Building rock foundation constraint area protection layer excavation construction method

Abstract

The application discloses a building rock foundation constraint area protection layer excavation construction method, comprising the following steps: the foundation excavation area is divided into a main blasting area and a protection layer from top to bottom as a whole, and the main blasting area is rapidly excavated to the position of the top surface of the protection layer by using a blasting process; after the main blasting area is excavated and the protection layer is formed, continuous closed-loop pre-cutting groove construction is carried out along the design contour line of the protection layer by using a cutting groove device, so that a continuous isolation boundary is formed; a slotting operation area is planned in the internal area of the protection layer surrounded by the pre-cutting groove, static slotting construction is carried out by using a pure static non-blasting process, and a regular free surface is formed; micro-difference precision controlled blasting operation is carried out on the remaining rock mass of the protection layer relying on the isolation boundary of the pre-cutting groove outside the protection layer and the free surface of the static slotting inside the protection layer, so that contour precision forming is realized; and slag cleaning, finishing treatment and detection and acceptance of the building base are carried out after blasting is completed. The construction method can realize low-damage, high-precision and high-efficiency excavation of the hard constraint area rock mass.

Description

Technical Field

[0001] This invention relates to the field of rock foundation excavation and construction technology, specifically to a method for excavating and constructing a protective layer in the confined zone of a building's rock foundation. Background Technology

[0002] The core foundation components of major infrastructure projects such as water conservancy and hydropower, nuclear power, and large bridges, such as generator pits, nuclear island pits, surge tank bottom plates, and large bridge pier foundations, are the core load-bearing carriers of the buildings. They have extremely stringent design and specification requirements for the integrity, bearing capacity, geometric accuracy, and flatness of the foundation rock mass.

[0003] The foundations of this type of project are mostly excavated in medium-to-high strength rock strata, with a large overall excavation depth. The rock mass is in a complex stress state with multiple open surfaces and bidirectional constraints at the lateral and bottom. The construction conditions have three core characteristics: First, the rock has high compressive strength and good rock mass integrity, making crushing and excavation difficult; second, the constraints are complex, and blasting energy is easy to accumulate and difficult to dissipate; third, the construction space is limited, and the precision and quality control standards are far higher than those of ordinary rock and soil excavation projects.

[0004] The industry's general construction principle is as follows: The upper part of the foundation rock mass is rapidly excavated using conventional stepped blasting. A certain thickness of protective rock layer is reserved near the designed foundation surface. This protective layer is then removed using refined excavation techniques to maximize the protection of the underlying bedrock from construction disturbance. This is the universal construction logic for all rock foundation protective layer excavations. Currently, the mainstream protective layer excavation techniques in the industry are divided into two main categories: blasting excavation and purely static mechanical excavation.

[0005] Traditional hand-operated shallow-hole blasting technology suffers from several drawbacks. Without physical isolation joints or pre-exposed free faces, the blasting energy in the confined area cannot be released directionally, resulting in a large accumulation of energy within the retained bedrock. This directly damages the deep rock mass, with blasting damage depths reaching 1.0–1.5 meters. Furthermore, the manual drilling without precise mechanical guidance leads to significant deviations in drilling position and verticality, inevitably causing severe over- and under-excavation (linear over-excavation of 20–35 cm) and poor foundation surface flatness. Additionally, the amount of explosive charge and vibration in a single blast cannot be precisely quantified and controlled, easily disturbing adjacent structures and resulting in substantial subsequent defect repair and concrete overfilling work.

[0006] Pure static excavation process: Due to the technical limitations of relying entirely on mechanical physical static rock breaking without blasting assistance, mechanical breaking resistance is extremely high and rock breaking efficiency is extremely low when facing hard rock masses such as high-strength and high-integrity granite. The average daily excavation volume of a single working face is less than 15m³. At the same time, the equipment wears out quickly and the labor time is long, which directly causes serious delays in the construction period and a significant increase in the overall construction cost, making it impossible to meet the core requirements of efficient construction of large-scale projects.

[0007] In summary, the two existing mainstream protective layer excavation technologies have core technical contradictions: precision and integrity cannot be simultaneously achieved, efficiency and quality are incompatible, and safety disturbance and construction cost cannot be balanced. No single technology can simultaneously meet the high standards required for the excavation of protective layers for major rock foundations. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of the two mainstream protective layer excavation techniques in the existing technology by providing a construction method for excavating the protective layer in the confined zone of a building's rock foundation. Through multi-process coupling innovation, this method completely overcomes the technical drawbacks of traditional blasting, such as large damage, poor precision, and large disturbance, as well as the low efficiency, high cost, and poor adaptability of purely static excavation. It achieves low rock mass damage, centimeter-level excavation precision, high-efficiency construction, and safe, environmentally friendly, and controllable construction results. This allows for the "carving-like" fine shaping of the rock foundation of important buildings, taking into account project quality, schedule, safety, and economic benefits, and is suitable for the construction needs of ultra-high standard major projects such as nuclear power, hydropower, and large bridges.

[0009] This invention is achieved through the following technical solution: This invention provides a method for excavating and constructing a protective layer in the confined zone of a building's rock foundation, comprising the following steps: Step 1: Divide the foundation excavation area into a main blasting zone and a protective layer from top to bottom, and use blasting technology to quickly excavate the main blasting zone to the location of the top surface of the protective layer. Step 2: After the main blasting area is excavated and the protective layer is formed, use a grooving device to carry out continuous closed-loop pre-grooving construction along the design outline of the protective layer to form a continuous isolation boundary; Step 3: Within the protective layer completely surrounded by the pre-cut groove, plan the trenching operation area and carry out static trenching construction using a pure static non-explosive process to form a regular free surface. Step 4: Relying on the pre-cut groove isolation boundary on the outer side of the protective layer and the free face of the static excavation on the inner side, carry out micro-differential precision controlled blasting operation on the remaining rock mass of the protective layer to achieve precise contour shaping; Step 5: After the blasting is completed, the foundation surface is cleaned, repaired, and inspected for acceptance.

[0010] As a further aspect of the present invention, in step one, the overall excavation area is divided according to the engineering design drawings, the lithology of the rock mass on site, and the blasting vibration control standards, wherein the main blasting area is excavated using step blasting or ordinary pre-splitting blasting technology.

[0011] As a further aspect of the present invention, the reserved thickness of the protective layer in step one is controlled between 1.5m and 3.5m, and dynamically adjusted according to the rock mass strength, with a larger value for high-strength rock masses and a smaller value for medium- and low-strength rock masses.

[0012] As a further embodiment of the present invention, the grooving equipment in step two can be one or a combination of several of the following: a disc saw rock cutter, a chainsaw rock cutter, and a high-pressure water jet cutter.

[0013] As a further aspect of the present invention, in step two, the width of the pre-cut groove during construction is 20mm to 50mm, and the depth of the groove is 10cm to 20cm greater than the total thickness of the preset protective layer, ensuring that the groove penetrates the entire vertical structure of the protective layer.

[0014] As a further embodiment of the present invention, the equipment for static trenching in step three can be a water drill or a hydraulic splitter.

[0015] As a further embodiment of the present invention, in step three, the drilling spacing during static trenching is set to 1.2 to 1.5 times the corresponding borehole diameter, the overall trench width is controlled between 0.4m and 0.8m, and the trench depth is slightly less than the overall thickness of the protective layer.

[0016] As a further embodiment of the present invention, in step four, the borehole diameter during blasting operations is 32mm to 42mm, the borehole mesh parameters are controlled between 0.8m×0.8m and 1.2m×1.0m, and are finely adjusted according to the rock hardness.

[0017] As a further aspect of the present invention, in step four, a radially decoupled charge or air-gap charge structure is used during blasting operations, and the linear charge density is strictly controlled between 100g / m and 200g / m; detonating cord detonators are used to achieve micro-delay initiation between holes and between rows, and vibration safety checks of the maximum charge amount in a single section are completed before blasting, and the charge amount in a single section is strictly controlled.

[0018] As a further aspect of the present invention, after the blasting is completed in step five, mechanical equipment is used to uniformly clean up the debris and remove loose loose stones; minor unevenness and corners are manually and meticulously repaired; the grooves left by the mechanical pre-cut grooves are roughened and cleaned to ensure that the foundation surface is flat and clean; then, sonic detection and drilling camera detection equipment are used to conduct comprehensive detection of the rock mass damage depth, wave velocity, and integrity. After all indicators meet the standards and are accepted, the subsequent concrete pouring operation is carried out.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention addresses the inherent technical deficiencies of traditional single blasting and purely static excavation processes. Through an innovative multi-process coupling technology system, it achieves a comprehensive upgrade in quality, efficiency, safety, and effectiveness. Compared to traditional blasting processes, this invention solves the problem of blasting energy accumulation in the confined area from the root by using mechanical pre-cut grooves for physical isolation and static trenching for pressure relief. This significantly reduces rock mass blasting damage, controlling the original damage depth of over 1.0m to within 0.3m. At the same time, by relying on mechanical rigid boundaries to replace manual hole drilling, it completely solves the problems of uncontrolled over- and under-excavation and poor foundation surface flatness, significantly reducing the amount of subsequent repair and concrete overfilling work. 2. Compared to purely static excavation, this invention introduces controllable micro-differential blasting to assist in rock breaking, solving the technical problems of extremely low efficiency and delayed construction period in static rock breaking of high-strength rocks. Construction efficiency is increased by 3-5 times, and equipment and labor costs are significantly reduced. At the same time, by quantitatively controlling blasting parameters, the advantages of low disturbance in static excavation are retained, and the blasting vibration, flyrock, noise, and dust are standardized and controllable. It takes into account the four core advantages of high precision, low damage, high efficiency, and safety and environmental protection, and is perfectly adapted to the stringent construction standards of core foundations of major projects such as nuclear power and hydropower. Its comprehensive promotion value and engineering practicality are significant. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of the construction method for excavating the protective layer in the confined zone of a building's rock foundation according to the present invention; Figure 2 This is a front view of the excavation of the protective layer in the rock foundation confinement zone in this invention; Figure 3 This is a plan view of the excavation of the protective layer in the rock foundation constraint zone in this invention; Figure 4 This is a block diagram illustrating the overall technical architecture of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0026] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0027] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0028] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0029] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0030] This application addresses the excavation of protective layers in the confined zone of rock foundations for major structures such as water conservancy and hydropower plants, nuclear power plants, and large bridges. Its core challenge lies in solving the technical difficulties of existing single excavation techniques in simultaneously achieving low rock mass damage, high excavation accuracy, high construction efficiency, and low safety disturbance. Specifically, the four core technical issues to be addressed are as follows: (1) Problem of severe damage to the rock mass in the confined area: Under the condition of complex stress and multiple open surfaces in the foundation confined area, the traditional blasting technology cannot fully release the blasting energy, which can easily cause deep cracks in the retained bedrock, damage the integrity of the rock mass, and result in a large blasting damage depth, which greatly reduces the bearing capacity of the foundation rock mass and affects the stability of the building foundation.

[0031] (2) Problems of poor excavation accuracy and uncontrolled over- and under-excavation: Traditional hand-operated pneumatic drills have no precise guidance, and the accuracy of manual hole making is low. In the corners and contours of the constrained area, the amount of over-excavation is large and under-excavation occurs frequently. The flatness of the foundation surface is poor, and the amount of subsequent defect repair and concrete over-filling is large, and the construction quality is uncontrollable.

[0032] (3) Problems of low construction efficiency and uncontrollable construction period and cost: The pure static excavation process is poorly adapted to high-strength intact rock. The single construction method of mechanical crushing and water-jetting is extremely inefficient. When faced with large-scale foundation excavation projects, it is easy to cause delays in the construction period. Moreover, the labor and equipment construction costs are too high, which cannot meet the requirements of major project nodes.

[0033] (4) Major problems of construction safety and environmental disturbance: The amount of explosives in a single stage of traditional blasting process is uncontrollable, and the blasting vibration, flying rocks, noise and dust disturbance exceed the standard, which can easily damage the adjacent building structure and construction equipment. It cannot be adapted to sensitive construction areas with high precision and high safety requirements such as nuclear power plants and hydropower stations.

[0034] In view of this, the applicant, in conjunction with the actual construction of the project, provides a combined rock protective layer excavation method that couples three steps: mechanical pre-splitting, static trenching, and micro-differential controlled blasting. Through a closed-loop process of "physical isolation constraint removal + static free face construction + directional micro-differential controlled blasting", it achieves low-damage, high-precision, and high-efficiency excavation of rock mass in hard-constrained areas.

[0035] Please refer to Figure 1 The present application provides a method for excavating the protective layer of a building's rock foundation confinement zone, which includes the following steps: Step 1: Layered delineation and excavation of the main blasting zone (basic pretreatment process) Based on the engineering design drawings, on-site rock lithology, and blasting vibration control standards, the overall excavation area of ​​the rock foundation is divided into two functional zones from top to bottom, such as... Figure 2 As shown. The first is the main blasting zone, which is rapidly excavated using conventional step blasting or ordinary pre-splitting blasting techniques. Excavation ends at a safe distance from the designed foundation surface, completing the efficient removal of most of the rock mass. The second is the foundation protective layer, which serves as the final refined excavation layer. The thickness of the protective layer is uniformly controlled between 1.5m and 3.5m, dynamically adjusted according to the rock mass strength, with a larger value for high-strength rock masses and a smaller value for medium- and low-strength rock masses.

[0036] By employing blasting techniques to rapidly excavate large areas of rock mass and reserving standardized protective layers, a foundation is laid for subsequent refined construction. The necessary equipment for this step may include: conventional blasting drilling equipment, explosives, detonating cord initiation systems, and earthmoving equipment.

[0037] Step 2: Construction of contour pre-cut groove (mechanical pre-splitting, core isolation process) After the main blasting zone is excavated and the protective layer is formed, continuous closed-loop pre-grooving is carried out along the entire designed outline of the protective layer using specialized mechanical grooving equipment, such as... Figure 3 As shown. The grooving equipment can be a single type or a combination of several types of rock cutting machines, including circular saw rock cutting machines, chainsaw rock cutting machines, and high-pressure water jet cutting machines. The pre-grooving parameters are strictly controlled quantitatively: the grooving width is 20mm to 50mm, and the cutting depth is 10cm to 20cm greater than the total thickness of the preset protective layer, ensuring that the pre-grooving penetrates the entire vertical structure of the protective layer to form a complete, uninterrupted contour isolation seam.

[0038] The weak isolation joints formed by mechanical grooving block the transmission of blasting stress to the bedrock, while simultaneously releasing the lateral constraints on the rock mass, providing boundary conditions for subsequent directional stripping. This pre-grooving creates a continuous physical isolation boundary, completely removing the lateral constraints on the protective layer rock mass, limiting the extent of blasting crack propagation, and controlling over-excavation and deep rock damage from the source. The necessary equipment for this step may include: a rock saw, a chainsaw, a high-pressure water jet cutting machine, and precise positioning equipment.

[0039] Step 3: Internal static trenching (free face construction process) Within the protective layer completely surrounded by the pre-cut groove, a trenching operation area is planned, and static trenching construction is carried out using a purely static, non-explosive process, such as... Figure 3 As shown. The equipment used for trenching can be a water-cooled drill with a diameter of Φ150mm to 250mm or a hydraulic splitter; standardized control of drilling parameters: the drilling spacing is set to 1.2 to 1.5 times the corresponding borehole diameter, and a regular trench is formed by continuous annular drilling and cutting; the overall trench width is controlled at 0.4m to 0.8m, and the trench depth is slightly less than the overall thickness of the protective layer to avoid damaging the original rock at the bottom of the foundation surface during trenching.

[0040] Traditional blasting lacks a dedicated free face, leaving the rock mass in a triaxially constrained state. All blasting energy is compressed and damaged within the rock mass. This process creates a free face through static grooving, allowing for directional fracturing and release of energy in the rock mass during subsequent blasting, fundamentally reducing the destructive force of the blast. By constructing a regular free face within the protective layer, stress accumulation in the rock mass is eliminated, significantly reducing the amount of explosive charge and blasting vibration, achieving "statically guided rock breaking." The necessary equipment for this step may include: a large-diameter water-cooled drill, a hydraulic rock splitter, and small debris removal tools.

[0041] Step 4: Controlled blasting stripping (core process of fine rock breaking) Relying on the pre-cut groove isolation boundary on the outer side of the protective layer and the free face of the static excavation on the inner side, micro-delay precision controlled blasting operations are carried out on the remaining rock mass of the protective layer. Drilling parameters: Small-diameter boreholes of 32mm to 42mm are used, and the borehole network parameters are controlled within 0.8m×0.8m to 1.2m×1.0m, with minor adjustments based on lithological hardness. Charging method: Radial decoupled charging or air-gap charging structure is adopted to weaken the peak blasting pressure, and the linear charge density is strictly controlled within 100g / m to 200g / m. Initiation method: Detonating cord detonators are used to achieve micro-delay initiation between holes and between rows. Vibration safety checks are performed on the maximum charge amount of each stage before blasting, and the charge amount of each stage is strictly controlled.

[0042] In this process, under the constraint of a bidirectional free surface, the blasting energy no longer diffuses randomly, but is released directionally only towards the pre-cut groove and the free face of the cut, achieving layered and precise stripping of the rock mass. This ensures rock-breaking efficiency while preventing deep damage to the original rock and over-excavation of the outline. By precisely stripping the remaining rock mass of the protective layer with a small amount of explosive and low disturbance, precise outline shaping is achieved, controlling safety risks such as blasting vibration and flyrock. The supporting equipment required in this step may include: a small precision drilling machine, detonating cord detonators, emulsion explosives, vibration monitoring equipment, etc.

[0043] Step 5: Foundation Surface Treatment and Acceptance (Forming Quality Control Process) After the blasting is completed, mechanical equipment is used to clean up the debris and remove loose stones. Minor unevenness and corners are manually trimmed. Grooves left by the mechanical pre-cut grooves are roughened and cleaned to ensure that the foundation surface is flat and clean. Then, sonic testing and drilling camera testing equipment are used to conduct comprehensive testing on the depth of rock damage, wave velocity and integrity. After all indicators meet the standards and are accepted, the subsequent concrete pouring operation can be carried out.

[0044] This process involves repairing minor defects after the rock foundation construction, inspecting the integrity of the rock mass and the accuracy of the construction, and ensuring that the foundation construction quality meets standards. The necessary equipment for this step may include: a slag remover, a handheld chisel, an acoustic detector, and a borehole imaging system.

[0045] The overall technical architecture principle block diagram of this application is as follows: Figure 4 As shown. The overall technical architecture of this application is a three-layer progressive closed-loop control system: the first layer (boundary protection layer): mechanical pre-cutting groove → constructing physical isolation and releasing lateral constraints; the second layer (stress relief layer): static excavation → creating free face and reducing blasting energy consumption; the third layer (precision forming layer): micro-differential controlled blasting → directional stripping of rock mass and precise forming of foundation surface; finally, through closed-loop testing and acceptance, the system achieves full-dimensional control of quality, safety, and accuracy. The three layers are mutually coupled and indispensable, together forming the core system of refined excavation.

[0046] This application utilizes three major processes—mechanical pre-splitting with grooving, static grooving with water-jet drilling, and low-charge micro-delay blasting—to form a closed-loop combined excavation system of "static constraint release + dynamic precise stripping," breaking through the technical barriers of traditional single-process methods. By employing a continuous mechanical pre-grooving structure (groove width 20–50 mm, groove depth 10–20 cm) along the protective layer contour, it actively constructs stress-relieving weak surfaces, solving the core problems of blasting energy accumulation and deep-seated damage to the original rock in the constrained area. For cases where there is no free surface in the constrained area, a large-diameter water-jet drilling annular grooving process is adopted, limiting the grooving size and drilling spacing parameters to efficiently construct a regular internal free surface, significantly reducing the amount of blasting charge and disturbance. Through a combination of quantitative blasting parameters—small-hole mesh in the protective layer, low linear charge density, and micro-delay blasting—directional stripping of the rock mass is achieved, precisely controlling over- and under-excavation and vibration. Using continuous mechanical grooving as a physical rigid boundary replaces the free contour of traditional manual blasting, achieving centimeter-level precision forming of the foundation surface and completely eliminating corner over-excavation defects. By employing a multi-level damage control mode combining pre-splitting isolation, static pressure relief, and micro-delay controlled blasting, the blasting damage depth and rock wave velocity attenuation rate are quantified and controllable, maximizing the preservation of the original rock integrity. Through a combination of charge verification, micro-delay, and physical isolation, the four major disturbance indicators of blasting vibration, flyrock, noise, and dust are quantified and controllable, making it suitable for sensitive construction areas.

[0047] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for excavating and constructing a protective layer in the confined zone of a building's rock foundation, characterized in that, Includes the following steps: Step 1: Divide the foundation excavation area into a main blasting zone and a protective layer from top to bottom, and use blasting technology to quickly excavate the main blasting zone to the location of the top surface of the protective layer. Step 2: After the main blasting area is excavated and the protective layer is formed, use a grooving device to carry out continuous closed-loop pre-grooving construction along the design outline of the protective layer to form a continuous isolation boundary; Step 3: Within the protective layer completely surrounded by the pre-cut groove, plan the trenching operation area and carry out static trenching construction using a pure static non-explosive process to form a regular free surface. Step 4: Relying on the pre-cut groove isolation boundary on the outer side of the protective layer and the free face of the static excavation on the inner side, carry out micro-differential precision controlled blasting operation on the remaining rock mass of the protective layer to achieve precise contour shaping; Step 5: After the blasting is completed, the foundation surface is cleaned, repaired, and inspected for acceptance.

2. The method for excavating and constructing the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step one, the overall excavation area is divided according to the engineering design drawings, the lithology of the rock mass on site, and the blasting vibration control standards. The main blasting area is excavated using step blasting or ordinary pre-splitting blasting technology.

3. The method for excavating and constructing the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step one, the reserved thickness of the protective layer is controlled between 1.5m and 3.5m, and is dynamically adjusted according to the rock mass strength, with a larger value for high-strength rock masses and a smaller value for medium- and low-strength rock masses.

4. The method for excavating and constructing the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step two, the grooving equipment can be one or a combination of several types of rock cutting machines, such as disc saw rock cutting machines, chainsaw rock cutting machines, and high-pressure water jet cutting machines.

5. The method for excavating the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step two, the width of the pre-cut groove during construction is 20mm to 50mm, and the depth of the groove is 10cm to 20cm greater than the total thickness of the pre-set protective layer, ensuring that the groove penetrates the entire vertical structure of the protective layer.

6. The method for excavating the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step three, the equipment for static trenching can be either a water drill or a hydraulic splitter.

7. The method for excavating the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step three, the drilling spacing during static trenching is set to 1.2 to 1.5 times the corresponding borehole diameter, the overall trench width is controlled between 0.4m and 0.8m, and the trench depth is slightly less than the overall thickness of the protective layer.

8. The method for excavating and constructing the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step four, the borehole diameter during blasting operations is 32mm to 42mm, and the borehole mesh parameters are controlled between 0.8m×0.8m and 1.2m×1.0m, with fine adjustments made according to the rock type and hardness.

9. The method for excavating the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step four, the blasting operation adopts a radially decoupled charge or air-gap charge structure, and the linear charge density is strictly controlled between 100g / m and 200g / m. Detonating cord detonators are used to achieve micro-delay initiation between holes and between rows. Before blasting, vibration safety verification of the maximum charge amount in a single section is completed, and the charge amount in a single section is strictly controlled.

10. The method for excavating the protective layer in the confined zone of a building's rock foundation according to claim 1, characterized in that, In step five, after the blasting is completed, mechanical equipment is used to uniformly clean up the debris and remove loose stones; minor unevenness and corners are manually trimmed; the grooves left by the mechanical pre-cut grooves are roughened and cleaned to ensure that the foundation surface is flat and clean; then, sonic detection and drilling camera detection equipment are used to conduct comprehensive detection of the rock mass damage depth, wave velocity and integrity. After all indicators meet the standards and are accepted, the subsequent concrete pouring operation is carried out.

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