CN114810097A - Method for determining maximum fracture angle of brittle rock body in high or ultrahigh ground stress area - Google Patents
Method for determining maximum fracture angle of brittle rock body in high or ultrahigh ground stress area Download PDFInfo
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- 239000011435 rock Substances 0.000 title claims abstract description 164
- 238000000034 method Methods 0.000 title claims abstract description 72
- 239000011241 protective layer Substances 0.000 claims abstract description 73
- 238000009412 basement excavation Methods 0.000 claims abstract description 37
- 238000005422 blasting Methods 0.000 claims description 53
- 238000005336 cracking Methods 0.000 claims description 32
- 230000006378 damage Effects 0.000 claims description 25
- 238000011144 upstream manufacturing Methods 0.000 claims description 17
- 239000010410 layer Substances 0.000 claims description 11
- 238000004873 anchoring Methods 0.000 claims description 9
- 238000005553 drilling Methods 0.000 claims description 8
- 239000010438 granite Substances 0.000 claims description 8
- 238000013461 design Methods 0.000 claims description 3
- 238000010276 construction Methods 0.000 abstract description 21
- 238000010586 diagram Methods 0.000 description 9
- 238000004364 calculation method Methods 0.000 description 8
- 230000008569 process Effects 0.000 description 6
- 238000011835 investigation Methods 0.000 description 5
- 238000011160 research Methods 0.000 description 5
- 241000234282 Allium Species 0.000 description 3
- 235000002732 Allium cepa var. cepa Nutrition 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 2
- 244000007853 Sarothamnus scoparius Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000011081 inoculation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000004901 spalling Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/006—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries by making use of blasting methods
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F42—AMMUNITION; BLASTING
- F42D—BLASTING
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- F42D3/04—Particular applications of blasting techniques for rock blasting
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Abstract
In order to solve the technical problem that the prior art lacks a method for determining the maximum fracture angle of the brittle rock mass underground chamber in a high or extremely high ground stress region, the embodiment of the invention provides a method for determining the maximum fracture angle of the brittle rock mass in a high or ultrahigh ground stress region, which comprises the following steps: the maximum break angle is determined according to equation (1): wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer. According to the embodiment of the invention, the fan-shaped plate crack lifting structure is formed through construction, and is divided into a damaged area and an undamaged area through a damaged boundary when the brittle rock mass is excavated, so that the tangent value of the maximum fracture angle can be calculated through the ratio of the depth H of the pull groove to the width L of the protective layer, the size of the maximum fracture angle is conveniently determined, then construction is carried out according to the maximum fracture angle, and the fine excavation of the brittle rock mass is conveniently realized.
Description
Technical Field
The invention relates to a method for determining the maximum fracture angle of a brittle rock body in a high or ultrahigh ground stress area.
Background
At present, only about the calculation of the rock slope fracture angle, two methods for determining the rock slope fracture angle exist at present. The method is specified in technical Specification for slope support of buildings (DB50/2018-2001), and the method is specified in the following steps: for rock slope without camber structural surface, breaking angle is taken
(
Is the internal friction angle of the side slope). The other is a method (manual method for short) specified in engineering geology handbook, third edition, which specifies that numerous straight lines which may break at an angle theta to the horizontal line can be drawn through the slope toe, the surface with the smallest safety factor is called the critical surface, and the angle formed by the critical surface and the horizontal line
Referred to as the critical angle (beta is the inclination of the side slope angle,
is the internal friction angle of the side slope). In a large amount of slope management projects, the rock slope fracture angles determined by the two methods have large difference, and the method has direct influence on project investment and safety. At present, the method generally relates to the calculation of the rock slope fracture angle, namely the calculation of the groundThe method for determining the fracture angle of the lower chamber is also lacking, and particularly the calculation of the maximum fracture angle of the brittle rock body in the high or extremely high geostress zone is very important.
Disclosure of Invention
In order to solve the technical problem that a method for determining the maximum fracture angle of the brittle rock mass underground chamber in a high or extremely high ground stress area is lacked in the prior art, the embodiment of the invention provides a method for determining the maximum fracture angle of the brittle rock mass in a high or ultrahigh ground stress area.
The embodiment of the invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides a method for determining a maximum fracture angle of a brittle rock body in a high or ultrahigh ground stress region, including:
the maximum break angle is determined according to the following equation:
β＝H/L (1)
wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer.
Further, the determination method comprises:
performing groove drawing excavation on the middle position of a chamber to be excavated by brittle rock masses by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock masses with certain thicknesses are reserved on one side of the guide groove close to an upstream side wall of the chamber and one side of the guide groove close to a downstream side wall of the chamber as protective layers;
inserting an anchor rod into surrounding rock outside an excavation boundary to perform pre-anchoring;
blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
dividing the fan-shaped plate cracking lifting type rock burst structure into two areas with triangular structures, namely a damaged area and an undamaged area, by damaging a boundary;
the included angle between the damage boundary and the width direction of the protective layer is the maximum fracture angle.
Further, the maximum fracture angle is given by:
β＝H/L (1)
wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer.
Further, the brittle rock body is brittle granite.
Further, adopt the blasting region of smooth blasting method blasting protective layer, obtain the rock mass structure who has sector plate and split the lift type structure, include:
determining the projection length of the rock anchor beam in the width direction of the protective layer according to the included angle between the rock anchor beam of the side wall and the protective layer in the width direction and the design height of the rock anchor beam, taking the area where the projection length of the rock anchor beam in the width direction of the protective layer is subtracted from the width of the protective layer as the blasting area of the protective layer, and blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain the rock mass structure with the sector plate cracking lifting type structure.
In a second aspect, an embodiment of the present invention provides a method for determining a maximum fracture angle of a brittle rock body in a high or ultrahigh ground stress region, including:
adopting layered excavation for a chamber to be excavated in a brittle rock mass;
the excavation method of each layer of brittle rock mass comprises the following steps:
performing groove-drawing excavation on the middle position of the chamber to be excavated of each layer of brittle rock mass by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock mass with certain thickness is reserved on one side of the guide groove close to the upstream side wall of the chamber and one side of the guide groove close to the downstream side wall of the chamber as a protective layer;
inserting an anchor rod into surrounding rocks outside an excavation boundary to perform pre-anchoring;
blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
dividing the fan-shaped plate cracking lifting type rock burst structure into two areas with triangular structures, namely a damaged area and an undamaged area, by damaging a boundary;
the included angle between the damage boundary and the width direction of the protective layer is the maximum fracture angle.
Further, the span of the chamber is 28-29 m; the width of the protective layer on one side of the guide groove close to the upstream side wall of the chamber and one side of the guide groove close to the downstream side wall of the chamber are both 9-10 m; the width of the protective layer is the distance between the pull groove and the cavern rock mass.
Further, the span of the chamber is 28.3 m; the width of the protective layer on the side of the guide groove near the upstream side wall of the chamber and the side of the guide groove near the downstream side wall of the chamber were both 9.5 m.
Furthermore, the width of the pull groove is 9-10 m.
Further, the width of the pull groove is 9.3 m.
Compared with the prior art, the embodiment of the invention has the following advantages and beneficial effects:
according to the method for determining the maximum fracture angle of the brittle rock mass in the high or ultrahigh ground stress area, the unique fan-shaped plate crack uplift structure is formed through construction, the fan-shaped plate crack uplift structure is divided into a damaged area and an undamaged area through a damaged boundary line when the brittle rock mass is excavated, and therefore the tangent value of the maximum fracture angle can be obtained through calculation of the ratio of the depth H of the pull groove to the width L of the protection layer, the size of the maximum fracture angle is conveniently determined, construction is carried out according to the maximum fracture angle, and fine excavation of the brittle rock mass is conveniently achieved.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and that those skilled in the art may also derive other related drawings based on these drawings without inventive effort.
Fig. 1 is a schematic flow chart of a method for determining the maximum fracture angle of a brittle rock body in a high or ultrahigh ground stress area.
FIG. 2 is a schematic view of the relationship between the crack angles of the fan-shaped plate crack lift-type structure of the protective layer.
FIG. 3 is a schematic view of the downstream side protective layer damage site after groove drawing.
FIG. 4 is a schematic view of the upstream side protective layer damage site after groove drawing.
Fig. 5 is a structural schematic diagram of a fan-shaped plate cracking and lifting type structure.
FIG. 6 is a graph showing the relationship between rock mass fracture and the variation of the width of the pull groove when the depth of the pull groove is not changed; wherein, fig. 6a is a schematic diagram of a rock mass fracture structure with a 9.3m pull groove width, fig. 6b is a schematic diagram of a rock mass fracture structure with a 16m pull groove width, and fig. 6c is a schematic diagram of a rock mass fracture structure with a 17.3m pull groove width.
FIG. 7 is a graph showing the relationship between rock mass fracture and the variation of the depth of the pull groove when the width of the pull groove is not changed; fig. 7a is a schematic diagram of a rock mass fracture structure when the depth of the pull groove is 3.8m and the width of the pull groove is 9.3m, fig. 7b is a schematic diagram of a rock mass fracture structure when the depth of the pull groove is 5m and the width of the pull groove is 9.3m, and fig. 7c is a schematic diagram of a rock mass fracture structure when the depth of the pull groove is 7.6m and the width of the pull groove is 9.3 m.
FIG. 8 is a comparative plot of the rock mass failure structure for both overbreak and non-overbreak situations; wherein, FIG. 8a is a schematic diagram of a rock mass fracture structure under the condition that the depth of the pull groove is not over excavated by 3.8 m; FIG. 8b is a schematic diagram of a rock mass fracture structure under a condition of 3.8m pull groove depth overbreak.
Reference numbers and corresponding part names in the drawings:
1-fracture plane of slab, 2-rock anchor beam, 3-depth of groove, 4-boundary of damage, 5-width of protective layer, 6-horizontal plane in front of groove, and 7-supported unearthed part.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known structures, circuits, materials, or methods have not been described in detail so as not to obscure the present invention.
Throughout the specification, reference to "one embodiment," "an embodiment," "one example," or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrases "one embodiment," "an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "upper", "lower", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be construed as limiting the scope of the present invention.
Examples
In order to solve the technical problem that the prior art lacks a method for determining the maximum fracture angle of the brittle rock mass underground chamber in a high or extremely high ground stress region, the embodiment of the invention provides a method for determining the maximum fracture angle of the brittle rock mass in a high or ultrahigh ground stress region, which comprises the following steps:
the maximum break angle is determined according to the following equation:
β＝H/L (1)
wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer.
The principle is as follows: by definition of the failure angle, the failure angle is the most unfavorable failure angle for the rock mass at strength control. The fracture angle is mainly used for determining the range of a collapse area and the starting point of an anchor rod anchoring section, and sometimes the fracture angle contained in a rock pressure formula is also used for calculating the rock load borne by a slope supporting structure controlled by the rock strength.
The fan-shaped plate crack lifting type structure is shown in fig. 2 and fig. 5, after the construction method is carried out, the obtained fan-shaped plate crack lifting type structure has an obvious damaged area and a non-damaged area, the damaged area and the non-damaged area divide the protective layer into two areas through a damaged boundary, and the damaged boundary plays a role in separating the damaged area and the non-damaged area. Thus, the angle between the damage boundary and the protective layer width direction of the non-damaged region of the protective layer is the maximum fracture angle.
Illustratively, a rock anchor beam at a third layer of an underground main workshop at the left bank of a double-estuary power station is taken as a research object, rock burst damage condition investigation in the excavation process of a brittle granite rock anchor beam is carried out under the action of ultrahigh ground stress, macroscopic development rule characteristics are summarized through investigation and statistics of a large number of rock burst damage phenomena and types, and a 'fan-shaped plate crack lifting type' rock burst damage type at the rock anchor beam part is provided.
On-site investigation finds that the rock mass damage characteristics on two sides after groove drawing are generally area damage taking the joint part of the upper layer and the lower layer of the side wall as the circle center and the upper elevation and the lower elevation of the groove drawing as boundary lines. And (3) destroying the actual excavation surface controlled by the groove drawing, wherein the maximum destruction angle is the connecting line angle between the circle center and the groove drawing bottom elevation.
The derivation process of the fan-shaped plate crack lifting type crack angle is as follows:
the angle of the plate cracking block is shown in a calculation formula (2) and the angle of the rock destruction range is shown in a formula (1).
β≈H/L (1)
α≈h 1 /L (2)
γ≈h/l 1 (3)
In the formula: l is the width of the protective layer, /) 1 The overhanging width of the rock anchor beam is adopted; h is the depth of the groove, H 1 The approximate thickness of the plate crack is adopted, and h is the height of the rock anchor beam; alpha is a plate crack angle; beta is the maximum slab cracking angle, and gamma is the dip angle of the rock anchor beam.
The maximum fracture angle of the brittle rock body under the action of high or extremely high ground stress is expressed by the formula (2). The concept and the calculation method of the maximum fracture angle of the brittle rock body utilize the maximum fracture angle beta to develop the concept of natural forming of the inclined plane (gamma) of the rock anchor beam, namely
β＝γ＝h/l 1 (4)
Therefore, when the maximum fracture angle is equal to the inclination angle of the rock anchor beam, the fan-shaped plate fracture lifting type structure is convenient to form, construction is carried out according to the maximum fracture angle, and fine excavation of brittle rock mass is convenient to realize.
Therefore, the fan-shaped plate crack lifting type structure formed by the construction method is divided into a damaged area and an undamaged area by a damaged boundary line when the brittle rock mass is excavated, so that the tangent value of the maximum fracture angle can be calculated by the ratio of the groove-drawing depth H to the protective layer width L, the size of the maximum fracture angle is conveniently determined, construction is carried out according to the maximum fracture angle, and the fine excavation of the brittle rock mass in a high or extremely high ground stress area is conveniently realized.
Optionally, the construction method specifically includes:
a construction method of a sector plate cracking and lifting type structure of a brittle rock body comprises the following steps:
s1, performing groove-drawing excavation at the middle position of a chamber to be excavated by brittle rock masses by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock masses with certain thicknesses are reserved at one side of the guide groove close to an upstream side wall of the chamber and one side of the guide groove close to a downstream side wall of the chamber and are used as protective layers;
s2, inserting an anchor rod into surrounding rocks outside the excavation boundary to perform pre-anchoring;
s3, blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
referring to fig. 2, a blasting area is arranged above the failure area.
And S4, determining a maximum fracture angle and excavating by using the maximum fracture angle to obtain the underground chamber.
Optionally, the method further comprises the steps of: and S5, permanently supporting the surrounding rock to complete construction.
Therefore, the embodiment of the invention obtains the sector plate crack lifting type structure of the brittle rock body by carrying out slot-drawing excavation, pre-anchoring and smooth blasting on the brittle rock body such as the brittle granite rock body in a high or extremely high ground stress region by using a drilling and blasting method; by adopting the construction method provided by the embodiment of the invention to construct the brittle rock mass, the fan-shaped plate crack uplift structure of the brittle rock mass convenient for subsequent fine construction can be obtained, and targeted construction treatment is carried out based on the damage characteristic of the fan-shaped plate crack uplift structure, such as excavation construction is carried out according to the maximum fracture angle of the fan-shaped plate crack uplift structure, so that the fine excavation of the brittle rock mass is favorably realized.
Based on the construction method, further, the determination method is shown in fig. 1 and includes:
s1, performing groove-drawing excavation at the middle position of a chamber to be excavated by brittle rock masses by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock masses with certain thicknesses are reserved at one side of the guide groove close to an upstream side wall of the chamber and one side of the guide groove close to a downstream side wall of the chamber and are used as protective layers;
s2, inserting an anchor rod into surrounding rocks outside the excavation boundary to perform pre-anchoring;
s3, blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
s4, dividing the fan-shaped plate cracking lifting type rock burst structure into two triangular areas, namely a damaged area and an undamaged area, by damaging a boundary;
and S5, the included angle between the damage boundary and the width direction of the protective layer is the maximum fracture angle, namely beta in the graph 2.
Further, the formula for the maximum rupture angle is:
β＝H/L (1)
wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer.
Further, the brittle rock body is brittle granite.
Further, adopt the blasting region of smooth blasting method blasting protective layer, obtain the rock mass structure who has sector plate and split the lift type structure, include:
determining the projection length of the rock anchor beam in the width direction of the protective layer according to the included angle between the rock anchor beam of the side wall and the protective layer in the width direction and the design height of the rock anchor beam, taking the area where the projection length of the rock anchor beam in the width direction of the protective layer is subtracted from the width of the protective layer as the blasting area of the protective layer, and blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain the rock mass structure with the sector plate cracking lifting type structure.
In a second aspect, an embodiment of the present invention provides a method for determining a maximum fracture angle of a brittle rock body in a high or ultrahigh ground stress region, including:
adopting layered excavation for a chamber to be excavated in a brittle rock mass;
the excavation method of each layer of brittle rock mass comprises the following steps:
performing groove-drawing excavation on the middle position of the chamber to be excavated of each layer of brittle rock mass by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock mass with certain thickness is reserved on one side of the guide groove close to the upstream side wall of the chamber and one side of the guide groove close to the downstream side wall of the chamber as a protective layer;
inserting an anchor rod into surrounding rock outside an excavation boundary to perform pre-anchoring;
blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
dividing the fan-shaped plate cracking lifting type rock burst structure into two areas with triangular structures, namely a damaged area and an undamaged area, by damaging a boundary;
the included angle between the damage boundary and the width direction of the protective layer is the maximum fracture angle.
Therefore, the embodiment of the invention provides a method for determining the maximum fracture angle under the condition of layered excavation.
Further, the span of the chamber is 28-29 m; the width of the protective layer on one side of the guide groove close to the upstream side wall of the chamber and one side of the guide groove close to the downstream side wall of the chamber are both 9-10 m; the width of the protective layer is the distance between the pull groove and the cavern rock mass.
Further, the span of the chamber is 28.3 m; the width of the protective layer on the side of the guide groove near the upstream side wall of the chamber and the side of the guide groove near the downstream side wall of the chamber were both 9.5 m.
Furthermore, the width of the pull groove is 9-10 m.
Further, the width of the pull groove is 9.3 m.
Examples of the implementation
The rock burst damage condition investigation in the excavation process of the brittle granite rock anchor beam is carried out by taking the rock anchor beam at the third layer of the underground main workshop at the left bank of the double-estuary power station as a research object under the action of ultrahigh ground stress, and the 'fan-shaped plate crack lifting type' rock burst damage type at the rock anchor beam part is provided by summarizing the characteristics of the macroscopic development law through the investigation and statistics of a large number of rock burst damage phenomena and types. Through microscopic research on fracture surfaces, the primary structure of a rock body and the integrity degree of the rock body, the 'sector plate crack lifting type' rock burst failure type is obtained, is a series of sector plate crack surfaces in a tendency hole generated in the high stress release process, belongs to a new crack of the rock body, and is a typical rock burst failure type of ultrahigh ground stress and brittle granite.
The underground workshop adopts a construction mode that a groove is drawn in the middle, protective layers are reserved on side walls of the upstream and the downstream, and then the protective layers are excavated. Specifically, the construction method of the above embodiment is adopted for construction, which is not described herein again.
Under the condition of ultrahigh ground stress, after the underground cavern is subjected to groove drawing, the residual rock mass has horizontal and lateral blank surfaces and is influenced by ground stress and relaxation unloading, fresh, rock mass and dry brittle granite are easy to generate a tension-shear type 'new crack' which is nearly consistent with the section surface towards the blank surfaces, and a large amount of phenomena of step-shaped slab cracking, rib spalling and the like are formed, namely a fan-shaped slab cracking and lifting type structure. The site of the downstream side protective layer after groove drawing is schematically shown in FIG. 3.
Referring to fig. 3, it can be seen that the split lifting type structure of the downstream sector plate after slot drawing has the following characteristics:
(1) on the outer side of the rock anchor beam, the crack combination shows the phenomena of slow shearing and steep tensioning, and the arc unloading crack also develops. The cracks are lifted upwards, the distance is about 30cm, and the unloading cracks are characterized in that the angle is gradually steep from top to bottom. And (3) developing a group of steep dip relief fractures parallel to the trend of the cavern, wherein the interval is 30-50cm, and the fractures are tension fractures.
(2) Under the influence of excavation unloading, the side wall forms step-shaped plate cracks and damages, the plate cracks develop strongly, the plate thickness is different from 10 cm to 30cm, the rock mass is broken, the cracks are opened to form hollow joints, the width of each joint is 1cm to 2cm, and the width of each joint is 5 cm.
(3) The phenomena of onion skin-shaped unloading crack development exist, the onion skin-shaped unloading crack is flaky and has the thickness less than 1cm, and the thickness of the onion skin-shaped unloading crack individually reaches about 1.5 cm. The unloading crack shows obvious parallel or nearly parallel characteristic with the excavation surface and is strongly controlled by the shape of the excavation surface.
(4) The excavation of the middle groove, the unloading crack develops into obvious broom shape, namely the unloading crack has similar tendency, the dip angle is gradually increased from the top to the lower part, and a plurality of groups of main cracks have the appearance: 82 degrees and 21 degrees; ② 64 degrees and 42 degrees; ③ 54 degrees and 65 degrees; and fourthly, 66 degrees and less than 50 degrees, as shown in figure 3.
Referring to fig. 4, it can be seen that the split lifting type structure of the downstream sector plate after slot drawing has the following characteristics:
(5) rockburst mainly produces 3 groups of new fractures: the slow inclination angle (nearly horizontal) is 5-20 degrees, and the slow inclination angle occurs on the bottom plate. The middle dip angle and the two sides of the dip angle are respectively 30-50 degrees in the hole and are generated on the protective layers at the two sides behind the groove drawing. Steep dip angle, 60-85 degree in the hole of both sides inclination respectively, take place in the side wall position.
The new cracks develop and move nearly uniformly (along the axis of the hole), the trends are similar, the two sides of the new cracks respectively develop towards the inside of the hole, the inclination angles of the holes gradually increase from top to bottom, and the new cracks are characterized by being gradually steep from top to bottom. The inoculation process of rock burst destruction from the outside to the inside is proved.
The fan-shaped plate cracking lift-type structure is shown with reference to fig. 5. The fan-shaped plate crack lifting type structure forms a plurality of plate crack structures at various plate crack angles from the horizontal plane 6 in front of the slot drawing and the part 7 which is not excavated and supported.
Under the condition of ultrahigh ground stress, under the influence of ground stress and relaxation unloading, brittle rock mass generally generates cracks towards a lateral face to the empty face, and a large number of rock blasting bad phenomena such as step-shaped plate cracks, caving and the like are formed. The following researches are respectively carried out on the aspects of rock mass fracture, slot width, slot depth and the like. The inventor researches and discovers that the width, the depth, the overbreak and the like of the pull groove have certain influence on the new cracks.
Specifically, the fan-shaped plate cracking and lifting type structure and the pull groove have the following relationship:
the relationship between the fan-shaped plate cracking and lifting structure and the pull groove meets the condition that:
under the condition that the depth of the pull groove is not changed, the number and the angle of the newly-generated cracks of the fan-shaped plate crack lifting type structure are increased along with the increase of the width of the pull groove; as shown with reference to fig. 6.
Under the condition that the width of the pull groove is not changed, the number and the angle of the newly-generated cracks of the fan-shaped plate crack lifting type structure are increased along with the increase of the depth of the pull groove; as shown with reference to fig. 7.
Under the condition that the depth and the width of the pull groove are not changed, the overexcavation enables the number of cracks of the fan-shaped plate crack lifting type structure to be increased and the angle to be enlarged; as shown with reference to fig. 8.
Under the condition that the width and the depth of the pull groove are not changed, the number of cracks of the downstream side sector plate cracking and lifting type structure is more than that of cracks of the upstream side sector plate cracking and lifting type structure, and the maximum angle of the cracks of the downstream side sector plate cracking and lifting type structure is larger than that of the cracks of the upstream side sector plate cracking and lifting type structure.
Therefore, by adopting the method for determining the maximum fracture angle in the embodiment of the invention, a predictable rock burst structure, namely a fan-shaped plate cracking and lifting type structure, is obtained according to the construction method, and meanwhile, the fan-shaped plate cracking and lifting type structure has an obvious damaged area and an undamaged area, so that the maximum fracture angle can be conveniently obtained according to an included angle between a damage boundary and the width direction of a protective layer of the undamaged area.
In addition, the construction method is convenient for fine excavation by arranging the rock anchor beam and determining the blasting area on the protective layer, so that the excavation process is smoother.
In addition, the method for determining the maximum fracture angle of the embodiment of the invention also has the following advantages:
1. the embodiment of the invention is used for actually measuring the angle and the side length of the crack, the measured angle and the measured length are the actual angle and the actual length, the measurement result is accurate, and the accuracy is high;
2. the operation is simple, the fracture angle can be directly converted after field statistics, and the cost is very low;
3. only one or more groups of caverns and cracks of the same type can be measured, so that the workload is low, the efficiency is high, and the time is saved.
4. The measurement calculation can be carried out on rocks with any shapes and any fracture angles.
5. The method provided by the embodiment of the invention provides support for reasonably evaluating the stability and safety of rock engineering and correctly analyzing and predicting the deformation and damage conditions of the rock.
6. The method provided by the embodiment of the invention is clear and clear in thought, and the parameter determination method is simple, convenient and effective and has strong applicability.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method of determining the maximum fracture angle of a brittle rock mass in a region of high or ultra-high ground stress, comprising:
the maximum break angle is determined according to the following equation:
β＝H/L (1)
wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer.
2. A method of determining the maximum fracture angle of a brittle rock mass in a region of high or ultra-high ground stress, comprising:
performing groove drawing excavation on the middle position of a chamber to be excavated by brittle rock masses by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock masses with certain thicknesses are reserved on one side of the guide groove close to an upstream side wall of the chamber and one side of the guide groove close to a downstream side wall of the chamber as protective layers;
inserting an anchor rod into surrounding rock outside an excavation boundary to perform pre-anchoring;
blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
dividing the fan-shaped plate cracking lifting type rock burst structure into two areas with triangular structures, namely a damaged area and an undamaged area, by damaging a boundary;
the included angle between the damage boundary and the width direction of the protective layer is the maximum fracture angle.
3. A method of determining the maximum fracture angle of a brittle rock body in a region of high or ultra-high geostress as claimed in claim 2, characterised in that the maximum fracture angle is given by the formula:
β＝H/L (1)
wherein beta is the tangent value of the maximum fracture angle, H is the depth of the pull groove, and L is the width of the protective layer.
4. A method of determining the maximum fracture angle of a brittle rock body in a region of high or ultra-high geostress as claimed in claim 3, characterised in that the brittle rock body is brittle granite.
5. A method of determining the maximum fracture angle of a brittle rock mass in areas of high or ultra-high ground stress as claimed in claim 3, characterized in that blasting area of the protective layer is blasted by smooth blasting to obtain a rock mass structure with a segmental slab cracking uplift type structure, comprising:
determining the projection length of the rock anchor beam in the width direction of the protective layer according to the included angle between the rock anchor beam of the side wall and the protective layer in the width direction and the design height of the rock anchor beam, taking the area where the projection length of the rock anchor beam in the width direction of the protective layer is subtracted from the width of the protective layer as the blasting area of the protective layer, and blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain the rock mass structure with the sector plate cracking lifting type structure.
6. A method of determining the maximum fracture angle of a brittle rock mass in a region of high or ultra-high ground stress, comprising:
adopting layered excavation for a chamber to be excavated in a brittle rock mass;
the excavation method of each layer of brittle rock mass comprises the following steps:
performing groove-drawing excavation on the middle position of the chamber to be excavated of each layer of brittle rock mass by adopting a drilling and blasting method, and excavating a guide groove, wherein the brittle rock mass with certain thickness is reserved on one side of the guide groove close to the upstream side wall of the chamber and one side of the guide groove close to the downstream side wall of the chamber as a protective layer;
inserting an anchor rod into surrounding rock outside an excavation boundary to perform pre-anchoring;
blasting the blasting area of the protective layer by adopting a smooth blasting method to obtain a rock mass structure with a sector plate cracking lifting type structure;
dividing the fan-shaped plate cracking lifting type rock burst structure into two areas with triangular structures, namely a damaged area and an undamaged area, by damaging a boundary;
the included angle between the damage boundary and the width direction of the protective layer is the maximum fracture angle.
7. The method for determining the maximum fracture angle of a brittle rock body in a high or ultra-high geostress area as claimed in claim 6, wherein the chamber has a span of 28-29 m; the width of the protective layer on one side of the guide groove close to the upstream side wall of the chamber and one side of the guide groove close to the downstream side wall of the chamber are both 9-10 m; the width of the protective layer is the distance between the pull groove and the cavern rock mass.
8. A method of determining the maximum fracture angle of a brittle rock body in areas of high or ultra-high geostress as claimed in claim 7, characterised in that the chamber span is 28.3 m; the width of the protective layer on the side of the guide groove near the upstream side wall of the chamber and the side of the guide groove near the downstream side wall of the chamber were both 9.5 m.
9. The method for determining the maximum fracture angle of a brittle rock body in a high or ultra-high geostress area as claimed in claim 7, wherein the width of the pull groove is 9-10 m.
10. A method of determining the maximum fracture angle of a brittle rock body in a region of high or ultra-high geostress as claimed in claim 9, characterised in that the drawgroove width is 9.3 m.
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