Method for layered excavation of arch seat foundation pit

Abstract

The present invention discloses a method for layered excavation of an arch abutment foundation pit. The arch abutment foundation pit includes a left-bank arch abutment and a right-bank arch abutment which are arranged at intervals, and an excavation surface to be excavated is provided on both the left-bank arch abutment and the right-bank arch abutment. The method includes: using a working platform, on the left-bank arch abutment, performing construction on the excavation surface to be excavated of the left-bank arch abutment layer by layer and level by level along the elevation direction of the existing foundation pit slope platform to form a six-layer left slope platform; using the working platform, performing construction on the excavation surface to be excavated of the right-bank arch abutment to form a first-level right slope platform; combining the six-layer left slope platform and the first-level right slope platform to form a secondary arch abutment foundation pit. By forming a six-layer left slope platform and a first-level right slope platform on the left-bank arch abutment and the right-bank arch abutment respectively, the present invention is more suitable for construction operation environments with steep slopes, thin overburden, partial exposure of bedrock, and limited working platform range, providing a reference basis for similar construction situations.

Description

Technical Field

[0001] The present invention relates to the technical field of arch seat foundation pit excavation, and particularly relates to a method for layered excavation of an arch seat foundation pit. Background Art

[0002] In the related art, it is necessary to carry out additional excavation when the original arch seat has been excavated to the designed base, and the terrain where the original arch seat is located is complex, the surrounding rock of the arch seat base is broken, fissures are developed, and the surrounding rock of the lower slope of the arch seat is in a strongly weathered zone.

[0003] However, since the excavation of the arch seat foundation pit is secondary excavation, it is necessary to re-slope the excavation foundation pit slope. Moreover, the slope is relatively steep, the overburden soil is thin, some bedrocks are exposed, and the working platform range is limited.

[0004] Therefore, when the conventional construction method is applied to a construction environment similar to this, the construction efficiency is low and the construction requirements cannot be met. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for layered excavation of an arch seat foundation pit, aiming to solve the technical problems that when the conventional construction method in the prior art is applied to a construction environment similar to this, the construction efficiency is low and the construction requirements cannot be met.

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

[0007] The present invention provides a method for layered excavation of an arch seat foundation pit. The arch seat foundation pit includes 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. Working surfaces to be excavated are arranged on both the left bank arch seat and the right bank arch seat. The method includes:

[0008] Excavate a construction passage in the existing foundation pit to form a working platform;

[0009] Utilize the working platform to perform operations on the working surface to be excavated on the left bank arch seat of the existing foundation pit slope platform layer by layer and step by step in the elevation direction of the existing foundation pit slope platform to form a left six-layer slope platform;

[0010] Utilize the working platform to perform operations on the working surface to be excavated on the right bank arch seat to form a right first-level slope platform;

[0011] Combine the left six-layer slope platform and the right first-level slope platform to form a secondary arch seat foundation pit.

[0012] Optionally, in the above method for layered excavation of the abutment foundation pit, the left-bank abutment includes a plurality of blasting steps to be carried out. The step of using the working platform to carry out construction on the left-bank abutment of the existing foundation pit slope platform in the elevation direction of the existing foundation pit slope platform from top to bottom in layers and levels on the excavation surface to be excavated of the left-bank abutment to form a left six-layer slope platform includes:

[0013] Construct blast holes on each of the blasting steps to be carried out;

[0014] Fill the blast holes with a charge structure to form a blasting excavation structure for the left-bank abutment foundation pit;

[0015] Utilize the blasting excavation structure for the left-bank abutment foundation pit to form a first-level left slope platform, a second-level left slope platform, a third-level left slope platform, a fourth-level left slope platform, a fifth-level left slope platform, and a sixth-level left slope platform on the left-bank abutment to form the left six-layer slope platform.

[0016] Optionally, in the above method for layered excavation of the abutment foundation pit, the step of constructing blast holes on each of the blasting steps to be carried out includes:

[0017] Set a minimum resistance line at the bottom side of the blasting step to be carried out, and obtain the length of the minimum resistance line;

[0018] Set a bench upper brow line at the top side of the blasting step to be carried out, and obtain the length of the bench upper brow line;

[0019] Obtain the slope angle of the blasting step to be carried out according to the length of the minimum resistance line and the length of the bench upper brow line;

[0020] Preset the over-depth of the blast hole;

[0021] Drill holes on the surface of the blasting step to be carried out to form the blast holes according to the slope angle of the blasting step to be carried out, the height of the blasting step to be carried out, and the over-depth of the blast hole;

[0022] Obtain the charge amount according to the type of the blast hole;

[0023] Fill the charge structure into the blast hole according to the charge amount to form the blasting excavation structure for the abutment foundation pit.

[0024] Optionally, in the above method for layered excavation of the abutment foundation pit, the type of the blast hole is a multi-row blast hole. The multi-row blast hole includes a front-row blast hole and a second-row blast hole arranged at intervals with the front-row blast hole. The front-row blast hole is composed of a plurality of the blast holes arranged at intervals, and the second-row blast hole is composed of a plurality of the blast holes arranged at intervals;

[0025] The step of obtaining the charge amount according to the type of the blast hole includes:

[0026] Obtain the charge amount of the front row of blast holes according to the unit explosive consumption, the spacing between the blast holes in the front row of blast holes, the hole depth of the front row of blast holes, and the minimum burden;

[0027] Obtain the charge amount of the second row of blast holes according to the unit explosive consumption, the spacing between the blast holes in the second row of blast holes, the hole depth of the second row of blast holes, and the spacing between the second row of blast holes and the front row of blast holes.

[0028] Optionally, in the above method for layered excavation of the arch seat foundation pit, the type of the blast holes is smooth blasting holes;

[0029] The step of setting a minimum burden at the bottom side of the bench to be blasted and obtaining the length of the minimum burden includes:

[0030] Obtain the length of the minimum burden of the smooth blasting holes according to the hole diameter of the smooth blasting holes;

[0031] Wherein, the hole diameter of the smooth blasting holes is D 光 , and the length of the minimum burden of the smooth blasting holes is W 光 , W 光 =β*D 光 , 15≤β≤25.

[0032] Optionally, in the above method for layered excavation of the arch seat foundation pit, the step of using the working platform to construct the surface to be excavated of the right bank arch seat to form the right first-level slope platform includes:

[0033] Perform hole position lofting on the surface to be excavated of the right bank arch seat to obtain the hole positions to be formed;

[0034] Drill the hole positions to be formed to form the holes to be split;

[0035] Split the holes to be split to form a split area;

[0036] Form the arch seat foundation pit according to the split area.

[0037] Optionally, in the above method for layered excavation of the arch seat foundation pit, the step of splitting the holes to be split to form a split area includes:

[0038] Use an excavator to assist in sending the splitting machine head into the holes to be split;

[0039] Use the machine head to extrude the holes to be split, so that the surface to be excavated cracks into a line to form the split area.

[0040] Optionally, before the step of splitting the holes to be split to form a split area in the above method for layered excavation of the arch seat foundation pit, the method includes:

[0041] Check the depth of the hole to be split.

[0042] Determine whether the depth of the hole to be split meets the preset depth condition.

[0043] If so, split the hole to be split.

[0044] If not, adjust the depth of the hole to be split so that the depth of the hole to be split meets the preset depth condition.

[0045] Optionally, in the above method for layered excavation of the arch abutment foundation pit, the outer contour of the right bank arch abutment is stepped, and the arch abutment foundation pit of the right bank arch abutment includes a plurality of excavation surfaces arranged in layers from top to bottom in sequence. A plurality of the hole positions to be formed are evenly distributed on each of the excavation surfaces to be formed. The plurality of excavation surfaces to be formed are a first excavation surface and a second excavation surface stacked below the first excavation surface. It is characterized in that, before the step of forming the arch abutment foundation pit according to the splitting area, the method includes:

[0046] Drill the hole positions to be formed on the first excavation surface, and perform splitting construction on the first excavation surface to form a first splitting area.

[0047] Obtain the splitting situation according to the first splitting area.

[0048] Adjust the hole spacing between the hole positions to be formed on the second excavation surface according to the splitting situation.

[0049] Drill the hole positions to be formed on the second excavation surface, and perform splitting construction on the second excavation surface to form a second splitting area.

[0050] Optionally, in the above method for layered excavation of the arch abutment foundation pit, the row spacing between the plurality of hole positions to be formed is 80 cm.

[0051] One or more of the above technical solutions provided by the present invention may have the following advantages or at least achieve the following technical effects:

[0052] A method for layered excavation of an arch abutment foundation pit proposed by the present invention forms a left six-layer slope platform and a right first-level slope platform on the left bank arch abutment and the right bank arch abutment respectively on the existing foundation pit slope platform, reducing the construction difficulty of the arch abutment foundation pit, and ensuring the stability of the arch abutment foundation pit through the left six-layer slope platform and the right first-level slope platform. Different construction methods are adopted for the left bank arch abutment and the right bank arch abutment, which is more suitable for the construction operation environment with steep slopes, thin overburden, partial exposure of bedrock, and limited working platform range, providing a reference basis for similar construction situations. Description of the Drawings

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these provided drawings.

[0054] Figure 1 It is a schematic flow chart of the construction method for the secondary structure of the arch seat foundation pit of the present invention;

[0055] Figure 2 It is a schematic diagram of the distribution of the secondary excavation slope platforms of the left-bank arch seat related to the present invention;

[0056] Figure 3 It is a schematic diagram of the distribution of the secondary excavation slope platforms of the right-bank arch seat related to the present invention;

[0057] Figure 4 It is a schematic diagram of the charging structure related to the present invention;

[0058] Figure 5 It is a schematic diagram of the charging structure related to the present invention;

[0059] Figure 6 It is a schematic diagram of the charging structure of the smooth blasting holes related to the present invention;

[0060] Figure 7 It is a schematic diagram of the main smooth blasting holes and smooth blasting holes related to the present invention;

[0061] Figure 8 It is a schematic diagram of the cut hole layout related to the present invention.

[0062] Explanation of the reference numerals in the drawings:

[0063] Label Name Label Name 100 Borehole 110 Main blasting hole 120 Smooth blasting hole 101 In-hole detonator 102 Detonating fuse 103 Charged section 104 Stemming section 200 Enhanced charging section 300 Normal charging section 400 Reduced charging section 500 Detonating cord 600 Hole to be split 700 Auxiliary hole

[0064] The realization, functional characteristics and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Specific embodiments

[0065] To make the object, technical solution and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0066] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back...) are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the attached drawings). If the specific posture changes, the directional indications will change accordingly.

[0067] In the present invention, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or system comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or system. Without further limitation, elements defined by the statement "comprising..." do not preclude the existence of additional identical elements in the process, method, article or system comprising such element. Additionally, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously.

[0068] In the present invention, unless otherwise clearly defined and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the communication inside two elements or the interaction relationship between two elements.

[0069] In the present invention, if there are descriptions involving "first", "second", etc., such descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" can expressly or implicitly include at least one such feature.

[0070] In the present invention, the suffixes used to represent elements such as "module", "component", "part", "member" or "unit" are only for the convenience of explaining the present invention and have no specific meaning in themselves. Therefore, "module", "member" or "unit" can be used interchangeably.

[0071] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Additionally, the technical solutions of each embodiment can be combined with each other, provided that it is based on what can be achieved by those of ordinary skill in the art. When the combination of technical solutions results in contradictions or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0072] The inventive concept of the present invention will be further elaborated below in conjunction with some specific embodiments.

[0073] The present invention provides a method for layered excavation of an arch abutment foundation pit.

[0074] Referring to Figures 1 to 3 , Figure 1 is a schematic flow chart of the construction method for the secondary structure of the arch abutment foundation pit of the present invention; Figure 2 is a schematic diagram showing the distribution of the secondary excavation slope platforms of the left-bank arch abutment related to the present invention; Figure 3 is a schematic diagram showing the distribution of the secondary excavation slope platforms of the right-bank arch abutment related to the present invention.

[0075] In an embodiment of the present invention, as shown in Figures 1 to 3 , a method for layered excavation of an arch abutment foundation pit, the arch abutment foundation pit includes an existing foundation pit slope platform, the existing foundation pit slope platform includes a left-bank arch abutment and a right-bank arch abutment arranged at intervals, and excavation surfaces to be excavated are provided on both the left-bank arch abutment and the right-bank arch abutment. The method includes:

[0076] Step S100: Excavate a construction passage in the existing foundation pit to form a working platform;

[0077] Step S200: Utilize the working platform to perform construction on the excavation surface to be excavated on the left-bank arch abutment of the existing foundation pit slope platform layer by layer and level by level along the elevation direction of the existing foundation pit slope platform to form a left six-layer slope platform;

[0078] Step S300: Utilize the working platform to perform construction on the excavation surface to be excavated on the right-bank arch abutment to form a right first-level slope platform;

[0079] Step S400: Combine the left six-layer slope platform and the right first-level slope platform to form a secondary arch abutment foundation pit.

[0080] For ease of understanding, a specific embodiment is shown below:

[0081] A certain bridge is a Y-shaped steel box arch bridge, and the bridge spans across both banks of the river. The river valley in the bridge site area is in a "V" shape. The bedrock is exposed on both banks, the slopes are steep, the natural slope is 60° - 75°, and locally it is 75° - 85°. The elevation of the river surface during the normal water period is 590m, and the water surface width is 15 - 30m.

[0082] According to the requirements of the change drawings, it is necessary to excavate 10m deeper at the original design elevation of the left-bank downstream arch abutment, and 2m deeper at the original design elevation of the left-bank upstream arch abutment, and re-slope the originally excavated slope of the arch abutment foundation, and add temporary and permanent slope protection. Considering the construction of the anchor cables under the arch abutment, 3 slope platforms are added on the left bank and 1 slope platform is added on the right bank in the design drawings as the anchor cable construction platforms.

[0083] Deep gully is not developed on both sides of the river. The scale of the gully is small, the cutting depth is shallow, the extension is short, and the gully mouth is generally above 690m. The terrain on the left bank is generally intact, the mountain body is thick, the gully is steep, and there is no large deep gully. Huofanggou, 350m upstream of the bridge axis on the right bank, has a gully mouth elevation of 730m, a gully length of about 150m, and a cutting depth of less than 20m; Huashi Gully, 140m upstream of the bridge axis on the right bank, has a gully mouth elevation of 675m and a gully depth of 30m - 60m. The rocks on both banks of the bridge site are exposed, and the lithology is thick-layered limestone, with hard rock quality.

[0084] The river bridge is about 550m upstream from the dam site of Dongzhuang Water Control Project and 3.0km downstream from the completed river cable-stayed bridge. The plane of the bridge axis is a straight line section. The right bank is connected to the external traffic T-shaped intersection, and the left bank is connected to the tunnel.

[0085] In this secondary excavation, the terrain was re-excavated on the basis that the original arch seat had been excavated to the design base. The terrain is complex and generally intact. The surrounding rock at the base of the arch seat is broken and the fissures are developed. The surrounding rock on the lower slope of the arch seat is in the strongly weathered zone. After the excavation of the arch seat foundation of the project, shotcrete and bolting protection have been carried out.

[0086] The river valley in the bridge site area is a "V"-shaped valley. The bedrock on both banks is exposed, the hillside is steep, the natural slope is 60° - 75°, and locally 75° - 85°.

[0087] Stratum lithology: The bedrock on both banks of the bridge site is exposed, and the lithology is thick-layered limestone, with hard rock quality. The main stratum is the Middle Ordovician (O2) limestone. The stratum structure is as follows:

[0088] ① Upper Pleistocene alluvial layer (Q3al): The lithology is alluvial sand, gravel and cobbles, distributed above the elevation of 775m on the left bank. The parent rock components of the gravel and cobbles are mainly limestone, sandstone and very little granite.

[0089] ③ Middle Ordovician (O2): Thick-layer to massive limestone, light gray, grayish white, locally intercalated with cryptocrystalline biogenic limestone.

[0090] According to the on-site geological mapping, in-situ testing, laboratory tests and combined with regional engineering experience, through the principle of engineering geological analysis, the bearing capacity of the foundation soil along the highway is proposed. The allowable bearing capacity and the side friction resistance of each layer of soil are as follows:

[0091] ① Sand, gravel and cobbles (Q3al) [σ0] = 300kPa [τi] = 120kPa;

[0092] ③ Limestone (O2) [σ0] = 1300kPa [τi] = 1500kPa;

[0093] Hydrogeological situation: According to the hydrological introduction in the construction drawing design document, no groundwater is seen, and the influence of groundwater on the bridge can be ignored.

[0094] Adverse geological disasters: No adverse geological phenomena such as landslides, debris flows, and collapses were found. The karst traces are manifested as solution fissures and solution pores, and the karst development is weak.

[0095] Main technical standards: ⑴ Road grade: Secondary highway; ⑵ Number of traffic lanes: Two-way two lanes;

[0096] ⑶ Design speed: 40 km / h; ⑷ Design service life: Main structure: 100 years; Suspender: 20 years; Bridge deck pavement: 12 years; ⑸ Longitudinal slope: Two-way 0.5%; ⑹ Cross slope: Cross slope of traffic lane 2.0%, cross slope of sidewalk 1.0%; ⑺ The plane is a straight line, and the longitudinal curve radius is 9100 m; ⑻ Design flood level: 629.5 m, corresponding frequency is 1 / 100; ⑼ Navigation requirements: None; ⑽ Design load standard:

[0097] 1) Design reference period of bridge structure: 100 years; 2) Vehicle load grade: Highway-I; Pedestrian load: 2.5 kN / ㎡ 3) Seismic fortification standard: Basic intensity 7 degrees, peak ground acceleration: 0.115g

[0098] 4) Wind resistance design standard: Basic wind speed value: V10 = 25.3 m / s.

[0099] Resource preparation: (1) Mechanical equipment: The Material and Equipment Department is responsible for the arrival of mechanical equipment such as 200t crawler cranes, down-the-hole drills, excavators, and dump trucks before construction, and for the inspection and maintenance of mechanical equipment. (2) Material preparation: The Material and Equipment Department is responsible for going through the filing procedures for blasting materials before construction to ensure the timely arrival of blasting materials. (3) Human resource preparation: The Planning and Cost Department is responsible for the arrival of team workers before construction.

[0100] Preparation for temporary water and electricity: (1) Temporary water: A temporary water tank is set up on the platform above the arch seat for construction water, and water trucks are used for transportation. (2) Temporary electricity: Electricity is introduced from a transformer 400 m away from the construction site to the primary distribution box to supply electricity for this project. The primary distribution box is set at the foot of the slope on the right side of the line on the Xiejiashan platform on the left bank.

[0101] Construction plan for the second excavation of the arch seat

[0102] 1. Overall construction plan for the second excavation of the arch seat

[0103] This project is the second excavation of the arch seat foundation of the Jinghe Bridge, mainly including the excavation of the slope above the arch seat base, the excavation of the slope below the arch seat foundation, and the slope protection around the arch seat.

[0104] 2. Construction plan for slope and foundation pit excavation

[0105] 1.1 Construction preparation

[0106] This project is constructed in accordance with the principle of "layered construction from top to bottom, graded excavation and construction, and protection for each level after excavation". Before excavating the slope, the slope drainage and surface clearing work should be done first. During the excavation process, the slope rate and platform elevation should be strictly controlled. After the excavation is completed, the slope surface should be re-measured and repaired in time, and the slope surface protection should be carried out according to the design requirements.

[0107] Construction method:

[0108] The left and right bank arch seats were excavated twice. The left bank arch seat has a sixth-level slope. The upper and lower slopes have been divided according to the arch seat design base elevation. The upper slope is a first to fourth-level slope, and the lower slope is a fifth and sixth-level slope, including two places where the upstream and downstream arch seat foundations are replaced. The right bank arch seat has a first-level slope.

[0109] Left bank arch seat: the first-level slope is 794.491~787.648, the slope height is 6.843m, the slope ratio is 1:0.9, and the platform width is 2m; the second-level slope is 787.648~780.498, the slope height is 7.15m, the slope ratio is 1:0.5, and the platform width is 2m; the third-level slope is 780.498~773.417, the slope height is 7.081m, the slope ratio is 1:0.5, and the platform width is 2m; the fourth-level slope is 773.417~763.417, the slope height is 10m, the slope ratio is 1: 0.3, platform width 2m; level five slope 763.417~755.417, slope height 8m, slope ratio 1:0.25, platform width 2m; level six slope 755.417~747.417, slope height 8m, slope ratio 1:0.9, platform width 3m; upstream arch seat foundation replacement 763.417~761.417, replacement height 2m, slope ratio 1:0.1; downstream arch seat foundation replacement 763.417~753.417, replacement height 10m, slope ratio 1:0.2.

[0110] 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.

[0111] Since the excavation of the arch foundation pit is a secondary excavation, the slope of the excavated foundation pit needs to be re-slope-cut, and the slope is steep, the covering soil is thin, part of the bedrock is exposed, and the working platform is limited. Therefore, an excavator is used to build a slope excavation construction access road to 790.491 on the downstream side of the 794.491 platform, and the 794.491-790.491 slope is excavated and repaired by an excavator. After the excavator repairs the access road to 790.419, the excavator is used to remove the covering soil and then drill and blast the stone. The stone excavation is mainly constructed by deep hole blasting and supplemented by shallow hole blasting. The slope is blasted with smooth surface, and the breaker hammer is used to chisel it off locally. Step-by-step excavation is carried out from top to bottom, and a 2m horseway is set between each level.

[0112] To ensure the stability of the slope and form a flat slope, smooth blasting is adopted for the slope. The diameter of the blasting holes is 90 mm, and the spacing of the blast holes 100 is arranged at 50 cm. A Φ90 down-the-hole drill is used to drill the holes; Φ32 mm rock emulsion explosive is used and detonated with non-electric millisecond detonator 102.

[0113] The slag and stones are removed by an excavator. The slope is excavated and trimmed level by level, and at the same time, dangerous rocks are removed. After each layer of excavation is completed, the slope edge line and slope ratio are re-measured. One level of excavation is followed by one level of protection. Before protection, a scaffold and a construction platform are erected, and the slope protection is carried out according to the design protection requirements.

[0114] The technical solution of the present invention forms 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, reducing the construction difficulty of the arch seat foundation pit, and ensuring the stability of the arch seat foundation pit through the left six-layer slope platform and the right first-level slope platform. Different construction methods are adopted for the left bank arch seat and the right bank arch seat, which is more suitable for the construction operation environment with a relatively steep slope, thin overburden, partial exposure of bedrock, and limited working platform range, providing a reference basis for similar construction situations.

[0115] Continue to participate in the exhibition Figures 1 to 3 and refer to Figures 4 to 7 , Figure 4 is a schematic diagram of the charge structure involved in the present invention; Figure 5 is a schematic diagram of the charge structure involved in the present invention; Figure 6 is a schematic diagram of the charge structure of the smooth blasting hole 120 involved in the present invention; Figure 7 is a schematic diagram of the main smooth blasting hole 100 and the smooth blasting hole 120 involved in the present invention.

[0116] In an embodiment, as Figures 1 to 7 shown, the left bank arch seat includes a plurality of steps to be blasted. Using the working platform, on the left bank arch seat of the existing foundation pit slope platform, the surfaces to be excavated of the left bank arch seat are constructed layer by layer and level by level along the elevation direction of the existing foundation pit slope platform. The steps to form the left six-layer slope platform include:

[0117] Step A100: Drill blast holes 100 on each step to be blasted;

[0118] Step A200: Stuff the charge structure into the blast holes 100 to form the blasting excavation structure of the left bank arch seat foundation pit;

[0119] Step A300: Using the blasting excavation structure of the left bank arch seat foundation pit, form 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 on the left bank arch seat to form the left six-layer slope platform.

[0120] In one embodiment, the steps of forming blast holes 100 on each bench to be blasted include:

[0121] Step B100: Set the minimum burden on the bottom side of the bench to be blasted and obtain the length of the minimum burden;

[0122] Step B200: Set the upper bench line on the top side of the bench to be blasted and obtain the length of the upper bench line;

[0123] Step B300: Obtain the slope angle of the bench to be blasted according to the length of the minimum burden and the length of the upper bench line;

[0124] Step B400: Preset the overbreak depth of the blast hole 100;

[0125] Step B500: Drill holes on the surface of the bench to be blasted to form blast holes 100 according to the slope angle of the bench to be blasted, the height of the bench to be blasted and the overbreak depth of the blast hole 100;

[0126] Step B600: Obtain the charge amount according to the type of the blast hole 100;

[0127] Step B700: Tamp the charging structure into the blast hole 100 according to the charge amount to form the blasting excavation structure for the arch seat foundation pit.

[0128] In one embodiment, the type of the blast hole 100 is multi-row blast holes 100. The multi-row blast holes 100 include the front-row blast holes 100 and the second-row blast holes 100 arranged at intervals with the front-row blast holes 100. The front-row blast holes 100 are composed of a plurality of blast holes 100 arranged at intervals, and the second-row blast holes 100 are composed of a plurality of blast holes 100 arranged at intervals;

[0129] The steps of obtaining the charge amount according to the type of the blast hole 100 include:

[0130] Step C100: Obtain the charge amount of the front-row blast holes 100 according to the unit explosive consumption, the spacing between the blast holes 100 in the front-row blast holes 100, the hole depth of the front-row blast holes 100 and the minimum burden;

[0131] Step C200: Obtain the charge amount of the second-row blast holes 100 according to the unit explosive consumption, the spacing between the blast holes 100 in the second-row blast holes 100, the hole depth of the second-row blast holes 100 and the spacing between the second-row blast holes 100 and the front-row blast holes 100.

[0132] In one embodiment, the type of the blast hole 100 is a smooth blasting hole 120;

[0133] The steps of setting the minimum burden on the bottom side of the bench to be blasted and obtaining the length of the minimum burden include:

[0134] Step D100: Obtain the length of the minimum burden line of the smooth blasting hole 120 according to the aperture of the smooth blasting hole 120.

[0135] Among them, the aperture of the smooth blasting hole 120 is D_light, the length of the minimum burden line of the smooth blasting hole 120 is W_light, and W_light = β * D_light, where 15 ≤ β ≤ 25.

[0136] For the convenience of understanding, a specific implementation manner is shown below:

[0137] The excavation adopts a vertical drilling form, and the hole layout method of the blast hole 100 is plum blossom-shaped hole layout;

[0138] It is determined according to the on-site excavation height. In the construction of this project, it is generally taken as 2m in principle. When the bench height is relatively large, bench excavation should be carried out;

[0139] A down-the-hole drill is used for drilling. At present, a drill bit with a diameter of Φ40mm is mostly selected, so the aperture D = 40mm is taken;

[0140] It is determined by the determined bench height (H) and the overbreak (h). The overbreak of the drill hole is based on the empirical formula:

[0141] Then the hole depth L = H / Sin a + h, where L—the length of the blast hole 100 (m); H—the bench height (m); a—the drilling inclination angle (°); h—the overbreak (m) (the overbreak formula h = (0.1 - 0.15)H, and in actual situations, h = 0.3 - 0.5m is taken);

[0142] Based on the equipment capacity, working conditions, and slope gradient requirements, a suitable drilling inclination angle can be selected. According to the selected bench height of 2m, the actual hole depth L = 2.3 - 2.5m is taken. During construction, the depth parameters of the blast hole 100 should be appropriately adjusted according to the actual situation to ensure that the bottom of the hole is located on the planned bench plane;

[0143] According to the empirical formula: W_bottom = (30 - 50)D; in hard and difficult-to-blast rock masses, or when the bench height H is relatively high, a larger coefficient should be taken during calculation. During construction, it is generally taken as 0.8 - 1.5m;

[0144] (6) The hole spacing (a) and row spacing (b) of the blast hole 100; a = (1 - 1.5)W_bottom; b = (0.8 - 1.0)a;

[0145] In this project, it is taken as: a = (0.8 - 1.5)m; b = (0.6 - 1.2)m;

[0146] According to the requirements of this project, the stemming length should be L_stem ≥ 1.2W_bottom;

[0147] According to the properties and structures of the rocks in the project area, as well as practical experience, the q value generally ranges from 0.3 to 0.4 kg / m3. Based on the rock properties and structures of this project, the q value is taken as: q = 0.28 - 0.35 kg / m3. However, during the actual operation process, necessary adjustments should be made in a timely manner according to the changes in rock properties;

[0148] The type of explosive is No. 2 rock emulsion explosive, and the cartridge diameter is Ф25mm;

[0149] The charge amount Q per single hole: Q = qV; where: Q - the charge amount of each blast hole in kg; q - the explosive consumption per unit volume of rock, kg / m3; V - the volume of the rock to be blasted in m3, V = Lab; L - the hole depth; W - the resistance line; a - the hole spacing; b - the row spacing;

[0150] For the calculation of the charge amount of multi-row blast hole blasting, the charge amount Q per hole in the front row is Q = qaLW; the charge amount Q of the holes in the second row is Q = qabL; due to the different heights of the excavation benches, the resistance line changes at any time, and the hardness of the rock is different, etc., the charge amount per single hole should be calculated to obtain a reasonable charge amount according to the on-site situation. When the unit explosive consumption q is 0.35 kg / m3, the selection of the following parameters can be referred to;

[0151]

[0152] Adopt a continuous decoupled charge structure: Before charging, the charge amount per single hole should be calculated. When charging, gently put the explosive into the blast hole. The bottom of the blast hole is slightly larger, and the hole mouth is smaller, which is 2 / 3 of the hole bottom. Use stone powder or clay (the water content of the clay is 10% - 30%.) as the stemming material;

[0153] As another implementation method of this embodiment: (1) Blast hole arrangement method: Adopt the vertical drilling form, and the blast hole layout method is the plum blossom type layout. The layout form is similar to that of short-hole blasting.

[0154] (2) Bench height: According to the drawing design, the bench height is H = 10m. According to the rock conditions and the surrounding environment of the blasting area, it is designed as: H = 7m, H = 10m.

[0155] (3) Selection of the unit explosive consumption q value: q refers to the amount of explosive consumed by the rock per unit volume (or weight) of the blasting medium. Its value is related to factors such as rock properties, explosive properties, drilling diameter, and slope requirements. Considering various factors comprehensively, it is selected and adjusted based on experience, tests, and data from similar projects. According to the rock hardness and fracture development situation of this project, the unit consumption is taken as:

[0156] q = 0.25 - 0.40 kg / m 3 , and during the construction process, it is adjusted appropriately according to the trial blasting.

[0157] (4) Selection of the hole diameter D and the burden W_bottom

[0158] The diameter of the down-the-hole drill bit used in this project is Φ90. Based on past construction experience, taking 25 - 50 times the hole diameter, it is more appropriate to select W_bottom of 2.5 - 3.0m for this project. During blasting operations, appropriate adjustments can be made according to the blasting effect of the previous blast.

[0159] (5) Hole depth L and overbreak h

[0160] The hole depth is determined according to the actual terrain, facilitating the formation of a bench working face for the next blasting, and the surrounding environment on-site. The bench height H takes two values of 7m and 10m. The overbreak takes 8 - 12 times the hole diameter. In this project, according to the actual construction situation, h = 0.5m is taken.

[0161] (6) Selection of the hole spacing a and the row spacing b

[0162] The hole spacing a refers to the distance between the center lines of two adjacent holes in the same row of deep holes. Since this project is a cutting excavation, combining actual experience and the empirical formula a = mW_bottom (m is the hole density coefficient, m = 0.8 - 1.4m), when the bench height is 5m in this project, the hole spacing a = 2.5 - 3.0m is taken, and the row spacing b is calculated according to the formula b = (0.8 - 1.0)a, taking the row spacing b = 2.0 - 2.5m; when the bench height is 10m, the hole spacing a = 3.0 - 3.5m is taken, and the row spacing b is calculated according to the formula b = (0.8 - 1.0)a, taking the row spacing b = 2.5 - 3.0m. Appropriate adjustments can be made according to the different topographies and to meet the requirements of the surrounding environment on-site.

[0163] (7) Type of explosive

[0164] The variety of explosives for deep hole charging is emulsion explosive (cartridge diameter is Ф70).

[0165] (8) Charge amount per hole (Q)

[0166] According to the empirical formula Q = q·a·b·H, where q is the standard explosive consumption per unit volume, a is the hole spacing, b is the row spacing, and H is the bench height, the charge amount per hole Q5 = 11.5kg can be calculated (taking H = 5.0m, a = 3.0m, b = 2.5m, q = 0.30kg), and Q10 = 36kg (taking H = 10.0m, a = 4.0m, b = 3.0m, q = 0.30kg).

[0167] (9) Charge structure

[0168] The charge in the blast hole 100 adopts a continuous columnar charge structure. For deep holes, 2 detonators are used, and the detonators are respectively placed at the 1 / 3 and 2 / 3 positions of the charge column. During the charging process, there are no sundries in the hole, and the charge is continuous to naturally compact the explosive, ensuring the charging density. The backfill is sealed with stemming. During the backfilling process, the blocking material should be continuous (not in an air-supported state) and naturally compacted to ensure the blocking quality;

[0169] According to the requirements of this project, the stemming length is generally 20 - 30 times the hole diameter based on experience. Depending on the on-site terrain and surrounding environment conditions, the stemming length is 3 - 4.5 m.

[0170] The specific blasting-related parameters are shown in the following table

[0171]

[0172] The above parameters are adjusted according to the actual on-site geological conditions and the trial blasting effect. When the burden is too large, according to the design requirements, a hydraulic breaker or short-hole blasting is used to trim the burden to within the allowable value of the designed blasting parameters.

[0173] As an option in this embodiment, in the smooth blasting design: (1) Bench height H: It is the same as the designed slope height. (2) Drilling hole diameter D: Take D = 90 mm. (3) Drilling inclination angle: It is determined according to the design requirements of the slope gradient. (4) Minimum burden Ws. The minimum burden Ws of smooth blasting is a key parameter affecting the smooth blasting effect.

[0174] Ws = (15 - 25)D = 1.35 - 2.25 m, take Ws = 1.8 m.

[0175] (5) Spacing a of blast holes 100:

[0176] The spacing of blast holes 100 in smooth blasting can be selected according to the following formula; a = (10 - 20)D = 0.9 - 1.8 m. A smaller value is taken in rocks with relatively developed joints and fractures, and a larger value is taken in rocks with good integrity. Take a = 1.5 m.

[0177] (6) Non-coupling charge coefficient m: m = 2 - 5, and take 2.8 this time.

[0178] (7) Linear charge density qs

[0179] Take qs = 0.3 - 0.45 kg / m, and q at the bottom qb = (1.2 - 2.0)qs.

[0180] (8) Length Ls of smooth blasting holes 120: Ls = (H + h) / sinθ, where θ is the drilling inclination angle, take 53°, h is the overbreak, take 0.5 m, (H + h) / sinθ = 11.0÷sin53° = 13.6 m.

[0181] Where θ - refers to the slope angle

[0182] (9) Charge amount Qlight in blast hole 100 = qlight × Llight

[0183] (10) Charge structure

[0184] The smooth blasting holes 120 adopt uncoupled charging. The emulsion explosive cartridges with a diameter of φ32mm are tied to the detonating cord 500 and bamboo strips. The cartridges are close to the detonating cord 500 and are charged in three sections, namely: the reduced charge section 400 with a length of 2.0m at the top, the normal charge section 300 in the middle;

[0185] The enhanced charge section 200 with a length of 2m at the bottom (10m bench), and the enhanced charge section 1.2m with a 5m bench;

[0186] (11) Charging and stemming

[0187] The stemming length Lstem ≥ 1.5m, and 2.0m is taken in this case.

[0188] Enhanced charging at the bottom of the hole. Before charging, the linear charge density and the charge amount per single hole should be calculated. The explosive is evenly and firmly tied to the detonating cord 500500, and then carefully placed into the blast hole 100100. The stemming material uses woven bags and kraft paper, which are placed at the lower part of the stemming section 104104, and then backfilled with drill cuttings or clay. The stemming length is not less than 1.5m.

[0189] Summary table of design parameters for smooth blasting of slope

[0190]

[0191]

[0192] The technical solution of the present invention forms a secondary excavation on the blasting platform of the existing foundation pit by setting blast holes 100 on the existing foundation pit, forming a secondary foundation pit that meets the construction requirements, which is conducive to the subsequent construction of the secondary arch seat foundation pit, provides construction conditions for the subsequent construction steps, and improves the blasting excavation effect of the blast holes 100 by controlling the specific formation structure of the blast holes 100, improves the construction quality of the project, and provides a reference for similar construction modes.

[0193] Use a crawler down-the-hole drill. Excavate the slope ratio strictly in accordance with the construction drawings. After measuring and setting out the hole positions, drill the main blasting holes 110 and pre-splitting holes. During the drilling process, ensure that the longitudinal and transverse errors of the hole positions do not exceed ±50 mm, and the elevation error is strictly controlled to exceed the buried depth of large-diameter boulders. Ensure that the support of the drill is firm and stable, and there should be no shaking during the hole-making process. Use an air compressor to supply air, and ensure that the drill pipe aligner is in good condition for dry hole formation without water. The diameter of the bit used shall not be less than the designed hole diameter. Drill layer by layer from top to bottom. The drilling speed, air pressure, and propulsion shall be strictly controlled according to the performance of the drill and the actual situation of the underlying layer to prevent drilling distortion, diameter change, cave-in, or other accidents. After the air compressor starts, start the down-the-hole drill. According to the terrain and geological conditions, adjust the drill angle of the drill before drilling. After drilling, pay attention to the control of the hole depth, and it must exceed the bottom layer of the large boulder layer by 0.5 - 1.0 m. Avoid secondary alignment drilling and fully meet the requirements of the pilot hole. Arrange a special person to be responsible during the drilling process, and make detailed records of the geological conditions, hole opening, hole formation, and hole depth. During the drilling process, timely feedback and take measures for the formation changes, drilling status, groundwater, and some special situations of each hole.

[0194] In areas where the crawler drill cannot operate due to terrain reasons, use a manual air drill for drilling or use machinery for direct excavation. When using manual drilling, the excavation depth each time shall not be greater than 4 m, and the precautions are the same as those for the crawler drill.

[0195] After the holes are inspected by the blasting company, design the blasting plan. According to the geological conditions and the blasting design plan, and considering the requirements of slope stability and environmental conditions, adopt a reasonable blasting method to organize the blasting construction. During the blasting construction process, charge and control the charging strictly in accordance with the blasting design requirements to ensure the slope ratio of the slope, reduce the disturbance to the foundation and slope stability. And do a good job in safety warning and safety liaison work, and strictly prohibit other personnel from entering the blasting area.

[0196] For the second excavation slope blasting of the left bank downstream arch seat, the slag of the first three levels of slopes is cleared to the bottom of the downstream side arch seat foundation pit in turn by an excavator. When the slope is excavated to the fourth level of slope, use an excavator to uniformly discard it to the Jinghe River downstream channel. After the excavation of the sixth level of slope is completed, use a dump truck to transport it to the designated waste dump through the Jinghe River channel.

[0197] For the blasting of the fifth and sixth levels of slopes on the river-facing side, due to terrain reasons, the excavator cannot carry out mechanical slag removal, so use manual labor to clean the slag to the lower Jinghe River. When using manual slag cleaning, the slag cleaning personnel shall strictly wear safety protection equipment such as safety helmets, anti-slip shoes, safety ropes, and safety belts in accordance with the project safety management measures.

[0198] By setting blast holes 100 on an existing foundation pit and using the blast holes 100 to conduct secondary excavation on the blasting platform of the existing foundation pit, a secondary foundation pit that meets the construction requirements is formed, which is conducive to subsequent construction of the secondary arch seat foundation pit, provides construction conditions for subsequent construction steps, and improves the blasting excavation effect of the blast holes 100 by controlling the specific formation structure of the blast holes 100, improves the construction quality of the project, and provides a reference for similar construction modes.

[0199] Continue to refer to Figures 1 to 3 and refer to Figure 8 , Figure 8 is the schematic diagram of cut hole layout involved in the present invention.

[0200] In one embodiment, as shown in Figures 1 to 3 and Figure 8 , the steps of using a working platform to construct the to-be-excavated surface of the right-bank arch seat to form the right first-stage slope platform include:

[0201] Step E100: Layout the hole positions on the to-be-excavated surface of the right-bank arch seat to obtain the to-be-drilled hole positions;

[0202] Step E200: Drill the to-be-drilled hole positions to form the to-be-split holes 600;

[0203] Step E300: Split the to-be-split holes 600 to form a split area;

[0204] Step E400: Form the arch seat foundation pit according to the split area.

[0205] In one embodiment, the steps of splitting the to-be-split holes 600 to form a split area include:

[0206] Step F100: Use an excavator to assist in sending the splitting machine gun head into the to-be-split hole 600;

[0207] Step F200: Use the gun head to squeeze the to-be-split hole 600 to make the to-be-excavated surface crack into a line to form a split area.

[0208] In one embodiment, before the steps of splitting the to-be-split holes 600 to form a split area, the method for layered excavation of the arch seat foundation pit includes:

[0209] Step G100: Check the depth of the to-be-split hole 600;

[0210] Step G200: Judge whether the depth of the to-be-split hole 600 meets the preset depth condition;

[0211] Step G300: If so, split the to-be-split hole 600;

[0212] Step G400: If not, adjust the depth of the to-be-split hole 600 so that the depth of the to-be-split hole 600 meets the preset depth condition.

[0213] In one embodiment, the outer contour of the right bank arch abutment is stepped, and the arch abutment foundation pit of the right bank arch abutment includes a plurality of excavation surfaces to be excavated that are stacked in sequence from top to bottom. A plurality of holes to be formed are evenly distributed on each excavation surface to be excavated. The plurality of excavation surfaces to be excavated are the first excavation surface and the second excavation surface stacked below the first excavation surface. It is characterized in that, before the steps of forming the arch abutment foundation pit according to the splitting area, the method for layered excavation of the arch abutment foundation pit includes:

[0214] Step H100: Drill the holes to be formed on the first excavation surface, and perform splitting construction on the first excavation surface to form a first splitting area;

[0215] Step H200: Obtain the splitting situation according to the first splitting area;

[0216] Step H300: Adjust the hole spacing between the holes to be formed on the second excavation surface according to the splitting situation;

[0217] Step H400: Drill the holes to be formed on the second excavation surface, and perform splitting construction on the second excavation surface to form a second splitting area.

[0218] In one embodiment, the row spacing between a plurality of holes to be formed is 80 cm.

[0219] For easy understanding, a specific embodiment is shown below:

[0220] Both the arch abutments on both banks are located on the weakly weathered rock stratum, the foundation bearing capacity is not less than 1200 kPa, and the base elevation is 763.417 m. The 2# arch abutment is a solid integral inverted trapezoidal ordinary reinforced concrete arch abutment, and the outer contour dimensions are 18.82 m * 19.44 m * 17.21 m; the 3# arch abutment is a solid separated inverted trapezoidal ordinary reinforced concrete arch abutment, which is symmetrically arranged upstream and downstream along the center line of the line, and the outer contour dimensions are 18.8 m * 13.8 m * 17.23 m.

[0221] The arch abutments of the Jinghe River Bridge are excavated by the bench method with splitting construction. After the construction platforms on the left and right banks are excavated to 794.491 m (construction platform elevation), the arch abutments on the left and right banks are excavated in layers by the bench method with splitting method, and the excavation height of each bench is 1.2 m.

[0222] The arch abutments on the left and right banks are both divided into 4 areas for a total of 28 benches for excavation, and the excavation height of each bench is about 1.2 m.

[0223] The excavation range of the first area on the left bank is 794.494 - 787.648 m, the excavation height is 7.478 m, the slope ratio of the abutment back slope is 1:0.5, and it is excavated in 1 - 7 steps; the excavation range of the second area is 787.648 - 780.498 m, the excavation step height is 7.15 m, the excavation slope ratio is 1:0.1, and it is excavated in 8 - 13 steps; the excavation range of the third area is 780.498 - 771.091 m, the excavation step height is 9.407 m, the excavation slope ratio is 1:0.1 and it is excavated in 14 - 21 steps; the excavation range of the fourth area is 771.091 - 764.417 m (the elevation of the platform in front of the arch seat is 764.417 m), the excavation step height is 6.674 m, 1 m is reserved, and mechanical excavation is used for 764.417 - 763.417 m, the excavation slope ratio is 1:1.18, and it is excavated in 22 - 28 steps; for the fifth excavation, mechanical slope repair is adopted, the undercut parts of the slope are chiseled, and the slope ratio of the second - layer step slope is changed from 1:0.2 to 1:0.5. The excavation range of the first area on the right bank is 794.494 - 787.013 m, the excavation height is 7.478 m, the slope ratio of the abutment back slope is 1:0.2, the slope ratios of the slopes on both sides of the abutment are 1:0.3, and it is excavated in 1 - 7 steps; the excavation range of the second area is 787.013 - 780.477 m, the excavation height is 6.536 m, the excavation slope ratio is 1:0.2, and it is excavated in 8 - 13 steps; the excavation range of the third area is 780.477 - 771.063 m, the excavation step height is 9.414 m, the excavation slope ratio is 1:0.1, and it is excavated in 14 - 21 steps; the excavation range of the fourth layer is 771.063 - 764.417 m, the excavation step height is 7.646 m, 1 m is reserved, and mechanical excavation is used for 764.417 - 763.417 m, the excavation slope ratio is 1:1.18, and it is excavated in 22 - 28 steps; for the fifth excavation, mechanical slope repair is adopted, the undercut parts of the slope are chiseled, and the slope ratio of the second - layer step slope is changed from 1:0.2 to 1:0.75. The excavation sequence is as shown in the figure.

[0224] Construction process flow of foundation pit excavation:

[0225] According to the actual site conditions and combined with the construction experience of previous similar projects, the shallow - hole bench splitting method is proposed for the foundation pit excavation. During construction, it should be carried out step - by - step from top to bottom, and a 200 - cm slag - retaining wall should be reserved at the riverside slope to prevent construction slag from slipping and causing safety risks.

[0226] Splitting method:

[0227] According to the geological conditions and the foundation pit design scheme, and considering the environmental conditions and safety requirements around the foundation pit, the stepped down-the-hole controlled splitting method is adopted. That is, below the elevation of 794.417m, a 160cm area is selected in the middle of each layer for straight drilling splitting cuttings to form a splitting extrusion surface. Then, splitting drilling is carried out from both sides according to the row spacing of 80cm, and the height of each layer is about 1.2m.

[0228] Splitting process:

[0229] (1) Hole layout: Conduct measurement and lofting, release the contour line according to the arch seat position, and then mark the hole positions on the base surface. The hole spacing is 80cm for the row spacing and 200cm for the interval, the hole depth is 120cm, and all the holes in the middle part are vertical holes. Near the designed slope position of the foundation pit, after adjusting the drilling angle according to the designed slope gradient, drilling is carried out.

[0230] (2) Drilling: Use a down-the-hole drill for drilling. After drilling, use high-pressure air to clean the holes. After the cleaning is completed, temporarily block the holes with geotextiles or woven belts to ensure the smooth installation of the splitting machine gun head.

[0231] (3) Splitting: Use an excavator to assist in sending the 6 gun heads equipped with the splitting machine into the drilled holes, start the oil pump to pressurize, and the 6 gun heads simultaneously generate extrusion force on the rock mass, causing the rock mass to crack into a line along the row of holes.

[0232] (4) Breaking large stones: Use a hydraulic breaker to break the large stones into small stones for convenient loading and transportation.

[0233] Mucking method and process:

[0234] For the mucking of the arch seat foundation pit, use an excavator to load the buckets, a crawler crane to lift, and a dump truck to transport out.

[0235] Each foundation pit is equipped with two excavators to excavate and load the blasted rock in layers.

[0236] For the excavation of the 2# and 3# arch seat foundation pits, each is equipped with a 200t crawler crane. A 6m to 8m wide construction platform (where the 1m range at the edge of the foundation pit is the berm) is left around the excavation line of the foundation pit for the crawler crane to move and construct; the platform roadbed is strongly weathered limestone, and the bearing capacity does not need to be treated to meet the working requirements of the crawler crane.

[0237] The maximum excavation side length of the foundation pit is close to 44.36m (the longitudinal direction along the bridge of the 2# arch seat), and the maximum working radius of the excavator is 10m. Considering the farthest distance from the bottom of the foundation pit to the crane, the boom length of the crawler crane is selected as 27.45m, which can meet the construction requirements. Under this working condition configuration, the common maximum working radius is 26m, the lifting capacity is 25.4t, and the counterweight is 86.3t.

[0238] The 200t crawler crane is equipped with a 2×2×2m lifting bucket, with a capacity of 8m3 per bucket, weighing about 16t. The hoisting steel wire rope is arranged according to the running 2, and the lifting speed is 60m / min.

[0239] The muck is transported out by 10t dump trucks. The muck on the Chunhua bank is transported to a muck yard 2km upstream of the bridge site, and the muck yard on the Liquan bank is located 500m upstream of the bridge site.

[0240] The technical solution of the present invention is to arrange splitting holes 600 on the surface to be excavated of the existing foundation pit, and use the splitting holes 600 to perform splitting construction on the surface to be excavated of the existing foundation pit, which reduces the forming difficulty of the secondary excavation of the arch seat foundation pit, and is more suitable for the construction operation environment with steep slopes, thin overburden, partial exposure of bedrock, and limited working platform range, providing a reference basis for similar construction situations.

[0241] It should be noted that the serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments. The above embodiments are only optional embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or directly or indirectly applied to other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for layered excavation of an arch seat foundation pit, characterized in that, The arch abutment foundation pit includes an existing foundation pit slope platform, the existing foundation pit slope platform includes a left bank arch abutment and a right bank arch abutment arranged at intervals, and an excavation surface is provided on both the left bank arch abutment and the right bank arch abutment. The method includes: Excavate a construction passage in the existing foundation pit to form a working platform; Utilize the working platform to perform operations on the excavation surface of the left bank arch abutment of the existing foundation pit slope platform layer by layer and level by level from top to bottom along the elevation direction of the existing foundation pit slope platform to form a six-layer left slope platform; Utilize the working platform to perform operations on the excavation surface of the right bank arch abutment to form a first-layer right slope platform; Combine the six-layer left slope platform and the first-layer right slope platform to form a secondary arch abutment foundation pit.

2. The method for layered excavation of the arch seat foundation pit according to claim 1, wherein, The left bank arch abutment includes multiple blasting steps. The step of utilizing the working platform to perform operations on the excavation surface of the left bank arch abutment of the existing foundation pit slope platform layer by layer and level by level from top to bottom along the elevation direction of the existing foundation pit slope platform to form a six-layer left slope platform includes: Drill holes on each of the blasting steps to form blast holes; Fill the blast holes with a charging structure to form a blasting excavation structure for the left bank arch abutment foundation pit; Utilize the blasting excavation structure for the left bank arch abutment foundation pit to form a first-layer left slope platform, a second-layer left slope platform, a third-layer left slope platform, a fourth-layer left slope platform, a fifth-layer left slope platform, and a sixth-layer left slope platform on the left bank arch abutment to form the six-layer left slope platform.

3. The method for layered excavation of the arch seat foundation pit according to claim 2, characterized in that, The step of drilling holes on each of the blasting steps to form blast holes includes: Set a minimum resistance line at the bottom side of the blasting step and obtain the length of the minimum resistance line; Set a step upper brow line at the top side of the blasting step and obtain the length of the step upper brow line; Obtain the slope angle of the blasting step according to the length of the minimum resistance line and the length of the step upper brow line; Preset the over-depth of the blast holes; Drill holes on the surface of the blasting step to form the blast holes according to the slope angle of the blasting step, the height of the blasting step, and the over-depth of the blast holes; Obtain the charge amount according to the type of the blast holes; Fill the blast holes with the charging structure according to the charge amount to form the blasting excavation structure for the arch abutment foundation pit.

4. The method for layered excavation of the arch seat foundation pit according to claim 3, characterized in that, The type of the blast holes is multi-row blast holes. The multi-row blast holes include front-row blast holes and second-row blast holes arranged at intervals with the front-row blast holes. The front-row blast holes are composed of multiple blast holes arranged at intervals, and the second-row blast holes are composed of multiple blast holes arranged at intervals; The step of obtaining the charge amount according to the type of the blast holes includes: Obtain the charge amount of the front-row blast holes according to the unit explosive consumption, the spacing between the blast holes in the front-row blast holes, the hole depth of the front-row blast holes, and the minimum resistance line; Obtain the charge amount of the second-row blast holes according to the unit explosive consumption, the spacing between the blast holes in the second-row blast holes, the hole depth of the second-row blast holes, and the spacing between the second-row blast holes and the front-row blast holes.

5. The method for layered excavation of the arch seat foundation pit according to claim 3, characterized in that, The type of the blast holes is smooth blasting holes; The step of setting a minimum burden line at the bottom side of the bench to be blasted and obtaining the length of the minimum burden line includes: Obtaining the length of the minimum burden line of the smooth blasting holes according to the aperture of the smooth blasting holes; Among them, the aperture of the smooth blasting hole is D 光 , and the length of the minimum burden of the smooth blasting hole is W 光 , W 光 =β*D 光 , 15≤β≤25 6. The method for layered excavation of the arch seat foundation pit according to any one of claims 1 to 5, characterized in that, The step of using the working platform to construct the to-be-excavated surface of the right-bank arch abutment to form the right first-stage slope platform includes: Performing hole position lofting on the to-be-excavated surface of the right-bank arch abutment to obtain the to-be-drilled hole positions; Drilling the to-be-drilled hole positions to form the to-be-split holes; Splitting the to-be-split holes to form a split area; Forming the arch abutment foundation pit according to the split area.

7. The method for layered excavation of the arch seat foundation pit according to claim 6, characterized in that, The step of splitting the to-be-split holes to form a split area includes: Using an excavator to assist in sending the splitting machine gun head into the to-be-split holes; Using the gun head to extrude the to-be-split holes, causing the to-be-excavated surface to crack into a line to form the split area.

8. The method for layered excavation of the arch seat foundation pit according to claim 7, characterized in that, Before the step of splitting the to-be-split holes to form a split area, the method includes: Checking the depth of the to-be-split holes; Judging whether the depth of the to-be-split holes meets the preset depth condition; If so, splitting the to-be-split holes; If not, adjusting the depth of the to-be-split holes so that the depth of the to-be-split holes meets the preset depth condition.

9. The method for layered excavation of the arch seat foundation pit according to claim 7, characterized in that, The outer contour of the right-bank arch abutment is in a stepped shape. The arch abutment foundation pit of the right-bank arch abutment includes multiple to-be-excavated surfaces stacked in sequence from top to bottom. A plurality of the to-be-drilled hole positions are evenly arranged on each of the to-be-excavated surfaces. The multiple to-be-excavated surfaces are the first to-be-excavated surface and the second to-be-excavated surface stacked below the first to-be-excavated surface. It is characterized in that before the step of forming the arch abutment foundation pit according to the split area, the method includes: Drilling the to-be-drilled hole positions on the first to-be-excavated surface and splitting and constructing on the first to-be-excavated surface to form a first split area; Obtaining the splitting condition according to the first split area; Adjusting the hole spacing between the to-be-drilled hole positions on the second to-be-excavated surface according to the splitting condition; Drilling the to-be-drilled hole positions on the second to-be-excavated surface and splitting and constructing on the second to-be-excavated surface to form a second split area.

10. The method for layered excavation of the arch seat foundation pit according to claim 9, characterized in that, The row spacing between the multiple to-be-drilled hole positions is 80 cm.

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