CN111910681A

CN111910681A - Rock wall crane beam structure and construction method thereof

Info

Publication number: CN111910681A
Application number: CN202010749751.9A
Authority: CN
Inventors: 谭永华; 许长红; 覃玉兰; 王宏贵; 刘朝晖; 吴徐华
Original assignee: PowerChina Zhongnan Engineering Corp Ltd
Current assignee: PowerChina Zhongnan Engineering Corp Ltd
Priority date: 2020-07-17
Filing date: 2020-07-30
Publication date: 2020-11-10

Abstract

The invention discloses a rock wall crane beam structure and a construction method thereof, wherein the rock wall crane beam structure comprises a rock wall crane beam fixed on the wall surface of surrounding rock and a prestressed anchor rod connecting the surrounding rock and the rock wall crane beam; the wall surface of the surrounding rock is provided with an anchoring hole, the rock wall crane beam is provided with a through hole penetrating through the two wall surfaces of the rock wall crane beam along the length direction of the prestressed anchor rod, the anchoring hole is communicated with the through hole to form a containing hole, one end of the prestressed anchor rod forms an anchoring end, the other end of the prestressed anchor rod forms a locking end, and a free section is formed between the anchoring end and the locking end; the anchoring end is anchored in the anchoring hole, the free section is stretched in the accommodating hole, and the locking end is locked on the free face of the rock wall crane beam. The invention innovatively adopts a new force transmission mode, so that the tensile force is directly transmitted to the deep part of the rock wall, the tensile shearing action of cement mortar is avoided, the advantage of high compressive strength of cement mortar in a three-dimensional compressive stress state is fully exerted, the anchoring end is far away from the face of the vacancy, and the stability of the cavern is effectively ensured.

Description

Rock wall crane beam structure and construction method thereof

Technical Field

The invention relates to the technical field of underground cavern infrastructure, in particular to a rock wall crane beam structure and a construction method thereof.

Background

In the practice of the field of underground cavern engineering related to water conservancy and hydropower engineering and other infrastructures, the span of the underground cavern is a control index with strong sensitivity, and particularly for large-span underground caverns such as underground powerhouses, main transformer chambers, tail water gate chambers and the like, the larger the span is, the larger the structural design difficulty and the safety risk of the cavern are, and the effective measure for ensuring the stability of the underground cavern and reducing the safety risk is to reduce the cavern span as much as possible. In order to minimize the chamber span or meet layout requirements, a bedrock that eliminates the rock wall crane beam may be necessary.

Compared with the conventional rocky-platform rock-wall crane beam, the rocky-platform-free rockwall crane beam is not supported by a rock pillar, and has the advantages that the rocky-wall crane beam is directly attached to the wall of the cave, so that the span of the cave is reduced, and meanwhile, the excavation construction is more convenient; the disadvantage is that the bearing is more difficult and the safety is more sensitive than the conventional rock wall crane beam with the rock platform because of no supporting function of the rock platform. Therefore, the stress analysis and structural design of the rockless rock wall crane beam structure are well made, and the method has great significance in the engineering safety.

The typical section of the conventional rockwall crane beam with the bedrock is shown in figure 1, the rockwall crane beam 2 is poured between surrounding rock 1 and the bedrock 60, the rockwall crane beam 2 is supported by the bedrock 60, and anchor rods 20 extending into the surrounding rock 1 are embedded in the rockwall crane beam 2. The conventional bedrock wall crane beam has mature structural design and calculation, and has the following characteristics according to the specification of NBT 35079-:

1) the rock wall crane beam mainly bears eccentric vertical load and simultaneously bears horizontal outward load under transient and accidental working conditions.

2) The rock wall crane beam is used as a carrier, and all the applied external loads are transmitted to the rock wall side wall, so that the surrounding rock stability is a precondition for the stability of the rock wall crane beam.

3) Conventional bedded bedrock wall crane beams primarily utilize the bedrock to carry vertical forces.

4) When the integral anti-overturning stability of the rock wall crane beam is calculated, the action of the cohesive force between the rock wall crane beam and surrounding rock is partially considered, and a tensile anchor rod is generally a non-prestressed anchor rod and is passively stressed; the contact part of the top surface of the rock wall crane beam and the surrounding rock is easy to crack.

5) The actual stress state of the conventional rock wall crane beam is that the top of the contact surface of the beam body and the surrounding rock is cracked first, and the crack does not develop after extending to a certain length; meanwhile, the surrounding rock of the lower table top generates certain deformation, the compression anchor rod and the beam body generate tiny rotation together, but the rotation point and the rock entering point of the compression anchor rod are not overlapped, but are deviated to a certain position above the rock entering point. For the convenience of calculation, the standard safely takes the rock entry point of the pressed anchor rod as a rotation point, which is not in accordance with the actual situation.

The main difference between a rockless wall beam and a rocky wall beam is the presence or absence of a bedrock. When the lower part of the beam body is not supported by the rock platform, if the calculation is still carried out according to the conventional calculation method of the rock-platform rock-wall beam, the cohesive force between the beam body and the surrounding rock is not considered completely, which means that all the loads are borne by the anchor rods, and the anchor rods bear large shearing force and tensile force, so that the requirements are often difficult to meet. In order to seek a safer and more efficient design, it is necessary to improve the conventional design to meet the actual needs of the project.

The tension anchor rod of the conventional rocky-platform rock-wall crane beam structure is generally a non-prestressed anchor rod and is passively stressed; if the anchor rod is used in a rockless platform rock-wall crane beam, the contact surface of the crane beam and surrounding rock will crack under the eccentric action of crane load, the beam loses the capability of resisting external bending moment and the capability of resisting vertical load, all external vertical loads are born by the anchor rod in a shearing mode, but the shearing capability of the anchor rod is weak, the structural damage of the beam body is directly caused, and the functional requirement and the structural safety requirement can not be met. And, crane beam can produce tiny deformation downwards along the contact surface under huge vertical force, if stock and country rock and rock wall crane beam are consolidated by cement mortar completely, the stock will receive the shearing action along with the roof beam body under the exogenic action, and the size of shearing action is directly proportional with shear strain. The anchor rod has the characteristics of strong tensile strength and weak shearing resistance. For the strong point of anchor rod, avoid the weak short of anchor rod shear capacity, traditional measure is like chinese utility model patent CN202899128U, refer to fig. 2, be close to in 1m length within range of country rock 1 mountain of rock-entering point of last two rows of tensile anchor rods 20 and the cliff crane roof beam 2 and set up the anchor rod free section to the country rock 10cm length within range, specific way is to wrap up in order to adapt to small downward deflection with flexible bed course 30 for the anchor rod at this section within range, directly pass to the mountain with the pulling force, also protect the face of country rock side wall when guaranteeing the anchor rod only to bear the pulling force.

The above conventional measures are disadvantageous in that when the anchor rod is pulled, the cement mortar (anchor body 30) of the anchoring section is subjected to a great tensile and shearing force, and the cement mortar serving as the anchoring function is at risk of gradually disintegrating and failing from the outer side to the mountain; meanwhile, the distance between the free section and the ground is only 1m, so that the stability of the cavern is not good in the core influence range of the tensile force.

Specifically, the conventional force transmission mode of the bonded anchor rod is that the anchor rod transmits the tension force applied by the anchor rod to a cement mortar anchoring section bonded with the anchor rod, and then the tension force is transmitted to surrounding rocks of a mountain through the anchoring section. When the anchor rod is pulled, the stress characteristic of the anchoring section is that the maximum concentrated tensile shear stress is generated at the anchoring initial end, and gradually attenuates towards the inner side end in a nonlinear mode, the stress is smaller when the anchoring section is closer to the inner side end, and the stress approaches to 0 after the anchoring section reaches a certain length. The anchor rod receives external tension and is all born by the anchor section, and the anchor rod atress is big more, and the concentrated tensile shear stress at anchor section top is big more, if external tension is big to certain extent, and the concentrated tensile shear stress that produces at anchor section top has surpassed cement mortar's the allowable value of pulling and shearing, then tip cement mortar disintegrates and destroys and progressively transmits to the mountain, until all anchor sections all suffer destruction, the anchor rod became invalid completely, the bearing capacity is lost to the structure. This is the reason why the conventional bonding anchor is regulated to be limited in length of the anchor segment, and the fundamental reason is that simply increasing the length of the anchor segment does not fundamentally solve the problem of insufficient anchoring force. If still adopt traditional biography power mode, it is still applicable when the load value is less, but can not satisfy the structure safety requirement when the load value is very big, need adopt new biography power mode to solve the problem. From the angle of stress, no matter the anchor rod is bonded or the end anchor rod, the tensile force borne by the anchor rod is finally transmitted to the mountain, but for the conventional bonded anchor rod, because the free section is close to the face, a large adverse external load is applied to a large underground workshop where the contradiction of the stability of the cavern is outstanding, the cavern is more adverse to stability, the situation is avoided to the greatest extent, and the problem lies in that the force transmission mode necessarily causes the adverse situation.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides a rock wall crane beam structure which enables the section at the joint of a beam body and surrounding rock to be in a compressed state under various working conditions and ensures that the shearing resistance of the section is not damaged, and also provides a construction method of the rock wall crane beam structure correspondingly.

In order to solve the technical problems, the invention adopts the following technical scheme:

a rock wall crane beam structure comprises a rock wall crane beam fixed on the wall surface of surrounding rock and a prestressed anchor rod connecting the surrounding rock and the rock wall crane beam; the wall surface of the surrounding rock is provided with an anchoring hole, the rock wall crane beam is provided with a through hole penetrating through the two wall surfaces of the rock wall crane beam along the length direction of the prestressed anchor rod, the anchoring hole is communicated with the through hole to form a containing hole, one end of the prestressed anchor rod forms an anchoring end, the other end of the prestressed anchor rod forms a locking end, and a free section is formed between the anchoring end and the locking end; the anchoring end is anchored in the anchoring hole, the free section is stretched in the accommodating hole, and the locking end is locked on the free face of the rock wall crane beam.

The design concept of the invention is as follows:

referring to FIG. 3, according to the specification of item 4.3.3 of NBT 35079-;

A_s1L_t2＝A_s2L_t1 (4.3.3-1)

in the formula: gamma ray₀The structural importance coefficient is 1.1 and 1.0 corresponding to the rock wall crane beam with the structural safety level of I and II respectively;

Ψ -design Condition coefficients, corresponding to persistent conditions, transient conditions, 1.0, 0.95, respectively;

γ_dthe structural coefficient of the calculation of the bearing capacity of the tensile anchor rod of the rock wall crane beam is not less than 1.65;

m is the sum (N.mm) of the moment of the intersection point of the compression anchor rod of the rock wall crane beam and the rock wall inclined plane by the design values of the unit beam length vertical wheel pressure, the horizontal load, the self weight of the rock wall crane beam, the gravity of the track and accessories, the gravity of the damp-proof partition wall on the beam and other loads;

f_ydesign value of tensile strength (N/mm) of tensile anchor rod²)；

A_s1、A_s2-calculated cross-sectional area (mm) of unit beam length of first and second rows of tensile anchors²)；

L_t1、L_t2The moment arm (mm) from the first row of tension anchor rods to the intersection point of the compression anchor rods and the rock wall inclined plane.

According to the specification of No. 4.3.4 of NBT 35079-2016 underground workshop rock wall crane beam design specification, the anti-skid stability safety factor of the rock wall crane beam is calculated according to the following formula:

A_s1L_t2＝A_s2L_t1 (4.3.3-1)

S(·)＝(G+F_v+W)cosβ+F_hsinβ (4.3.4-2)

in the formula: s (-) a down-slip force (N) along the rock wall slope;

r (-) slip resistance (N) along the slope of the rock wall;

F_v-design value (N) for vertical wheel pressure per beam length;

F_h-design value of horizontal load (N) for crane per unit beam length;

g is the design value (N) of the self weight of the crane beam with the unit beam length;

w is the design value (N) of the gravity of the track and accessories on the unit beam, the gravity of the moisture-proof partition wall on the beam and the like;

beta-wall angle (°);

α_i-inclination (°) of the tensile anchor in row i;

a-area of the unit beam long rock wall inclined plane (mm)²)；

A’_si-real matched cross-sectional area (mm) of unit beam length of ith row of tensile anchor rod²)；

f’_k-a shear-resistant friction coefficient standard value on the rock wall slope;

γ’_f-the subentry coefficient of the shear-resistant friction coefficient is taken as 1.7;

c’_k-standard value of shear-resistant cohesion (N/mm) on the slope of rock wall²)；

γ’_c-taking the fractional coefficient of shear cohesion to be 2.0;

γ_d-the anti-skid stability structure factor should not be less than 1.65;

from the above formulas 4.3.3-1 to 4.3.3-2 and 4.3.4-1 to 4.3.4-3, the stress calculation of the traditional crane beam with the rock wall of the rock platform has the following characteristics:

1) passive stressing, that is, the upper two rows of tensioned anchors, which are the primary stressed members, are only active when a load is placed on the beam.

2) Assume the point of rotation at which the compressed bolt enters the rock. This assumption is subject to large deviations from the actual force conditions. In fact, the center of rotation changes due to changes in force and is not fixed at a certain point.

3) The full section of the inclined plane of the rock platform is assumed not to crack. This assumption also has a large deviation from the actual force state. In fact, fracture cracking may occur only in the vertical plane, and may also extend to the sloping face of the bedrock.

4) It is assumed that there is a coupling relationship between the first row of tensioned anchors and the second row of tensioned anchors. The assumption is that no internal logic relation exists at all, and the relation is artificially imposed, and the aim is to add a condition so that the cross-sectional area of the anchor rod can be calculated. The assumption can be made on the design level, but the assumption does not exist in fact, the two rows of anchor rods are all the anchor rods with the same specification in all the projects which are implemented at present, and the case that the specifications of the two rows of anchor rods are inconsistent is not found.

For the rockless bedrock wall beam, the length of the non-cracking section cannot be determined, and further the anti-sliding stability safety factor cannot be calculated, so that the design idea does not have operability on the design level.

In view of the above circumstances, the present invention proposes the following solutions:

1) the stress of the crane beam is determined, the passive mode is changed into the active mode, and the upper two rows of common anchor rods are changed into prestressed anchor rods to resist the rotating moment generated by the load and the horizontally outward braking force.

2) The strong shearing resistance between the junction surfaces of the crane beam and the surrounding rock is fully exerted to resist the external force vertically downwards.

For the purpose of illustration, assuming that the contact surface is not used to shear at all, and the anchor is used to resist the vertical load only, the design value of the pure shear force that a single anchor can bear is taken as an example to illustrate the problem, as shown in the following table 1:

TABLE 1 vertical shear strength calculation table that anchor rod can provide

Anchor rod diameter (mm)	Design value of vertical resistance (kN) provided by shearing of single anchor rod
		32	153
36	193
		40	239
50	373

From table 1 above, the shear resistance of the anchor is weak, and even if the diameter reaches the unconventional 50mm, the shear resistance can be provided with only 373 kN.

The types of wall crane beams that are generally applicable to surrounding rocks are type I, type II and type III, according to the provisions of article 1.0.2 of NB/T35079-2016 underground building wall crane beam design Specification. According to the specification of D.0.1 in appendix D of NB/T35026-:

TABLE 2 anti-shear parameter table for contact surface of crane beam and different types of rock mass and rock mass

Taking the height of the bottom surface of the crane beam as an example of 2.5m, the standard values of the vertical resistance provided by the contact surface in a unit length under the condition of no cracking are calculated and are shown in the following tables 3 and 4:

TABLE 3 vertical resistance calculation Table provided by the contact surface of the crane beam and different types of rocks (only the cohesion is considered)

Rock mass classification	Standard value of vertical resistance (kN) that the contact surface can provide
		Class I	3750～3250
Class II	3250～2750
		Class III	2750～1750

Table 4 vertical resistance calculation table provided by contact surface of crane beam and different kinds of rocks (considering cohesiveness and considering 1000KN pre-pressure)

Rock mass classification	Standard value of vertical resistance (kN) that the contact surface can provide
		Class I	5250～4550
Class II	4550～3850
		Class III	3850～2650

From the above table 3, it can be seen that, under the premise of no cracking, the shearing resistance generated by the cohesive force of the contact surface is only considered, and the beneficial effect generated by the prestressed anchor rod is not considered, so that the vertical resistance of at least 1750N can be generated on the contact surface even under the condition of class III surrounding rocks. As can be seen from table 4 above, under the premise of no cracking, when the pre-pressure acting on the beam body is 1000kN, the shearing resistance generated by the contact surface cohesive force and the pre-pressure should be considered at the same time, and the vertical resistance of at least 2650N can be generated on the contact surface even under the condition of class iii surrounding rocks; the standard value of the long vertical wheel pressure of the unit beam of the underground powerhouse, the tail gate chamber and the main transformer chamber generally does not exceed 1000kN, for example, 942.9kN/m is applied to a hydropower station of a family dam, 867.2kN/m is applied to a hydropower station of a dragon beach, 840.0kN/m is applied to a small bay hydropower station, and 809.5kN/m is applied to a water-pumping and energy-storing power station of a white lotus river.

In order to achieve the above purpose, the core of the arrangement of the prestressed anchor rod is to have a certain safety margin for balancing the external rotation moment and the horizontal braking force, wherein the safety margin not only refers to the safety margin for overcoming the rotation moment, the horizontal force and the vertical force corresponding to the external load, but also refers to the safety margin for the prestressed anchor rod, and the prestressed anchor rod also has a certain safety margin because the anchor rod is the prestressed anchor rod, the tensile stress of the prestressed anchor rod can be further increased after the external load acts on the crane beam, and therefore the prestressed anchor rod also has a certain safety margin.

Through the structural design, the end anchor prestressed anchor rods are adopted in the rockless bedrock wall beam, and the positions and the prestress of the prestressed anchor rods are adjusted and optimized, so that the contact surface of the beam body and the surrounding rock is in a compression state rather than in a tension state under various working conditions, the bonding force and the friction force between the beam body and the surrounding rock can be ensured, the beam body is used for resisting external vertical load, and the structural safety is ensured; the traditional force transmission mode cannot avoid the cracking of the contact surface, the contact surface loses the capability of resisting external vertical load once the contact surface is cracked, the external load can only be borne by the anchor rod in a shearing mode, the capability of bearing the external vertical load by the anchor rod which is longer than the anchor rod under the shearing mode in tension is limited, the beam body can be damaged, and the structural safety requirement and the safety operation requirement of a crane cannot be met.

The prestressed anchor rod of the end anchor does not change the requirement of anti-sliding stability, but is more suitable for fully playing the advantages of various materials, improving the unreasonable position of the traditional force transmission mode, more conforming to the stress principle and more easily meeting the requirement of anti-sliding stability of the beam body and the requirement of stable cavern.

The invention can bring the following advantages:

1) the crane beam is definite in overall stress, the rotation center of the cross section can be determined to be the central point of the cross section of the bottom of the crane beam, design and operation are convenient, simplicity and reliability are realized, uncertain fuzzy space does not exist, and safety risks and design risks caused by uncertain cracking surfaces can be completely avoided.

2) The crane beam is ensured to be perfectly bonded with the surrounding rock, and the strong shearing resistance of the joint surface of the concrete and the surrounding rock can be fully exerted to resist the vertical force.

3) Whether the magnitude of the main stress on the combined surface exceeds the limit or not can be directly checked according to a fourth strength theory, and the method is more reasonable, safe and reliable compared with the stress checking calculation in a single direction.

4) The coupling relationship between the two rows of anchors need not be assumed in advance. The specifications of the two rows of anchor rods can be designed and combined at will according to the stress requirement.

5) The arrangement mode that there is the horizontal contained angle in traditional stock has been changed, and all change into the level setting, construction, installation are more convenient.

6) The prestressed anchor rod is more beneficial to the stability of surrounding rocks, can replace a cavern at the position to stabilize the prestressed anchor cable, and achieves the effect of killing two birds with one stone.

7) The invention is also suitable for the design of the bedrock wall beam, and only needs to slightly process the inclined plane of the bedrock.

The core calculation formula of the method is shown as the following formula 1.1-1-1.1-5.

The anchoring length of the tension anchor rod in the stable rock mass can be calculated according to the specification of NB/T35079 and 2016 (design Specification for underground plant rock wall crane beam) item 4.3.7, as shown in the following formulas 1.1-1 and 1.1-2:

in the formula L_a-the length of the anchoring section of the tensioned bolt in the stabilization mass (mm);

γ_d-calculating the structural coefficient of the anchoring length of the tensioned anchor rod, and notLess than 1.35;

γ_b-the coefficient of the adhesive strength is 1.25;

f_ydesign value of tensile strength (N/mm) of tensile anchor rod²)；

f_rb,k-standard value of adhesion strength of cementitious material to hole wall (N/mm)²)；

f_b,k-standard value of bonding strength (N/mm) of cementing material and anchor rod²)；

d-anchor diameter (mm);

d-anchor rod hole diameter (mm);

d-anchor diameter (mm);

A_sthe cross-sectional area (N/mm) of a single anchor²)。

The stress of the top end and the bottom end of the section is calculated according to the following formula 1.1-3-1.1-4:

σ_{top roof}The normal pressure stress (kPa) at the top end of the contact surface of the rock wall beam and the surrounding rock is not less than 0 and is positive

σ_BottomThe normal pressure stress (kPa) at the bottom end of the contact surface of the rock wall beam and the surrounding rock is not less than 0 and the pressure is positive

ΣN_KSum of standard values of the pre-stresses acting on the wall beams (kN)

ΣM_KRelative to the sum of the standard values of all the turning moments of the contact surfaces of the rock-wall beam and the surrounding rock (kN m)

The cross section anti-skid stability calculation is calculated according to the specification of NB/T35079-2016 underground powerhouse rock wall crane beam design Specification 4.3.4, as shown in the following formulas 1.1-5:

in the formula F_vDesign value of vertical wheel pressure per unit beam length (kN)

F_hDesign value of horizontal load of crane per unit beam length (kN)

G-design value of self-weight of crane beam with unit beam long rock wall (kN)

W-design values of unit beam length upper track and accessory gravity and damp-proof partition wall gravity on beam (kN)

A-area of cross section of contact surface between crane wall and rock wall with unit beam length (m)²)

f’_k-Standard value of coefficient of friction against shear on rock wall slope (kPa)

γ’_f-the subentry coefficient of the shear coefficient of friction, taken as 1.7

c’_k-standard value for shear strength on rock wall slope (kPa)

γ’_c-the fractional coefficient of shear cohesion, taken as 2.0

γ_dThe anti-skid stable structural coefficient should not be less than 1.65.

As a further improvement of the above technical solution:

the free section comprises a first section and a second section, the first section is arranged in the anchoring hole, the second section is arranged in the through hole, an anchoring body for anchoring the anchoring end in the anchoring hole is poured in the anchoring hole, and a barrier layer for blocking the first section from contacting with the anchoring body is coated on the outer circumference of the first section.

Preferably, the barrier layer is formed by wrapping an insulating tape around the first segment, and the outer circumference of the first segment is coated with an adhesive, preferably hot asphalt, for connecting the first segment and the barrier layer.

And the through hole is filled with anti-rust oil for preventing the second section from rusting. Meanwhile, the section of the anchor rod exposed outside the beam body is also coated with grease for protection, so that key force transmission components such as threads and nuts are always in a grease-coated protection state, and the durability of the anchor rod is ensured. In addition, the corrosion prevention of the whole anchor rod and the anchor head is highly valued from each link of the manufacturing of the fine steel prestressed anchor rod, which is the key for ensuring the stress according to the design intention. After the anchor rod is rusted, the stressed cross-sectional area of the anchor rod can be directly reduced, and the stress capacity of the anchor rod is reduced, so that proper measures must be taken to prevent the anchor rod from being rusted. The anchor rod is generally made of finish-rolled deformed steel bar, has no antirust capability, is easy to rust, and can be remarkably accelerated in a high-prestress state, so that the durability and the structural safety of the anchor rod are seriously influenced.

The through hole is internally provided with an accommodating pipe, the second section is arranged in the accommodating pipe, and the anti-rust oil is arranged between the inner wall of the accommodating pipe and the outer wall of the second section.

In order to fully discharge the air in the through hole and ensure the antirust effect of the second section, an oil injection pipe and an exhaust pipe are pre-embedded in the rock wall crane beam, one end of the oil injection pipe is fixedly connected and communicated with one end, close to the anchoring hole, of the accommodating pipe, and the other end of the oil injection pipe is provided with an oil injection port which is positioned on the free face of the rock wall crane beam; one end of the exhaust pipe is fixedly connected and communicated with one end, far away from the anchoring hole, of the holding pipe, the other end of the exhaust pipe is provided with an exhaust port, and the exhaust port is located on the face of the rock wall crane beam.

The anchor end is provided with a force transmission plate which is penetrated and fixed with the inner wall of the anchor hole and is abutted against the inner wall of the anchor hole, so that the tension borne by the anchor rod is transmitted to the anchor end. The force transmission plate is provided with a pulp passing hole.

An anchor backing plate is pre-embedded in the rock wall crane beam, the outer side face of the anchor backing plate is located on the face empty face of the rock wall crane beam, and the locking end is locked on the outer side face of the anchor backing plate.

The effect of anchor backing plate is pressed on the anchor backing plate and makes the stock produce prestressing force when the bolt of stock outer end head is screwed up, and the anchor backing plate still plays the effect of the concentrated load protection roof beam body of dispersion simultaneously, otherwise under the powerful local pressure that the bolt produced roof beam body concrete pressurized destruction lead to the stock prestressing force to lose, roof beam body structural damage.

As a general inventive concept, the present invention also provides a construction method of the above-described rock wall crane beam structure, including the steps of:

s1: drilling holes in the surrounding rock to form anchoring holes;

s2: anchoring the anchoring end of the prestressed anchor rod in the anchoring hole;

s3: assembling a rock wall crane beam mold to form a crane beam pouring cavity and a through hole which is positioned in the crane beam pouring cavity and is not communicated with the crane beam pouring cavity; the through hole is communicated with the anchoring hole, and one section of the free section extending out of the anchoring hole is arranged in the through hole;

s4: pouring a rock wall crane beam;

s5: and tensioning the prestressed anchor rod to the design requirement, and locking the locking end on the free face of the rock wall crane beam.

As a further improvement of the above technical solution:

in the step S3, an accommodating tube communicated with the anchoring hole is fixed in the crane beam pouring cavity, and the through hole is formed in an inner cavity of the accommodating tube.

In the step S3, an oil injection pipe and an exhaust pipe are fixed in the crane beam pouring cavity, one end of the oil injection pipe is communicated with one end of the accommodating pipe close to the anchoring hole, and the other end of the oil injection pipe is abutted against the inner wall surface of one end of the rock wall crane beam mould close to the cavity; one end of the exhaust pipe is communicated with one end, far away from the anchoring hole, of the containing pipe, and the other end of the exhaust pipe is abutted against the inner wall face of one end, close to the cavity, of the rock wall crane beam mold.

Compared with the prior art, the invention has the advantages that:

1. the invention innovatively adopts a new force transmission mode, so that the tensile force is directly transmitted to the deep part of the rock wall, the tensile shearing action of cement mortar is avoided, the advantage of high compressive strength of cement mortar in a three-dimensional compressive stress state is fully exerted, the anchoring end is far away from the face of the vacancy, and the stability of the cavern is effectively ensured. And the prestress borne by the anchor rod can be dynamically adjusted according to the requirement.

Drawings

FIG. 1 is a typical cross-sectional view of a conventional bedrock wall crane beam.

Fig. 2 is a schematic view of a conventional bedrock wall crane beam structure.

FIG. 3 is a graph showing the calculation of the cross-sectional area of the tension anchor rod of the unit beam long rock wall crane beam.

Figure 4 is a schematic view of the rock wall crane beam structure of the present invention.

Illustration of the drawings: 1. surrounding rocks; 11. an anchoring hole; 2. a rock wall crane beam; 21. a through hole; 3. a pre-stressed anchor rod; 31. an anchoring end; 32. a locking end; 33. a first stage; 34. a second stage; 4. a barrier layer; 5. antirust oil; 6. an accommodating tube; 7. an oil filling pipe; 8. an exhaust pipe; 71. an oil filling port; 81. an exhaust port; 9. a force transmission plate; 10. and (5) anchoring a backing plate.

Detailed Description

The invention is further described below with reference to specific preferred embodiments, without thereby limiting the scope of protection of the invention.

Example (b):

as shown in fig. 4, the rock wall crane beam structure of the present embodiment includes a rock wall crane beam 2 fixed to a wall surface of a surrounding rock 1, and a plurality of prestressed anchors 3 connecting the surrounding rock 1 and the rock wall crane beam 2.

The wall of the surrounding rock 1 is provided with anchoring holes 11 corresponding to the prestressed anchor rods 3 one by one, the rock wall crane beam 2 is pre-embedded with accommodating pipes 7 corresponding to the prestressed anchor rods 3 one by one, oil injection pipes 7 and exhaust pipes 8, the accommodating pipes 7 penetrate through two walls of the rock wall crane beam 2 along the length direction of the prestressed anchor rods 3, inner cavities of the accommodating pipes 7 form through holes 21, and the anchoring holes 11 are communicated with the corresponding through holes 21 to form the accommodating holes.

One end of the oil injection pipe 7 is fixedly connected and communicated with one end, close to the anchoring hole 11, of the accommodating pipe 6, the other end of the oil injection pipe 7 is provided with an oil injection port 71, and the oil injection port 71 is positioned on the free face of the rock wall crane beam 2; one end of the exhaust pipe 8 is fixedly connected and communicated with one end, far away from the anchoring hole 11, of the accommodating pipe 6, the other end of the exhaust pipe 8 is provided with an exhaust port 81, and the exhaust port 81 is located on the face of the rock wall crane beam 2. The through hole 21 is filled with anti-rust oil 5 for preventing the second section 34 from rusting through the oil filling pipe 7, and the anti-rust oil 5 is butter.

One end of the prestressed anchor rod 3 forms an anchoring end 31, the other end of the prestressed anchor rod 3 forms a locking end 32, and a free section is formed between the anchoring end 31 and the locking end 32; the anchoring end 31 is anchored in the anchoring hole 11, the anchoring end 31 is provided with a force transmission plate 9 which is connected with the inner wall of the anchoring hole 11 in a penetrating way and is fixed, and the force transmission plate 9 is provided with a pulp passing hole. The free section is stretched in the containing hole, an anchor backing plate 10 is embedded in the rock wall crane beam 2, the outer side face of the anchor backing plate 10 is located on the free face of the rock wall crane beam 2, and the locking end 32 is locked on the outer side face of the anchor backing plate 10.

Wherein the free section comprises a first section 33 arranged in the anchoring hole 11 and a second section 34 arranged in the through hole 21, an anchoring body 40 for anchoring the anchoring end 31 in the anchoring hole 11 is poured in the anchoring hole 11, and the anchoring body 40 is cement mortar. The first section 33 is coated on its outer circumference with a barrier layer 4 that blocks the first section 33 from contact with the anchor.

The barrier layer is formed by winding the first section with an insulating tape, and hot asphalt for connecting the first section and the barrier layer is coated on the outer circumference of the first section before winding the insulating tape.

The construction method of the rock wall crane beam structure comprises the following steps:

s1: and (3) accurately positioning the position of the prestressed anchor rod, and drilling holes on the surrounding rock 1 strictly according to the design requirement to form anchor holes 11.

S2: coating an epoxy coating on the outer layer of the prestressed anchor rod 3, wrapping a barrier layer, installing in place, pouring cement mortar for anchoring strictly according to the design requirement, and anchoring the anchoring end 31 of the prestressed anchor rod 3 in the anchoring hole 11.

S3: assembling a rock-wall crane beam mould, binding rock-wall crane beam steel bars, sleeving and fixing a pre-embedded steel pipe as a containing pipe 7 at the exposed section of the pre-stressed anchor rod, and binding an anchor backing plate 10. The pre-buried steel pipe should be strictly positioned according to the design requirement and protected, and concrete is prevented from permeating into the pre-buried pipeline in the pouring process.

S4: and (5) pouring the rock wall crane beam 2.

S5: after the rock wall crane beam 2 reaches the design strength, the prestressed anchor rods 3 are stretched according to the design requirements, and then the locking ends 32 are locked on the outer side surfaces of the anchor backing plates 10. And the grease is injected into the prestressed anchor rod through the pre-buried pipeline under pressure to protect the free section of the prestressed anchor rod, and after the grease injection is finished, the leakproof plugs 50 are plugged into the grease injection port 71 and the exhaust port 81. Meanwhile, the locking end 32 exposed outside the beam body is also coated with grease for protection, so that key force transmission components such as threads, screw caps and the like are always in a grease-coated protection state, and the durability of the anchor rod is ensured. After coating is complete, the locking end 32 is capped with a boot 60.

S6: regularly patrolling and filling and coating butter, timely adjusting the prestress of the anchor rod according to the stable monitoring condition of the surrounding rock, ensuring the structure safety and meeting the normal operation requirement.

The construction process is as follows:

1) and each load working condition is fully considered during calculation, so that the tensile stress does not appear on the section under each working condition, and the shearing capacity of the section is protected under a pressure state.

2) During loading, each prestressed anchor rod is subjected to small-amplitude cyclic loading step by step according to a graded loading principle, and the loading amplitude is strictly controlled, so that the section is always in a pressed state, and the shearing resistance of the section is ensured not to be damaged.

3) The stressed anchoring ends of the prestressed anchor rods are typical end anchors, and the arrangement needs to be carried out at intervals to reduce the group anchor effect.

4) The corrosion prevention of the whole anchor rod and the anchor head is highly valued from the production of the fine steel prestressed anchor rod in each link, which is the key for ensuring the stress according to the design intention.

5) When pouring cement mortar, grouting from the bottom of the hole to the orifice and returning the grout, and taking certain protection measures to ensure that the grout is fully filled.

The prestress is generated by screwing bolts at the end part of the anchor rod, during actual construction, the anchor rod is tensioned by a jack, the tension force borne by the anchor rod is strictly controlled, and the tension force is read by a pressure gauge matched with the jack. When the jack is tensioned to reach the designed tonnage, the bolt is manually screwed down, and then the jack is loosened, so that the bolt is tightly pressed on the anchor backing plate. And if the prestress needs to be adjusted, tensioning the anchor rod again by using the jack, and manually adjusting the bolt again to finish the prestress adjustment. Therefore, it is necessary to install stress monitoring devices on the upper and lower edges of the contact surface between the beam body and the surrounding rock, so that the prestress of the anchor rod can be dynamically adjusted according to the stress conditions of the upper and lower edges of the contact surface.

The above description is only for the preferred embodiment of the present application and should not be taken as limiting the present application in any way, and although the present application has been disclosed in the preferred embodiment, it is not intended to limit the present application, and those skilled in the art should understand that they can make various changes and modifications within the technical scope of the present application without departing from the scope of the present application, and therefore all the changes and modifications can be made within the technical scope of the present application.

Claims

1. A rock wall crane beam structure comprises a rock wall crane beam (2) fixed on the wall surface of surrounding rock (1) and a prestressed anchor rod (3) connecting the surrounding rock (1) and the rock wall crane beam (2); the wall surface of the surrounding rock (1) is provided with an anchoring hole (11), the rock wall crane beam (2) is provided with a through hole (21) penetrating through the two wall surfaces of the rock wall crane beam (2) along the length direction of the prestressed anchor rod (3), the anchoring hole (11) is communicated with the through hole (21) to form a containing hole, one end of the prestressed anchor rod (3) forms an anchoring end (31), the other end of the prestressed anchor rod (3) forms a locking end (32), and a free section is formed between the anchoring end (31) and the locking end (32); the anchoring end (31) is anchored in the anchoring hole (11), the free section is stretched in the accommodating hole, and the locking end (32) is locked on the free face of the rock wall crane beam (2).

2. A rock wall crane beam structure according to claim 1, characterized in that the free section comprises a first section (33) placed in the anchoring hole (11), and a second section (34) placed in the through hole (21), the anchoring hole (11) being poured with an anchoring body (40) anchoring the anchoring end (31) in the anchoring hole (11), the outer circumference of the first section (33) being coated with a barrier layer (4) blocking the first section (33) from contact with the anchoring body.

3. A rock wall crane beam structure according to claim 1, characterized in that the through hole (21) is filled with rust preventive oil (5) preventing the second section (34) from rusting.

4. A rock wall crane beam structure according to claim 3, characterized in that the through hole (21) is provided with a receiving tube (6), the second section (34) is placed in the receiving tube (6), and the rust preventive oil (5) is provided between the inner wall of the receiving tube (6) and the outer wall of the second section (34).

5. The rock wall crane beam structure as claimed in claim 4, wherein an oil injection pipe (7) and an exhaust pipe (8) are embedded in the rock wall crane beam (2), one end of the oil injection pipe (7) is fixedly connected and communicated with one end of the accommodating pipe (6) close to the anchoring hole (11), the other end of the oil injection pipe (7) is provided with an oil injection port (71), and the oil injection port (71) is positioned on the face of the rock wall crane beam (2); one end of the exhaust pipe (8) is fixedly connected and communicated with one end, far away from the anchoring hole (11), of the accommodating pipe (6), the other end of the exhaust pipe (8) is provided with an exhaust port (81), and the exhaust port (81) is located on the empty face of the rock wall crane beam (2).

6. A rock wall crane beam structure according to any one of claims 1-5, characterized in that the anchoring end (31) is provided with a force transmission plate (9) which is in contact with the inner wall of the anchoring hole (11) in a penetrating way and is fixed, and the force transmission plate (9) is provided with a grout passing hole.

7. A rock wall crane beam structure according to any one of claims 1-5, characterized in that an anchor backing plate (10) is embedded in the rock wall crane beam (2), the outer side surface of the anchor backing plate (10) is located on the face of the rock wall crane beam (2), and the locking end (32) is locked on the outer side surface of the anchor backing plate (10).

8. A method of constructing a rock wall crane beam structure as claimed in any one of claims 1 to 7, comprising the steps of:

s1: drilling a hole in the surrounding rock (1) to form an anchoring hole (11);

s2: anchoring the anchoring end (31) of the prestressed anchor rod (3) in the anchoring hole (11);

s3: assembling a rock wall crane beam mold to form a crane beam pouring cavity and a through hole (21) which is positioned in the crane beam pouring cavity and is not communicated with the crane beam pouring cavity; the through hole (21) is communicated with the anchoring hole (11), and one section of the free section extending out of the anchoring hole (11) is arranged in the through hole (21);

s4: pouring a rock wall crane beam (2);

s5: and (3) stretching the prestressed anchor rod (3) to the design requirement, and locking the locking end (32) on the free face of the rock wall crane beam (2).

9. A construction method of a rock wall crane beam structure according to claim 8, characterized in that in step S3, a receiving tube (6) communicating with the anchoring hole (11) is fixed in the crane beam casting cavity, and the inner cavity of the receiving tube (6) forms the through hole (21).

10. The construction method of a rock wall crane beam structure as claimed in claim 9, wherein in the step S3, an oil injection pipe (7) and an exhaust pipe (8) are fixed in the crane beam pouring cavity, one end of the oil injection pipe (7) is communicated with one end of the accommodating pipe (6) close to the anchoring hole (11), and the other end of the oil injection pipe (7) is abutted against the inner wall surface of the empty end of the rock wall crane beam (2); one end of the exhaust pipe (8) is communicated with one end, far away from the anchoring hole (11), of the accommodating pipe (6), and the other end of the exhaust pipe (8) is abutted against the inner wall face of one end, close to the cavity, of the rock wall crane beam (2).