Secondary structure of arch foundation pit and its construction method

Abstract

The present invention discloses an arch base foundation pit secondary structure and a construction method thereof. The arch base foundation pit secondary structure is characterized by comprising: an existing foundation pit side slope platform, the existing foundation pit side slope platform comprising a left bank arch seat and a right bank arch seat arranged at intervals; a left six-layer side slope platform, the left six-layer side slope platform being formed on the left bank arch seat, the left six-layer side slope platform comprising a left first-level side slope platform, a left second-level side slope platform, a left third-level side slope platform, a left fourth-level side slope platform, a left fifth-level side slope platform and a left sixth-level side slope platform distributed in a stepped manner from top to bottom in the elevation direction of the existing foundation pit side slope platform; and a right first-level side slope platform being formed on the right bank arch seat. The present invention reduces the construction difficulty of the arch base foundation pit by forming the left six-layer side slope platform and the right first-level side slope platform on the existing foundation pit side slope platform, respectively, on the left bank arch seat and the right bank arch seat.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary excavation of an existing arch foundation pit, and in particular to an arch foundation pit secondary structure and a construction method thereof. Background Art

[0002] In the relevant technology, it is necessary to expand the excavation again after the original arch seat has been excavated to the designed base. In addition, the terrain of the original arch seat is complex, the surrounding rock of the arch seat base is broken, cracks are developed, and the surrounding rock of the slope below the arch seat is in a strong weathering zone.

[0003] However, since the excavation of the arch foundation pit is a secondary excavation, the slope of the excavated foundation pit needs to be re-slope treated. The slope is steep, the cover soil is thin, part of the bedrock is exposed, and the working platform range is limited.

[0004] Therefore, when conventional construction methods are applied to construction environments similar to this one, the construction efficiency is low and cannot meet the construction needs. Summary of the Invention

[0005] The main purpose of the present invention is to provide an arch base pit secondary structure and a construction method thereof, aiming to solve the technical problem that when the conventional construction method in the prior art is applied to a construction environment similar to this environment, the construction efficiency is low and it cannot meet the construction requirements.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an abutment foundation pit secondary structure, comprising:

[0008] An existing foundation pit slope platform, wherein the existing foundation pit slope platform includes a left bank abutment and a right bank abutment arranged at intervals;

[0009] A left six-layer side slope platform is formed on the left bank arch seat, and the left six-layer side slope platform includes a left first side slope platform, a left second side slope platform, a left third side slope platform, a left fourth side slope platform, a left fifth side slope platform and a left sixth side slope platform, which are distributed in a stepped manner from top to bottom in the elevation direction of the existing foundation pit side slope platform;

[0010] a right first-level side slope platform, formed on the right bank arch seat;

[0011] Among them, the left first-level slope platform, the left second-level slope platform, the left third-level slope platform, the left fourth-level slope platform, the left fifth-level slope platform and the left sixth-level slope platform are distributed in sequence along the first direction as their orthographic projections on the base of the existing foundation pit slope platform.

[0012] Optionally, in the above-mentioned abutment foundation pit secondary structure, a downstream abutment replacement portion is formed at the left fourth-level side slope platform, and an upstream abutment replacement portion is formed on one side of the left fifth-level side slope platform;

[0013] The upstream abutment replacement portion and the downstream abutment replacement portion are spaced apart along the second direction on the orthographic projection of the base of the existing foundation pit slope platform;

[0014] The first direction and the second direction intersect.

[0015] Optionally, in the above-mentioned abutment foundation pit secondary structure, the elevation range of the left first-level slope platform is 794.491m to 787.648m, and the height is 6.843m;

[0016] The elevation range of the left secondary slope platform is 787.648m to 780.498m, with a height of 7.15m;

[0017] The elevation range of the left third-level slope platform is 780.498m to 773.417m, with a height of 7.081m;

[0018] The elevation range of the left fourth-level slope platform is 773.417m to 763.417m, with a height of 10m;

[0019] The elevation range of the left five-level slope platform is 763.417m to 755.417m, with a height of 8m;

[0020] The elevation range of the left six-level slope platform is 755.417m to 747.417m, with a height of 8m;

[0021] The elevation range of the right first-level slope platform is 764.417m to 756.417m, with a height of 8m;

[0022] The elevation range of the upstream abutment foundation replacement part is 763.417m to 761.417m, and the replacement height is 2m;

[0023] The elevation range of the downstream arch seat foundation replacement part is 763.417m~753.417m, and the replacement height is 10m.

[0024] Optionally, in the above-mentioned abutment foundation pit secondary structure, the slope ratio of the left first-level slope platform is 1:0.9, and the platform width is 2m;

[0025] The slope ratio of the left secondary slope platform is 1:0.5, and the platform width is 2m;

[0026] The slope ratio of the left third-level slope platform is 1:0.5, and the platform width is 2m;

[0027] The slope ratio of the left fourth-level slope platform is 1:0.3, and the platform width is 2m;

[0028] The slope ratio of the left five-level slope platform is 1:0.25, and the platform width is 2m;

[0029] The slope ratio of the left six-level slope platform is 1:0.9, and the platform width is 3m;

[0030] The slope ratio of the right first-level slope platform is 1:0.5, and the platform width is 4.2m;

[0031] The slope ratio of the upstream abutment foundation replacement part is 1:0.1;

[0032] The slope ratio of the downstream abutment foundation replacement portion is 1:0.2.

[0033] Optionally, in the above-mentioned arch seat foundation pit secondary structure, horse paths are provided between the left first-level slope platform, the left second-level slope platform, the left third-level slope platform, the left fourth-level slope platform, the left fifth-level slope platform and the left sixth-level slope platform.

[0034] In a second aspect, the present invention provides a method for constructing a secondary structure of an arch foundation pit, for forming the above-mentioned secondary structure of an arch foundation pit, the method comprising:

[0035] Excavate a construction channel to form a working platform;

[0036] Using the working platform, on the left bank abutment of the existing foundation pit side slope platform, the left first side slope platform, the left second side slope platform, the left third side slope platform, the left fourth side slope platform, the left fifth side slope platform and the left sixth side slope platform are formed layered and graded from top to bottom along the elevation direction of the existing foundation pit side slope platform to form the left six-layer side slope platform;

[0037] The right first-level slope platform is formed on the right bank arch seat of the existing foundation pit slope platform.

[0038] Optionally, in the above-mentioned method for constructing the secondary structure of the arch foundation pit, the elevation range of the left primary slope platform is 794.491m to 787.648m, and the height is 6.843m. The step of excavating the construction channel to form the working platform includes:

[0039] Excavate the downstream side of the left first-level slope platform and build a slope excavation construction road so that the elevation of the construction road meets 790.491m;

[0040] Carry out rock excavation and slope repair on the slopes with elevations of 794.491m to 790.491m;

[0041] The overburden is removed and rock drilling and blasting are carried out to form the working platform.

[0042] Optionally, in the above-mentioned method for constructing the secondary structure of the arch foundation pit, the step of excavating and repairing the slope at an elevation of 794.491 m to 790.491 m includes:

[0043] Deep hole blasting and shallow hole blasting were used to excavate the slope with an elevation of 794.491m to 790.491m.

[0044] Optionally, in the above-mentioned method for constructing the secondary structure of the arch foundation pit, the step of excavating and repairing the slope at an elevation of 794.491 m to 790.491 m includes:

[0045] The slope with an elevation of 794.491m to 790.491m was repaired by smooth blasting and hammer chiseling.

[0046] Optionally, in the above-mentioned method for constructing the secondary structure of the arch foundation pit, the step of repairing the slope with an elevation of 794.491 m to 790.491 m by using smooth blasting and hammer chiseling includes:

[0047] A plurality of blasting holes are arranged according to a preset hole diameter and a preset hole spacing, so that the hole diameter of each blasting hole meets the preset hole diameter, and the spacing between adjacent blasting holes meets the preset hole spacing.

[0048] The above one or more technical solutions provided by the present invention may have the following advantages or at least achieve the following technical effects:

[0049] The present invention proposes a secondary structure of an arch foundation pit and a construction method thereof. The structure forms a left six-layer slope platform and a right first-layer slope platform on the left bank arch seat and the right bank arch seat respectively on the existing foundation pit slope platform, thereby reducing the construction difficulty of the arch foundation pit and ensuring the stability of the arch foundation pit through the left six-layer slope platform and the right first-layer slope platform. The structure is more suitable for construction working environments with steep slopes, thin cover, partially exposed bedrock, and limited working platform range, providing a reference basis for similar construction situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these provided drawings without paying any creative work.

[0051] Figure 1Schematic diagram of the process of the secondary structure construction method of the arch foundation pit of the present invention;

[0052] Figure 2 This is a schematic diagram of the distribution of the secondary excavation slope platform of the left bank abutment involved in the present invention;

[0053] Figure 3 This is a schematic diagram of the distribution of the secondary excavation slope platform of the right bank abutment involved in the present invention.

[0054] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0056] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0057] In the present invention, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "include..." does not exclude the presence of other identical elements in the process, method, article or system comprising the element. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which both A and B are satisfied.

[0058] In the present invention, unless otherwise clearly specified or limited, the terms "connection", "fixed", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection between two elements or the interaction relationship between two elements.

[0059] In the present invention, if there are descriptions involving "first," "second," etc., such descriptions are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly specifying the number of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of such features.

[0060] In the present invention, the suffixes such as "mechanism", "component" or "part" used to represent elements are only used to facilitate the description of the present invention and have no specific meaning. Therefore, "mechanism", "component" or "part" can be used interchangeably.

[0061] Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances. Furthermore, the technical solutions of the various embodiments may be combined with each other, but this is based on the ability of those skilled in the art to implement them. If a combination of technical solutions contradicts or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0062] The inventive concept of the present invention is further described below with reference to some specific embodiments.

[0063] The present invention provides an arch foundation pit secondary structure and a construction method thereof.

[0064] Reference Figure 2 and Figure 3 , Figure 2 This is a schematic diagram of the distribution of the secondary excavation slope platform of the left bank abutment involved in the present invention; Figure 3 This is a schematic diagram of the distribution of the secondary excavation slope platform of the right bank abutment involved in the present invention.

[0065] In one embodiment of the present invention, Figure 2 and Figure 3 As shown, in the first aspect, the present invention provides an arch seat foundation pit secondary structure, including: an existing foundation pit slope platform, the existing foundation pit slope platform includes a left bank arch seat and a right bank arch seat arranged at intervals; a left six-layer slope platform, a left six-layer slope platform is formed on the left bank arch seat, the left six-layer slope platform includes a left first-level slope platform, a left second-level slope platform, a left third-level slope platform, a left fourth-level slope platform, a left fifth-level slope platform and a left sixth-level slope platform distributed in a stepped manner from top to bottom in the elevation direction of the existing foundation pit slope platform; a right first-level slope platform is formed on the right bank arch seat; wherein, the orthographic projections of the left first-level slope platform, the left second-level slope platform, the left third-level slope platform, the left fourth-level slope platform, the left fifth-level slope platform and the left sixth-level slope platform on the base of the existing foundation pit slope platform are distributed in sequence along the first direction.

[0066] The technical solution of the present invention reduces the construction difficulty of the arch seat foundation pit by forming a left six-layer slope platform and a right first-level slope platform on the left bank arch seat and the right bank arch seat respectively on the existing foundation pit slope platform, and ensures the stability of the arch seat foundation pit through the left six-layer slope platform and the right first-level slope platform. It is more suitable for construction working environments with steep slopes, thin cover, partially exposed bedrock, and limited working platform range, providing a reference basis for similar construction situations.

[0067] In one embodiment, a downstream arch seat replacement portion is formed at the left fourth-level slope platform, and an upstream arch seat replacement portion is formed on one side of the left fifth-level slope platform; the upstream arch seat replacement portion and the downstream arch seat replacement portion are spaced apart along the second direction of the orthographic projection of the base of the existing foundation pit slope platform; wherein the first direction and the second direction intersect.

[0068] In one embodiment, the elevation range of the left first-level side slope platform is 794.491m~787.648m, and the height is 6.843m; the elevation range of the left second-level side slope platform is 787.648m~780.498m, and the height is 7.15m; the elevation range of the left third-level side slope platform is 780.498m~773.417m, and the height is 7.081m; the elevation range of the left fourth-level side slope platform is 773.417m~763.417m, and the height is 10m; the elevation range of the left fifth-level side slope platform is The elevation range of the left sixth-level slope platform is 755.417m~747.417m, with a height of 8m; the elevation range of the right first-level slope platform is 764.417m~756.417m, with a height of 8m; the elevation range of the upstream arch seat foundation replacement part is 763.417m~761.417m, with a replacement height of 2m; the elevation range of the downstream arch seat foundation replacement part is 763.417m~753.417m, with a replacement height of 10m.

[0069] In one embodiment, the slope ratio of the left first-level slope platform is 1:0.9, and the platform width is 2m; the slope ratio of the left second-level slope platform is 1:0.5, and the platform width is 2m; the slope ratio of the left third-level slope platform is 1:0.5, and the platform width is 2m; the slope ratio of the left fourth-level slope platform is 1:0.3, and the platform width is 2m; the slope ratio of the left fifth-level slope platform is 1:0.25, and the platform width is 2m; the slope ratio of the left sixth-level slope platform is 1:0.9, and the platform width is 3m; the slope ratio of the right first-level slope platform is 1:0.5, and the platform width is 4.2m; the slope ratio of the upstream arch seat foundation replacement part is 1:0.1; and the slope ratio of the downstream arch seat foundation replacement part is 1:0.2.

[0070] In one embodiment, a bridleway is provided between the left first-level side slope platform, the left second-level side slope platform, the left third-level side slope platform, the left fourth-level side slope platform, the left fifth-level side slope platform and the left sixth-level side slope platform.

[0071] Continue to refer to Figure 2 and Figure 3 , and refer to Figure 1 , Figure 1 It is a schematic flow chart of the construction method of the secondary structure of the arch foundation pit of the present invention.

[0072] In one embodiment of the present invention, Figures 1 to 3 As shown, in a second aspect, the present invention provides a method for constructing an abutment foundation pit secondary structure, which is used to form the above-mentioned abutment foundation pit secondary structure. The method includes:

[0073] Step S100: excavating a construction channel to form a working platform;

[0074] Step S200: Using a working platform, on the left bank abutment of the existing foundation pit side slope platform, layering and grading from top to bottom along the elevation direction of the existing foundation pit side slope platform to form a left first side slope platform, a left second side slope platform, a left third side slope platform, a left fourth side slope platform, a left fifth side slope platform and a left sixth side slope platform, so as to form a left six-layer side slope platform;

[0075] Step S300: forming a right first-level slope platform on the right bank abutment of the existing foundation pit slope platform.

[0076] In one embodiment, the elevation range of the left first-level slope platform is 794.491m to 787.648m, and the height is 6.843m. The steps of excavating a construction channel to form a working platform include:

[0077] Step S110: excavating the downstream side of the left first-level slope platform and constructing a slope excavation construction road so that the elevation of the construction road meets 790.491m;

[0078] Step S120: excavating and repairing the slope with an elevation of 794.491m to 790.491m;

[0079] Step S130: removing the overburden and performing rock drilling and blasting to form a working platform.

[0080] In one embodiment, the steps of excavating and repairing a slope with an elevation of 794.491 m to 790.491 m include:

[0081] Step S121: excavating the slope with an elevation of 794.491m to 790.491m by using deep hole blasting and shallow hole blasting.

[0082] In one embodiment, the steps of excavating and repairing a slope with an elevation of 794.491 m to 790.491 m include:

[0083] Step S122: Slope repair is performed on the slope with an elevation of 794.491 m to 790.491 m by using smooth blasting and hammer chiseling.

[0084] In one embodiment, the steps of repairing a slope with an elevation of 794.491 m to 790.491 m by using smooth blasting and hammer chiseling include:

[0085] Step S123: Arranging a plurality of blasting holes according to a preset hole diameter and a preset hole spacing, so that the hole diameter of each blasting hole meets the preset hole diameter, and the spacing between adjacent blasting holes meets the preset hole spacing.

[0086] For ease of understanding, a specific implementation is shown here:

[0087] A certain bridge is a Y-shaped steel box arch bridge spanning a river. The river valley at the bridge site is V-shaped. The bedrock on both sides is exposed, and the slopes are steep, with a natural gradient of 60° to 75°, and in some areas 75° to 85°. During normal water periods, the river surface elevation is 590 meters, and the water surface width is 15 to 30 meters.

[0088] According to the revised drawings, the original design elevation of the left bank downstream arch seat must be lowered by 10m, and the original design elevation of the left bank upstream arch seat must be lowered by 2m. The original excavated slope of the arch seat foundation must be re-slope excavated, and temporary and permanent slope protection must be added. To accommodate anchor cable installation under the arch seat, the design drawings include three slope platforms on the left bank and one on the right bank as anchor cable construction platforms.

[0089] Deep gullies are generally undeveloped on either side of the river. Gullies are small, shallow, and short, generally extending above 690 meters. The left bank boasts a generally intact terrain, with majestic mountains and steep gullies, but no large, deep gullies. Huofanggou, located 350 meters upstream of the bridge axis on the right bank, has an elevation of 730 meters, a length of approximately 150 meters, and a depth of less than 20 meters. Fossilgou, located 140 meters upstream of the bridge axis on the right bank, has an elevation of 675 meters and a depth of 30 to 60 meters. Rocks are exposed on both sides of the bridge site, consisting of thickly layered, hard limestone.

[0090] The river bridge is about 550m away from the dam site of Dongzhuang Water Conservancy Project and 3.0km away from the existing river cable-stayed bridge. The bridge axis is a straight line, with the right bank connected to the T-shaped intersection for external traffic and the left bank connected to the tunnel.

[0091] This secondary excavation involved further excavation after the original abutment had already been excavated to the designed base. The terrain was complex, but generally intact. The surrounding rock at the base of the abutment was broken and cracked, and the surrounding rock on the slope below the abutment was in a highly weathered zone. After the excavation of the abutment foundation was completed, sprayed anchor protection was implemented.

[0092] The river valley at the bridge site is a "V"-shaped valley with exposed bedrock on both sides and steep slopes, with a natural slope of 60° to 75°, and locally 75° to 85°.

[0093] Stratigraphic lithology:

[0094] The bedrock on both sides of the bridge site is exposed and is thick-layered limestone with a hard texture. The main stratum is the Middle Ordovician (O2) limestone. The stratigraphic structure is as follows:

[0095] ① Upper Pleistocene alluvial layer (Q3al): The lithology is alluvial sand and gravel, distributed above the elevation of 775m on the left bank. The parent rock components of the gravel are mainly limestone, sandstone and a very small amount of granite.

[0096] ③ Middle Ordovician (O2): thick to extremely thick limestone, light grey or greyish white, partially interbedded with cryptocrystalline biogenic limestone.

[0097] Based on on-site geological mapping, in-situ testing, indoor tests, and regional engineering experience, and using engineering geological analysis principles, the bearing capacity of foundation soil along the highway is proposed. The allowable bearing capacity of each layer of soil and the pile side friction resistance are as follows:

[0098] ① Sand and gravel (Q3al) [σ0]=300kPa[τi]=120kPa;

[0099] ③ Limestone (O2) [σ0] = 1300 kPa [τi] = 1500 kPa;

[0100] Hydrogeological conditions:

[0101] According to the hydrological description in the construction drawing design documents, no groundwater is found, so the impact of groundwater on the bridge can be ignored.

[0102] Adverse geological disasters:

[0103] No adverse geological phenomena such as landslides, debris flows, and collapses were found. Karst traces are manifested in solution cracks and solution pores, and karst development is relatively weak.

[0104] Main technical standards:

[0105] ⑴Road grade: Secondary highway;

[0106] ⑵Number of lanes: two lanes in both directions;

[0107] ⑶ Design speed: 40km / h;

[0108] (4) Design service life: Main structure: 100 years; Suspender: 20 years; Bridge deck: 12 years;

[0109] ⑸Longitudinal slope: 0.5% in both directions;

[0110] (6) Cross slope: 2.0% for carriageway and 1.0% for sidewalk;

[0111] ⑺The plane is a straight line, and the radius of the longitudinal curve is 9100m;

[0112] ⑻ Design flood level: 629.5m, corresponding frequency is 1 / 100;

[0113] ⑼Navigation requirements: None;

[0114] ⑽Design load standard:

[0115] 1) Bridge structure design reference period: 100 years;

[0116] 2) Vehicle load level: Highway-I; Crowd load: 2.5kN / ㎡

[0117] 3) Earthquake resistance standard: Base intensity 7, peak earthquake acceleration: 0.115g

[0118] 4) Wind-resistant design standard: Basic wind speed value: V10=25.3m / s.

[0119] Resource preparation:

[0120] (1) Mechanical equipment: The Materials and Equipment Department is responsible for ensuring that 200t crawler cranes, down-the-hole drills, excavators, dump trucks and other mechanical equipment are in place before construction begins, and for carrying out inspection, repair and maintenance of the mechanical equipment.

[0121] (2) Material preparation: The Materials and Equipment Department is responsible for completing the registration procedures for pyrotechnics before starting work to ensure that the pyrotechnics arrive on time.

[0122] (3) Human resource preparation: The Planning and Cost Department is responsible for the entry of team workers before work begins.

[0123] 4. Temporary water and electricity preparation

[0124] (1) Temporary water use: A temporary water tank is set up on the platform above the arch seat for construction water, and water is transported by water truck.

[0125] (2) Temporary power supply: Power is introduced from a transformer 400m away from the construction site to a first-level distribution box to provide power for this project. The first-level distribution box is set at the right foot of the slope of the Xiejiashan platform line on the left bank.

[0126] Construction plan for secondary excavation of arch seat:

[0127] 1. Overall plan for secondary excavation of arch seat

[0128] This project is the secondary excavation of the arch foundation of Jinghe Bridge, which mainly includes the excavation of the slope above the arch base, the excavation of the slope below the arch foundation, and the protection of the slope around the arch.

[0129] 2. Slope and foundation pit excavation construction plan

[0130] 1.1 Construction Preparation

[0131] This project was constructed using the principle of "layered excavation from top to bottom, with graded excavation and protection at each level." Before excavation, slope drainage and surface clearing were completed. During excavation, the slope gradient and platform elevation were strictly controlled. After excavation, the slope surface was promptly re-measured and repaired, and protection was implemented according to design requirements.

[0132] Construction method:

[0133] The left bank abutments were excavated twice. The left bank abutment had a grade 6 slope, which was divided into upper and lower slopes based on the designed base elevation of the abutment. The upper slope was graded from grade 1 to grade 4, and the lower slope was graded from grade 5 to grade 6. This included two replacements of the upstream and downstream abutment foundations. The right bank abutment had a grade 1 slope.

[0134] Left bank arch seat: first-level slope is 794.491~787.648, slope height is 6.843m, slope ratio is 1:0.9, platform width is 2m; second-level slope is 787.648~780.498, slope height is 7.15m, slope ratio is 1:0.5, platform width is 2m; third-level slope is 780.498~773.417, slope height is 7.081m, slope ratio is 1:0.5, platform width is 2m; fourth-level slope is 773.417~763.417, slope height is 10m, slope ratio is 1: 0.3, platform width 2m; fifth-level slope 763.417~755.417, slope height 8m, slope ratio 1:0.25, platform width 2m; sixth-level slope 755.417~747.417, slope height 8m, slope ratio 1:0.9, platform width 3m; upstream arch seat foundation replacement fill 763.417~761.417, replacement fill height 2m, slope ratio 1:0.1; downstream arch seat foundation replacement fill 763.417~753.417, replacement fill height 10m, slope ratio 1:0.2.

[0135] Right bank arch seat: the first-level slope is 764.417~756.417, the slope height is 8m, the slope ratio is 1:0.5, and the platform width is about 4.2m.

[0136] Because the arch foundation pit excavation is a secondary excavation, the excavated foundation pit slopes required re-grading. The slopes were steep, the overburden was thin, and some bedrock was exposed, limiting the working platform. Therefore, an excavator was first used to construct a slope access road downstream of the 794.491 platform to 790.491. The slopes between 794.491 and 790.491 were then broken down and excavated by the excavator. After the excavator completed the access road to 790.419, the overburden was removed by the excavator, and rock drilling and blasting were carried out. Rock excavation was primarily carried out using deep-hole blasting, supplemented by shallow-hole blasting. Smooth blasting was used for the slopes, with some areas removed using hammers. Excavation was carried out in a stepped, layered manner, from top to bottom, with 2-meter bridleways between each level.

[0137] In order to ensure the stability of the slope and form a flat slope, smooth blasting is adopted for the slope. The blasting hole diameter is 90mm, the blast hole spacing is 50cm, and the holes are drilled using a Φ90 down-the-hole drill rig; Φ32mm rock emulsion explosives are detonated using non-electric millisecond detonating cord detonators.

[0138] Excavators are used to remove debris and rock. Each level of excavation is followed by a level of finishing and removal of dangerous rocks. Slope lines and slope gradients are re-measured after each layer of excavation is completed. For each level of excavation, protection is applied. Before protection, scaffolding and construction platforms are erected, and slope protection is carried out according to the design requirements.

[0139] The technical solution of the present invention reduces the construction difficulty of the arch seat foundation pit by forming a left six-layer slope platform and a right first-level slope platform on the left bank arch seat and the right bank arch seat respectively on the existing foundation pit slope platform, and ensures the stability of the arch seat foundation pit through the left six-layer slope platform and the right first-level slope platform. It is more suitable for construction working environments with steep slopes, thin cover, partially exposed bedrock, and limited working platform range, providing a reference basis for similar construction situations.

[0140] It should be noted that the serial numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. The above embodiments are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structures or equivalent process transformations made by utilizing the contents of the present description and drawings under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A secondary structure of an arch foundation pit, characterized in that: include: An existing foundation pit slope platform, wherein the existing foundation pit slope platform includes a left bank abutment and a right bank abutment arranged at intervals; A left six-layer side slope platform is formed on the left bank arch seat, and the left six-layer side slope platform includes a left first side slope platform, a left second side slope platform, a left third side slope platform, a left fourth side slope platform, a left fifth side slope platform and a left sixth side slope platform, which are distributed in a stepped manner from top to bottom in the elevation direction of the existing foundation pit side slope platform; a right first-level side slope platform, formed on the right bank arch seat; Among them, the left first-level slope platform, the left second-level slope platform, the left third-level slope platform, the left fourth-level slope platform, the left fifth-level slope platform and the left sixth-level slope platform are distributed in sequence along the first direction of the orthographic projection of the base of the existing foundation pit slope platform; a downstream arch seat replacement part is formed at the left fourth-level slope platform, and an upstream arch seat replacement part is formed on one side of the left fifth-level slope platform; the upstream arch seat replacement part and the downstream arch seat replacement part are arranged at intervals along the second direction of the orthographic projection of the base of the existing foundation pit slope platform; the first direction and the second direction intersect.

2. The abutment foundation pit secondary structure according to claim 1, characterized in that: The elevation range of the left first-level slope platform is 794.491m to 787.648m, with a height of 6.843m; The elevation range of the left secondary slope platform is 787.648m to 780.498m, with a height of 7.15m; The elevation range of the left third-level slope platform is 780.498m to 773.417m, with a height of 7.081m; The elevation range of the left fourth-level slope platform is 773.417m to 763.417m, with a height of 10m; The elevation range of the left five-level slope platform is 763.417m to 755.417m, with a height of 8m; The elevation range of the left six-level slope platform is 755.417m to 747.417m, with a height of 8m; The elevation range of the right first-level slope platform is 764.417m to 756.417m, with a height of 8m; The elevation range of the upstream abutment replacement part is 763.417m to 761.417m, and the replacement height is 2m; The elevation range of the downstream arch seat replacement part is 763.417m~753.417m, and the replacement height is 10m.

3. The abutment foundation pit secondary structure according to claim 2, characterized in that: The slope ratio of the left first-level slope platform is 1:0.9, and the platform width is 2m; The slope ratio of the left secondary slope platform is 1:0.5, and the platform width is 2m; The slope ratio of the left third-level slope platform is 1:0.5, and the platform width is 2m; The slope ratio of the left fourth-level slope platform is 1:0.3, and the platform width is 2m; The slope ratio of the left five-level slope platform is 1:0.25, and the platform width is 2m; The slope ratio of the left six-level slope platform is 1:0.9, and the platform width is 3m; The slope ratio of the right first-level slope platform is 1:0.5, and the platform width is 4.2m; The slope ratio of the upstream abutment replacement portion is 1:0.1; The slope ratio of the downstream abutment replacement portion is 1:0.

2.

4. The abutment foundation pit secondary structure according to any one of claims 1 to 3, characterized in that: A bridleway is provided between the left first-level side slope platform, the left second-level side slope platform, the left third-level side slope platform, the left fourth-level side slope platform, the left fifth-level side slope platform and the left sixth-level side slope platform.

5. A method for constructing a secondary structure of an arch foundation pit, characterized in that: The method for forming the secondary structure of the abutment foundation pit according to any one of claims 1 to 4 comprises: Excavate a construction channel to form a working platform; Using the working platform, on the left bank abutment of the existing foundation pit side slope platform, the left first side slope platform, the left second side slope platform, the left third side slope platform, the left fourth side slope platform, the left fifth side slope platform and the left sixth side slope platform are formed layered and graded from top to bottom along the elevation direction of the existing foundation pit side slope platform to form the left six-layer side slope platform; The right first-level slope platform is formed on the right bank arch seat of the existing foundation pit slope platform.

6. The method for constructing the secondary structure of the arch foundation pit according to claim 5, characterized in that: The elevation range of the left first-level slope platform is 794.491m to 787.648m, and the height is 6.843m. The steps of excavating the construction channel to form the working platform include: Excavate the downstream side of the left first-level slope platform and build a slope excavation construction road so that the elevation of the construction road meets 790.491m; Carry out rock excavation and slope repair on the slopes with elevations of 794.491m to 790.491m; The overburden is removed and rock drilling and blasting are carried out to form the working platform.

7. The method for constructing the secondary structure of the arch foundation pit according to claim 6, characterized in that: The steps of excavating and repairing the slope with an elevation of 794.491m to 790.491m include: Deep hole blasting and shallow hole blasting were used to excavate the slope with an elevation of 794.491m to 790.491m.

8. The method for constructing the secondary structure of the arch foundation pit according to claim 7, characterized in that: The steps of excavating and repairing the slope with an elevation of 794.491m to 790.491m include: The slope with an elevation of 794.491m to 790.491m was repaired by smooth blasting and hammer chiseling.

9. The method for constructing the secondary structure of the arch foundation pit according to claim 8, characterized in that: The steps of repairing the slope with an elevation of 794.491m to 790.491m by using smooth blasting and hammer chiseling include: A plurality of blasting holes are arranged according to a preset hole diameter and a preset hole spacing, so that the hole diameter of each blasting hole meets the preset hole diameter, and the spacing between adjacent blasting holes meets the preset hole spacing.

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