the art can understand.

Claims

1. A method for investigating and evaluating harmful gases in coal-bearing strata tunnels, comprising the following steps: ①Based on the regional coal and rock geological background and tunnel geological conditions, the tunnel body is divided into engineering geological sections; ② Test boreholes were arranged on the engineering geological sections to measure the magnetic susceptibility of the coal-bearing strata. The gas content per ton of coal in the coal-bearing strata was detected in the same test borehole. The relationship between the gas content per ton of coal and the magnetic susceptibility was obtained by fitting analysis as shown in Equation (1): In the formula, Q0 is the gas content per ton of coal in the coal-bearing strata, and C is the magnetic susceptibility of the coal-bearing strata; ③ Arrange several drilling exploration holes on the engineering geological section, calculate the coal-bearing strata section of the tunnel body according to the occurrence, reveal the occurrence, location and thickness of the coal-bearing strata, and measure the magnetic susceptibility in the exploration hole through comprehensive logging test in the hole; ④ Based on the measured magnetic susceptibility within the exploration boreholes, calculate the gas content per ton of coal in each exploration borehole of the tunnel, plot the variation curve of gas content per ton of coal in coal-bearing tunnels, and conduct a comprehensive gas evaluation of each tunnel segment according to the following table of hazard level judgment for gas sections in coal-bearing strata tunnels:

2. The method for investigating and evaluating harmful gases in coal-bearing strata tunnels as described in claim 1, characterized in that: The engineering geological segmentation in step ① is based on the following: coal-bearing strata tunnels, coal-bearing strata, carbonaceous strata, oil-bearing strata, asphaltite strata, anticline structures, fault zones, densely jointed zones, and zones with relative differences in magnetic susceptibility in areas affected by tectonic activity in areas of intense crustal activity.

3. The method for investigating and evaluating harmful gases in coal-bearing strata tunnels as described in claim 1, characterized in that: The spacing between the drilling exploration holes in step ③ is 2 to 3 times the hole depth, and the hole depth should preferably exceed the tunnel foundation by 10 to 50 meters.

4. The method for investigating and evaluating harmful gases in coal-bearing strata tunnels as described in claim 1, characterized in that: Step ③ involves inferring the coal-bearing strata section of the tunnel body based on their occurrence, and revealing the occurrence, location, and thickness of the coal-bearing strata, as well as the apparent dip angle of the coal-bearing strata, through drilling exploration boreholes. Calculate according to formula (2): In the formula, α is the true dip angle of the coal-bearing strata, ω is the angle between the true dip and the apparent dip of the coal-bearing strata, and β is the angle between the strike of the coal-bearing strata and the tunnel axis. The relationship between the angle ω between the true dip and apparent dip of the coal-bearing strata and the angle β between the strike of the coal-bearing strata and the tunnel axis is shown in equation (3): ω+β=90° (3) The true thickness H of the coal-bearing strata revealed by drilling exploration boreholes is calculated according to formula (4): In the formula, M is the thickness of the coal-bearing strata revealed by the drilling exploration borehole; Based on the true thickness H, apparent dip angle, and strike of the coal-bearing strata revealed by the drilling exploration boreholes, the mileage range and length of the coal-bearing strata in the tunnel body are calculated. The length L of the coal-bearing strata in the tunnel body section is calculated according to formula (5):

5. The method for investigating and evaluating harmful gases in coal-bearing strata tunnels as described in claim 1, characterized in that: The drilling exploration holes include vertical exploration holes, horizontal exploration holes, upward-sloping exploration holes, and downward-sloping exploration holes.

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