Excavation method for brittle rock body rock wall crane beam forming under high ground stress condition

Abstract

The invention belongs to the technical field of rock wall crane beam construction, and particularly relates to an excavation method for brittle rock body rock wall crane beam forming under the high ground stress condition. According to the excavation method for forming the fragile rock wall crane beam under the high ground stress condition, excavation parameters are provided in real time by establishing a refined finite element model of rock mass near an excavation area, and in an expected range, a primary damage area and a secondary damage area in a protective layer are controlled within the expected range, so that the contour of the rock wall crane beam is drawn, and the rock wall crane beam is formed. The rock wall crane beam is formed, so that the excavation difficulty of the rock wall crane beam is reduced, and the forming quality of the rock wall crane beam is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rock wall crane beam construction, and particularly relates to an excavation method for forming a rock wall crane beam in brittle rock mass under high ground stress conditions. BACKGROUND

[0002] With the development of hydropower underground engineering in the southwest region of China, the hydropower underground engineering is expanding to 3000-meter-level buried depth tunnels; among them, the underground cavern groups are located in high ground stress geological environment; under high ground stress conditions, brittle rock strata often have different degrees of rock slab cracking, peeling and falling, and other damage phenomena during excavation.

[0003] The rock wall crane beam is a support structure fixed on the rock wall, mainly used for installing and operating the crane equipment, and plays an important role in hydropower underground engineering;

[0004] However, the excavation of the rock wall crane beam is difficult, and the forming quality is difficult to control, and under high ground stress conditions, the difficulty of the excavation of the rock wall crane beam increases sharply.

[0005] Therefore, it is necessary to provide an excavation method for forming a rock wall crane beam in brittle rock mass under high ground stress conditions. SUMMARY

[0006] The present application provides an excavation method for forming a rock wall crane beam in brittle rock mass under high ground stress conditions, to solve the technical problem of high difficulty in the excavation of the rock wall crane beam under high ground stress conditions in the prior art.

[0007] To solve the above problems, the present application realizes the following technical scheme:

[0008] An excavation method for forming a rock wall crane beam in brittle rock mass under high ground stress conditions, comprising the following steps:

[0009] S1: establishing a finite element model of the rock mass near the excavation area, obtaining the ground stress data of the rock mass near the excavation area, and inverting the ground stress of the finite element model through the obtained ground stress data of the nearby rock mass;

[0010] S2: establishing a refined finite element model of the rock mass near the excavation area, calculating the distribution of the ground stress field of the refined finite element model through the inversion results of the ground stress of the finite element model;

[0011] S3: according to the distribution of the ground stress field of the refined finite element model, excavating the upper region above the rock wall crane beam elevation in the excavation area, dynamically determining the excavation parameters in the excavation process of the upper region, and inputting the obtained excavation parameters into the refined finite element model to improve the refined finite element model; wherein the excavation parameters include the lithology and macroscopic mechanical parameters of the rock mass near the upper region;

[0012] S4: divide the excavation area into n sub-zones along the longitudinal axis direction of the cavern; wherein n≥1;

[0013] S51: excavate a guide trench in the middle of the cross section of one of the sub-zones, reserve a protective layer on the upstream sidewall and the downstream sidewall of the guide trench according to the refined finite element model after improvement, and obtain the macro-mechanical parameters of the protective layer; wherein the protective layer includes a primary damage zone and a secondary damage zone, the primary damage zone is a region where the rock mass appears slabbing and fragmentation due to disturbance during excavation of the guide trench, the secondary damage zone is a region where the rock mass appears slabbing and fragmentation without disturbance during excavation of the guide trench, and the rock wall crane beam that has not been excavated is ensured to be outside the primary damage zone;

[0014] S52: input the macro-mechanical parameters of the protective layer and the inclination of the rock wall crane beam into the refined finite element model after improvement, and obtain the excavation depth H and width L of the protective layer;

[0015] S53: excavate the protective layer according to the obtained excavation depth H and width L of the protective layer, so as to form the vertical surface of the first part of the rock wall crane beam and expose the inclined surface of the rock wall crane beam;

[0016] S54: continue to excavate along the vertical surface of the first part of the rock wall crane beam, so as to form the vertical surface of the second part of the rock wall crane beam, and support the vertical surface of the first part and the vertical surface of the second part; wherein the vertical surface of the first part and the vertical surface of the second part jointly constitute the overall vertical surface of the rock wall crane beam;

[0017] S6: repeat steps S51-S54 for other sub-zones in sequence to obtain the rock wall crane beam.

[0018] In order to better realize the present application, further optimization is made in the above method, in step S51, the obtaining of the macro-mechanical parameters of the protective layer includes the following steps:

[0019] obtain the rock mass acoustic wave longitudinal wave velocity C p,d and C p,ud of the protective layer before and after excavation of the guide trench respectively, determine the corresponding geological strength index GSI and the rock mass disturbance parameter D at different depths of the damage zone according to the obtained C p,d and C p,ud ;

[0020] GSI=13.64Cp,d-1.40;

[0021]

[0022] calculate the Hoek-Brown strength criterion material constant according to the obtained GSI and D:

[0023]

[0024] In the formula, m b , s, and a are all material constants of the rock mass; m i Material parameters related to the properties of intact rock masses;

[0025] Macroscopic mechanical parameters of the rock mass were obtained based on the material constants of the Hoek-Brown strength criterion; among them, the macroscopic mechanical parameters include the deformation modulus E. m Rock mass cohesion c and internal friction angle

[0026]

[0027] In the formula, σ c The uniaxial compressive strength of the rock mass;

[0028]

[0029] In the formula, σ′ 3n =σ 3max / σ c , where σ 3max It is the upper limit of the minimum principal stress.

[0030] To better realize the present invention, the above method is further optimized. In step S4, the rock mass in the excavation area is divided into n sub-regions according to the lithology or joint distribution; in the sub-regions, the macroscopic mechanical parameters of the rock mass are consistent.

[0031] To better realize the present invention, the above method is further optimized. In step S4, the excavation area is divided into n sub-areas along the longitudinal axis of the tunnel according to the length, and the length of each sub-area is 10-20m.

[0032] To better realize the present invention, the above method is further optimized. In step S54, the rock mass below the vertical plane of the first part of the rock wall crane beam is excavated in stages until the design elevation is reached.

[0033] To better realize the present invention, the above method is further optimized. In step S1, the range of the finite element model is 200-400m of the rock mass near the excavation area.

[0034] To better realize the present invention, the above method is further optimized. In step S1, the geostress data is obtained by geological exploration or water pressure testing.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The excavation method for forming a crane beam in brittle rock mass under high ground stress conditions provided by this invention provides excavation parameters in real time by establishing a refined finite element model of the rock mass near the excavation area. Within the expected range, the primary and secondary failure zones in the protective layer are controlled within the expected range, thereby outlining the contour of the crane beam and forming the crane beam, reducing the excavation difficulty of the crane beam and ensuring the forming quality of the crane beam. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart of an excavation method for forming a crane beam in a brittle rock mass under high ground stress conditions, according to the present invention.

[0039] Figure 2 This is a schematic diagram of the cross-section of the sub-region.

[0040] Figure 3 This is a structural diagram of the protective layer before excavation.

[0041] Figure 4 This is a schematic diagram of the secondary damage zone.

[0042] Figure 5 This is a schematic diagram of the secondary damage zone during excavation.

[0043] Figure 6 This is a structural diagram illustrating the support of the entire vertical plane of a crane beam on a rock face.

[0044] Figure 7 This is a schematic diagram showing the division of sub-regions within the excavation area.

[0045] In the picture:

[0046] 1. The upper area;

[0047] 2. Guide groove;

[0048] 3. Protective layer; 31. Primary damage zone; 32. Secondary damage zone; 321. Secondary damage zone;

[0049] 4. Outline of the crane beam on the rock face. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0052] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] In the embodiments of this application, such as Figures 1 to 7 As shown, the excavation method for forming a crane beam in a brittle rock mass under high ground stress conditions includes the following steps, see [link to excavation method]. Figure 1 :

[0054] S1: Establish a finite element model of the rock mass near the excavation area, obtain the geostress data of the rock mass near the excavation area by means of geological exploration or water pressure testing, and invert the geostress of the finite element model by using the obtained geostress data of the nearby rock mass.

[0055] S2: Establish a refined finite element model of the rock mass near the excavation area, and calculate the distribution of the in-situ stress field of the refined finite element model by analyzing the inversion results of the finite element model.

[0056] S3: Based on the distribution of the geostress field in the refined finite element model, in the region above the crane beam elevation of the excavated rock wall in the excavation area, see [reference 1]. Figure 2During the excavation of the upper region 1, the excavation parameters are dynamically determined and input into the refined finite element model to improve the model. The excavation parameters include the lithology and macroscopic mechanical parameters of the rock mass near the upper region 1. Dynamic determination refers to the real-time calculation of the excavation parameters during the excavation process.

[0057] S4: Divide the excavation area into n sub-areas (n≥1) along the longitudinal axis of the tunnel, based on the lithology of the rock mass. See [link / reference]. Figure 7 ;in,

[0058] The division of sub-zones should take into account factors such as construction progress, lithology, and joint distribution, and ensure that the macroscopic mechanical parameters of the rock mass in a single zone are consistent.

[0059] If a fault is encountered, the faulted section will be treated as a separate sub-region. See [reference needed]. Figure 7 Part of Neutron Region 2;

[0060] The above-mentioned construction schedule considerations can divide the excavation area into n sub-areas along the longitudinal axis of the tunnel, with each sub-area having a length of 10-20m, to facilitate the subsequent excavation process of the rock wall crane beam and ensure construction progress and efficiency.

[0061] S51: A guide trench 2 is excavated in the middle of one of the sub-region cross-sections using the drill-and-blast method. Based on the refined finite element model, protective layers 3 are reserved on the upstream and downstream sidewalls of the guide trench 2. (See [reference]). Figure 2 And obtain the macroscopic mechanical parameters of protective layer 3; among which,

[0062] Protective layer 3 includes primary damage zone 31 and secondary damage zone 32, participating in... Figure 3 The primary damage zone 31 is the area where the rock mass is disturbed and cracks and breaks during the excavation of the guide trench 2. The secondary damage zone 32 is the area where the rock mass is not disturbed and cracks and breaks during the excavation of the guide trench 2, ensuring that the unexcavated rock wall crane beam is outside the primary damage zone 31.

[0063] Before and after the excavation of guide trench 2, the longitudinal wave velocity C of the rock mass was obtained using an ultrasonic velocimeter. p,d and C p,ud According to the obtained C p,d and C p,ud Determine the corresponding geological strength index GSI and rock mass disturbance parameters D at different depths of the damaged area;

[0064] GSI = 13.64Cp,d - 1.40;

[0065]

[0066] Calculate the material constants for the Hoek-Brown strength criterion based on the obtained GSI and D:

[0067]

[0068] In the formula, m b , s, and a are all material constants of the rock mass; m i Material parameters related to the properties of intact rock masses;

[0069] Macroscopic mechanical parameters of the rock mass were obtained based on the material constants of the Hoek-Brown strength criterion; among them, the macroscopic mechanical parameters include the deformation modulus E. m Rock mass cohesion c and internal friction angle

[0070]

[0071] In the formula, σ c The uniaxial compressive strength of the rock mass;

[0072]

[0073] In the formula, σ′ 3n =σ 3max / σ c , where σ 3max It is the upper limit of the minimum principal stress.

[0074] S52: Input the obtained macroscopic mechanical parameters of protective layer 3 and the inclination angle of the rock wall crane beam into the refined finite element model to obtain the excavation depth H and width L of protective layer 3; wherein, the inclination angle of the rock wall crane beam can be obtained from the design drawings of the rock wall crane beam. Figure 3 In this context, α represents the inclination angle of the rock wall crane beam.

[0075] S53: Excavate the protective layer 3 according to the excavation depth H and width L of the obtained protective layer 3, so that the vertical surface of the first part of the rock wall crane beam is formed and the inclined surface of the rock wall crane beam is exposed.

[0076] It should be noted that the guide trench 2 was excavated using blasting. During blasting, some rock in the protective layer 3 was disturbed by the blasting, causing some rock in the protective layer 3 to exhibit phenomena such as plate cracking and fragmentation. This part is the primary failure zone 31, see [link to relevant documentation]. Figure 3 Cracked and / or broken rock masses can be cleaned directly by hand. See the diagram for the structure after cleaning. Figure 4 ;

[0077] The portion not affected by the blasting disturbance is the secondary damage zone 32. The outline of the aforementioned rock wall crane beam is located in the secondary damage zone 32. That is, the aforementioned rock wall crane beam is outside the primary damage zone 31. When excavating the guide trench 2, the rock wall crane beam is affected by the blasting disturbance, resulting in phenomena such as plate cracking and breakage, which affects the formation of the rock wall crane beam.

[0078] The secondary failure zone 32 is excavated based on its obtained excavation depth H and width L. The excavation method is smooth blasting, which shapes the vertical surface of the first part of the rock wall crane beam. Simultaneously, during smooth blasting, the rock mass above the outline 4 of the rock wall crane beam will be affected by the explosion process. (See [reference needed]). Figure 4 This caused phenomena such as plate cracking and fragmentation in the rock mass, and this part of the area is the secondary damage zone 321;

[0079] When cracks and fractures appear in the rock mass above the outline 4 of the rock wall crane beam, the inclined surface of the rock wall crane beam naturally takes shape. Then, the cracked rock mass in the associated damaged area 321 is manually cleared, exposing the inclined surface of the rock wall crane beam. At this point, both the vertical surface of the first part of the rock wall crane beam and the inclined surface of the rock wall crane beam are formed and exposed. See [link / reference]. Figure 5 .

[0080] S54: Excavate the rock mass below the area outside the secondary failure zone 321 within the secondary failure zone 32. That is, continue excavating downwards along the vertical plane of the first part of the rock wall crane beam to form the vertical plane of the second part of the rock wall crane beam, and provide support for the vertical planes of the first and second parts. Figure 6 The support can be anchored using anchor bolts; the vertical plane of the first part and the vertical plane of the second part together form the overall vertical plane of the rock wall crane beam.

[0081] It should be noted that the rock mass beneath the area outside of the secondary failure zone 321 in the excavation of secondary failure zone 32 refers to... Figure 5 The position marked by the horizontal dashed line.

[0082] S6: Repeat steps S51-S54 for the other sub-regions in sequence; obtain the naturally formed rock wall crane beam.

[0083] Preferably, in step S54, the rock mass below the secondary failure zone 32 and the non-attached failure zone 321 is excavated in stages, that is, the rock mass below the vertical plane of the first part of the crane beam along the rock wall is excavated in stages, and the excavation depth is up to the design elevation.

[0084] Preferably, the range of the finite element model is 200-400m of the rock mass near the excavation area, so as to reduce the workload of establishing the finite element model.

[0085] In addition, the excavation method for forming crane beams in brittle rock walls under high ground stress conditions also has the following technical advantages:

[0086] (1) Strong applicability: This excavation method can be used for various brittle rock masses with high and ultra-high ground stress during the excavation of underground caverns, and is not limited by rock type or excavation area;

[0087] (2) Good economic efficiency: The ultrasonic velocimeter and numerical calculation equipment required by this excavation method are low in cost and do not require expensive field tests;

[0088] (3) Convenient and fast: Compared with field tests, the process of ultrasonic velocimetry and numerical calculation of rock mass does not delay the construction period.

[0089] (4) Good forming effect: In most cases, it can be formed in one go. If it cannot be formed in one go, only a small amount of excavation is needed, and over-excavation is very rare.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An excavation method for forming a wall-mounted crane beam in a brittle rock mass under high ground stress conditions, characterized in that: The method comprises the following steps: S1: a finite element model of the rock mass near the excavation area is established, the in-situ stress data of the rock mass near the excavation area are obtained, and the in-situ stress of the finite element model is inverted through the obtained in-situ stress data of the rock mass near the excavation area; S2: a refined finite element model of the rock mass near the excavation area is established, and the distribution of the in-situ stress field of the refined finite element model is calculated through the inversion result of the in-situ stress of the finite element model; S3: according to the distribution of the in-situ stress field of the refined finite element model, an upper area (1) above the elevation of the rock wall crane beam in the excavation area is excavated, and during the excavation of the upper area (1), the excavation parameters are dynamically determined, and the obtained excavation parameters are input into the refined finite element model to improve the refined finite element model; wherein the excavation parameters include the lithology and macro mechanical parameters of the rock mass near the upper area (1); S4: the excavation area is divided into n sub-areas along the longitudinal axis direction of the cavern; wherein n≥1; S51: a guide trench (2) is excavated in the middle of the cross section of one of the sub-areas, a protective layer (3) is reserved on the upstream and downstream side walls of the guide trench (2) according to the improved refined finite element model, and the macro mechanical parameters of the protective layer (3) are obtained; wherein the protective layer (3) includes a primary failure zone (31) and a secondary failure zone (32), the primary failure zone (31) is a zone where the rock mass appears slabbing and fragmentation due to disturbance during the excavation of the guide trench (2), the secondary failure zone (32) is a zone where the rock mass appears slabbing and fragmentation without disturbance during the excavation of the guide trench (2), and the rock wall crane beam which has not been excavated is ensured to be outside the primary failure zone (31); S52: the macro mechanical parameters of the protective layer (3) and the inclination angle of the rock wall crane beam are input into the improved refined finite element model to obtain the excavation depth H and width L of the protective layer (3); S53: the protective layer (3) is excavated according to the obtained excavation depth H and width L of the protective layer (3), so that the vertical surface of the first part of the rock wall crane beam is formed, and the inclined surface of the rock wall crane beam is exposed; S54: the vertical surface of the first part of the rock wall crane beam is continuously excavated downward to form the vertical surface of the second part of the rock wall crane beam, and the vertical surface of the first part and the vertical surface of the second part are supported; wherein the vertical surface of the first part and the vertical surface of the second part jointly constitute the overall vertical surface of the rock wall crane beam; S6: steps S51-S54 are repeated for other sub-areas in turn to obtain the rock wall crane beam.

2. The excavation method of claim 1, wherein: In step S51, the obtaining of the macro mechanical parameters of the protective layer (3) comprises the following steps: The rock mass sound wave longitudinal wave velocity C of the protective layer (3) before and after the excavation of the guide groove (2) is obtained by an ultrasonic velocity meter p,d and C p,ud , the corresponding geological strength index GSI and the rock mass disturbance parameter D at different depths of the damage zone are determined according to the obtained C p,d and C p,ud ; GSI = 13.64 C p,d -1.40; Hoek-Brown strength criterion material constants are calculated according to the obtained GSI and D: wherein m b , s and a are material constants of the rock mass; m i is a material parameter related to the properties of the intact rock mass; According to the Hoek-Brown strength criterion material constant, macro-mechanical parameters of the rock mass are obtained; wherein, the macro-mechanical parameters include deformation modulus E m , cohesion c and internal friction angle φ of the rock mass. In the formula, σ c is the uniaxial compressive strength of the rock mass; where σ' 3n = σ 3max / σ c , where σ 3max is the upper limit value of the minimum principal stress.

3. The excavation method of claim 1, wherein: In step S4, the excavation area is divided into n sub-areas according to the lithology or joint distribution of the rock mass in the excavation area; in the sub-areas, the macro mechanical parameters of the rock mass are consistent.

4. The excavation method of claim 1, wherein: In step S4, the excavation area is divided into n sub-areas along the longitudinal axis direction of the cavern according to the length, and the length of each sub-area is 10-20 m.

5. The excavation method of claim 1, wherein: In step S54, the rock mass below the vertical surface of the first part of the rock wall crane beam is excavated in sections, and the excavation depth is until the design elevation.

6. The excavation method of claim 1, wherein: In step S1, the range of the finite element model is 200-400m of the rock mass near the excavation area.

7. The excavation method of claim 1, wherein: In step S1, the in-situ stress data is obtained by means of geological exploration or water pressure test.

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