Empty hole guide back break control blasting construction method for peripheral holes of weak surrounding rock tunnel

Abstract

The invention discloses a weak surrounding rock tunnel peripheral hole empty hole guide back break control blasting construction method. The method comprises the steps that the surrounding rock grade and the blasting circulation footage are determined; designing tunnel peripheral hole hollow guide drilling blasting parameters, and determining peripheral hole pitch and explosive load; performing drilling operation; after drilling of the rock drilling equipment is completed, hole-separated charging is carried out on the peripheral holes, and the distance L between the charging peripheral holes and the non-charging empty holes is preliminarily calculated by analyzing the stress state, the impact pressure and the failure criterion of rock; according to the distance L, non-charging empty holes are formed between the charging peripheral holes; after safety alert is ensured, blasting is carried out; the steps are repeated until the tunnel blasting back break value reaches the expected standard, the optimal tunnel peripheral hole hollow guide drilling blasting parameters can be determined, and construction is conducted according to the optimal parameters; over-excavation and under-excavation can be effectively controlled, the situations of block falling of weak surrounding rock and the like are effectively reduced, and the safety and working efficiency of follow-up construction operation are improved.

Description

Technical Field

[0001] This patent belongs to the field of tunnel engineering blasting technology, and specifically refers to a method for controlled blasting construction with empty holes and guided over- and under-excavation around soft surrounding rock tunnels. Background Art

[0002] At present, drilling and blasting is still the main construction method for tunnel excavation. However, during the tunnel blasting excavation in soft rock strata, due to the poor mechanical properties of the surrounding rock, the quality of the excavation contour surface is often poor, resulting in over-excavation and under-excavation. This not only seriously affects the construction progress and increases production costs, but also has a serious impact on the stability of the tunnel support structure system and even endangers the lives of construction workers.

[0003] At present, the key to controlling over-excavation and under-excavation in tunnel blasting is to reduce the external insertion angle of the peripheral holes and improve the smoothness of the cracks between the peripheral holes. Reducing the external insertion angle of the peripheral holes is mainly to improve the drilling accuracy, while improving the smoothness of the cracks between the peripheral holes is closely related to the peripheral hole drilling parameters and charge structure. At present, changing the charge structure of the peripheral holes, such as using shaped charge packs and slit charge packs, is not only complicated to operate but also greatly increases the cost of blasting excavation. Summary of the invention

[0004] The present invention aims to solve the problem that the method for controlling over-excavation and under-excavation in tunnel blasting excavation in the prior art is complicated to operate and greatly increases the cost of blasting excavation.

[0005] The present invention adopts the following scheme: a method for controlled blasting construction of peripheral holes and empty holes in soft surrounding rock tunnels, comprising the following steps:

[0006] S1. Determine the surrounding rock grade and blasting cycle footage based on the tunnel geological survey report and advanced geological forecast data of the tunnel face;

[0007] S2. Based on the tunnel surrounding rock grade, design the hollow guide drilling blasting parameters of the tunnel peripheral holes, determine the peripheral hole spacing and charge amount: the peripheral charge hole spacing is selected to be 5-20 times the blasthole diameter, the charge amount is determined according to the surrounding rock grade, and the peripheral charge holes are installed with the same section of detonators to ensure simultaneous detonation;

[0008] S3. Based on the hollow guide drilling and blasting parameters of the tunnel periphery holes, a blasthole layout diagram is drawn using the blasthole design software built into the mobile computer of the rock drilling equipment, and the blasthole layout diagram is uploaded to the rock drilling equipment operating device; the rock drilling equipment operator performs drilling operations according to the blasthole layout diagram;

[0009] S4. After the drilling equipment has completed drilling, the peripheral holes are charged with charges in separate holes, and the spacing L between the charged peripheral holes and the uncharged holes is preliminarily calculated by analyzing the stress state, impact pressure and failure criterion of the rock; referring to the spacing L, uncharged holes are arranged between the charged peripheral holes, so as to achieve the purpose of guiding the explosion cracks between the peripheral holes to expand in a directional manner;

[0010] S5. After testing the blast hole charging operation on the face, the detonators are connected to the network, and after ensuring safety alert, blasting is carried out;

[0011] S6. According to the tunnel blasting effect and the drilling log of the rock drilling equipment, the peripheral hole spacing and the charge amount are dynamically adjusted. On this basis, the tunnel peripheral hole hollow guide drilling blasting parameters are updated, and steps S3 to S5 are repeated until the tunnel blasting over-break and under-break values ​​reach the expected standards. The optimal tunnel peripheral hole hollow guide drilling blasting parameters matching the soft surrounding rock can be determined, and construction is carried out according to the optimal tunnel peripheral hole hollow guide drilling blasting parameters.

[0012] Furthermore, in step S3, the rock drilling equipment operator performs drilling operations according to the blasthole layout diagram and when drilling the peripheral holes of the tunnel, the peripheral hole external insertion angle is 2.5° to 7.5°.

[0013] Furthermore, in step S4, since the rock at the arch foot is difficult to blast out, the angle of the bottom plate hole of the arch foot will be slightly biased downward. In order to ensure that the side wall above the arch foot is not under-excavated, during the charging process of the outermost peripheral holes at the arch foot, the first peripheral hole of the arch foot on one side should be used as the charging hole 6, the second hole as the guide hole 7, and so on, until the peripheral holes of the arch foot on the other side are reached; the other slotted holes and auxiliary holes are charged normally.

[0014] Furthermore, in step S6, the principle of dynamically adjusting the peripheral hole spacing and charge amount is: when the surrounding rock blasting over-excavation value is large, the peripheral charge hole spacing is increased or the charge amount is reduced; when the surrounding rock blasting under-excavation occurs, the peripheral charge hole spacing is reduced or the charge amount is increased.

[0015] Furthermore, the method of analyzing the stress state, impact pressure and failure criterion of the rock in step S4 to preliminarily calculate the distance L between the charge peripheral holes and the uncharged empty holes includes:

[0016] (1) Establish radial stress, tangential stress and shear stress models considering the guide hole to conduct stress analysis;

[0017]

[0018] In the above formula, k = r B / r′,r B is the hole radius, r' is the distance from the rock particle to the hole center. r , σθ are the radial stress and tangential stress at a certain point in the rock respectively; σ rr is the radial stress after stress concentration occurs in the guide hole, MPa; σ θθ is the tangential stress after the guide hole generates stress concentration, MPa; τ rθ is the shear stress after stress concentration occurs in the guide hole, MPa; θ is the angle formed by the rock particle, the explosive hole and the empty hole.

[0019] (2) Calculate the impact pressure of particles on the wall of the empty hole and the blasthole wall when the charge is not coupled, and establish the failure criterion of rock failure conditions;

[0020] (3) Combined with the stress analysis and failure criteria in (1) and (2), the distance L between the charge hole and the empty hole is calculated;

[0021] Furthermore, the method for calculating the impact pressure of the particle on the wall of the empty hole and the blasthole wall when the charge is not coupled and establishing the failure criterion of the rock failure condition is specifically as follows:

[0022] In formula 2, when θ=0 or θ=180°, the radial stress, tangential stress and shear stress are at their maximum values. In the actual drilling process, the diameters of the empty hole and the charged hole are generally the same. Therefore, when the particle is on the wall of the empty hole, k=r B / r′=1, then σ rr =0,τ rθ =0,σ θθ =3σ θ +σ r ,Depend on θ=0, then we know that the maximum tensile stress appears on the line connecting the two blast holes. According to the blasting principle, when uncoupled charge is used, the impact pressure on the blast hole wall is:

[0023]

[0024] Where: ρ0 is the density of explosive; D is the detonation velocity of explosive; d c ,d b are respectively the diameter of the cartridge and the diameter of the blast hole; n is the pressure increase coefficient of the detonation products impacting the blast hole wall.

[0025] The rock is under tangential tensile stress σ θ Under the action of θ ≥S td , S td is the dynamic tensile strength of rock.

[0026] Furthermore, the method for calculating the distance L between the charge hole and the empty hole by combining the stress analysis and the failure criteria in (1) and (2) is as follows:

[0027] The minimum tensile stress failure criterion is used for the rock particle failure in the area between the charge hole and the empty hole. At the same time, the dynamic tensile strength value of the rock is used in this criterion. Among them, the radius of the fracture zone r k The calculation formula of the distance L between the charging hole and the empty hole is:

[0028]

[0029] 2r B P b =(L-2r k )S td (Formula 6)

[0030] Where: P a For explosion pressure, D i is the ideal detonation velocity of the explosive; P b is the quasi-static pressure when the explosion gas fills the blast hole; r B is the hole radius; V c V is the charge volume; b is the blasthole volume; k is the adiabatic index of the condensed explosive, which is taken as 1.4; h is the isentropic index of the condensed explosive, which is taken as 3; P k is the critical pressure of the explosion gas expansion process, approximately 100 MPa, a is the stress wave attenuation index, b is the ratio of tangential stress to radial stress, v is Poisson's ratio.

[0031] Furthermore, the rock drilling equipment is a rock drilling trolley.

[0032] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0033] (1) The method for controlling over-excavation and under-excavation by empty-hole guidance in the peripheral holes of a tunnel with weak surrounding rock of the present invention makes full use of the guiding effect of the empty holes on the blasting cracks in the peripheral holes, effectively controls the expansion and penetration of the blasting cracks between the peripheral holes along the center line connecting the blast holes, thereby improving the flatness of the tunnel blasting excavation contour surface, effectively controlling over-excavation and under-excavation while reducing the amount of explosives and detonators used in the peripheral holes, and reducing the disturbance of the blasting excavation to the surrounding rock, effectively reducing the falling of soft surrounding rocks, etc., improving the safety and work efficiency of subsequent construction operations, and being able to effectively save costs and shorten the construction period.

[0034] (2) The soft soil roadbed settlement observation device and settlement observation control method of the present invention preliminarily calculates the distance L between the charged peripheral holes and the uncharged empty holes, and dynamically adjusts the peripheral hole spacing and the charge amount according to the blasting effect of the previous cycle and the drilling log of the rock drilling equipment. On this basis, the tunnel peripheral hole hollow guide drilling blasting parameters are updated, and the blasthole layout diagram is re-imported into the rock drilling equipment for drilling and blasting construction until the tunnel blasting over-excavation and under-excavation value reaches the expected standard. The optimal tunnel peripheral hole hollow guide drilling blasting parameters matching the soft surrounding rock can be determined, thereby improving the efficiency of obtaining the optimal tunnel peripheral hole hollow guide drilling blasting parameters.

[0035] (3) The soft soil roadbed settlement observation device and settlement observation control method of the present invention adopts a rock drilling rig to perform drilling operations, which can reduce the number of drilling operators from more than 10 to 2-3 people, effectively saving manpower and improving drilling efficiency, and can ensure the drilling accuracy of the surrounding hole layout position and spacing and the uniformity of the external insertion angle. At the same time, it can effectively avoid the risk of block falling on the face when manually drilling holes in soft surrounding rocks, thereby improving the safety of tunnel drilling operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the external insertion angle of a preferred embodiment of the invention;

[0037] Figure 2 A schematic diagram of peripheral hole charging in a preferred embodiment of the invention;

[0038] 1. Palm face, 2. Blast hole, 3. External insertion angle, 4. Designed excavation contour line, 5. Over-excavation area, 6-Charging hole, 7-Guide hole. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Please refer to Figure 1 The present invention relates to a method for controlled blasting construction of a peripheral hole and empty hole guided over-break and under-break in a soft surrounding rock tunnel, comprising the following steps:

[0041] S1. Determine the surrounding rock grade and blasting cycle footage based on the tunnel geological survey report and advanced geological forecast data of the tunnel face;

[0042] S2. Based on the tunnel surrounding rock grade, design the hollow guide drilling blasting parameters of the tunnel peripheral holes, determine the peripheral hole spacing and charge amount: the peripheral charge hole spacing is selected to be 5-20 times the blasthole diameter, the charge amount is determined according to the surrounding rock grade, and the peripheral charge holes are installed with the same section of detonators to ensure simultaneous detonation;

[0043] S3. Based on the hollow guide drilling and blasting parameters of the tunnel periphery holes, a blasthole layout diagram is drawn using a built-in blasthole design software on a mobile computer of a rock drilling equipment (preferably a rock drilling trolley), and the blasthole layout diagram is uploaded to a rock drilling equipment operating device; the rock drilling equipment operator performs drilling operations according to the blasthole layout diagram;

[0044] The rock drilling equipment operator performs drilling operations according to the blasthole layout diagram and tries to reduce the external insertion angle of the peripheral holes as much as possible when drilling the peripheral holes of the tunnel. The soft surrounding rock section of the tunnel constructed by the drilling and blasting method needs to be closed as soon as possible. The initial support is close to the heading face 1, which will limit the drilling angle of the three-arm rock drilling rig drill arm, making it impossible for the drill rod to drill the peripheral holes on the designed excavation contour line at a zero-degree external insertion angle. Therefore, a certain angle of external insertion angle 3 will inevitably be generated, resulting in over-excavation. The external insertion angle is a key factor affecting over-excavation. If the external insertion angle is too large, the charge roll at the bottom of the blasthole 2 is far from the designed excavation contour line 4, and the over-excavation volume 5 is large, which significantly increases the initial support concrete backfill volume and increases the support cost. At the same time, the local excavation of the surrounding rock will cause stress concentration problems and reduce the stability and bearing capacity of the surrounding rock. Therefore, a suitable external insertion angle is of great significance for controlling over-excavation and under-excavation.

[0045] like Figure 1 As shown in the figure, there is a certain relationship between over-break depth, offset distance, blasthole depth and external insertion angle, that is, the formula for over-break depth is as follows:

[0046] h=ltanα (Formula 1)

[0047] Where: h is the over-excavation depth; l is the blasthole depth; α is the external insertion angle.

[0048] According to the actual situation of on-site construction, by reserving operating space between the primary support and the face, the external insertion angle α is generally taken as 2.5°~7.5°.

[0049] S4. After the drilling equipment completes the drilling, the peripheral holes are charged in separate holes, and the spacing L between the charged peripheral holes and the uncharged holes is preliminarily calculated by analyzing the stress state, impact pressure and failure criterion of the rock; referring to the spacing L, uncharged holes are arranged between the charged peripheral holes to achieve the purpose of guiding the directional expansion of the explosive cracks between the peripheral holes with the empty holes as the preferred solution. Because the rock at the arch foot is more difficult to blast out, the angle of the bottom plate hole of the arch foot will be slightly downward. In order to ensure that the side wall above the arch foot is not under-dug, during the charging process of the outermost peripheral holes at the arch foot, the first peripheral hole of one side of the arch foot should be used as the charging hole 6, and the second hole as the guiding empty hole 7, and so on, until the peripheral holes of the other side of the arch foot are reached; the other slotted holes and auxiliary holes are charged normally.

[0050] S5. After testing the blast hole charging operation on the face, the detonators are connected to the network, and after ensuring safety alert, blasting is carried out;

[0051] S6. According to the tunnel blasting effect and the drilling log of the rock drilling equipment, dynamically adjust the peripheral hole spacing and charge amount (the dynamic adjustment principle is: when the surrounding rock blasting over-excavation value is large, increase the peripheral charge hole spacing or reduce the charge amount; when the surrounding rock blasting under-excavation occurs, reduce the peripheral charge hole spacing or increase the charge amount). On this basis, update the tunnel peripheral hole hollow guide drilling blasting parameters, and repeat steps S3 to S5 until the tunnel blasting over-excavation and under-excavation value reaches the expected standard. The optimal tunnel peripheral hole hollow guide drilling blasting parameters matching the weak surrounding rock can be determined, and construction is carried out according to the optimal tunnel peripheral hole hollow guide drilling blasting parameters.

[0052] As a preferred solution, in order to facilitate unified construction and reduce operation costs, the diameter of the empty hole without charge in step S4 is taken to be the same as that of the surrounding holes.

[0053] As a preferred solution, in some embodiments, the method of analyzing the stress state, impact pressure, and failure criterion of the rock in step S4 to preliminarily calculate the distance L between the charge peripheral holes and the uncharged empty holes includes:

[0054] (1) Establish radial stress, tangential stress and shear stress models considering the guide hole to conduct stress analysis;

[0055]

[0056] In the above formula, k = r B / r′,r B is the hole radius, r' is the distance from the rock particle to the hole center; σ r , σ θ are the radial stress and tangential stress at a certain point in the rock respectively; σ rr is the radial stress after stress concentration occurs in the guide hole, MPa; σ θθis the tangential stress after the guide hole generates stress concentration, MPa; τ rθ is the shear stress after stress concentration occurs in the guide hole, MPa; θ is the angle formed by the rock particle, the explosive hole and the empty hole.

[0057] (2) Calculate the impact pressure of particles on the wall of the empty hole and the blasthole wall when the charge is not coupled, and establish the failure criterion of rock failure conditions;

[0058] (3) Combined with the stress analysis and failure criteria in (1) and (2), the distance L between the charge hole and the empty hole is calculated;

[0059] The method for calculating the impact pressure of the particle on the wall of the empty hole and the uncoupled charge and establishing the failure criterion of the rock failure condition is specifically as follows:

[0060] In formula 2, when θ=0 or θ=180°, the radial stress, tangential stress and shear stress are at their maximum values. In the actual drilling process, the diameters of the empty hole and the charged hole are generally the same. Therefore, when the particle is on the wall of the empty hole, k=r B / r′=1, then σ rr =0,τ rθ =0,σ θθ =3σ θ +σ r ,Depend on θ=0, then we know that the maximum tensile stress appears on the line connecting the two blast holes. According to the blasting principle, when uncoupled charge is used, the impact pressure on the blast hole wall is:

[0061]

[0062] Where: ρ0 is the density of explosive; D is the detonation velocity of explosive; d c ,d b are respectively the diameter of the cartridge and the diameter of the blast hole; n is the pressure increase coefficient of the detonation products impacting the blast hole wall.

[0063] The rock is under tangential tensile stress σ θ Under the action of θ ≥S td , S td is the dynamic tensile strength of rock.

[0064] The method for calculating the distance L between the charge hole and the empty hole by combining the stress analysis and failure criteria in (1) and (2) is as follows:

[0065] The minimum tensile stress failure criterion is used for the rock particle failure in the area between the charge hole and the empty hole. At the same time, the dynamic tensile strength value of the rock is used in this criterion. Among them, the radius of the fracture zone r k The calculation formula of the distance L between the charging hole and the empty hole is:

[0066]

[0067] 2r b P b =(L-2r j )S td (Formula 6)

[0068] Where: P a For explosion pressure, D i is the ideal detonation velocity of the explosive; P b is the quasi-static pressure when the explosion gas fills the blast hole; r B is the hole radius; V c V is the charge volume; b is the blasthole volume; k is the adiabatic index of the condensed explosive, which is taken as 1.4; h is the isentropic index of the condensed explosive, which is taken as 3; P k is the critical pressure of the explosion gas expansion process, approximately 100 MPa, a is the stress wave attenuation index, b is the ratio of tangential stress to radial stress, v is Poisson's ratio.

[0069] Taking the application of Yinjiayan Tunnel YK5+720~YK5+970, YK5+970~YK6+640 in the LXLX-1 section of Lichuan to Xianfeng Expressway as an example, the surrounding rock of this mileage section of the tunnel is Grade IV, mainly composed of medium-weathered sandstone and shale. During the blasting excavation process, the tunnel adopts the construction method of full-section mechanical excavation. However, since the Grade IV surrounding rock is mainly composed of medium-weathered sandstone and shale, the rock mass is relatively broken, and joints and fissures are developed, the early blasting effect is not very ideal. Therefore, a method of over-excavation controlled blasting construction with empty holes around soft surrounding rock tunnels based on a rock drilling trolley is proposed in this method, which is applied to the tunnel blasting construction operation in the soft surrounding rock section of this tunnel.

[0070] In the early stage, based on the use of PMMA as the model test material, single-shot electronic detonator as the explosion source, and the charge uncoupling coefficient and the spacing between the surrounding charge holes as variables, the tunnel peripheral hole empty hole guided double hole detonation model test was carried out. The model test results show that when the uncoupling coefficient is 1.5 and the hole spacing is 13D, the explosion cracks between the peripheral holes are the smoothest and the penetration effect is the best. At this time, the corresponding calculation formulas for the hole diameter, hole spacing, and charge amount of the tunnel peripheral holes are:

[0071] D=1.5d, E=13D, Q=qEWl;

[0072] In the formula, D is the diameter of the peripheral hole, d is the diameter of the cartridge, E is the hole distance, Q is the charge, q is the unit consumption of explosives, W is the thickness of the light explosion layer, and l is the depth of the blasthole. The calculation results are shown in Table 1.

[0073] Table 1 Parameters of empty hole guided blasting of initial peripheral holes of tunnel

[0074]

[0075] The blasting parameters shown in Table 1 are selected as the initial peripheral hole blasting parameters for the IV grade surrounding rock section of Yinjiayan Tunnel. During the drilling and charging process, an empty hole, i.e., a guide hole, is arranged between the two charged peripheral holes. The guide hole is not charged. At the same time, in order to minimize the impact on the on-site drilling progress, the diameter of the empty hole is set to be the same as the diameter of the charging hole.

[0076] After blasting excavation using the above tunnel initial peripheral hole empty hole guided blasting parameters, it was found that although the over-excavation situation was improved compared with the previous scheme, and the average over-excavation value was reduced from 50cm to 30cm, compared with the use of PMMA material, the joints and fissures in the IV-level surrounding rock were developed, so the flatness of the blasting excavation profile surface was insufficient. Therefore, based on the blasting effect of this cycle and the drilling log of the rock drilling rig, the blasting technicians analyzed the flatness of the blasting excavation profile surface, the over-excavation and under-excavation of the arch crown, the arch waists on both sides and the arch foot;

[0077] When the dynamic tensile strength of the rock is consistent with the tensile strength near the empty hole, the crushing area is the largest, the cracks in the hole wall are fully initiated and expanded, the cracks between the empty hole and the charge hole are interconnected, and the explosives are used most efficiently. According to the above formulas (4), (5), and (6), it can be calculated that the spacing between the empty hole and the charge hole is about 350 mm. However, the weak surrounding rock has developed joints and fissures, and the area of ​​damage to the surrounding rock by explosives is larger. Therefore, when the amount of charge in the surrounding charge holes remains unchanged, the hole spacing of the surrounding charge holes is adjusted to 75 cm and 85 cm respectively. By comparing and analyzing the blasting effect, it is found that under the condition of using the hole spacing of 85 cm for the surrounding charge holes, some areas of the tunnel blasting excavation contour surface are under-excavated, which increases the time for subsequent processing procedures. By adopting a peripheral charging hole spacing of 75cm, the average over-excavation and under-excavation value of the tunnel continued to decrease to 18cm. At the same time, the blasting cracks between the peripheral holes basically extended and penetrated along the center line of the blast holes. The blasting excavation contour surface was relatively smooth and the blasting effect was relatively good. Therefore, a peripheral charging hole spacing of 75cm was selected for the subsequent Yinjiayan Tunnel peripheral hole empty hole guided over-excavation and under-excavation controlled blasting construction, which effectively controlled the tunnel blasting over-excavation value and reduced the amount of initial support shotcrete.

[0078] The operation process of this method is simple and easy. Through on-site construction practice, the blasting effects of this method and conventional tunnel blasting methods are compared and analyzed. As shown in Table 2, it can be found that this construction method can reduce the amount of initial shotcrete and operation time while controlling the over-excavation and under-excavation effects. It can also reduce the disturbance of blasting excavation to soft surrounding rocks, effectively reduce the phenomenon of surrounding rock falling, improve the safety of subsequent construction operations, and effectively save costs and shorten the construction period.

[0079] Table 2 Comparison of conventional process and hole-guided process controlled blasting

[0080] category Average over-excavation / cm <![CDATA[Initial shotcrete consumption / m 3 > Drilling time / h Single cycle construction time / h Conventional process 50 60 4 24 Hole Guiding Process 18 40 3.5 20

[0081] At the same time, this method has obvious economic benefits. Taking the application of Yinjiayan Tunnel YK5+720~YK5+970, YK5+970~YK6+640 of LXLX-1 section of Lichuan to Xianfeng Expressway as an example, this method has significant economic benefits after trial. The average linear over-excavation volume is controlled from 50cm to 18cm, and the occurrence of falling blocks is greatly reduced, with less damage to the surrounding rock. The initial spraying concrete consumption per cycle is 60m 3 Reduced to 40m3 per cycle 3 , reduced by 33%. At the same time, the single-cycle excavation time was reduced from 24h to 20h, which can effectively shorten the construction period.

[0082] This patent provides a method for controlling over-excavation and under-excavation of tunnels with soft surrounding rocks by guiding empty holes in the surrounding holes of a rock drilling trolley. This method is based on the rock drilling trolley and combined with the empty hole guiding controlled blasting construction technology. It can make full use of the advantages of the rock drilling trolley with fast drilling speed, high precision, high quality, and the ability to dynamically adjust the hole layout parameters, and effectively control the over-excavation and under-excavation of tunnels with soft surrounding rocks. The empty hole guiding over-excavation and under-excavation controlled blasting construction technology mainly makes full use of the guiding effect of empty holes on the cracks generated by blasting in the surrounding holes, effectively controls the expansion and penetration of the cracks generated by blasting between the surrounding holes along the center line of the blastholes, thereby improving the flatness of the tunnel blasting excavation contour surface, effectively controlling over-excavation and under-excavation while reducing the amount of explosives and detonators used in the surrounding holes, and reducing the disturbance of blasting excavation to the surrounding rock, effectively reducing the falling of soft surrounding rocks, etc., improving the safety and work efficiency of subsequent construction operations, and can effectively save costs and shorten construction period.

[0083] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0084] This method is based on rock drilling equipment and combined with the peripheral hole empty hole guided controlled blasting construction technology. It can make full use of the advantages of rock drilling equipment with fast drilling speed, high precision and high quality, and can drill holes strictly according to the design, effectively controlling the over-excavation and under-excavation of soft surrounding rock tunnel surrounding rock. The tunnel peripheral hole empty hole guided over-excavation and under-excavation controlled blasting construction technology fully utilizes the guiding effect of the guide empty hole on the cracks generated by the explosion of the peripheral hole. An uncharged empty hole with the same aperture as the peripheral hole is arranged in the middle of the center line of the adjacent charge peripheral holes, and the length of the empty hole is equal to that of the peripheral hole. Due to the existence of the guide hole, from a macroscopic point of view, it is equivalent to adding a certain area of ​​free surface near the charge hole, so that the energy of the explosive is released to it; from a microscopic point of view, due to the existence of the guide empty hole, the stress concentration near the charge hole is changed, so that the microcracks at the center line of the blast hole of the guide empty hole wall are cracked first, and quickly expand through to the charge hole. By using the guiding effect of the empty holes on the blast cracks, the expansion direction of the blast cracks between the surrounding holes can be controlled, making the tunnel contour after blasting smoother and effectively controlling the over-excavation and under-excavation phenomenon. At the same time, due to the existence of the empty holes without charge, the use of explosives, detonators and other pyrotechnics and the number of surrounding holes that workers need to charge can be reduced, reducing the cost of blasting excavation and speeding up the charging efficiency, improving the safety and work efficiency of subsequent construction operations, and effectively saving costs and shortening construction periods.

[0085] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlled blasting construction of peripheral holes and empty holes in soft surrounding rock tunnels, characterized in that: The steps include: S1. Determine the surrounding rock grade and blasting cycle footage based on the tunnel geological survey report and advanced geological forecast data of the tunnel face; S2. Based on the tunnel surrounding rock grade, design the hollow guide drilling blasting parameters of the tunnel peripheral holes, determine the peripheral hole spacing and charge amount: the peripheral charge hole spacing is selected to be 5-20 times the blasthole diameter, the charge amount is determined according to the surrounding rock grade, and the peripheral charge holes are installed with the same section of detonators to ensure simultaneous detonation; S3. Based on the hollow guide drilling and blasting parameters of the tunnel periphery holes, a blasthole layout diagram is drawn using the blasthole design software built into the mobile computer of the rock drilling equipment, and the blasthole layout diagram is uploaded to the rock drilling equipment operating device; the rock drilling equipment operator performs drilling operations according to the blasthole layout diagram; S4. After the drilling equipment has completed drilling, the peripheral holes are charged with charges, and the spacing L between the charged peripheral holes and the uncharged empty holes is preliminarily calculated by analyzing the stress state, impact pressure and failure criterion of the rock; Referring to the spacing L, arrange the empty holes without charge between the holes around the charge; S5. After testing the blast hole charging operation on the face, the detonators are connected to the network, and after ensuring safety alert, blasting is carried out; S6. According to the tunnel blasting effect and the drilling log of the rock drilling equipment, the peripheral hole spacing and the charge amount are dynamically adjusted. On this basis, the tunnel peripheral hole hollow guide drilling blasting parameters are updated, and steps S3 to S5 are repeated until the tunnel blasting over-break and under-break values ​​reach the expected standards. The optimal tunnel peripheral hole hollow guide drilling blasting parameters matching the soft surrounding rock can be determined, and construction is carried out according to the optimal tunnel peripheral hole hollow guide drilling blasting parameters.

2. The method for controlled blasting construction of peripheral holes of soft surrounding rock tunnels according to claim 1 is characterized by: In step S3, the rock drilling equipment operator performs drilling operations according to the blasthole layout diagram and when drilling the peripheral holes of the tunnel, the peripheral hole external insertion angle is 2.5° to 7.5°.

3. The method for controlled blasting construction of peripheral holes of soft surrounding rock tunnels guided by empty holes with over-break and under-break according to claim 1 is characterized by: In step S4, the diameter of the empty hole without charge is the same as that of the surrounding holes.

4. The method for controlled blasting construction of peripheral holes of soft surrounding rock tunnels according to claim 1 is characterized by: In step S4, since the rock at the arch foot is difficult to blast out, the angle of the bottom plate hole of the arch foot will be slightly biased downward. In order to ensure that the side wall above the arch foot is not under-excavated, during the charging process of the outermost peripheral holes at the arch foot, the first peripheral hole of the arch foot on one side should be used as the charging hole, the second hole as the guide hole, and so on, until the peripheral holes of the arch foot on the other side are reached; the other slotted holes and auxiliary holes are charged normally.

5. The method for controlled blasting construction of peripheral holes of soft surrounding rock tunnels guided by empty holes with over-under excavation according to claim 1 is characterized by: In step S6, the principle of dynamically adjusting the peripheral hole spacing and charge amount is: when the surrounding rock blasting over-excavation value is large, the peripheral charge hole spacing is increased or the charge amount is reduced; when the surrounding rock blasting under-excavation occurs, the peripheral charge hole spacing is reduced or the charge amount is increased.

6. The method for controlled blasting construction of peripheral holes of soft surrounding rock tunnels guided by empty holes with over-under excavation according to claim 1 is characterized by: The method for analyzing the stress state, impact pressure and failure criterion of the rock in step S4 to preliminarily calculate the distance L between the charge peripheral holes and the uncharged empty holes includes: (1) Establish radial stress, tangential stress and shear stress models considering the guide hole to conduct stress analysis; In the above formula, k = r B / r′,r B is the hole radius, r' is the distance from the rock particle to the hole center; σ r , σ θ are the radial stress and tangential stress at a certain point in the rock respectively; σ rr is the radial stress after stress concentration occurs in the guide hole, MPa; σ θθ is the tangential stress after the guide hole generates stress concentration, MPa; τ rθ is the shear stress after stress concentration occurs in the guide hole, MPa; θ is the angle formed by the rock particle, the explosive hole and the empty hole. (2) Calculate the impact pressure of particles on the wall of the empty hole and the blasthole wall when the charge is not coupled, and establish the failure criterion of rock failure conditions; (3) Combining the stress analysis and failure criteria in (1) and (2), the distance L between the charge hole and the empty hole is calculated.

7. The method for controlled blasting construction of peripheral holes of soft surrounding rock tunnels according to claim 6 is characterized by: The method for calculating the impact pressure of the particle on the wall of the empty hole and the uncoupled charge and establishing the failure criterion of the rock failure condition is specifically as follows: In formula 2, when θ = 0 or θ = 180°, the radial stress, tangential stress and shear stress are at their maximum values. In the actual drilling process, the diameters of the empty hole and the charged hole are the same. Therefore, when the particle is on the wall of the empty hole, k = r B / r′=1, then σ rr =0,τ rθ =0,σ θθ =3σ θ +σ r ,Depend on It is obtained that θ = 0, and it can be known that the maximum tensile stress appears on the line connecting the two blastholes; according to the blasting principle, when uncoupled charge is used, the impact pressure P2 on the blasthole wall is: Where: ρ0 is the density of explosive; D is the detonation velocity of explosive; d c ,d b are respectively the diameter of the cartridge and the diameter of the blast hole; n is the pressure increase coefficient of the detonation products impacting the blast hole wall. The rock is under tangential tensile stress σ θ Under the action of θ ≥S td , S td is the dynamic tensile strength of rock.

8. The method for controlled blasting construction of peripheral holes and empty holes in soft surrounding rock tunnels according to claim 7 is characterized by: The method for calculating the distance L between the charge hole and the empty hole by combining the stress analysis and failure criteria in (1) and (2) is as follows: The minimum tensile stress failure criterion is used for the rock particle failure in the area between the charge hole and the empty hole. At the same time, the dynamic tensile strength value of the rock is used in this criterion. Among them, the radius of the fracture zone r k The calculation formula of the distance L between the charging hole and the empty hole is: 2r B P b =(L-2r k )S td (Formula 6) Where: P a For explosion pressure, D i is the ideal detonation velocity of the explosive; P b is the quasi-static pressure when the explosion gas fills the blast hole; r B is the hole radius; V c V is the charge volume; b is the blasthole volume; k is the adiabatic index of the condensed explosive, which is taken as 1.4; h is the isentropic index of the condensed explosive, which is taken as 3; P k is the critical pressure of the explosion gas expansion process, approximately 100 MPa, a is the stress wave attenuation index, b is the ratio of tangential stress to radial stress, V is Poisson's ratio.

9. The method for controlled blasting construction by empty hole guidance over-break and under-break of peripheral holes in soft surrounding rock tunnels according to any one of claims 1 to 8, characterized in that: The rock drilling equipment is a rock drilling trolley.

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