Open cut top-down ultra-deep working well construction method under rock stratum geology

Abstract

The invention relates to the technical field of large shield launching working well construction, in particular to ultra-deep open-cut top-down construction under the rock stratum geology, and particularly relates to an open-cut top-down ultra-deep working well construction method under the rock stratum geology. The problems that in the construction process of an open-cut top-down ultra-deep working well, collapse, water leakage, instability and other risks are prone to occurring are solved, excavation is conducted to the bottom face of a top beam, then the top beam is constructed, an annular frame beam is constructed, and a waterproof layer and a side wall are constructed in the area, between the annular frame beam and the top beam, of the side wall of a foundation pit; after the last annular frame beam and the side wall reach the design strength, the foundation pit continues to be excavated downwards to the bottom face of the next annular frame beam, the annular frame beam is constructed, and a waterproof layer and the side wall are constructed in the area, between the annular frame beam and the last annular frame beam, of the side wall of the foundation pit; and after the last annular frame beam and the side wall reach the design strength, the foundation pit continues to be excavated downwards, mortar anchor rods and steel frame supports are constructed on the portion, below the coverage area of the cast-in-situ bored piles, of the side wall of the foundation pit, and then concrete is sprayed.

Description

Technical Field

[0001] The invention relates to the technical field of large shield starting working shaft construction, in particular to ultra-deep open-cut reverse construction under rock strata geology, and specifically to an open-cut reverse ultra-deep working shaft construction method under rock strata geology. Background Art

[0002] During the construction of large shield tunneling, the working shaft is used as a vertical shaft for shield assembly, dismantling, turning, empty pushing, lifting pipe segments and conveying slag, etc. Especially as large shield tunneling continues to break world records in river crossing and sea crossing sections, deeper and deeper working shafts are being used, which has also become the focus of attention from all parties.

[0003] In areas with rock strata geology, the open-cut reverse working method is usually used for the construction of working wells. However, when it is necessary to construct an ultra-deep working well (generally, working wells over 50m are considered ultra-deep working wells), due to the characteristics of the rock strata geology area, which are, from top to bottom, miscellaneous fill layers, fully weathered dacite layers, strongly weathered dacite layers, and weakly weathered dacite layers, the open-cut reverse working well is prone to risks of collapse, leakage, instability, etc. during construction, and the construction cost is high. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for constructing an ultra-deep working well with open excavation and reverse excavation under rock strata geology, so as to solve the problem that the ultra-deep working well with open excavation and reverse excavation is prone to collapse, leakage, instability and other risks during the construction process.

[0005] The present invention is achieved through the following technical solutions: A method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology comprises the following steps: S10. Pre-design the dimensions of the ultra-deep working well and the dimension parameters of the crown beam and the ring frame beams of each layer; S20. Level the site in the construction area and build a good surface drainage system; S30, according to the measured layout position, before the excavation of the working well, bored cast-in-place pile construction work is carried out, and the bottom of the bored cast-in-place pile extends into the weakly weathered dacite layer; S40, excavate to the bottom of the crown beam, then construct the crown beam, and promptly construct a water collection well and intercepting ditch in the pit for open drainage; S50, after the crown beam reaches the designed strength, the foundation pit is excavated downward to the bottom surface of the first ring frame beam, a ring frame beam is constructed, and a waterproof layer and a side wall are constructed in the area between the ring frame beam and the crown beam on the side wall of the foundation pit; S60, after the previous ring frame beam and side wall reach the design strength, continue to excavate the foundation pit downward to the bottom surface of the next ring frame beam, install the next ring frame beam, and install a waterproof layer and side wall in the area between the next ring frame beam and the previous ring frame beam on the side wall of the foundation pit; S70, repeating step S60 in the coverage area of ​​bored piles, and applying each layer of ring frame beams, side walls and waterproof layers in sequence from top to bottom; S80, when the previous ring frame beam and side wall reach the design strength, continue to excavate the foundation pit downwards, apply mortar anchor rods and steel frame support on the side wall of the foundation pit below the coverage area of ​​bored piles, and then spray concrete; Then the ring frame beam, waterproof layer and side wall are applied in this area; S90, according to step S80, in the coverage area of ​​the mortar anchor rod and the steel frame support, the working ring frame beam, the waterproof layer and the side wall are constructed from top to bottom; S100. After the last ring frame beam and side wall have reached the designed strength, continue excavating to the bottom of the foundation pit and construct the base plate cushion layer, waterproof structure and base plate structure.

[0006] Furthermore, in step S30, the bottom of the bored pile extends into the weakly weathered dacite layer by no less than 6 m.

[0007] Furthermore, in step S30, a water-stop curtain is established on the outer side of the bored pile by high-pressure jet grouting, and the bottom of the water-stop curtain penetrates into the strongly weathered dacite layer by no less than 3 m.

[0008] Furthermore, in step S40, excavation is performed to the bottom surface of the crown beam, and then the bored pile head is chiseled out, and during the construction of the crown beam, the crown beam is connected to the bored pile head; Furthermore, in step S80, locking anchor rods and steel frame support are installed at the bottom of the bored pile, and then concrete is sprayed.

[0009] Furthermore, in step S50, during the construction of the side wall, the lightweight truss formwork is fixed by pre-embedded anchor bolts in the upper and lower walls of the ring frame beam, and then cast into the side wall.

[0010] Furthermore, in step S70, when installing the locking anchor and steel frame support at the bottom of the bored pile, an anchor drilling and injection machine is used for construction. The locking anchor is 7m long, the horizontal angle is 10°, the spacing is 0.5m×1.45m (vertical×horizontal), and the shotcrete uses 300mm thick C30 quick-hardening concrete.

[0011] Furthermore, the distance between upper and lower adjacent ring frame beams does not exceed 7m.

[0012] Furthermore, in step S100, the soil under the last ring frame beam is excavated to the bottom of the foundation pit in two steps.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology of the present invention can be used to construct an ultra-deep working well under rock strata geology, and bored cast-in-place piles and water-stop curtains are used to optimize the depth of pile foundation into the rock, thereby saving costs. The side walls of the foundation pit below the area covered by bored piles are supported by mortar anchors and steel frames, and then the ring frame beam, waterproof layer and side wall are constructed in this area; in the bored pile section without bedrock enclosure, the layered support and layered excavation method is adopted, and the side walls and ring frame beams of the open-cut reverse working pit form a stable structure to achieve the purpose of safe excavation; 2. The open-cut reverse ultra-deep working well construction method under rock strata geology of the present invention reduces the risks of collapse, leakage, instability, etc. during the construction process, and reduces the construction cost; 3. Locking anchor rods and steel frame support are installed at the bottom of the bored piles, and then concrete is sprayed, which effectively reduces the risk of settlement of the top of the retaining piles and the ground surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of an ultra-deep working well in an open-cut reverse operation according to the present invention; In the figure: 1. crown beam, 2. ring frame beam, 3. bored cast-in-place piles, 4. water-stop curtain, 5. side wall, 6. locking foot anchor rod, 7. mortar anchor rod. DETAILED DESCRIPTION

[0015] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0016] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0017] The rock formation geology is from top to bottom, which is mixed fill soil layer, fully weathered dacite layer, strongly weathered dacite layer, weakly weathered dacite layer, among which the weakly weathered dacite layer is the bedrock section. If the working well is constructed as usual, it is easy to have risks such as collapse, leakage, and instability, and the construction cost is high. To solve this problem, take the construction of a 58m deep working well in the area of ​​rock formation geology as an example. Figure 1 As shown, this embodiment discloses a method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology, comprising the following steps: S10, pre-design the size of the ultra-deep working well and the size parameters of the crown beam 1 and the ring frame beams 2 of each layer; In this embodiment, the well depth is 58m, and the number of ring frame beams 2 is eight; S20. Level the site in the construction area and build a good surface drainage system; S30, according to the measured layout position, before the excavation of the working well, the bored pile construction operation is carried out, and the pile bottom of the bored pile 3 extends into the weakly weathered dacite stratum. During the construction process, it is ensured that the pile bottom of the bored pile 3 extends into the weakly weathered dacite stratum by not less than 6m; A water-stop curtain 4 is built on the outside of the bored pile 3 by high-pressure jet grouting, and the bottom of the water-stop curtain 4 penetrates into the strongly weathered dacite layer by no less than 3m; S40, excavate to the bottom of the crown beam, then chisel out the pile heads of bored piles, and then construct the crown beam. During the construction of the crown beam, connect the crown beam with the pile heads of bored piles, so as to make the foundation pit more stable; and timely construct water collection wells and intercepting ditches in the pit for water collection and open drainage; S50, after the crown beam reaches the designed strength, the foundation pit is excavated downward to the bottom surface of the first ring frame beam, a ring frame beam is constructed, and a waterproof layer and a side wall 5 are constructed in the area between the ring frame beam 2 and the crown beam 1 on the side wall of the foundation pit; During the construction of the side wall, the lightweight truss formwork is fixed by pre-buried anchor bolts in the upper and lower walls of the ring frame beam, and waterproof measures such as water-stop steel plates are taken between the construction joints, and then the side wall 5 is cast; S60, after the previous ring frame beam and side wall reach the design strength, continue to excavate the foundation pit downward to the bottom surface of the next ring frame beam, install the next ring frame beam, and install a waterproof layer and side wall in the area between the next ring frame beam and the previous ring frame beam on the side wall of the foundation pit; S70, repeating step S60 in the coverage area of ​​bored piles, and applying each layer of ring frame beams, side walls and waterproof layers in sequence from top to bottom; In order to ensure the stability of the foundation pit, the distance between the upper and lower adjacent ring frame beams shall not exceed 7m; At the location where the coverage area of ​​bored piles is about to end, the foot anchor and steel frame support are installed at the bottom of the bored piles, and the construction is carried out using an anchor drilling and injection machine. The foot anchor 6 is 7m long, with a horizontal plane angle of 10° and a spacing of 0.5m×1.45m (vertical×horizontal). Then, shotcrete is sprayed, and the shotcrete is 300mm thick C30 fast-hardening concrete. S80, after the previous ring frame beam and side wall reach the design strength, continue to excavate the foundation pit downwards, use mortar anchor rods 7 and steel grids to apply mortar anchor rods and steel frame support on the side walls of the foundation pit below the coverage area of ​​the bored piles, and then spray concrete; Then the ring frame beam, waterproof layer and side wall are applied in this area; S90, according to step S80, in the coverage area of ​​the mortar anchor rod and the steel frame support, the working ring frame beam, the waterproof layer and the side wall are constructed from top to bottom; S100. When the last ring frame beam and side wall reach the designed strength, the soil under the last ring frame beam is excavated to the bottom of the foundation pit in two times, and the bottom plate cushion layer, waterproof structure and bottom plate structure are constructed.

[0018] Through the above-mentioned open-cut reverse ultra-deep working well construction method under rock strata geology, ultra-deep working well construction can be carried out under rock strata geology, and bored cast-in-place piles and water-stop curtains are used to optimize the depth of pile foundation into the rock, thereby saving costs; The side walls of the foundation pit below the coverage area of ​​the bored piles are supported by mortar anchors and steel frames, and then the ring frame beams, waterproof layers and side walls are constructed in this area. In the bored pile sections without bedrock enclosures, a layered support and layered excavation method is adopted, and a stable structure is formed by the side walls and ring frame beams of the open-cut reverse working shaft to achieve the purpose of safe excavation, reduce the risks of collapse, leakage, instability, etc. during construction, and reduce construction costs.

Claims

1. A method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata, characterized in that: The following steps are involved: S10. Pre-design the dimensions of the ultra-deep working well and the dimension parameters of the crown beam and the ring frame beams of each layer; S20. Level the site in the construction area and build a good surface drainage system; S30, according to the measured layout position, before the excavation of the working well, bored cast-in-place pile construction work is carried out, and the bottom of the bored cast-in-place pile extends into the weakly weathered dacite layer; S40, excavate to the bottom of the crown beam, then construct the crown beam, and promptly construct a water collection well and intercepting ditch in the pit for open drainage; S50, after the crown beam reaches the designed strength, the foundation pit is excavated downward to the bottom surface of the first ring frame beam, a ring frame beam is constructed, and a waterproof layer and a side wall are constructed in the area between the ring frame beam and the crown beam on the side wall of the foundation pit; S60, after the previous ring frame beam and side wall reach the design strength, continue to excavate the foundation pit downward to the bottom surface of the next ring frame beam, install the next ring frame beam, and install a waterproof layer and side wall in the area between the next ring frame beam and the previous ring frame beam on the side wall of the foundation pit; S70, repeating step S60 in the coverage area of ​​bored piles, and applying each layer of ring frame beams, side walls and waterproof layers in sequence from top to bottom; S80, when the previous ring frame beam and side wall reach the design strength, continue to excavate the foundation pit downwards, apply mortar anchor rods and steel frame support on the side wall of the foundation pit below the coverage area of ​​bored piles, and then spray concrete; Then the ring frame beam, waterproof layer and side wall are applied in this area; S90, according to step S80, in the coverage area of ​​the mortar anchor rod and the steel frame support, the working ring frame beam, the waterproof layer and the side wall are constructed from top to bottom; S100. After the last ring frame beam and side wall have reached the designed strength, continue excavating to the bottom of the foundation pit and construct the base plate cushion layer, waterproof structure and base plate structure.

2. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology according to claim 1 is characterized in that: In step S30, the bottom of the bored pile extends into the weakly weathered dacite layer by no less than 6 m.

3. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology according to claim 1, characterized in that: In step S30, a water-stop curtain is built on the outside of the bored pile by high-pressure jet grouting, and the bottom of the water-stop curtain penetrates into the strongly weathered dacite layer by no less than 3 m.

4. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology according to claim 1, characterized in that: In step S40, excavation is performed to the bottom surface of the cap beam, and then the bored pile heads are chiseled out. During the construction of the cap beam, the cap beam is connected to the bored pile heads.

5. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata geology according to claim 1, characterized in that: In step S80, anchor bolts and steel frame support are installed at the bottom of the bored pile, and then concrete is sprayed.

6. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata according to claim 5, characterized in that: In step S50, during the construction of the side wall, the lightweight truss formwork is fixed by pre-embedded anchor bolts in the upper and lower walls of the ring frame beam, and then cast into the side wall.

7. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata according to claim 6, characterized in that: In step S70, when installing the locking anchor and steel frame support at the bottom of the bored pile, an anchor drilling and injection machine is used for construction. The locking anchor is 7m long, the horizontal angle is 10°, the spacing is 0.5m×1.45m (vertical×horizontal), and the shotcrete is 300mm thick C30 quick-hardening concrete.

8. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata according to any one of claims 1 to 7, characterized in that: The distance between upper and lower adjacent ring frame beams shall not exceed 7m.

9. The method for constructing an ultra-deep working well by open-cut reverse excavation under rock strata according to any one of claims 1 to 7, characterized in that: In step S100, the soil under the last ring frame beam is excavated to the bottom of the foundation pit in two steps.

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