High-geothermal-tunnel geothermal resource quantity calculation method

Abstract

This invention provides a method for calculating the geothermal resources of high-temperature tunnels. It involves conducting a survey of tunnel heat hazard resources to obtain basic data including tunnel heat hazard temperature, exposure mileage, length, and lithological characteristics. Based on these survey results, the tunnel is initially divided into multiple heat hazard zones, and temperature sets are obtained. The lithological characteristics of the surrounding rock in different heat hazard zones are investigated, and test sample sets are collected. The thermal properties of the surrounding rock samples in the test sample sets are tested to obtain test results. The length and heat extraction depth of each heat hazard section are determined. Combining temperature, surrounding rock physical parameters, and annual average air temperature, the geothermal resources of the high-temperature tunnel surrounding rock are estimated and accumulated to obtain the total geothermal resources. By comprehensively considering the tunnel heat hazard resources, the lithological characteristics of the surrounding rock in the heat hazard zones, and the temperature data collected during tunnel construction, the geothermal resources of the high-temperature surrounding rock in high-temperature tunnels can be accurately calculated.

Description

Technical Field

[0001] This invention relates to the field of geothermal resource exploration technology for high-temperature tunnels, specifically to a method for calculating the amount of geothermal resources in high-temperature tunnels. Background Technology

[0002] Geothermal resources are a type of renewable and clean energy stored inside the Earth. They have advantages such as large reserves, high energy efficiency, and low operating costs. They are the only native renewable and clean energy source on Earth that is not affected by weather or seasonal changes, and are of great significance for achieving dual carbon targets.

[0003] With the continuous development of transportation infrastructure, the construction of bridges and tunnels is increasingly venturing into areas with more complex geological conditions. High-temperature tunnels passing through geothermal anomaly zones are severely affected by high-temperature heat hazards during construction and operation. Previously, the approach to this type of natural disaster was primarily to mitigate the impact of high temperatures through insulation, containment, and ventilation, neglecting the resource attributes of these heat hazards. This paper considers the heat hazards revealed during tunnel excavation as usable geothermal resources. To rationally develop and utilize these resources, minimize their negative impacts, and fully realize their resource attributes, it is necessary to estimate the amount of geothermal resources present in these heat hazards.

[0004] Under natural conditions, thermal energy deep underground is primarily transferred to the Earth's surface through heat conduction and convection. Therefore, during geothermal resource exploration, it is difficult to accurately determine the specific conditions deep underground, leading to significant uncertainties in estimating the amount of geothermal resources.

[0005] Currently, commonly used methods for estimating geothermal resources include the reservoir volume method, the hydrothermal equilibrium method, the numerical method, and the natural heat release method. The reservoir volume method calculates geothermal resources based on the distribution area, thickness, temperature, and related lithological parameters of underground reservoirs. However, due to the uncertainties in parameters such as reservoir temperature, area, and thickness, this method often uses average values ​​when assessing geothermal resources, resulting in insufficient estimation accuracy and failing to meet the accuracy requirements for estimating geothermal resources in high-temperature tunnels. The hydrothermal equilibrium method and the natural heat release method are not suitable for assessing thermal hazards in tunnels. The numerical method is too cumbersome and cannot quickly estimate thermal hazards.

[0006] In conclusion, there is an urgent need for a method that can accurately calculate the geothermal resources in high-temperature tunnels to solve the problems existing in current technologies. Summary of the Invention

[0007] The purpose of this invention is to provide a method for calculating the geothermal resources in high-temperature tunnels, and the specific technical solution is as follows: A method for calculating geothermal resources in high-temperature tunnels includes the following steps: S1: Conduct an investigation of tunnel thermal hazard resources and collect samples of surrounding rock thermal properties, including: S1-1: Conduct a survey of tunnel thermal hazards and obtain the survey results; S1-2: Based on the results of the S1-1 survey, the tunnel is initially divided into several different heat hazard zones. The working face of each heat hazard zone is measured to obtain temperature subsets of each heat hazard zone. The temperature subsets of all heat hazard zones are then summarized to obtain the temperature set. S1-3: Investigate the lithological characteristics of the surrounding rocks in different heat-affected areas obtained in S1-2 and collect thermal property samples of the surrounding rocks in each heat-affected area; summarize the thermal property samples of the surrounding rocks in all heat-affected areas to obtain a test sample set. S2: High-temperature tunnel rock thermal property test, specifically: test the thermal properties of surrounding rock samples in the test sample set to obtain test results; S3: Determine the length and heat extraction depth of each heat-affected section. Specifically, based on the tunnel length excavated in a single day and the test results of S2, the heat-affected area is further divided into heat-affected sections, and the length of each heat-affected section is obtained; the starting temperature and ending temperature of each heat-affected section are obtained based on the temperature set of S1-2; and the heat extraction depth of each heat-affected section is obtained based on the heat extraction depth of the heat extraction device. S4: Based on the length, starting temperature, ending temperature and heat extraction depth of each heat-affected section obtained in S3, calculate the geothermal resource volume of each heat-affected section in the tunnel, and sum the geothermal resource volume of each heat-affected section to obtain the geothermal resource volume of the high-temperature tunnel.

[0008] Preferably, the survey results in S1-1 include the distribution characteristics and range of thermal hazards within the tunnel, such as the tunnel mileage and exposure length where thermal hazards are mainly exposed.

[0009] Preferably, the measurement of the working face in the heat-affected area is specifically carried out by using temperature measuring elements to perform distributed temperature measurements on the left, middle, and right sides of the working face, and then calculating the average value of the three measurements.

[0010] Preferably, the investigation in S1-3 specifically involves recording the lithological type of the surrounding rock and observing the development of fractures and joints in the surrounding rock.

[0011] Preferably, obtaining the geothermal resource quantity of the surrounding rock of the high-temperature tunnel in S4 specifically includes the following steps: First, the area of ​​each heat-affected zone is calculated using the following formula: ; in: For the first i The area of ​​each heat-affected zone, For the first i The depth of heat extraction in each heat-affected section For the first iThe radius of the tunnel in each heat-affected section; i=1,2,3,... , , Indicates the total number of heat-affected zones; Secondly, calculate the heat flux density per unit area within each heat-affected zone. The formula is as follows: ; in: For the first i Thermal conductivity of each heat-damaged section; For the first i Temperature difference in each heat-affected zone; For the first i The length of each heat-affected section; For the first i Thermal resistance of the heat-damaged section; No. i The starting temperature of each heat-affected zone; No. i The final temperature of each heat-affected section; The temperature at any point within a heat-affected zone can be calculated using the heat flux density per unit area, as shown in the following formula: ; in: Let be the calculated length of the i-th heat hazard segment, with a value of 0 < 1. ≤ ; For the i-th heat hazard section Temperature at the location.

[0012] Finally, by combining the area of ​​the heat-affected zone, the heat flux density per unit area, and the temperature at any point within the heat-affected zone with the rock's thermal conductivity, specific heat, porosity, and annual average air temperature, the following formula is obtained for calculating the geothermal resources of the surrounding rock of high-temperature tunnels: ; in, This indicates the amount of geothermal resources in the surrounding rock of high-temperature tunnels; For the first Density of surrounding rock in each heat-affected zone; For the first Specific heat capacity of the surrounding rock in each heat-affected zone; For the first Porosity of the surrounding rock in each heat-affected zone; Let be the calculated length of the i-th heat-affected section. This represents the local annual average temperature.

[0013] The beneficial effects of applying the technical solution of this invention are as follows: This invention provides a method for calculating the geothermal resources of high-temperature tunnels. First, a survey of tunnel heat hazard resources is conducted to obtain survey results. Then, based on the survey results, the tunnel is initially divided into multiple heat hazard zones, and temperature sets are obtained. Next, the lithological characteristics of the surrounding rock in different heat hazard zones are investigated, and thermal property samples of the surrounding rock in these zones are collected to obtain a test sample set. The thermal property samples of the surrounding rock in the obtained test sample set are tested to obtain test results. The length and heat extraction depth of each heat hazard section are further determined. Finally, based on the length, starting temperature, ending temperature, and heat extraction depth of each heat hazard section, the geothermal resources of each heat hazard section in the tunnel are calculated, and the resource amounts of each heat hazard section are summed to obtain the geothermal resources of the high-temperature tunnel. By comprehensively considering the tunnel heat hazard resources, the lithological characteristics of the surrounding rock in the heat hazard zones, and the temperature data collected during the tunnel construction process, the geothermal resources of the surrounding rock of high-temperature tunnels can be accurately calculated at a low cost.

[0014] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to embodiments. Detailed Implementation

[0015] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0016] Example: A method for calculating geothermal resources in high-temperature tunnels includes the following steps: S1: Conduct an investigation of tunnel thermal hazard resources and collect samples of surrounding rock thermal properties, specifically: S1-1: Conduct a survey of thermal hazards in tunnels, identify the distribution characteristics and range of thermal hazards within tunnels, and obtain survey results, including the tunnel mileage and exposure length where thermal hazards are mainly exposed. S1-2: Based on the investigation results of S1-1, the tunnel is initially divided into several different heat hazard zones. Distributed measurements are then performed on the tunnel face of each heat hazard zone to obtain temperature subsets for each zone. The temperature subsets from all heat hazard zones are then aggregated to obtain a temperature set. For example, temperature measuring elements are used to measure the temperatures on the left, middle, and right sides of the tunnel face, and then the average of the three values ​​is calculated. S1-3: Investigate the lithological characteristics of the surrounding rocks in different heat-affected areas obtained in S1-2 and obtain thermal property samples of the surrounding rocks in the heat-affected areas; summarize the thermal property samples of the surrounding rocks in all heat-affected areas to obtain a test sample set; S2: Thermal property testing of rocks in high-temperature tunnels, details are as follows: Different types of surrounding rocks exhibit significant differences in their thermal properties, including thermal conductivity, heat storage capacity, specific heat capacity, density, and porosity. Therefore, this invention selects three thermal properties that significantly influence the calculation of surrounding rock resources in high-temperature tunnels: specific heat capacity, density, and porosity, to test and analyze the thermal conductivity and heat storage capacity of the tunnel surrounding rock. Specifically, thermal property tests are conducted on collected surrounding rock samples. S2-1: Select and calibrate the measuring equipment. In this embodiment, a multifunctional rapid thermal conductivity meter (DRE-III) is used for specific heat capacity testing; a solid-liquid dual-purpose density meter (DH-300X) is used for density testing; and a Smart-Por porosity testing system is used for porosity testing. The calibration of the measuring equipment includes: first, directly measuring the parameter range of the standard sample using the instrument; comparing the measured standard sample parameters with the standard parameters of the standard sample; if the difference is large, inputting the uncalibrated parameters and the standard parameters into the instrument calibration interface for calibration. For example, the multifunctional rapid thermal conductivity meter uses quartz glass for instrument calibration. First, directly test its thermal conductivity and specific heat using the multifunctional rapid thermal conductivity meter, and compare the test results with the standard parameters.

[0017] S2-2: The test samples obtained in S1-3 are collected from various surrounding rock thermophysical property samples and prepared into corresponding test samples, that is, processed into samples usable by the relevant measuring equipment. For example, when conducting specific heat capacity testing, the equipment requires the thermophysical property sample to have two smooth surfaces to install the test probe. Since the collected surrounding rock samples are mostly irregular in shape, they need to be cut into two appropriately sized thermophysical property samples with two smooth surfaces, and the samples should be as complete as possible, with minimal fractures. S2-3: Conduct thermophysical property tests and obtain the test results.

[0018] S3: Determine the length and heat extraction depth of each heat-affected section, specifically: Based on the tunnel length excavated in a single day and the test results of S2-3, the heat hazard area was further divided into heat hazard sections and the length of each heat hazard section. The heat extraction depth of each heat-affected section is obtained based on the heat extraction depth of the heat extraction device. In this embodiment, the heat extraction depth is 15 meters.

[0019] S4: Obtain the total resources of the high-temperature surrounding rock in the tunnel, as follows: The resource quantity of each heat-affected section in the tunnel is calculated, and the geothermal resource quantities of each heat-affected section are summed to obtain the total resource quantity of the high-temperature surrounding rock of the tunnel. Specifically: First, the area of ​​each heat-affected zone is calculated using the following formula: ; in: For the first i The area of ​​each heat-affected zone, For the first i The depth of heat extraction in each heat-affected section For the first i The radius of the tunnel in each heat-affected section; i=1,2,3,... , , Indicates the total number of heat-affected zones; Secondly, calculate the heat flux density per unit area within each heat-affected zone. The formula is as follows: ; in: For the first i Thermal conductivity of each heat-damaged section; For the first i Temperature difference in each heat-affected zone; For the first i The length of each heat-affected section; For the first i Thermal resistance of the heat-damaged section; No. i The starting temperature of each heat-affected zone; No. i The final temperature of each heat-affected section; The temperature at any point within a heat-affected zone can be calculated using the heat flux density per unit area, as shown in the following formula: ; in: Let be the calculated length of the i-th heat hazard segment, with a value of 0 < 1. ≤ ; For the i-th heat hazard section Temperature at the location.

[0020] Finally, by combining the area of ​​the heat-affected zone, the heat flux density per unit area, and the temperature at any point within the heat-affected zone with the rock's thermal conductivity, specific heat, porosity, and annual average air temperature, the following formula is obtained for calculating the geothermal resources of the surrounding rock of high-temperature tunnels: ; in, This indicates the amount of geothermal resources in the surrounding rock of high-temperature tunnels; For the first Density of surrounding rock in each heat-affected zone; For the first Specific heat capacity of the surrounding rock in each heat-affected zone; For the first Porosity of the surrounding rock in each heat-affected zone; Let be the calculated length of the i-th heat-affected section. This represents the local annual average temperature.

[0021] Taking a section of a thermal hazard area in an ultra-long, deeply buried tunnel on the Qinghai-Tibet Plateau as an example, calculations were performed on six thermal hazard sections, as detailed below: The investigation of tunnel thermal hazard resources and the collection of thermal property samples of surrounding rock were carried out. Specifically, the temperature of the tunnel surrounding rock and the tunnel face was measured on-site, and the lithological characteristics of the thermal hazard exposure locations were recorded, including the lithology of the surrounding rock and the development of joints. In this embodiment, the highest exposure temperature of the tunnel thermal hazard resources exceeded 70℃. The main exposed lithologies were granite and granitic gneiss, which were relatively intact overall, but some areas were severely fractured due to the influence of faults, and fissures were developed. Based on the results of the thermal hazard resource survey, the tunnel is initially divided into thermal hazard areas. Specifically, the thermal hazard resources of the tunnel are initially divided according to the daily tunneling mileage. For example, if the daily tunneling is 10 meters, it is initially considered a thermal hazard area, and corresponding rock samples are collected based on its lithological characteristics. If the lithology is consistent with that of the previous thermal hazard area, there is no need to collect samples again. In this embodiment, the main lithology is granite and granitic gneiss.

[0022] The thermal properties of rocks in high-temperature tunnels were tested, as follows: The collected rock samples were prepared and tested using appropriate instruments. In this embodiment, the following instruments were used for sample testing: specific heat capacity was tested using a multifunctional rapid thermal conductivity meter (DRE-III); density was tested using a solid-liquid dual-purpose density meter (DH-300X); and porosity was tested using a Smart-Por porosity testing system. The test results are shown in Table 1.

[0023] The length and heat extraction depth of each heat-affected zone are determined as follows: In this embodiment, heat-affected areas with consistent surrounding rock thermal properties are merged into one heat-affected zone; heat-affected zones with significant variations in temperature and lithological parameters are divided into different heat-affected zones, ultimately yielding the length of each heat-affected zone. The heat extraction depth is determined based on the heat extraction depth of the heat exchanger; here, it is set to 15 meters.

[0024] The results obtained after calculation are shown in Table 1: Table 1. Data Statistics and Calculation Results

[0025] In summary, this invention integrates the geothermal resources of the surrounding rock in high-temperature tunnels, the lithological characteristics of the surrounding rock in the heat-affected area, and the temperature data collected during the tunnel construction process, enabling accurate calculation of the geothermal resources of the surrounding rock.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating geothermal resources in high-temperature tunnels, characterized in that, Includes the following steps: S1: Conduct an investigation of tunnel thermal hazard resources and collect samples of surrounding rock thermal properties, including: S1-1: Conduct a survey of tunnel thermal hazards and obtain the survey results; S1-2: Based on the results of the S1-1 survey, the tunnel is initially divided into several different heat hazard zones. The working face of each heat hazard zone is measured to obtain temperature subsets of each heat hazard zone. The temperature subsets of all heat hazard zones are then summarized to obtain the temperature set. S1-3: Investigate the lithological characteristics of the surrounding rocks in different heat-affected areas obtained in S1-2 and collect thermal property samples of the surrounding rocks in each heat-affected area; summarize the thermal property samples of the surrounding rocks in all heat-affected areas to obtain a test sample set. S2: High-temperature tunnel rock thermal property test, specifically: test the thermal properties of surrounding rock samples in the test sample set to obtain test results; S3: Determine the length and heat extraction depth of each heat-affected section. Specifically, based on the tunnel length excavated in a single day and the test results of S2, the heat-affected area is further divided into heat-affected sections, and the length of each heat-affected section is obtained; the starting temperature and ending temperature of each heat-affected section are obtained based on the temperature set of S1-2; and the heat extraction depth of each heat-affected section is obtained based on the heat extraction depth of the heat extraction device. S4: Based on the length, starting temperature, ending temperature and heat extraction depth of each heat-affected section obtained in S3, calculate the geothermal resource volume of each heat-affected section in the tunnel, and sum the geothermal resource volume of each heat-affected section to obtain the geothermal resource volume of the surrounding rock of the high-temperature tunnel.

2. The calculation method according to claim 1, characterized in that, The survey results in S1-1 include the temperature, exposure distance, length, and lithological characteristics of thermal hazard resources within the tunnel.

3. The calculation method according to claim 1, characterized in that, The specific method for measuring the working face in the heat-affected area is as follows: temperature measuring elements are used to perform distributed temperature measurements on the left, middle, and right sides of the working face, and then the average value of the three measurements is calculated.

4. The calculation method according to claim 3, characterized in that, The investigation in S1-3 specifically involves recording the lithological type of the surrounding rock and observing the development of fractures and joints in the surrounding rock.

5. The calculation method according to any one of claims 1-4, characterized in that, The process of obtaining geothermal resources from the surrounding rock of high-temperature tunnels in S4 includes the following steps: First, the area of ​​each heat-affected zone is calculated using the following formula: ； in: For the first i The area of ​​each heat-affected zone, For the first i The depth of heat extraction in each heat-affected section For the first i The radius of the tunnel in each heat-affected section; i=1,2,3,... , , Indicates the total number of heat-affected zones; Secondly, calculate the heat flux density per unit area within each heat-affected zone. The formula is as follows: ； in: For the first i Thermal conductivity of each heat-damaged section; For the first i Temperature difference in each heat-affected zone; For the first i The length of each heat-affected section; For the first i Thermal resistance of the heat-damaged section; No. i The starting temperature of each heat-affected zone; No. i The final temperature of each heat-affected section; The temperature at any point within a heat-affected zone can be calculated using the heat flux density per unit area, as shown in the following formula: ； in: For the first i The calculated length of each heat-affected zone, with a value of 0 < ≤ ; For the i-th heat hazard section Temperature at the location; Finally, by combining the area of ​​the heat-affected section, the temperature at any point within the heat-affected section, the physical properties of the surrounding rock, and the annual average air temperature, the geothermal resources of the surrounding rock of the high-temperature tunnel are obtained. The calculation formula is as follows: ； in, This indicates the amount of geothermal resources in the surrounding rock of high-temperature tunnels; For the first Density of surrounding rock in each heat-affected zone; For the first Specific heat capacity of the surrounding rock in each heat-affected zone; For the first Porosity of the surrounding rock in each heat-affected zone; Let be the calculated length of the i-th heat-affected section. This represents the local annual average temperature.

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