阅读说明：本技术 一种地下球冠型穹顶的开挖方法 (Excavation method of underground spherical crown type dome ) 是由 任长春 聂文俊 叶明� 何金星 王洪松 于 2020-12-16 设计创作，主要内容包括：本发明提供一种地下球冠型穹顶的开挖方法,包括球冠型穹顶由上而下划分为Ⅰ-Ⅴ层；Ⅰ层依次开挖环形导洞区、中心岩柱区、拉槽区、环形扩挖区以及周边保护层；Ⅱ-Ⅴ层均采取中间梯段爆破、两侧预留保护层的方式开挖。Ⅰ层采用先挖环形导洞、预留中间岩柱支撑、周边环形扩挖的穹顶开挖方法充分利用球形体水平剖切面为标准圆的规律特点,围绕穹顶中心轴线按不同半径圆周水平钻孔的方法进行开挖,实现以圆削球目的,解决了超大跨度球冠穹顶的开挖成型质量和围岩稳定难题。本申请提供的方法具有精度高、成型质量好、轮廓面规整、超欠挖小的优点。(The invention provides an excavation method of an underground spherical crown type dome, which comprises the steps that the spherical crown type dome is divided into I-V layers from top to bottom; the layer I is sequentially excavated into an annular pilot tunnel area, a central rock pillar area, a slot-drawing area, an annular expanding excavation area and a peripheral protective layer; and the II-V layers are excavated by adopting the modes of middle bench blasting and reserved protective layers on two sides. A dome excavation method of firstly excavating an annular pilot tunnel, reserving a middle rock pillar support and annularly expanding and excavating the periphery of the layer I fully utilizes the regular characteristic that the horizontal cutting plane of a spherical body is a standard circle, and excavates the layer I by a method of horizontally drilling holes around the central axis of the dome according to circumferences with different radiuses, so that the purpose of round ball cutting is achieved, and the problems of excavation forming quality and surrounding rock stability of the spherical crown dome with the ultra-large span are solved. The method provided by the application has the advantages of high precision, good forming quality, regular profile surface and small super-back digging.)

1. An excavation method of an underground spherical crown type dome is characterized by comprising the following steps: the spherical crown type dome is divided into I-V layers from top to bottom;

the layer I is sequentially excavated into an annular pilot tunnel area, a central rock pillar area, a slot-drawing area, an annular expanding excavation area and a peripheral protective layer; the annular pilot tunnel region surrounds the central rock pillar region, the slot drawing region is positioned below the annular pilot tunnel region and the central rock pillar region, the annular expanding and digging region is positioned on the outer side of the annular pilot tunnel region and the slot drawing region, and the peripheral protective layer is positioned on the outer side of the annular expanding and digging region;

and the II-V layers are excavated by adopting the modes of middle bench blasting and reserved protective layers on two sides.

2. The method for excavating an underground spherical crown type dome according to claim 1, wherein the excavating of the annular pilot tunnel region, the central rock pillar region, the slot pulling region, the annular expanding excavation region and the peripheral protective layer in sequence for the layer I comprises:

reserving a central rock pillar by taking the center of the spherical crown-shaped dome as a base point to form a central rock pillar area;

excavating along the outer side of the central rock pillar area to form an annular pilot tunnel area, and supporting a top arch of the annular pilot tunnel area;

excavating the central rock pillar area, and supporting a dome of the central rock pillar area;

excavating the lower parts of the annular pilot tunnel area and the central rock pillar area to form a groove drawing area;

excavating along the outer sides of the annular pilot tunnel area and the groove-drawing area to form an annular expanding excavation area, and supporting a top arch of the annular expanding excavation area;

and excavating the peripheral protective layer on the outer side of the annular expanding excavation area and the layer II together.

3. The method of excavating an underground spherical cap dome according to claim 2, wherein excavating along the outside of the central pillar region to form an annular pilot tunnel region comprises:

the excavation drilling adopts horizontal drilling in the tangential direction of concentric circles, wherein the hole pitch of the blasting holes in the annular pilot tunnel area is 80-90cm, and the row pitch is 70-80 cm; the hole pitch of the light explosion holes close to the central rock pillar area is 50 cm; the distance between the light explosion holes close to the contour line of the dome of the spherical crown is 40 cm;

and after the drilled hole is checked to meet the requirement, charging and blasting to form an annular pilot tunnel region.

4. The excavation method of an underground spherical crown type dome according to claim 3, wherein, in the blast holes of the annular pilot tunnel region, the maximum hole depth of the outermost arc blast holes is 1.5m, and the minimum hole depth of the innermost arc blast holes is 0.6 m.

5. The method of excavating an underground spherical cap dome according to claim 2, wherein excavating the central pillar region comprises: excavating a reserved protective layer at the upper part above the lower pilot tunnel after excavating the lower pilot tunnel of the central rock pillar; and the upper reserved protective layer is radially drilled by taking the center of the spherical crown dome as an axis, and the annular pilot tunnel area excavates the spherical crown dome layer by layer from the center of the spherical crown dome.

6. The method for excavating an underground spherical crown type dome according to claim 5, wherein the blast holes of the central rock pillar region are distributed as follows: the row pitch is 70-80cm, the hole pitch is 80-90cm, and the hole pitch at the dome is 40 cm.

7. The excavation method of an underground spherical crown type dome according to claim 1, wherein the excavation of the two side reserved protective layers comprises:

the protective layer comprises an inner protective layer and an outer protective layer;

excavating the inner protective layer after blasting the middle bench; and the outer protective layer is excavated along with the lower layer.

8. The method for excavating an underground spherical crown type dome according to any one of claims 1 to 7, wherein the method further comprises, before excavating the underground spherical crown type dome:

simulating the excavation of the underground spherical crown type dome by adopting a numerical simulation analysis technology and combining the space position factors of the construction channel and the adjacent cavern;

and determining an excavation mode of dividing the spherical crown type dome into I-V layers from top to bottom according to the comparative analysis of the deformation, the stress and the stability of the surrounding rock.

9. The excavation method of an underground spherical-crown-type dome according to any one of claims 1 to 7, wherein a plurality of the underground spherical-crown-type domes are excavated at intervals.

Technical Field

The invention relates to the technical field of building construction, in particular to an excavation method of an underground spherical crown type dome.

Background

The tail water surge chamber of the Wudongde hydropower station is independent at the lower part and independent at the upper partA communicated giant semi-cylindrical structure, the maximum excavation section area of the tail adjusting chamber is 1725m²The total excavation height is 113.5m, the maximum excavation diameter is 53m, and the method is the largest tail-regulated chamber vertical well group in the world at present.

As shown in attached figure 1, the top arch of a single tail water surge chamber is of a spherical crown shape, the middle part is a huge semi-cylindrical shaft section with the excavation diameter of 53m, and the bottom part is a tail water turnout section. The spherical crown type dome at the top of the tail adjusting chamber has a continuously-changed curved surface structure, so that the excavation forming quality is difficult to control.

At present, the existing method for excavating the underground spherical crown dome generally excavates a middle pilot tunnel, after entering the dome through the middle pilot tunnel, drills radiation holes to the periphery and the top, and then controls the excavation profile of the dome by controlling the depth of the drilled holes. The method has the problems of low excavation precision, poor forming quality, irregular profile surface and larger super-short excavation.

Disclosure of Invention

The invention provides an excavation method of an underground spherical crown type dome, which solves the problems of low excavation precision, poor forming quality, irregular profile surface and larger super underexcavation of the existing excavation method.

The invention provides an excavation method of an underground spherical crown type dome, which comprises the following steps: the spherical crown type dome is divided into I-V layers from top to bottom;

the layer I is sequentially excavated into an annular pilot tunnel area, a central rock pillar area, a slot-drawing area, an annular expanding excavation area and a peripheral protective layer; the annular pilot tunnel region surrounds the central rock pillar region, the slot drawing region is positioned below the annular pilot tunnel region and the central rock pillar region, the annular expanding and digging region is positioned on the outer side of the annular pilot tunnel region and the slot drawing region, and the peripheral protective layer is positioned on the outer side of the annular expanding and digging region;

and the II-V layers are excavated by adopting the modes of middle bench blasting and reserved protective layers on two sides.

Preferably, I layer excavates annular pilot tunnel district, central rock pillar district, trompil district, annular expand and dig district and peripheral protective layer in proper order and includes:

reserving a central rock pillar by taking the center of the spherical crown-shaped dome as a base point to form a central rock pillar area;

excavating along the outer side of the central rock pillar area to form an annular pilot tunnel area, and supporting a top arch of the annular pilot tunnel area;

excavating the central rock pillar area, and supporting a dome of the central rock pillar area;

excavating the lower parts of the annular pilot tunnel area and the central rock pillar area to form a groove drawing area;

excavating along the outer sides of the annular pilot tunnel area and the groove-drawing area to form an annular expanding excavation area, and supporting a top arch of the annular expanding excavation area;

and excavating the peripheral protective layer on the outer side of the annular expanding excavation area and the layer II together.

Preferably, excavating along the outside of the central pillar region to form an annular pilot tunnel region comprises:

the excavation drilling adopts horizontal drilling in the tangential direction of concentric circles, wherein the hole pitch of the blasting holes in the annular pilot tunnel area is 80-90cm, and the row pitch is 70-80 cm; the hole pitch of the light explosion holes close to the central rock pillar area is 50 cm; the distance between the light explosion holes close to the contour line of the dome of the spherical crown is 40 cm;

and after the drilled hole is checked to meet the requirement, charging and blasting to form an annular pilot tunnel region.

Preferably, in the blast holes of the annular pilot tunnel region, the maximum hole depth of the outermost arc blast hole is 1.5m, and the minimum hole depth of the innermost arc blast hole is 0.6 m.

Preferably, excavating the central pillar zone comprises: excavating a reserved protective layer at the upper part above the lower pilot tunnel after excavating the lower pilot tunnel of the central rock pillar; and the upper reserved protective layer is radially drilled by taking the center of the spherical crown dome as an axis, and the annular pilot tunnel area excavates the spherical crown dome layer by layer from the center of the spherical crown dome.

Preferably, the blast holes in the excavation of the central rock pillar area are distributed as follows: the row pitch is 70-80cm, the hole pitch is 80-90cm, and the hole pitch at the dome is 40 cm.

Preferably, the excavation of the two side reserved protective layers comprises:

the protective layer comprises an inner protective layer and an outer protective layer;

excavating the inner protective layer after blasting the middle bench; and the outer protective layer is excavated along with the lower layer.

Preferably, the underground spherical crown type dome further comprises, before excavation:

simulating the excavation of the underground spherical crown type dome by adopting a numerical simulation analysis technology and combining the space position factors of the construction channel and the adjacent cavern;

and determining an excavation mode of dividing the spherical crown type dome into I-V layers from top to bottom according to the comparative analysis of the deformation, the stress and the stability of the surrounding rock.

Preferably, a plurality of the underground spherical crown type domes are excavated at intervals.

The technical scheme provided by the embodiment of the invention can have the following beneficial effects:

the invention provides an excavation method of an underground spherical crown type dome, which comprises the following steps: the spherical crown type dome is divided into I-V layers from top to bottom; the layer I is sequentially excavated into an annular pilot tunnel area, a central rock pillar area, a slot-drawing area, an annular expanding excavation area and a peripheral protective layer; the annular pilot tunnel region surrounds the central rock pillar region, the slot drawing region is positioned below the annular pilot tunnel region and the central rock pillar region, the annular expanding and digging region is positioned on the outer side of the annular pilot tunnel region and the slot drawing region, and the peripheral protective layer is positioned on the outer side of the annular expanding and digging region; and the II-V layers are excavated by adopting the modes of middle bench blasting and reserved protective layers on two sides. In the application, the layer I is excavated by adopting a dome excavation method of firstly excavating an annular pilot tunnel, reserving a middle rock pillar support and annularly expanding and excavating the periphery, the regular characteristic that the horizontal section of a spherical body is a standard circle is fully utilized, excavation is carried out by adopting a method of horizontally drilling holes according to different radiuses around the central axis of a dome, the blasting scale and the single-section dosage are controlled, the purpose of cutting a ball by a circle is realized, and the problems of excavation forming quality and surrounding rock stability of the spherical crown dome with the super-large span are solved. Meanwhile, the method that the peripheral protective layer is excavated along with the lower layer can solve the problems that drilling precision control is difficult to carry out due to the space height problem and the primary support anchor rod cannot be implemented, further, overbreak caused by too much outer edge blast holes invading the designed section is avoided, and the relaxation depth of dangerous rocks is too large due to the fact that the primary support cannot be implemented timely, and finally dome forming and surrounding rock stability are ensured. The method provided by the application has the advantages of high precision, good forming quality, regular profile surface and small super-back digging.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without any creative effort.

Fig. 1 is a schematic partial structural diagram of a tail water surge chamber of an udon hydropower station provided in an embodiment of the invention;

FIG. 2 is a layered view of a spherical crown type dome excavation of a single tail water surge chamber provided by an embodiment of the invention;

FIG. 3 is a sectional view of a layer I excavation provided by an embodiment of the present invention;

fig. 4 is a three-dimensional simulation diagram of an excavation process of a spherical crown type dome of a single tail water surge chamber according to an embodiment of the present invention;

fig. 5 is a schematic diagram of excavation of an annular pilot tunnel area according to an embodiment of the present invention;

fig. 6 is a layout diagram of blast holes excavated in the annular pilot tunnel region according to the embodiment of the present invention;

FIG. 7 is a diagram illustrating arrangement of blast holes excavated in the central rock pillar region according to an embodiment of the present invention;

fig. 8 is a diagram of a blast hole arrangement of an upper reserved protective layer in a central rock pillar zone provided by an embodiment of the present invention.

Detailed Description

For the convenience of description of the excavation method provided in the embodiment of the present application, the description will be given by taking the stern transfer chamber of the udder hydropower station with the maximum excavation diameter of 53m as an example.

The embodiment of the application provides an excavation method of an underground spherical crown type dome, which comprises the following steps: the spherical crown type dome is divided into I-V layers from top to bottom; wherein, the layer I is sequentially excavated into an annular pilot tunnel area, a central rock pillar area, a slot-pulling area, an annular expanding excavation area and a peripheral protective layer; and the II-V layers are excavated by adopting the modes of middle bench blasting and reserved protective layers on two sides.

In order to ensure excavation quality and safety, the method also comprises the following steps before the excavation of the underground spherical crown type dome:

s01: simulating the excavation of the underground spherical crown type dome by adopting a numerical simulation analysis technology and combining the space position factors of the construction channel and the adjacent cavern;

in the embodiment of the application, according to the structural characteristics of the tail water surge chamber and the performance of construction machinery, a numerical simulation analysis technology is adopted, and the factors such as the space position of a construction channel and an adjacent cavern are combined to simulate the whole process excavation of the tail water surge chamber vertical well group, so that a plurality of excavation schemes are formed.

S02: and determining an excavation mode of dividing the spherical crown type dome into I-V layers from top to bottom according to the comparative analysis of the deformation, the stress and the stability of the surrounding rock.

According to the excavation simulation of the tail water surge chamber shaft well group, analyzing surrounding rock deformation, stress and stability caused by different excavation schemes, and determining an excavation mode of dividing the spherical crown type dome into I-V layers from top to bottom, wherein the layer I excavates an annular pilot tunnel region, a central rock pillar region, a slot pulling region, an annular expanding excavation region and a peripheral protective layer in sequence; and the II-V layers are excavated by adopting the modes of middle bench blasting and reserved protective layers on two sides. Namely, the method is a dome excavation method which firstly excavates an annular pilot tunnel, reserves a middle rock pillar support and annularly expands and excavates the periphery. The method fully utilizes the regular characteristic that the horizontal section of the spherical body is a standard circle, excavates by a method of drilling holes horizontally around the central axis of the dome according to the circumferences with different radiuses, controls the blasting scale and the single-section dosage, realizes the purpose of 'cutting the ball by the circle', and solves the difficult problems of excavation forming quality and surrounding rock stability of the spherical crown dome with super-large span. Feedback and dynamic control are monitored in real time in the process of excavating the spherical crown type dome, and the deformation and stability of the excavation of the tail water surge chamber can be effectively controlled.

Further, because the Udongde hydropower station right bank tail transfer room comprises a plurality of tail water pressure regulating rooms, for reducing the stable adverse effect of adjacent cavern blasting to the spherical crown dome in the work progress, a plurality of underground spherical crown type domes are excavated according to the interval and are constructed, if: and the No. 6 tail water pressure regulating chamber → the No. 4 tail water pressure regulating chamber → the No. 5 tail water pressure regulating chamber.

Referring to fig. 3 and 4, wherein fig. 3 shows a sectional view of the excavation of a layer i, and fig. 4 shows a three-dimensional simulation diagram of the excavation process of a spherical crown type dome of a single tail water surge chamber. As shown in fig. 3 and 4, the excavation process of the spherical crown type dome of the single tail water surge chamber specifically includes:

the spherical crown type dome is divided into I-V layers from top to bottom for construction, and the excavation layering diagram is shown as an attached figure 2. Wherein, the maximum excavation height of the layer I is 10.9m, and the layering height of the rest layers is 5-7 m. The I layer excavates according to five regions in annular pilot tunnel district, central rock pillar district, trompil district, annular expand and dig district and peripheral protective layer in proper order, and wherein, annular pilot tunnel district encircles central rock pillar district, and the trompil district is located the below in annular pilot tunnel district and central rock pillar district, and annular expands digs the outside that the district was excavated in annular pilot tunnel district and trompil district, and peripheral protective layer is located the annular and expands the outside of digging the district.

Further, the excavation process in each district on I layer specifically is:

s11: and reserving a central rock pillar by taking the center of the spherical crown-shaped dome as a base point to form a central rock pillar area.

And reserving a central rock pillar with the diameter of 10m by taking the center of the spherical crown-shaped dome as a base point to form a central rock pillar area.

S12: and excavating along the outer side of the central rock pillar area to form an annular pilot tunnel area, and supporting a top arch of the annular pilot tunnel area.

Undercutting is performed along the outer side of the central rock pillar region, and then the upper protective layer is excavated to form an annular pilot tunnel region, as shown in fig. 5. Wherein the excavation width of the annular pilot tunnel area is 8.0m, and the height is 7.49m-10.42 m.

When the annular pilot tunnel area is excavated, a manual YT-28 hand-held pneumatic drill is matched with a drilling and blasting trolley to drill holes, and then manual charging and blasting are carried out. Specifically, before drilling, the line position and the tail line point of each blast hole and the hole forming depth of each blast hole are determined by measuring and setting out the line and according to a blasting design drawing and an actual excavation side line. The excavation drilling adopts the concentric circle tangential direction horizontal drilling, namely, the hand pneumatic drill drills horizontal holes along the arc tangential direction, wherein the hole pitch of the blasting holes of the annular pilot tunnel area is 80-90cm, and the row pitch is 70-80 cm; the hole pitch of the light explosion holes close to the central rock pillar area is 50 cm; the distance between the light explosion holes close to the contour line of the dome of the spherical cap is 40cm, as shown in the attached figure 6.

In the embodiment of the application, the hole depth of the blast hole drilled in the annular pilot tunnel region is gradually changed, for example, the maximum hole depth of the outermost arc is 1.5m, and the minimum hole depth of the innermost arc is 0.6 m. In order to control the overowing and undermining of the top side line of the spherical crown vault to the maximum extent, the depth of a blasting hole, the hole position and the charging parameters of the standard excavation section of the annular pilot tunnel are programmed and calculated every cycle so as to ensure the optimal blasting data. After each row of blast holes are drilled, the depth of the blast hole is measured by field quality testing personnel by using a steel tape. If the depth of the blast hole exceeds the design requirement, the blast hole is plugged by the stemming until the depth meets the requirement, then the powder is charged and blasted, and an annular pilot tunnel area is formed. And after the excavation of the annular pilot tunnel area is finished, supporting the top arch of the annular pilot tunnel area in time.

S13: and excavating the central rock pillar area, and supporting a dome of the central rock pillar area.

And after the excavation of the annular pilot tunnel area is finished and the top arch support of the annular pilot tunnel area is finished, excavating the central rock pillar area. And after the excavation of the central rock pillar area is finished, supporting a dome of the central rock pillar area. In the embodiment of the application, the central rock pillar is divided into an upper part and a lower part for excavation, wherein the upper part is provided with the reserved protective layer on the upper part, and the lower part is provided with the guide hole on the lower part. Specifically, the pilot tunnel at the lower part of the central rock pillar is excavated, the excavation size is 10 × 7.9m, and the excavation is carried out in left and right halves. And after the excavation of the lower guide tunnel is finished, excavating the upper reserved protective layer with the thickness of 2.5-3 m. The protective layer reserved on the upper portion is drilled radially by taking the center of the spherical crown-shaped dome as an axis, and the spherical crown-shaped dome is excavated layer by layer from the annular pilot tunnel area to the center of the spherical crown-shaped dome.

When the central rock pillar area is excavated, a manual YT-28 hand-held pneumatic drill is matched with a drilling and blasting trolley to drill holes, and then manual charging and blasting are carried out. Specifically, before drilling, the line position and the tail line point of each blast hole and the hole forming depth of each blast hole are determined by measuring and setting out the line and according to a blasting design drawing and an actual excavation side line. Hand pneumatic drill bores the horizontal hole along circular arc tangential direction, wherein, the big gun hole when central pillar district excavation distributes and is: the row spacing is 70-80cm, the hole spacing is 80-90cm, the hole spacing at the dome is 40cm, the hole depth ultra-deep 20cm is 1.5m, the specific blasting parameters are shown in table 1, and the blast hole distribution diagrams are shown in figures 7 and 8. After each row of blast holes are drilled, the depth of the blast hole is measured by field quality testing personnel by using a steel tape. And if the depth of the blast hole exceeds the design requirement, the blast hole is plugged by the stemming until the blast hole meets the requirement, then the powder is loaded and blasted, and then the central rock pillar area is formed.

Table 1: blasting design main technical parameters of central rock pillar zone

S14: and excavating the lower parts of the annular pilot tunnel area and the central rock pillar area to form a groove drawing area.

In order to satisfy the annular pilot tunnel district and prevent that the long stock construction space demand of crown arch 9m and drilling and blasting platform truck size demand in this application embodiment, excavation in central rock pillar district is accomplished and excavate the below in annular pilot tunnel district and central rock pillar district after the vault of central rock pillar district is strutted and is accomplished, forms the trompil district that the groove depth is 3.5 m. And D7 hydraulic drilling is adopted to drill holes in the slot drawing area, and drilling bench blasting is carried out.

S15: and excavating along the outer sides of the annular pilot tunnel area and the groove broaching area to form an annular expanding excavation area, and supporting a top arch of the annular expanding excavation area.

After the excavation construction of the slot-drawing area is completed, excavation is performed along the outer sides of the annular pilot tunnel area and the slot-drawing area to form an annular expanded excavation area, and simultaneously, a top arch of the annular expanded excavation area is supported. The excavation width of the annular expanding excavation area is 5.4m, and the height is 6.56-10.84 m. When the annular expanding excavation area is excavated, a manual YT-28 hand-held pneumatic drill is matched with a drilling and blasting trolley to drill holes, and then manual charging and blasting are carried out. The blasting drilling and charging parameters of the annular expanding and digging area are controlled to be consistent with those of the annular pilot tunnel area.

S16: and excavating the peripheral protective layer on the outer side of the annular expanding excavation area and the layer II together.

The peripheral protective layer outside the annular expanded excavation area is a narrow area at the outer edge of the dome. Because this space is narrow and small, therefore can not satisfy the required minimum space of rig drilling, consequently, the protective layer that reserves certain thickness with the dome edge in this application embodiment excavates along with the next floor together, and peripheral protective layer is put and is excavated together with the next floor in the next floor promptly, also excavates along with II layers together. If there is a dome structure outside the peripheral protective layer, this part of the structure is excavated together with the layer iii, as shown in fig. 3. Because the central rock pillar area, the annular pilot tunnel area, the slot-broaching area and the annular expanding excavation area are excavated, the dome has enough space for arranging a drilling machine to carry out drilling and supporting construction. Therefore, the peripheral protective layer and the edge part can be excavated simultaneously during lower-layer excavation, so that the problems that drilling precision is not easy to control and an anchor rod of primary support cannot be implemented due to the problem of space height are avoided, overbreak caused by too much invasion of an outer edge blast hole into a designed section is avoided, and the loose depth of dangerous rocks is too large due to the fact that primary support cannot be implemented timely, and finally dome forming and surrounding rock stability are ensured.

For the excavation of the peripheral protective layers in the spherical crown type dome II-V layer and the spherical crown type dome I layer, the mode that middle bench blasting is adopted and the protective layers are reserved on two sides is adopted in the embodiment of the application. Specifically, reserve the thick protective layer of 5.5m in the design sideline of interlude, for guaranteeing design structure line excavation shaping quality in the embodiment of this application, the protective layer is divided twice and is excavated, and the protective layer includes inlayer protective layer and outer protective layer promptly. After blasting of the middle bench, an inner protective layer and a peripheral protective layer in the layer I within a range close to the middle 3m are excavated, and the remaining outer protective layer of 2.5m is excavated along with the lower layer, namely, the layer III. And when the II-V layer is excavated, the middle section is vertically drilled by adopting an ROC-D7 type hydraulic drill, and the bench is blasted after charging. And drilling a horizontal hole in the inner protective layer by adopting a hand pneumatic drill, and excavating in an annular direction. The blasting drilling and charging parameters of the II-V layer are controlled to be consistent with those of the annular pilot tunnel.

In the method for excavating the underground spherical crown type dome, the layer I is excavated by adopting a dome excavating method of firstly excavating an annular pilot tunnel, reserving a middle rock pillar support and annularly expanding and excavating the periphery, the method of horizontally drilling holes according to different radiuses around the central axis of the dome is adopted to excavate by fully utilizing the rule characteristic that the horizontal section of a spherical body is a standard circle, the blasting scale and the single-section dosage are controlled, the purpose of 'cutting a ball by a circle' is realized, and the problems of excavation forming quality and surrounding rock stability of the spherical crown dome with the super-large span are solved. Meanwhile, the method that the peripheral protective layer is excavated along with the lower layer can solve the problems that drilling precision control is difficult to carry out due to the space height problem and the primary support anchor rod cannot be implemented, further, overbreak caused by too much outer edge blast holes invading the designed section is avoided, and the relaxation depth of dangerous rocks is too large due to the fact that the primary support cannot be implemented timely, and finally dome forming and surrounding rock stability are ensured. The method provided by the application has the advantages of high precision, good forming quality, regular profile surface and small super-back digging.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It is to be understood that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The invention is not limited to the precise arrangements described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.