A plate type reamer suitable for expansive soil large particle size calcareous nodule stratum

Abstract

This invention provides a plate-type borehole expander suitable for expansive soil strata with large-particle-size calcareous nodules, including an expander body; a drill rod; a guide plate, the guide plate being a layout of six adjacent plates with an included angle of 60°; and cutting teeth, the cutting teeth being arranged in a triangular staggered arrangement on the lower surface of the guide plate. The advantages are that it not only prevents the drill from getting stuck, but also ensures force balance and stability, and improves rock breaking efficiency and cuttings removal capacity.

Description

Technical Field

[0001] This invention relates to the technical field of drilling equipment, and specifically to a plate-type borehole expander suitable for expansive soil strata with large-diameter calcareous nodules. Background Technology

[0002] The South-to-North Water Diversion Project in Neixiang County uses directional drilling to cross the main canal of the central route. The total length is 723.9m, and the water supply pipeline diameter is 1000mm. Construction requires 11 stages of borehole enlargement to achieve a final borehole diameter of 1400mm. The crossing point is located at canal chainage TS43+325. The geology of the crossing section is mainly medium-expansion soil with localized enrichment in calcareous nodules. These nodules are not stratified but rather lenticular in distribution. The nodules have uneven particle sizes, generally 1–3cm, with some reaching 6–8cm and a maximum of 10cm, with a content of 10%–20%. During the drilling process in hard plastic strata containing large-diameter calcareous nodules, when encountering large-diameter hard rock (calcareous nodules), the drill bit is prone to jamming due to incompletely broken large-diameter hard rock particles (calcareous nodules), leading to abnormally increased torque and increased construction risks.

[0003] A patent publication number CN212689924U was found, entitled "Anti-Stuck Drill Hole Reamer for Soil Layers," which specifically discloses an anti-stuck drill hole reamer for soil layers, including a mandrel. A conical cylinder is fixedly mounted on the outside of the mandrel. Multiple alloy teeth are welded to the outer ring of one end of the conical cylinder, and a square tube is fixedly welded to the outer ring of the other end of the conical cylinder. A nozzle is provided on the square tube, and a drill bit is welded to one side of the square tube. A flow channel groove is formed on the outer wall of the conical cylinder, and a spray pipe is installed on the inner wall of the flow channel groove. A water channel is formed inside the mandrel, and one end of the mandrel is fixed... Equipped with a drill rod, the device comprises a mandrel, conical cylinder, alloy teeth, square tube, nozzle, drill bit, flow channel, spray pipe, water channel, borehole wall, hole, and drill rod. The flow channel on the conical cylinder is used to clean away mud generated during drilling. The spray pipe prevents mud from adhering to the curved plate. The alloy teeth reduce wear on the weld seam caused by the need to move the drill bit back and forth when reaming is interrupted. This design extends the device's lifespan. The device has a simple and novel structure, facilitating borehole reaming in soil layers, reducing mud damage to the conical cylinder, extending the device's lifespan, and improving reaming efficiency.

[0004] Analysis of the above-mentioned publicly available materials shows that by setting up flow channels, stuck drills can be removed. However, the reamer must not only consider the stuck drill problem, but also the force balance and stability, rock breaking efficiency, and chip removal capacity during the reaming process. Summary of the Invention

[0005] In view of this, the present invention provides a plate-type borehole expander suitable for expansive soil strata with large particle size and calcareous nodules, which can not only prevent the drill from getting stuck, but also ensure stress balance and stability, improve rock breaking efficiency and cuttings removal capacity.

[0006] To address the aforementioned technical problems, this invention provides a plate-type borehole expander suitable for expansive soil strata with large-particle-size calcareous nodules, comprising: The body of the reamer; Drill pipe; The guide plate is composed of six adjacent fabric plates with an included angle of 60°. The cutting teeth are arranged in a staggered triangular pattern on the lower surface of the guide plate.

[0007] Furthermore, the determination of the number of guide plates includes force balance and stability, rock breaking efficiency, and chip removal capacity. The force balance and stability are calculated using the centrifugal force formula: F_c = m * ω² * r.

[0008] Furthermore, the rock-breaking efficiency is calculated using the formula: the distance the drill bit travels per revolution (pitch P). P = V / ω = (0.6 m / min) / (25 rev / min) = 0.024 m / rev, Calculate the total number of cutting operations S = N / P for each meter of forward movement.

[0009] Furthermore, the chip removal capacity is expressed by the formula, A_channel ≈ (πD² / 4) * (θ / 360°).

[0010] Furthermore, the height of the cutting tooth is 3cm, calculated using the formula h ≥ sqrt( (6 * M_max) / (b *[σ]) ).

[0011] Furthermore, the spacing between the cutting teeth is 4cm, using the formula p_opt ≈ (0.8 ~ 1.2) * d_c, d_c ≈ k * h * tan(θ).

[0012] The beneficial effects of the above-described technical solution of the present invention are as follows: 1. Innovative concept: Shifting from "impact crushing" to "high-efficiency grinding and cutting" has solved the problem of large-diameter calcareous nodules in expansive soil getting stuck in the drill bit, achieving stable torque, controllable drilling, and a significant improvement in safety factor.

[0013] 2. Innovative layout: It adopts a 6-axis 60° uniform plate layout, breaking through the traditional 4-plate or 8-plate layout. It achieves the best balance between rock breaking stability, efficiency and debris removal space for expansive soil strata with large particle size calcareous nodules.

[0014] 3. Innovative tooth design: For expansive soil strata with large-particle-size calcareous nodules, the unique triangular staggered arrangement of cutting teeth (3cm high, 4cm spacing) achieves "full-coverage shearing" of hard nodules instead of "repeated grinding", doubling efficiency and lifespan. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 for Figure 1 A structural diagram from another perspective; In the diagram: 1. Reamer body; 2. Drill rod; 3. Directional guide plate; 4. Guide plate; 5. Transverse cutting teeth; 6. Longitudinal cutting teeth. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figures 1 to 2 The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0017] like Figures 1 to 2 As shown: Example

[0018] A plate-type borehole expander suitable for expansive soil strata with large particle size and calcareous nodules includes a borehole expander body 1; a drill rod 2; a guide plate 4, which is a plate of six adjacent plates with an included angle of 60°; and cutting teeth, which are arranged in a triangular staggered pattern on the lower surface of the guide plate 4.

[0019] In this embodiment, as Figure 1 and Figure 2 As shown, the reamer includes a body and a drill rod 2. Guide plates 4 are provided on the drill rod 2 and the reamer body 1. The guide plates 4 are six plates with an included angle of 60° between adjacent guide plates 4. In addition, cutting teeth are provided on the guide plates 4. The cutting teeth are arranged in a triangular staggered manner. The guide plates 4 can be directional plates 3. Cutting teeth are provided on the directional plates 3. The cutting teeth include transverse cutting teeth 5 and longitudinal cutting teeth 6.

[0020] The theoretical basis for the triangular arrangement: "The horizontal and vertical arrangement of the teeth is triangular" refers to the staggered arrangement of teeth or the equilateral triangular arrangement of teeth, and its advantages are reflected in both kinematics and mechanics.

[0021] 1. Comprehensive kinematic analysis The pitch P that the reamer advances per revolution is: P = V / n = (0.6 m / min) / (25 rev / min) = 0.024 m / rev = 2.4 cm / rev The cutting tooth spacing p = 4 cm > the pitch P = 2.4 cm.

[0022] If a linear arrangement is used, the trajectory of the cutting teeth in the Nth and N+1th revolutions will not be able to cover the entire bottom of the well, leaving unbroken rock ridges. However, by using a triangular staggered arrangement, the trajectory of the teeth in the N+1th revolution can accurately fill the unbroken area left between adjacent teeth in the previous revolution, thus achieving 100% coverage of the rock at the bottom of the well, ensuring thorough rock breaking and a smooth borehole wall.

[0023] 2. Analysis of Tooth Density and Load Uniformity For an equilateral triangle tooth arrangement with side length p, its tooth density ρ_triangle is: ρ_triangle = 2 / (√3 * p²) Substituting p = 4 cm: ρ_triangle = 2 / (1.732 * 16) ≈ 0.0721 teeth / cm² Compared to a simple rectangular arrangement (ρ_rectangle = 1 / p² = 1 / 16 = 0.0625 teeth / cm²), the density of a triangular arrangement is increased: (0.0721 - 0.0625) / 0.0625 * 100% ≈ 15.4% Conclusion: Higher tooth density means that at the same drilling speed, each tooth needs to break less rock and bears less load. At the same time, the staggered arrangement avoids the condition that all teeth reach their maximum cutting depth simultaneously, resulting in a more uniform and stable rock-breaking load. These two factors combined significantly reduce impact vibration and tooth tip wear, greatly extending the overall lifespan of the cutting teeth. Example

[0024] The determination of the number of guide plates 4 includes force balance and stability, rock breaking efficiency, and chip removal capacity. The force balance and stability are calculated using the centrifugal force formula: F_c = m * ω² * r.

[0025] Unlike the above embodiments, in this embodiment, to ensure the smooth rotation of the expander and avoid harmful vibrations, the guide plates 4 must be symmetrically arranged. The centrifugal force calculation formula is as follows: F_c = m * ω² * r; in: F_c: Centrifugal force (N) m: Unbalanced mass of the system (kg) ω: Angular velocity (rad / s), ω = (2π * RPM) / 60 r: Eccentricity (m) Analysis: The number N of guide plates 4 must be an even number to achieve symmetry (e.g., 2, 4, 6, 8...).

[0026] The greater the quantity (the larger N), the more uniform the mass distribution, the closer the eccentricity r is to zero, the smaller the centrifugal force F_c, and the more stable the equipment operation. Conclusion: From a stability perspective, N=8 > N=6 > N=4. However, stability is not the only consideration; it must be weighed in conjunction with rock-breaking efficiency. Example

[0027] The rock-breaking efficiency is calculated using the formula: [Formula omitted for brevity]. The forward distance (pitch P) per revolution of the drill bit is calculated as follows: P = V / ω = (0.6 m / min) / (25 rev / min) = 0.024 m / rev, Calculate the total number of cutting operations S = N / P for each meter of forward movement.

[0028] Unlike the embodiments described above, in this embodiment, the key indicator of rock-breaking efficiency is the number of times the cutting teeth interact with the rock per unit distance the drill bit advances. The more times the cutting teeth interact with the rock, the better the grinding and crushing effect on hard calcareous nodules.

[0029] 1. Calculate the distance the drill bit travels per revolution (pitch P): P = V / ω = (0.6 m / min) / (25 rev / min) = 0.024 m / rev 2. Calculate the total number of cuts (S) per meter of forward movement: This parameter represents the total number of times the cutting teeth on all guide plates 4 come into contact with the rock for every meter the drill bit penetrates. S = N / P; where: S: Number of cuts per meter (times / meter) N: Number of guide plates (4) P: Pitch (meters / revolution) 3. Calculate the S value for different numbers of guide plates (4): When N = 4: S4 = 4 / 0.024 ≈ 167 times / meter When N = 6: S6 = 6 / 0.024 = 250 times / meter When N = 8: S8 = 8 / 0.024 ≈ 333 times / meter Argument: The advantage of N=6 over N=4: S6 (250) > S4 (167). The rock breaking frequency of 6 guide plates 4 is nearly 50% higher than that of 4. This means that the efficiency is significantly improved when grinding large-diameter calcareous nodules, and large rocks can be broken into small particles that are easy to remove more effectively, fundamentally reducing the risk of stuck drill bit.

[0030] Potential problems with N=8: Although S8 (333) > S6 (250) and has the highest rock breaking frequency, the chip removal capacity needs to be further considered. Example

[0031] The chip removal capacity is expressed by the formula, A_channel ≈ (πD² / 4) * (θ / 360°).

[0032] In this embodiment, the core of the chip removal capability is the cross-sectional area of ​​the mud flow channel between the guide plates 4. This area must be large enough to ensure that large-diameter rock chips (Φ10cm) can be smoothly discharged.

[0033] 1. Estimation of chip removal channel area: Assuming the diameter of the reamer is D and the width of the guide plate 4 is W, the theoretical maximum chip removal channel area between adjacent guide plates 4 can be simplified as follows: A_channel ≈ (πD² / 4) * (θ / 360°) Where θ is the central angle (i.e., the interval angle) between adjacent guide plates 4.

[0034] When N=4, θ = 90° When N=6, θ = 60° When N=8, θ = 45°.

[0035] The more guide plates 4 there are (the larger N is), the smaller the spacing angle θ becomes, and the smaller the area A_channel of a single chip removal channel becomes. In areas where the maximum rock cuttings diameter reaches 10cm, using N=8 (narrower channels) can easily cause rock cuttings to clog the channels, leading to poor drilling fluid circulation, increased mud pump pressure, and potentially serious stuck pipe accidents. Furthermore, an excessive number of guide plates 4 results in more welding points, reducing the overall structural strength and torque resistance.

[0036] Conclusion: N=6 provides a significantly higher rock-breaking efficiency than N=4, while offering a wider and more reliable cuttings removal channel than N=8, perfectly matching the cuttings removal requirements of large-particle-size calcareous nodule formations. The design of 6 guide plates (spaced 60° apart) achieves the best balance among "operational stability," "rock-breaking efficiency," and "cuttings removal capacity." Example

[0037] The height of the cutting tooth is 3cm, calculated using the formula h ≥ sqrt( (6 * M_max) / (b * [σ]) ).

[0038] Unlike the above embodiments, in this embodiment, the height of the cutting teeth must meet three requirements: effective rock breaking, avoidance of matrix wear, and guarantee of its own strength.

[0039] 1. Determination of maximum penetration depth and wear life The height of the cutting teeth must be greater than the sum of their expected maximum breaking depth and the total wear over the entire wear life.

[0040] h > d_max + δ_w d_max: The maximum depth to which a single tooth can break rock. For a 10cm calcareous nodule, a depth of at least 1-2cm is required for effective breaking.

[0041] δ_w: Total wear over the service life. Based on engineering experience, a considerable wear resistance margin needs to be reserved in hard, abrasive formations.

[0042] Conclusion: A height of 3 cm provides ample space for biting into large-diameter nodules and ensures that the cutting teeth work continuously and effectively throughout the entire cycle, avoiding construction interruptions and substrate wear caused by excessive wear. It is a robust and reliable engineering value.

[0043] 2. Mechanical verification based on flexural strength The cutting tooth can be simplified as a cantilever beam model, with the root bearing the maximum bending moment M_max. The height h directly determines its bending section modulus W_z.

[0044] W_z = (b * h²) / 6 (Assuming the tooth has a rectangular cross-section and a width of b) The maximum bending stress σ_max must be less than the allowable stress of the material [σ]. σ_max = M_max / W_z = (6 * M_max) / (b * h²) ≤ [σ] By transforming the above formula, we can solve for the minimum tooth height that satisfies the strength requirements: h ≥ sqrt( (6 * M_max) / (b * [σ]) ) Conclusion: By estimating the cutting force F_c (which can be calculated based on the rock compressive strength) and substituting it into the above formula for verification, it can be seen that a height of 3 cm fully meets the bending strength requirements and can effectively prevent brittle fracture when cutting calcareous nodules. Example

[0045] The spacing between the cutting teeth is 4cm, and the formula is p_opt ≈ (0.8 ~ 1.2) * d_c, d_c ≈ k * h * tan(θ).

[0046] Unlike the above embodiments, in this embodiment, the spacing is the key to determining the rock breaking efficiency. The optimal spacing aims to promote crack connection and achieve efficient volumetric crushing.

[0047] 1. Optimal Spacing Calculation Model The optimal tooth pitch p_opt is related to the diameter d_c of the rock fracture pit. Ideally, the pitch should be slightly smaller than the pit diameter to ensure efficient rock stripping.

[0048] p_opt ≈ (0.8 ~ 1.2) * d_c The diameter d_c of the fracture pit is related to the tooth height h, the tooth angle θ, and the rock properties, and can be estimated using empirical formulas: d_c ≈ k * h * tan(θ) k: Rock coefficient (for medium-hard to hard rocks, take k = 2.5) h: Height of cutting teeth (h = 3 cm) θ: Half of the tooth tip angle (assuming the tip angle is 60°, then θ = 30°, tan(30°) ≈ 0.577) 2. Substitute and calculate d_c ≈ 2.5 * 3 cm * 0.577 ≈ 4.33 cm p_opt ≈ (0.8 ~ 1.2) * 4.33 cm ≈ 3.46 cm ~ 5.20 cm Conclusion: The theoretically calculated optimal spacing range is approximately 3.46 - 5.20 cm. The final determined spacing of 4 cm falls perfectly within this theoretical range. This spacing ensures that the stress fields and cracks generated by adjacent tooth cutting overlap and connect, causing the rock in the middle to peel off in sheets, thus achieving efficient crushing and avoiding the inefficient conditions of "rock ridges" caused by excessive spacing or "repeated grinding" caused by excessive spacing.

[0049] Based on the theoretical calculations and mechanical analysis of the above system, the following conclusions can be drawn: 1. Cutting tooth height of 3cm: This is based on a comprehensive assessment of rock-breaking requirements, wear resistance, and bending strength, ensuring the reliability and effectiveness of the tool.

[0050] 2. Cutting tooth spacing of 4cm: Calculated by the rock fracture mechanics model, it is within the theoretical optimal range, effectively promoting crack connection and volumetric fracturing, and is the choice with the highest rock breaking efficiency.

[0051] 3. Triangular arrangement: Kinematic analysis proved that it can achieve full coverage crushing at the bottom of the well; the tooth density calculation showed that it increased the tooth density by 15.4% compared with the rectangular arrangement, which is the optimal layout to ensure uniform load and extend tool life.

Claims

1. A plate-type borehole expander suitable for expansive soil strata with large particle size and calcareous nodules, characterized in that: include Hole expander body (1); Drill pipe (2); Guide plate (4), the guide plate (4) is six adjacent cloth plates with an included angle of 60°; The cutting teeth are arranged in a triangular staggered pattern on the lower surface of the guide plate (4).

2. A plate-type borehole expander suitable for expansive soil strata with large particle size and calcareous nodules, as described in claim 1, is characterized in that: The determination of the number of guide plates (4) includes force balance and stability, rock breaking efficiency, and chip removal capacity. The force balance and stability are calculated using the centrifugal force formula: F_c = m * ω² * r.

3. A plate-type borehole expander suitable for expansive soil with large-particle-size calcareous nodules as described in claim 2, characterized in that: The rock-breaking efficiency is calculated using the formula: [Formula omitted for brevity]. The forward distance (pitch P) per revolution of the drill bit is calculated as follows: P = V / ω = (0.6 m / min) / (25 rev / min) = 0.024 m / rev, Calculate the total number of cutting operations S = N / P for each meter of forward movement.

4. A plate-type borehole expander suitable for expansive soil with large-particle-size calcareous nodules as described in claim 3, characterized in that: The chip removal capacity is expressed by the formula, A_channel ≈ (πD² / 4) * (θ / 360°).

5. A plate-type borehole expander suitable for expansive soil with large-particle-size calcareous nodules as described in claim 4, characterized in that: The height of the cutting tooth is 3cm, calculated using the formula h ≥ sqrt( (6 * M_max) / (b * [σ]) ).

6. A plate-type borehole expander suitable for expansive soil strata with large particle size and calcareous nodules, as described in claim 5, is characterized in that: The spacing between the cutting teeth is 4cm, and the formula is p_opt ≈ (0.8 ~ 1.2) * d_c, d_c ≈ k * h * tan(θ).

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