Rotary drilling rig large pile diameter rock geological drill assembly guide vertical drilling process

Abstract

The application discloses a rotary drilling rig large-pile-diameter rock stratum drilling tool combination guiding vertical drilling process and belongs to the field of rotary drilling in rock strata. In view of the problems of poor adaptability, insufficient deviation correction and low drilling verticality of the large-pile-diameter rock drilling tool, a square connecting head is welded on the top center of the reaming drill bit, the large and small reaming drill bits and the rock core drilling tool are integrated, the central positioning is relied on to realize the guiding deviation correction and the vertical drilling, and the single-time downhole drilling is synchronous with reaming, hole repairing and coring. The process constructs a double guiding mechanism, is suitable for 260MPa rock strata with the highest single-axis compressive strength, improves the adaptability, guiding precision and drilling efficiency of the drilling tool, and the hole verticality deviation can be controlled within 0.3%, and is suitable for the rotary drilling construction of 100cm-300cm large-pile-diameter rock strata. The existing drilling rig does not need to be transformed and can be widely used in bridge, building and wind power pile foundation engineering.

Description

Technical Field

[0001] This invention relates to the field of rotary drilling rig pile foundation construction technology, specifically to a drill bit combination type guided vertical drilling process suitable for large-diameter rock strata, which can be widely used in rotary drilling construction of large-diameter hard rock strata for bridge pile foundations, building pile foundations, wind power foundations and other projects. Background Technology

[0002] With the rapid advancement of infrastructure construction in my country, the construction scenarios for pile foundation engineering are gradually extending to complex geological conditions. Among these, rotary drilling in large-diameter rock strata is a key focus and challenge in the current engineering field. Rotary drilling rigs, with their advantages of mobility, high drilling efficiency, and environmental friendliness, have become the core equipment for pile foundation construction. However, when facing moderately weathered, slightly weathered, and other hard rock strata, as well as complex rock geological conditions such as interbedded soft and hard layers and fractured zones, conventional drilling techniques are gradually revealing many limitations.

[0003] Currently, the industry commonly employs a staged reaming process for rotary drilling in large-diameter rock formations. This involves first drilling a pilot hole using a small-diameter drill bit, then gradually replacing it with larger-diameter drill bits to ream the hole until the designed diameter is reached. This process requires multiple tripping and re-drilling operations to change drilling tools. Different specifications of drill tools and drill rods have varying compatibility, and repeated disassembly and reassembly not only significantly prolong the construction period but also easily lead to borehole coaxiality deviations due to accumulated gaps in the drill tool connections, affecting borehole quality. Furthermore, large-diameter rock formation construction demands higher drilling verticality. Existing processes lack a unified positioning benchmark for the guide structure and reaming drill bit, easily resulting in borehole deviation and insufficient verticality.

[0004] To improve drilling verticality, some construction schemes add guide structures such as centralizers to the drilling tools. However, conventional centralizers are mostly attached to the outside of the drill pipe or drill bit, which is prone to jamming and wear against the borehole wall. Furthermore, their effectiveness in correcting deviation in uneven rock formations is very limited, failing to fundamentally solve the drill bit sway problem. In addition, existing split-type drilling tool assemblies have independently designed components, resulting in poor overall rigidity matching. Under the high torque and high drill pressure conditions of hard rock drilling, this easily leads to failures at connection points and drill bit wear, resulting in high equipment wear costs. In actual projects, problems such as insufficient pile bearing capacity and rework of abandoned holes due to substandard drilling verticality frequently occur, increasing project costs and posing hidden dangers to construction safety and project quality.

[0005] In summary, existing rotary drilling techniques for large-diameter piles in rock geology generally suffer from drawbacks such as poor compatibility of drill bit sets, cumbersome procedures, low drilling efficiency, insufficient guidance and correction capabilities, and difficulty in ensuring vertical drilling accuracy. These drawbacks not only restrict construction period and economic benefits but also fail to meet the hole formation quality requirements of high-standard large-diameter pile foundation projects. Therefore, it is urgent to develop an integrated, high-precision, and high-efficiency drilling technique to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to address the numerous shortcomings of existing rotary drilling techniques for large-diameter rock and geological conditions, such as poor drill bit compatibility, cumbersome process separation, low drilling efficiency, insufficient guidance and correction capabilities, and difficulty in ensuring vertical drilling accuracy. This invention provides a rotary drilling rig-based vertical drilling process for large-diameter rock and geological conditions, using a combined drill bit design and a central rigid guidance mechanism. This allows for simultaneous core sampling, drilling, and borehole enlargement, while effectively improving vertical drilling accuracy, simplifying the construction process, and reducing project costs.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The rotary drilling rig's large-diameter rock geological drilling tool combination directional vertical drilling process includes the following steps: S1. Drill tool prefabrication: Weld the connecting square head to the top center point of the reaming drill bit, calibrate and ensure that the axis of the connecting square head is completely coaxial with the rotation axis of the reaming drill bit; S2. Integrated Assembly: The large reaming drill bit, the small reaming drill bit, and the core drilling tool are coaxially connected in sequence through the connecting square head to form an integrated drilling tool; S3. Core drilling tool positioning: Connect the integrated drilling tool to the rotary drilling rig rod and lower it to the rock formation to carry out core drilling operation; S4. Guiding and Correction: During the staged reaming drilling process, the rigid center positioning constraint of the connecting square head and the positioning function of the guide drill bit are used to counteract the lateral swaying force caused by the unevenness of the rock strata and maintain the stable vertical drilling posture of the reaming drill bit.

[0008] Furthermore, in step S1, the connecting square head adopts a square hollow cross-section structure. Before welding, the coaxiality is calibrated by positioning fixtures. The welding adopts a full welding process for fixation. After welding, the coaxiality tolerance between the central axis of the connecting square head and the rotation center axis of the large reaming drill bit is controlled within 0.5cm.

[0009] Furthermore, in step S2, the large reaming drill bit and the small reaming drill bit are arranged coaxially in a stepped manner. The drilling end face of the small reaming drill bit is 150cm to 300cm ahead of the large reaming drill bit. The diameter of the small reaming drill bit is 1 / 3 to 1 / 2 of the diameter of the large reaming drill bit. Both types of drill bits have cutting teeth evenly distributed on their cutting end faces.

[0010] Furthermore, in step S2, the core drilling tool is coaxially installed in the central cavity of the drilling tool assembly. The top of the guide drill bit of the core drilling tool is matched with the inner cavity of the connecting square head for limiting. During the drilling process, the guide drill bit extends synchronously with the rock strata, thereby strengthening the central positioning constraint effect.

[0011] Furthermore, in step S3, pilot drilling and staged reaming are continuous synchronous operations. A single drilling run can simultaneously complete multiple processes, including pilot drilling, staged reaming, and borehole wall trimming. There is no need to pull out the drill string and change the drill bit throughout the entire drilling process, and the cuttings are discharged synchronously through the internal slag discharge channel of the drill bit.

[0012] Furthermore, in step S4, a dual-guided correction mechanism is formed during the drilling process. The primary guide is achieved by the pilot hole formed by the pre-arranged small reaming drill bit, which achieves initial positioning. The secondary guide is achieved by the rigid coaxial constraint of the connecting square head and the center positioning of the guide drill bit, which together achieve precise correction. The two guides work together to maintain the vertical drilling state of the drill string.

[0013] Furthermore, during the drilling process in step S3, the drilling parameters are adjusted according to the uniaxial compressive strength of the rock: for soft rock with a uniaxial compressive strength below 30MPa, the drilling pressure is controlled at 80kN~120kN and the rotation speed is controlled at 15r / min~20r / min; for medium-hard rock and hard rock with a uniaxial compressive strength of 30MPa~260MPa, the drilling pressure is controlled at 120kN~180kN and the rotation speed is controlled at 10r / min~15r / min.

[0014] Furthermore, in the drill bit prefabrication stage of step S1, the cutting tooth end faces of the large and small reaming drill bits and the outer side of the drill bit body are all treated with wear-resistant overlay welding. The wear-resistant layer thickness is not less than 3cm, which improves the service life of the drill bit in rock formations.

[0015] Compared with the prior art, the present invention has the following significant advantages: (1) The process integration is high, with drilling and core sampling integrated, resulting in a significant improvement in efficiency.

[0016] This invention integrates a large reaming drill bit, a small reaming drill bit, and a core drilling tool into a single unit by connecting a square head. This enables simultaneous operation of multiple processes, including core extraction, pilot drilling, staged reaming, and borehole wall trimming. The entire process of core extraction and borehole formation can be completed in a single drilling run, eliminating the need for multiple trips to change drilling tools and separate core extraction. Compared with traditional staged drilling technology, the overall drilling efficiency can be increased by more than 40%, significantly shortening the construction period.

[0017] (2) High guiding accuracy and stable and reliable hole formation quality.

[0018] This invention constructs a dual guiding mechanism of "preliminary positioning of the pilot hole + rigid correction of the central square head and the guide drill bit". It forms a rigid positioning constraint from the center of the drill bit, which can effectively counteract the lateral eccentric force caused by soft and hard interlayers, fractured rock layers and extremely hard rock layers, automatically correct the drill bit swaying trend, and control the verticality deviation of the hole to within 0.3%, which is far superior to the construction accuracy of conventional processes and can meet the quality requirements of high-standard large-diameter pile foundation projects.

[0019] (3) The drilling tools are highly adaptable, reducing construction costs.

[0020] The integrated drill bit assembly of this invention achieves rigid connection of each component through a unified connecting square head, eliminating the connection gap and adaptation error of split drill bits. It has stronger overall rigidity and load-bearing capacity, and better operational stability under high drilling pressure and high torque conditions for hard rocks up to 260MPa. At the same time, the wear-resistant and reinforced surface treatment of the drill bit effectively extends its service life and reduces drill bit wear and maintenance costs.

[0021] (4) The process is widely applicable, easy to operate and promote.

[0022] This technology requires no modification to existing rotary drilling rigs and can be directly adapted to conventional rotary drilling rig drill rod interfaces. It is suitable for various rock geological conditions such as soft rock, medium-hard rock, hard rock, interbedded soft and hard rock, and fractured zones. It has good application value in various large-diameter pile foundation projects such as bridge pile foundations, building pile foundations, and wind power foundations, and has broad prospects for promotion. Attached Figure Description

[0023] Figure 1 is a flowchart of the implementation process of the rotary drilling rig for large-diameter rock geological drilling combined with directional vertical drilling technology of the present invention. Figure 2 is a front sectional view of the integrated drill assembly equipped with a core drilling tool according to the present invention; Figure 3 is a top view of the integrated drill assembly equipped with the core drilling tool of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] The rotary drilling rig's large-diameter rock geological drilling tool combination directional vertical drilling process proposed in this invention includes the following steps: S1. Drill tool prefabrication: Weld the connecting square head to the top center point of the reaming drill bit, calibrate and ensure that the axis of the connecting square head is completely coaxial with the rotation axis of the reaming drill bit; S2. Integrated Assembly: The large reaming drill bit, the small reaming drill bit, and the core drilling tool are coaxially connected in sequence through the connecting square head to form an integrated drilling tool; S3. Core drilling tool positioning: Connect the integrated drilling tool to the rotary drilling rig rod and lower it to the rock formation to carry out core drilling operation; S4. Guiding and Correction: During the staged reaming drilling process, the rigid center positioning constraint of the connecting square head and the positioning function of the guide drill bit are used to counteract the lateral swaying force caused by the unevenness of the rock strata and maintain the stable vertical drilling posture of the reaming drill bit.

[0026] Furthermore, in step S1, the connecting square head adopts a square hollow cross-section structure. Before welding, the coaxiality is calibrated by a special positioning tool. The welding adopts a full circumferential welding process for fixation. After welding, the coaxiality tolerance between the central axis of the connecting square head and the rotation center axis of the large reaming drill bit is controlled within 0.5cm, thus ensuring the coaxial accuracy of the drill assembly from the source.

[0027] Furthermore, in step S2, the large reaming drill bit and the small reaming drill bit are arranged coaxially in a stepped manner. The drilling end face of the small reaming drill bit is 150cm to 300cm ahead of the large reaming drill bit. The diameter of the small reaming drill bit is 1 / 3 to 1 / 2 of the diameter of the large reaming drill bit. Both types of drill bits have cutting teeth evenly distributed on their cutting end faces. During drilling, the small diameter drill bit first breaks the central rock layer and works with the core drilling tool to complete the core cutting, forming a regular pilot hole while releasing the ground stress, creating favorable conditions for subsequent large diameter reaming.

[0028] Furthermore, in step S2, the core drilling tool is coaxially installed in the central cavity of the drilling tool assembly. The top of the guide drill bit of the core drilling tool is matched with the inner cavity of the connecting square head for limiting. During the drilling process, the guide drill bit extends synchronously with the rock layer, which strengthens the central positioning constraint effect and avoids the drilling tool from swaying due to lateral forces.

[0029] Furthermore, in step S3, pilot drilling and staged reaming are continuous synchronous operations. Multiple processes, including pilot drilling, staged reaming, and borehole wall trimming, can be completed simultaneously in a single drilling run. There is no need to pull out the drill string and change the drill bit throughout the entire drilling process. Rock cuttings are discharged synchronously through the internal slag discharge channel of the drill string, which greatly reduces the auxiliary operation time.

[0030] Furthermore, in step S4, a dual-guided correction mechanism is formed during the drilling process. The first-level guide is achieved by the pilot hole formed by the pre-arranged small reaming drill bit, which constrains the overall sway of the drill string. The second-level guide is achieved by the rigid coaxial constraint of the connecting square head and the center positioning of the guide drill bit, which together achieves precise correction and offsets the lateral eccentric force from the center of the drill string. The two levels of guide work together to maintain the stable vertical drilling state of the drill string.

[0031] Furthermore, during the drilling process in step S3, the drilling parameters are adjusted according to the uniaxial compressive strength of the rock: for soft rock with a uniaxial compressive strength below 30MPa, the drilling pressure is controlled at 80kN~120kN and the rotation speed is controlled at 15r / min~20r / min; for medium-hard and hard rock with a uniaxial compressive strength of 30MPa~260MPa, the drilling pressure is controlled at 120kN~180kN and the rotation speed is controlled at 10r / min~15r / min. The balance between drilling efficiency and drill bit life is ensured through parameter adaptation.

[0032] Furthermore, in the drill bit prefabrication stage of step S1, the cutting tooth end faces of the large and small reaming drill bits and the outer side of the drill bit body are all treated with wear-resistant overlay welding. The thickness of the wear-resistant layer is controlled at 3cm~5cm, which effectively improves the wear resistance and service life of the drill bit in high-strength hard rock formations.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling technology described in this embodiment relies on a drilling tool combination main body including a large reaming bit, a small reaming bit, a connecting square head, and a core sampling tool. The large reaming bit has evenly arranged cutting teeth on its bottom circumference for breaking rock formations; the small reaming bit has a smaller diameter than the large reaming bit and is used to drill a pilot hole first; the connecting square head serves as the core connecting and positioning component, realizing the coaxial integration of various drilling tool components; the core sampling tool is set in the center of the drilling tool, simultaneously completing core collection and center positioning constraint, and assisting in guidance and correction.

[0035] The specific implementation process of this technology is as follows: The first step is the prefabrication of drilling tools; A square hollow cross-section connecting head is pre-fabricated, with its upper interface dimensions matching the square head connection specifications of conventional rotary drilling rig drill rods. Before welding, the large reaming drill bit is fixed on a positioning fixture platform, and the rotation center axis of the large reaming drill bit is calibrated using a laser calibrator. Then, the connecting head is hoisted to the top center point of the large reaming drill bit, and its position is adjusted until the axes of the two are completely coincident, with the coaxiality tolerance controlled within 0.5cm. After calibration, the connecting head and the large reaming drill bit are welded together using a circumferential full welding process. After welding, annealing treatment is performed to eliminate welding stress and ensure connection strength and structural stability. During the prefabrication stage, wear-resistant alloy layers are simultaneously overlaid on the cutting tooth end faces of both the large and small reaming drill bits and on the outer side of the drill bit body. The thickness of the wear-resistant layer is controlled between 3cm and 5cm to improve the wear resistance of the drill bit to withstand 260MPa hard rock. The second step is the integration and assembly of the drilling tools. The small reamer bit is installed at the lower center of the connecting square head. After assembly, the drilling end face of the small reamer bit is 200cm ahead of the large reamer bit, forming a stepped drilling structure. The diameter of the small reamer bit is set to 1 / 2 of the diameter of the large reamer bit to ensure that the pilot hole has sufficient guiding space. Then, the core drilling tool is inserted into the central cavity of the drilling tool assembly from the bottom of the drill bit, so that the top of the guide drill bit of the core drilling tool forms a limiting fit with the inner cavity of the connecting square head, ensuring that the guide drill bit and the drilling tool as a whole remain coaxial. During the drilling process, the guide drill bit can be independently fed with the rock strata advance, continuously strengthening the center positioning constraint. After assembly, the large reamer bit, the small reamer bit, and the core drilling tool are rigidly coaxially connected through the connecting square head, forming a complete integrated drilling tool. The third step is to perform core drilling operations to locate and drill the core sampler. The assembled integrated drill bit is connected to the lower end of the drill rod of the rotary drilling rig via the connecting square head. After checking that the connection is secure, the drilling rig is operated to lower the drill bit to the top surface of the target rock formation. The drilling rig is then started to carry out core drilling operations. The drilling parameters are adjusted according to the rock hardness revealed on site: if it is soft rock with a uniaxial compressive strength of about 20MPa, the drilling pressure is set to 100kN and the rotation speed is set to 18r / min; if it is hard rock with a uniaxial compressive strength of about 160MPa, the drilling pressure is increased to 150kN and the rotation speed is reduced to 12r / min. During drilling, the small reaming bit, positioned at the front end, first breaks the rock in the central area, while the core drilling tool simultaneously extracts a complete core, forming a regular pilot hole and releasing the stress in the rock strata, reducing the drilling resistance of subsequent reaming. Then, the large reaming bit follows to break the outer rock strata, completing the reaming operation of the designed diameter in one go. At the same time, the outside of the drill bit is used to trim the hole wall to ensure the regularity of the hole wall. The rock cuttings generated during drilling are discharged from the hole through the slag removal channel inside the drill bit and are circulated with the mud. In a single drilling run, all processes, including core extraction, pilot drilling, staged reaming, and hole wall trimming, can be completed simultaneously without the need to pull out the drill string and change the drill bit. The fourth step is to control the vertical drilling. Throughout the staged reaming drilling process, the drill string assembly maintains its vertical drilling posture through a dual guiding mechanism. The first stage of guidance is achieved by the advanced small reaming bit. The pilot hole formed by the small reaming bit provides initial constraint on the entire drill string assembly, limiting significant sway and providing initial guidance. The second stage of guidance is achieved jointly by the central connecting square head and the guide bit integrated into the core drilling tool. The connecting square head serves as the rigid central node of the entire drill string, providing strong coaxial constraint on each stage of the drill bit and the core drilling tool. The guide bit extends continuously along the drilling direction, further enhancing the central positioning effect. When the drill bit encounters uneven rock formations, locally fractured zones, or high-strength hard rock, resulting in lateral sway and eccentric forces, the rigid positioning of the connecting square head and the guide bit can directly offset the lateral sway force from the center, automatically and precisely correcting the drill string assembly to maintain the overall vertical drilling posture. The synergistic effect of the two stages of guidance effectively ensures the verticality accuracy of the hole and avoids quality defects such as inclined holes and bent holes. Once the drilling reaches the designed depth and core samples are collected, the drill string is raised to the ground, the drill teeth and slag discharge channels are cleaned, and the core samples are removed before proceeding to the next borehole.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rotary drilling rig for large-diameter rock geological drilling with combined directional drilling tools, characterized in that: Includes the following steps: S1. Drill tool prefabrication: Weld the connecting square head to the top center point of the reaming drill bit, calibrate and ensure that the axis of the connecting square head is completely coaxial with the rotation axis of the reaming drill bit; S2. Integrated Assembly: The large reaming drill bit, the small reaming drill bit, and the core drilling tool are coaxially connected in sequence through the connecting square head to form an integrated drilling tool; S3. Core drilling tool positioning: Connect the integrated drilling tool to the rotary drilling rig rod and lower it to the rock formation to carry out core drilling operation; S4. Guiding and Correction: During the staged reaming drilling process, the rigid center positioning constraint of the connecting square head and the positioning function of the guide drill bit are used to counteract the lateral swaying force caused by the unevenness of the rock strata and maintain the stable vertical drilling posture of the reaming drill bit.

2. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, In step S1, the connecting square head adopts a square hollow cross-section structure. Before welding, the coaxiality is calibrated by positioning fixture. The welding adopts a full welding process for fixation. After welding, the coaxiality tolerance between the central axis of the connecting square head and the rotation center axis of the large reaming drill bit is controlled within 0.5cm.

3. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, In step S2, the large reaming drill bit and the small reaming drill bit are arranged coaxially in a stepped manner. The drilling end face of the small reaming drill bit is 150cm to 300cm ahead of the large reaming drill bit. The diameter of the small reaming drill bit is 1 / 3 to 1 / 2 of the diameter of the large reaming drill bit. Both types of drill bits have cutting teeth evenly distributed on their cutting end faces.

4. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, In step S2, the core drilling tool is coaxially installed in the central cavity of the drilling tool assembly. The top of the guide drill bit of the core drilling tool is matched with the inner cavity of the connecting square head for limiting. During the drilling process, the guide drill bit extends synchronously with the rock layer advance, which strengthens the central positioning constraint effect.

5. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, In step S3, pilot drilling and staged reaming are continuous and synchronous operations. A single drilling run can simultaneously complete multiple processes such as pilot drilling, staged reaming, and borehole wall trimming. There is no need to pull out the drill string and change the drill bit throughout the entire drilling process, and the cuttings are discharged synchronously through the internal cuttings discharge channel of the drill bit.

6. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, In step S4, a dual guidance and correction mechanism is formed during the drilling process. The first-level guidance is achieved by the pilot hole formed by the pre-arranged small reaming drill bit to achieve initial positioning. The second-level guidance is achieved by the rigid coaxial constraint of the connecting square head and the center positioning of the guide drill bit to achieve precise correction. The two levels of guidance work together to maintain the vertical drilling state of the drill string.

7. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, During the drilling process in step S3, the drilling parameters are adjusted according to the uniaxial compressive strength of the rock: for soft rock with a uniaxial compressive strength of less than 30 MPa, the drilling pressure is controlled at 80 kN to 120 kN and the rotation speed is controlled at 15 r / min to 20 r / min; for medium-hard rock and hard rock with a uniaxial compressive strength of 30 MPa to 260 MPa, the drilling pressure is controlled at 120 kN to 180 kN and the rotation speed is controlled at 10 r / min to 15 r / min.

8. The rotary drilling rig large-diameter rock geological drilling tool combination directional vertical drilling process according to claim 1, characterized in that, In the drill bit prefabrication stage of step S1, the cutting tooth end faces of the large and small reaming drill bits and the outer side of the drill bit body are all treated with wear-resistant overlay welding. The wear-resistant layer thickness is not less than 3cm, which improves the service life of the drill bit in rock formations.

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