Rapid presplitting method suitable for entrance and exit of subway station under hard rock geology

Abstract

The invention belongs to the technical field of tunnel construction, and particularly relates to a rapid presplitting method suitable for an entrance and exit of a subway station under hard rock geology, a high-energy expanding agent is used for expanding and breaking rock, large-section segmented construction is performed by designing the dosage of the high-energy expanding agent and drilling arrangement parameters and combining a special filling mode, and the construction efficiency is improved. Compared with traditional non-explosion excavation and high-pressure gas expansion rock breaking, high-energy expanding agent presplitting can make full use of original fractures of rocks, is suitable for various hard rock geological conditions, does not have sympathetic detonation distance, can achieve a good presplitting effect no matter deep holes or shallow holes, and is flexible in construction and low in cost. The device is suitable for construction scenes with diversified sections such as subway station entrances and exits, can greatly improve work efficiency, is low in generated vibration velocity, controllable in noise, simple to operate, safe and reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a rapid pre-cracking method suitable for entrances and exits of subway stations under hard rock geology. Background Art

[0002] At present, the rapid excavation of subway station entrances and exits under hard rock geology has certain difficulties due to the diversity of entrance and exit cross-section changes. In addition, since the station entrances and exits are close to the ground, it is particularly important to control vibration and noise during construction. In the existing technology, although there are many non-explosive excavation solutions such as hydraulic breakers, cantilever tunneling machines, and rock breaking using high-pressure gas expansion, the common non-explosive tunnel excavation technologies each have certain limitations.

[0003] For example, the equipment selection of hydraulic breaker is greatly affected by the cross-section, and it is not suitable for dark excavation construction, and it will generate significant vibration and noise; cantilever tunneling machines are prone to rapid wear of the drill bit in hard rock geology with surrounding rock strength exceeding 80 MPa, thereby reducing construction efficiency and increasing construction costs; and the combination of water-abrasive drill and splitting rod not only has low construction efficiency, but also poor economy; and the non-explosion method of using high-pressure gas for expansion has a phase change reaction process, low energy release efficiency, and high manufacturing and maintenance costs of expansion tubes and related equipment. It is difficult to operate and requires the accompaniment of professionals. At the same time, improper operation during the filling and release of high-pressure gas may cause pressure loss or equipment damage.

[0004] Therefore, it is urgent to introduce a new non-explosive excavation method that is low in vibration, high in efficiency, economical, safe and reliable and suitable for urban hard rock areas to meet the needs of construction in environmentally sensitive areas. Summary of the invention

[0005] In order to solve the defects of existing non-explosive excavation, such as poor safety and difficulty in adapting to construction scenarios with diverse cross-sections, a rapid pre-cracking method suitable for subway station entrances and exits under hard rock geology is proposed. The dosage of high-energy expansion agent and drilling arrangement parameters are designed to greatly improve the work efficiency, and the method has strong operability and good pre-cracking effect.

[0006] The present invention is implemented by adopting the following technical solution: a rapid pre-cracking method suitable for subway station entrances and exits under hard rock geology, comprising the following steps: Step 1: Conduct geological surveys on the areas where the subway station entrances and exits are located to obtain geological survey parameters, and arrange blasting vibration velocity monitors and sound level meters for monitoring in the most susceptible areas according to the surrounding environment; the geological survey parameters include rock tensile strength, compressive strength, elastic modulus and permeability; Step 2: Based on the geological survey parameters of the subway station entrance and exit obtained, the dosage of high-energy expansion agent and drilling parameters are designed, and a drilling layout diagram is drawn; The drilling parameters include the fracture hole diameter, hole spacing and hole depth, which are determined as follows: The crack-causing holes are evenly distributed in a "plum blossom" spacing. The hole spacing ranges from 1.0 to 1.5 m. The number of holes is reasonably arranged according to the cross-sectional size and hole spacing. The crack-causing hole diameter is determined by the following method: ;in, Refers to tensile stress, which is equivalent to the tensile strength of rock measured by geological survey. It refers to the uniform pressure generated by the high-energy expansion agent. refers to the formation pressure, r refers to the arbitrary radius, a refers to the radius of the high-energy expansion agent roll, and b refers to the diameter of the fracture hole; The hole depth is determined by the following method: D = k·R, where D is the hole depth, k is the thickness of the rock to be broken, and R is an empirical coefficient with a value of 1.2~1.5; The dosage of high-energy expander is determined by: determining the required energy based on the rock compressive strength and the expected fracture volume, solving the required number of moles in combination with the combustion equation, and then obtaining the gas volume required for effective rock crushing, and then determining the dosage of high-energy expander in combination with the gas production of the high-energy expander; Step 3: Use a borehole television imager to detect the development of joints and fissures inside the rock mass in the hole to design the filling method of the high-energy expansion agent; when filling the high-energy expansion agent, arrange the expansion agent in the fissure and joint development section according to the borehole television imaging, and set a fracture-inducing hole near or in the middle of the main fracture.

[0007] Step 4: Perform high-energy expansion agent pre-cracking construction according to the drilling arrangement and high-energy expansion agent filling method determined in steps 2 and 3, and use a drilling television imager and an acoustic wave detector to evaluate the pre-cracking effect of the high-energy expansion agent.

[0008] Compared with the prior art, the advantages and positive effects of the present invention are: This scheme uses high-energy expansion agent to expand and break rock. By designing the high-energy expansion agent dosage and drilling arrangement parameters, combined with a special filling method, large-section segmented construction is carried out. Compared with traditional non-explosive excavation and high-pressure gas expansion rock breaking, high-energy expansion agent pre-cracking can make full use of the original cracks in the rock, is suitable for a variety of hard rock geological conditions, and there is no sympathetic explosion distance. Whether deep or shallow holes, it can achieve a good pre-cracking effect. The construction is flexible and suitable for construction scenes with diverse sections such as subway station entrances and exits. It can greatly improve work efficiency, and the vibration velocity generated is small, the noise is controllable, and the operation is simple, the equipment cost is low, and it is safe and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of surrounding rock stress distribution under a high-energy expansion agent according to an embodiment of the present invention; Figure 2 This is a diagram showing the internal structure of a high-energy expansion agent according to an embodiment of the present invention; Figure 3 A schematic diagram of a drilling arrangement according to an embodiment of the present invention; Figure 4 Schematic diagram of high energy expansion agent filling in an embodiment of the present invention, (a) filling method 1; (b) filling method 2; Among them, 1. high-energy expansion agent; 2. wire connector; 3. starter; 4. fuse; 5. drilling. DETAILED DESCRIPTION

[0010] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below. Embodiment, a rapid pre-cracking method applicable to the entrance and exit of a subway station under hard rock geology, comprising the following steps: Step 1: Conduct geological surveys of the areas where subway station entrances and exits are located, and arrange blasting vibration velocity monitors and sound level meters for monitoring in the most susceptible areas according to the surrounding environment; When carrying out construction at the entrances and exits of subway stations, it is first necessary to conduct a detailed geological survey of the area where the entrances and exits are located in order to understand the geological structure and structural characteristics of the area, measure the physical and mechanical properties of the soil and rock (including tensile strength, compressive strength, elastic modulus, and permeability, etc.), and understand the distribution and flow characteristics of groundwater and its impact on station construction.

[0011] In addition, subway stations under existing operating lines and residential buildings that are close to them are generally identified as the most vulnerable areas. The specific situation can be determined based on the actual situation. Vibration velocity monitors and sound level meters are set up in the most vulnerable areas. Through vibration velocity and noise monitoring, the impact of the high-energy expansion agent pre-cracking process on the surrounding environment and buildings can be assisted in judging. Once an abnormal situation is found, timely measures can be taken to correct the pre-cracking parameters. For example, taking a certain subway as an example, the vibration velocity during construction exceeds the vibration safety standard (2~3cm / s) and the allowable standard of a certain subway (the allowable vibration standard for gas pipelines is 0.5cm / s, and the allowable standard for buildings is 1.0cm / s). Once an abnormal situation occurs, construction will be stopped immediately, and the charge will be re-evaluated through the vibration velocity formula. The vibration velocity calculation formula is: , V refers to the vibration velocity at a certain measuring point (usually expressed in cm / s), K is an empirical constant that depends on geological conditions and rock properties and is usually determined by experimental data, W is the effective equivalent of the high-energy expansion agent (i.e. weight, expressed in kg), and R is the distance from the pre-splitting point to the measuring point (in meters). In the abnormal section, the charge is reduced and the pre-splitting footage is shortened once to meet safety standards.

[0012] Step 2: Based on the geological survey parameters of the subway station entrance and exit obtained, the dosage of high-energy expansion agent and drilling parameters are designed, and a drilling layout diagram is drawn; (1) The dosage of high energy expander is determined by: The working principle of high-energy expansion agent is that after being ignited, the high-energy expansion agent will quickly generate high-pressure gas to wedge into the original cracks of the rock mass, generating shear stress inside the rock to expand the cracks. While the high-pressure gas forms a gas wedge, the pressure continues to rise. When the set pressure is reached, the agent changes from combustion to detonation, further developing the cracks and performing network-type fracturing and crushing of the rock blocks wrapped between the cracks.

[0013] In this embodiment, Figure 2 As shown, the high-energy expansion agent adopts D type, and the size of the high-energy expansion agent is 30mm×300mm. The amount of gas required for effective pre-cracking of rocks is calculated by the following formula. The ideal gas equation is used to calculate the amount of gas to ensure that the required gas can effectively release energy at a specific pressure and temperature. The calculation formula is: ; Where P is the gas pressure (Pa), V is the gas volume (m 3 ), n is the number of moles of gas (mol), R is the ideal gas constant (8.314 J / (mol·K)), and T is the gas temperature (K); The rock compressive strength σ(Pa) and the predicted fracture volume V1(m 3 ) Calculate the required energy E: ; Substituting the energy E into the combustion equation yields the number of moles n: ; The above formula can be used to derive the formula for the gas volume required to effectively crush rocks: In addition, the test of high-energy expansion agent shows that the average gas production per kg is about 600L, and the dosage of high-energy expansion agent can be determined.

[0014] The mass of each section of high-energy expansion agent is 0.3 kg. In this embodiment, it is preferred to fill 7 / 8 sections in a single hole, that is, the mass of a single hole is 2.1 / 2.4 kg.

[0015] (2) Drilling parameters include fracture hole diameter, hole depth and hole spacing, which are determined as follows: The diameter of the crack hole is based on the stress component expression of a ring or cylinder under uniform pressure in elastic mechanics. The high-energy expansion agent pre-cracking rock mainly overcomes the tensile stress inside the rock by generating gas expansion. Therefore, the tensile stress expression is used, and the calculation formula is: ; in, Refers to the tensile stress calculation equivalent to the tensile strength of the rock measured by geological survey in the early stage. It refers to the uniform pressure generated by the high-energy expansion agent. refers to the formation pressure, r refers to the arbitrary radius, a refers to the radius of the high-energy expansion agent roll, and b refers to the diameter of the fracture hole. Figure 1 ; In general, the diameter of the fissure hole ranges from 35 to 60 mm, and 42 mm is preferred in this embodiment; The design value of the hole depth is determined by the thickness of the rock to be broken and the empirical coefficient. The calculation formula is D=k·R, where D is the hole depth, k is the thickness of the rock to be broken, and R is the empirical coefficient determined according to geological conditions and other factors, usually taking a value of 1.2~1.5; The design values ​​of the hole spacing and hole number are mainly determined by considering the mechanical properties of the rock and the influence range of the high-energy expansion agent. The fracture-causing holes are evenly distributed in the common "plum blossom" spacing arrangement form, such as Figure 3 As shown, the range of the hole spacing L is 1.0~1.5m, and the specific arrangement of the hole spacing needs to be appropriately adjusted in combination with other factors. The number of holes is reasonably arranged according to the cross-sectional size and the hole spacing. Figure 3 As shown, in this embodiment, the distance between holes #1, 2, and 3 is 4.0 m from the upper edge of the step; the distance between holes #1 and 6 is 4.0 m from the side edge; the hole depth is 5 m; and the diameter of the crack-causing hole is 42 mm.

[0016] Step 3: Use a borehole television imager to detect the development of joints and fissures inside the rock mass in the hole, so as to design the filling method of the high-energy expansion agent; In this embodiment, the high-energy expansion agent filling method arranges the expansion agent in the crack joint development section according to the borehole TV imaging, and sets the crack-inducing hole near or in the middle of the main crack, so as to better utilize the advantages of the crack and achieve a more effective crushing effect. Try to avoid setting the explosive hole in the solid part of the solid rock, but should be close to the crack so as to use the crack for crack propagation. Therefore, this construction section derives two filling methods ( Figure 4), where filling method 1 is: high-energy expansion agents are combined in pairs, and there are empty tubes between the high-energy expansion agents in adjacent pairs. The starters are set on the 1st, 3rd, and 6th high-energy expansion agents, respectively, and the last combination is not set with a starter; filling method 2 is: the empty tube is next to the sealing cement section, and the last one is filled with a high-energy expansion agent. The middle part uses high-energy expansion agents in pairs, and there are empty tubes between the high-energy expansion agents in adjacent pairs. The starters are set on the 1st, 3rd, and 6th high-energy expansion agents, respectively. The use of air-interval charging can effectively improve the pre-splitting quality and reduce the amount of expansion agent. Compared with traditional continuous charging, air-interval charging can effectively reduce the scattering of small gravel and dust during pre-splitting, providing a more efficient, environmentally friendly and controllable solution for the pre-splitting process. The specific filling method during construction in other areas should also consider the development of fissures and joints in the hole. The purpose is to make the gas flow more effectively in the original cracks and expand the cracks. The hole is sealed at 1.7m. In this embodiment, 1, 3, 4, and 7# holes are equipped with 8 expansion agents, 3 starters, and 3 30*300mm empty tubes; 2, 5, 6, and 8# holes are equipped with 7 expansion agents, 3 starters, and 3 30*300mm empty tubes.

[0017] Then the hole is sealed and the foot line is connected. The sealing is to mix high-strength quick-setting cement and water in proportion, and then put it into the drill hole and tamp it with a blasting stick after mixing evenly. The specific method should be flexible according to the actual situation. After the hole is sealed, wait for more than 30 minutes to allow the sealing material to fully solidify; the foot line connection adopts parallel connection inside the hole and series connection outside the hole. The triggering operation adopts FD200 coal mine capacitor detonator, connects the busbar, and starts ignition; Step 4: Carry out high-energy expansion agent pre-cracking construction according to the high-energy expansion agent pre-cracking parameters and construction schematic diagram at the entrance and exit of the subway station. Before starting the ignition, it is necessary to confirm that all personnel have evacuated outside the warning area; use a borehole television imager and an acoustic wave detector to evaluate the pre-cracking effect of the high-energy expansion agent; To evaluate the pre-splitting effect, a multifunctional borehole imaging analyzer is used to detect the pre-splitting effect of the cracks in the hole, and the conditions in the hole are monitored and photographed in real time; an acoustic wave detector is used to evaluate the integrity and physical properties of the rock mass after pre-splitting. The propagation speed of the sound wave in the rock mass is closely related to the mechanical properties and crack state of the rock. The development characteristics of the rock mass cracks can be obtained by detecting the wave velocity. The more cracks in the rock mass, the smaller the wave velocity, and vice versa. After the pre-splitting is completed, an excavator is used for processing and slag removal.

[0018] Although the weakening mechanisms of high-energy expansion agent pre-cracking and explosive fracturing are similar, both achieve their effects through the combined action of shock waves, stress waves and explosive gas, but the energy released by the explosion is extremely rapid, and the accompanying shock wave propagates very quickly, so the vibrations excited are usually high-frequency and high-intensity. Relatively speaking, high-energy expansion agents will pre-generate high-pressure gas when they act, promoting the expansion of primary cracks around the borehole. This process helps to reduce the consumption of detonation energy by crushing shock, weaken the inhibitory effect of ground stress on stress wave propagation, and reduce the attenuation rate of stress waves. As a result, high-energy expansion agents can delay the release rate of energy, while reducing vibration intensity and improving the pre-cracking effect.

[0019] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A rapid pre-cracking method suitable for subway station entrances and exits under hard rock geology, characterized in that: The following steps are involved: Step 1: Conduct geological surveys on the areas where the subway station entrances and exits are located to obtain geological survey parameters, and arrange blasting vibration velocity monitors and sound level meters for monitoring in the most susceptible areas according to the surrounding environment; the geological survey parameters include rock tensile strength, compressive strength, elastic modulus and permeability; Step 2: Based on the geological survey parameters of the subway station entrance and exit obtained, the dosage of high-energy expansion agent and drilling parameters are designed, and a drilling layout diagram is drawn; The drilling parameters include the fracture hole diameter, hole spacing and hole depth, which are determined as follows: The crack-causing holes are evenly distributed in a "plum blossom" spacing, with the hole spacing ranging from 1.0 to 1.5 m. The number of holes is reasonably arranged according to the cross-sectional size and hole spacing. The crack-causing hole diameter is determined by the following method: ;in, Refers to tensile stress, which is equivalent to the tensile strength of rock measured by geological survey. It refers to the uniform pressure generated by the high-energy expansion agent. refers to the formation pressure, r refers to the arbitrary radius, a refers to the radius of the high-energy expansion agent roll, and b refers to the diameter of the fracture hole; The hole depth is determined by the following method: D = k·R, where D is the hole depth, k is the thickness of the rock to be broken, and R is an empirical coefficient with a value of 1.2~1.5; Step 3: Use a borehole television imager to detect the development of joints and fissures inside the rock mass in the hole to design the filling method of the high-energy expansion agent; Step 4: Perform high-energy expansion agent pre-cracking construction according to the drilling arrangement and high-energy expansion agent filling method determined in steps 2 and 3, and use a drilling television imager and an acoustic wave detector to evaluate the pre-cracking effect of the high-energy expansion agent.

2. The rapid pre-splitting method for subway station entrances and exits under hard rock geology according to claim 1 is characterized in that: In step 2, the dosage of the high-energy expander is determined in the following manner: the required energy is determined based on the rock compressive strength and the expected fracture volume, and the required number of moles is solved in combination with the combustion equation, and then the gas volume required for effectively crushing the rock is obtained, and then the dosage of the high-energy expander is determined in combination with the gas production of the high-energy expander.

3. The rapid pre-splitting method for subway station entrances and exits under hard rock geology according to claim 1 is characterized in that: In step 3, when the high-energy expansion agent is filled, the expansion agent is arranged in the fissure joint development section according to the borehole television imaging, and the fracture-inducing hole is set near the main fissure or in the middle thereof.

4. The rapid pre-splitting method for subway station entrances and exits under hard rock geology according to claim 2 is characterized in that: In step 3, there are two ways to fill the high energy expansion agent: One of the loading methods is: high-energy expanders are combined in pairs, empty tubes are provided between the high-energy expanders in adjacent pairs, starters are evenly arranged on the high-energy expanders in the pairs, and the last pair is not provided with a starter; Another filling method is: the tube next to the sealing cement section is an empty tube, and the last one is filled with a high-energy expansion agent. The middle part uses high-energy expansion agents in pairs. The empty tubes are between the adjacent pairs of high-energy expansion agents, and the starters are evenly set on the high-energy expansion agents in pairs.

5. The rapid pre-splitting method for subway station entrances and exits under hard rock geology according to claim 1 is characterized in that: In step 1, the blasting vibration velocity monitor and the sound level meter are used for monitoring. If any abnormality is found, the construction is stopped immediately and the charge amount is re-evaluated using the vibration velocity formula: The vibration velocity calculation formula is: , V refers to the vibration velocity at a certain measuring point, K is an empirical constant, W is the effective equivalent of the high-energy expansion agent, and R is the distance from the pre-cracking point to the measuring point. In the abnormal section, the charge is reduced and the pre-cracking footage is shortened to meet the safety standard.

6. The rapid pre-splitting method for subway station entrances and exits under hard rock geology according to claim 1 is characterized in that: In step 4, the pre-cracking effect is evaluated by using a multifunctional borehole imaging analyzer to detect the pre-cracking effect of the cracks in the hole, and real-time monitoring and photography of the hole conditions; and an acoustic wave detector is used to evaluate the integrity and physical properties of the rock mass after pre-cracking.

7. The rapid pre-splitting method for subway station entrances and exits under hard rock geology according to claim 1 is characterized in that: In step 2, the diameter of the fissure hole ranges from 35 mm to 60 mm.

8. The rapid pre-splitting method for subway station entrances and exits in hard rock geology according to claim 1 is characterized in that: The high-energy expansion agent is of D type, and the size of the high-energy expansion agent is 30mm×300mm.

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