Closed quaternary stratum directional sampling drilling method for environmental protection

Abstract

The invention relates to the technical field of quaternary formation directional sampling, in particular to a closed quaternary formation directional sampling drilling method for environmental protection, which comprises the following steps: performing drilling test on a first soil layer above a quaternary formation through a drilling rod; the vibration spectrum of the drilling rod in the drilling test process is obtained; the drilling angle is determined according to the energy ratio of the low-frequency band in the vibration spectrum; drilling sampling is conducted according to the drilling angle, and the drilling strength is determined based on the maximum temperature value of the drilling rod in the first soil layer; drilling sampling continues to be carried out according to the drilling strength, and the bottom lip surface sand carrying amount is calculated based on the bottom lip surface area of the drilling rod and the drilling distance of the first soil layer on the drilling track; determining the rotating speed of the drilling rod according to the sand amount of the bottom lip surface and the vibration frequency of the drilling rod in the second soil layer; and drilling sampling of the quaternary stratum is completed according to the rotating speed. According to the invention, the accuracy of closed quaternary stratum directional drilling sampling is improved.

Description

Technical Field

[0001] This invention relates to the field of Quaternary strata directional sampling technology, and in particular to a closed-loop Quaternary strata directional sampling drilling method for environmental protection. Background Technology

[0002] Quaternary strata are the youngest sedimentary layers in geological time, mainly composed of unconsolidated or semi-consolidated loose sediments, including alluvial, diluvial, and aeolian deposits. In environmental geological surveys, groundwater monitoring, and soil pollution assessments, closed-loop directional sampling of Quaternary strata is crucial for obtaining accurate environmental data. Within Quaternary strata, there are significant differences in mechanical properties at the boundary between sand and clay layers. Sand layers are characterized by high permeability, low cohesion, and a high angle of internal friction, while clay layers exhibit low permeability, high cohesion, and a low angle of internal friction. This difference is evident during drilling operations. The soft-hard interface causes drilling trajectory vibration, and in the sand and clay layers, capillary water migrates upward from the groundwater level. Its dynamic changes directly affect the mechanical properties of the formation. Existing research shows that when the ambient temperature rises, surface evaporation increases, leading to a faster rate of capillary water rise and significant changes in the water content of the sand layer. However, current drilling techniques generally ignore this dynamic process and determine drilling parameters only based on static exploration data. Therefore, there is an urgent need for a closed-loop Quaternary strata directional sampling drilling method that can monitor the dynamic changes of the formation in real time, predict mechanical abrupt changes at the interface, and dynamically adjust drilling parameters.

[0003] Chinese Patent Publication No. CN111287743A discloses an air reverse circulation continuous sampling drilling system and process for water-bearing formations. The system includes a reverse circulation drilling rig, drilling tools, an air compressor, a forward / reverse circulation remote switching joint, a forward circulation slag discharge and diversion device, a separation and collection device for forward circulation rock cuttings, and a separation and collection device for reverse circulation rock cuttings. The forward / reverse circulation remote switching joint is closed, and the inner pipe channel of the double-wall drill rod is shut off. Under the action of high-pressure air underground, formation water flows through the bottom of the borehole, sequentially passing through the gap between the borehole wall and the outer wall of the double-wall drill rod, the forward circulation slag discharge and diversion device, and the forward circulation slag discharge and diversion device. The rock cuttings separation and collection device discharges and monitors formation water, and the forward and reverse circulation remote switching connector is activated to achieve the collection of dry rock cuttings samples. It can be seen that the air reverse circulation continuous sampling drilling system and process for water-bearing formations have problems such as capillary water moving upward from the groundwater level due to the rise in ambient temperature, causing a disturbance effect on the formation during the drilling process, which in turn causes axial vibration of the drill rod. In addition, when the drill bit drills into the sand layer, the high-purity quartz sand particles attached to it will embed into the surface of the clay layer and form micro-protrusions, resulting in nonlinear fluctuations in rotational resistance and reducing the accuracy of drilling and sampling. Summary of the Invention

[0004] To address these issues, the present invention provides a closed-loop directional sampling drilling method for Quaternary strata for environmental protection. This method overcomes the problems in existing technologies, such as capillary water moving upwards from the groundwater level due to rising ambient temperature, causing disturbance to the strata during drilling and resulting in axial vibration of the drill rod; and high-purity quartz sand particles attached to the drill bit embedding into the surface of the clay layer when drilling into the clay layer, forming micro-protrusions, leading to nonlinear fluctuations in rotational resistance and reducing the accuracy of drilling and sampling.

[0005] To achieve the above objectives, the present invention provides a closed-loop directional sampling drilling method for Quaternary strata for environmental protection, comprising: Drilling tests were conducted on the first soil layer above the Quaternary strata using a drill rod. Obtain the vibration spectrum of the drill rod per unit frequency monitoring cycle during the drilling test process; The drilling angle is determined based on the energy proportion of the low-frequency band in the vibration spectrum. Continue drilling tests at the stated drilling angle, and determine the drilling intensity based on the maximum temperature value of the drill rod in the first soil layer. Continue drilling tests according to the drilling intensity, and calculate the amount of sand carried on the bottom lip based on the bottom lip area of ​​the drill rod and the drilling distance of the first soil layer on the drilling trajectory; The rotation speed of the drill rod is determined based on the amount of sand carried on the bottom lip and the vibration frequency of the drill rod in the second soil layer. The drill rod is controlled to complete the actual drilling and sampling of the Quaternary strata according to the drilling angle, drilling intensity, and rotation speed, wherein... The second soil layer is the soil between the first soil layer and the fourth stratum.

[0006] Further, determining the drilling angle based on the energy proportion of the low-frequency band in the vibration spectrum includes: The proportion of low-frequency energy in the vibration spectrum within a unit frequency monitoring period is compared with the preset energy proportion. If the energy percentage is greater than the preset energy percentage, it is determined that the impact on the mechanical properties of the interface caused by the passive rise of capillary water in the groundwater does not meet the requirements, and the drilling angle is reduced. Wherein, the horizontal axis of the vibration spectrum is the vibration frequency of the drill rod, and the vertical axis is the power spectral density of the drill rod; the energy ratio is the ratio of the integral area of ​​the power spectral density in the low-frequency band to the integral area of ​​the power spectral density in the vibration spectrum.

[0007] Furthermore, the low-frequency band is the frequency range in the vibration spectrum where the vibration frequency is less than the first preset vibration frequency.

[0008] Furthermore, the drilling angle is the acute angle formed by the drill rod and the horizontal surface of the ground.

[0009] Furthermore, the drilling angle is negatively correlated with the energy percentage.

[0010] Further, determining the drilling intensity based on the maximum temperature value of the drill rod within the first soil layer includes: Obtain the temperature value at the temperature sampling point on the drill rod within the first soil layer; The temperature value at the temperature sampling point with the highest temperature value among all temperature sampling points is determined as the maximum temperature value; If the maximum temperature value is greater than the preset temperature value, it is determined that the friction of the drill rod in the first soil layer has increased abnormally, and the drilling intensity is reduced.

[0011] Furthermore, the drilling intensity is negatively correlated with the maximum temperature value.

[0012] Furthermore, the amount of sand carried on the bottom lip surface is the product of the area of ​​the bottom lip surface, the drilling distance of the first soil layer on the drilling trajectory, and the sand grain adhesion fitting conversion coefficient.

[0013] Further, determining the rotation speed of the drill rod based on the amount of sand on the bottom lip surface and the vibration frequency of the drill rod within the second soil layer includes: If the amount of sand on the bottom lip surface is greater than the preset amount of sand, and the vibration frequency is greater than the first preset vibration frequency but less than the second preset vibration frequency, then it is determined that the attached sand particles on the drill rod undergo an electrochemical reaction with the second soil layer, resulting in an impact on the stability of the drilling that does not meet the requirements, and the rotation speed of the drill rod is increased.

[0014] Furthermore, the rotation speed of the drill rod is positively correlated with the amount of sand carried on the bottom lip surface.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: This invention involves drilling and testing the sand layer above the Quaternary strata, i.e., drilling and testing the first soil layer. Since the actual drilling and sampling environment for the Quaternary strata is an outdoor railway construction site, the removal of vegetation and exposure of the surface due to construction activities reduces surface albedo and transpiration cooling, leading to an increase in surface temperature. Furthermore, soil compaction, such as by transport or construction vehicles, reduces porosity but creates cracks below the surface. The heat generated by the operation or transport of these vehicles is conducted into the environment, making the railway construction area a local heat island, further amplifying the evaporation effect and accelerating the migration of moisture to the surface via capillary action. Therefore, by obtaining the vibration spectrum of the drill rod during the drilling test, it can be characterized that under the influence of increased ambient temperature, surface evaporation is enhanced, leading to a faster passive rise rate of capillary water from groundwater, resulting in an increase in water content in the sand layer. The energy proportion of the low-frequency band in the dynamic spectrum characterizes the softening degree and water content change of the sand layer. When the energy proportion is greater than the preset energy proportion, it indicates that the sand layer has softened due to the increase in water content. The mechanical abrupt change at the interface between the sand layer and the clay layer below it shifts upward earlier, that is, the mechanical abrupt change at the interface between the first soil layer and the second soil layer shifts upward earlier. Due to its low permeability, the clay layer exhibits a lag effect in softening time due to water absorption and expansion. Therefore, a soft-hard interface is formed between the first soil layer and the second soil layer. If the drive device of the drill rod is activated at this time... Increasing drilling intensity due to misjudging the softened sand layer as a drill rod stuck can lead to localized compaction of the clay layer and uneven distribution of soil adhering to the drill bit. Consequently, uneven mass distribution during rotating sampling in the Quaternary strata can cause resonance. Therefore, by reducing the acute angle between the drill rod and the horizontal surface, the mechanical transition at the interface between the first and second soil layers can be further smoothed, avoiding vertical impact on the softened sand layer. This suppresses vibration sources, prevents stress concentration points from forming in the softened sand layer, and further improves the stability of directional sampling drilling in the Quaternary strata.

[0016] Furthermore, this invention determines the drilling intensity based on the maximum temperature value of the drill rod within the first soil layer. This maximum temperature value represents the sand layer losing water due to the mechanical energy of the drill rod being converted into heat during drilling, resulting in reduced interparticle cohesion of the sand particles. This leads to an abnormal increase in friction between the rear end of the drill rod and the sand layer during drilling, and the dry sand particles are more easily embedded in the microcracks on the drill rod surface, further increasing friction. When this maximum temperature value exceeds a preset temperature value, it indicates that the increased friction leads to increased frictional power consumption at the rear end of the drill rod and the sand layer, manifested as an abnormal temperature rise at this contact surface. Therefore, by reducing the drilling intensity, the normal pressure of sand particles intruding into the drill rod surface is reduced, weakening the mechanical meshing effect and further compensating for the water loss caused by the conversion of mechanical energy into heat during drilling. Furthermore, by reducing the drilling intensity, a buffer window is provided for the temperature rise of the drill rod, improving the stability of the drilling process.

[0017] Furthermore, this invention calculates the amount of sand carried on the bottom lip surface based on the area of ​​the bottom lip surface of the drill rod and the drilling distance of the first soil layer on the drilling trajectory. The product of the bottom lip surface area, the drilling distance of the first soil layer on the drilling trajectory, and the sand grain adhesion fitting conversion coefficient is determined as the amount of sand carried on the bottom lip surface. The sand grain adhesion fitting conversion coefficient is the mass of sand grains adhering to a unit contact area of ​​the bottom lip surface when drilling a unit drilling distance in the sand layer. When this amount of sand carried on the bottom lip surface is greater than a preset amount, it indicates that the drilling rod has penetrated... When softening the sand layer, high-purity quartz sand particles adhere to the bottom lip of the drill rod. As the bottom lip penetrates the underlying clay layer, the quartz sand particles embed themselves into the surface of the relatively soft clay minerals under drilling pressure. Due to the high water content of the clay layer, the surface of the quartz sand particles is weakly acidic in the moist clay environment, while the surface of clay minerals, such as montmorillonite, is weakly alkaline. A microscopic pH gradient field is formed at the interface between the two. Under the catalysis of moisture and mechanical pressure, a local dissolution and reprecipitation reaction occurs at the interface. Aluminosilicates in quartz and clay minerals form an amorphous aluminum silicate gel at the interface. This gel has instantaneous adhesion capabilities. When the drill rod rotates, the gel causes strong adhesion between quartz sand grains and clay. When the rotational torque accumulates to exceed the gel strength, the adhesion point breaks, and the drill rod resistance decreases. As rotation continues, new gel is formed at the interface, creating a periodic nonlinear rotational resistance fluctuation. If the frequency of this fluctuation is close to or matches the natural frequency of the drill rod, it will trigger structural resonance, manifested as resonant vibration of the drill rod, which will reduce the directional accuracy of the drilling trajectory. Therefore, by increasing the rotational speed of the drill rod, the excitation frequency of the nonlinear rotational resistance fluctuation process is changed, making the excitation frequency far away from the natural frequency of the drill rod, thus destroying the resonance condition. Furthermore, the shear force provided by the increased rotational speed is used to destroy the gel in the early stage of gel formation, inhibiting the gel from reaching the level of generating strong adhesion, and further improving the accuracy of closed-loop Quaternary strata directional drilling sampling. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of the closed-loop Quaternary strata directional sampling drilling method for environmental protection according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the elevation construction of a closed-type Quaternary strata directional sampling drilling method for environmental protection according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating the determination of the drilling angle in a closed-loop Quaternary strata directional sampling drilling method for environmental protection, as described in an embodiment of the present invention. Figure 4 This is a flowchart illustrating the determination of drilling intensity in a closed-type Quaternary strata directional sampling drilling method for environmental protection, as described in an embodiment of the present invention. Explanation of reference numerals in the attached drawings: 1-Drill rod, 2-First soil layer, 3-Second soil layer, 4-Railway, 5-Sound barrier, 6-Fence, 7-Foundation reinforcement, 8-Horizontal surface. Detailed Implementation

[0019] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0020] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0021] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0022] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Please see Figure 1The diagram shown is an overall flowchart of a closed-loop Quaternary strata directional sampling drilling method for environmental protection according to an embodiment of the present invention. The closed-loop Quaternary strata directional sampling drilling method for environmental protection according to an embodiment of the present invention includes: Step S1: Drilling test is performed on the first soil layer above the Quaternary strata using a drill rod; Step S2: Obtain the vibration spectrum of the drill rod per unit frequency monitoring cycle during the drilling test. Step S3: Determine the drilling angle based on the energy proportion of the low-frequency band in the vibration spectrum; Step S4: Continue drilling tests according to the drilling angle, and determine the drilling intensity based on the maximum temperature value of the drill rod in the first soil layer. Step S5: Continue drilling tests according to the drilling intensity, and calculate the amount of sand carried on the bottom lip based on the bottom lip area of ​​the drill rod and the drilling distance of the first soil layer on the drilling trajectory. Step S6: Determine the rotation speed of the drill rod based on the amount of sand on the bottom lip surface and the vibration frequency of the drill rod in the second soil layer; Step S7: Control the drill rod to complete the actual drilling and sampling of the Quaternary strata according to the drilling angle, drilling intensity, and rotation speed, wherein... The second soil layer is the soil between the first soil layer and the fourth stratum.

[0024] Specifically, the Quaternary strata are the newest geological units that have been deposited since the Earth's surface.

[0025] As will be understood by those skilled in the art, the division of Quaternary strata and their basic engineering geological characteristics are conventional technical means well known to those skilled in the art, and therefore will not be elaborated upon here.

[0026] Please see Figure 2 As shown, it is a vertical construction schematic diagram of the closed-type Quaternary stratum directional sampling drilling method for environmental protection according to an embodiment of the present invention. The soil layer above the Quaternary stratum is the overburden soil layer located above the Quaternary stratum in the vertical section and below the ground surface.

[0027] Specifically, the overlying soil layers include, but are not limited to: 8 is the surface level, which is located at the top layer of the overlying soil. The first soil layer 2 is located below the surface level 8 and is usually a layer of silt, fine sand or medium sand. The second soil layer 3, located below the first soil layer 2, is usually a clay layer or a silty clay layer.

[0028] Specifically, a railway 4, a sound barrier 5, and a fence 6 are constructed above the topsoil layer.

[0029] Specifically, a foundation reinforcement body 7 is installed under the railway at equal intervals.

[0030] Specifically, the drill rod is a hollow, threaded drill rod made of high-strength alloy steel used for directional sampling.

[0031] Please see Figure 3 The diagram shows a flowchart of the method for determining the drilling angle in a closed-loop Quaternary strata directional sampling drilling method for environmental protection, as described in an embodiment of the present invention. The step of determining the drilling angle based on the energy proportion of the low-frequency band in the vibration spectrum includes: The proportion of low-frequency energy in the vibration spectrum within a unit frequency monitoring period is compared with the preset energy proportion. If the energy percentage is greater than the preset energy percentage, it is determined that the impact on the mechanical properties of the interface caused by the passive rise of capillary water in the groundwater does not meet the requirements, and the drilling angle is reduced. Wherein, the horizontal axis of the vibration spectrum is the vibration frequency of the drill rod, and the vertical axis is the power spectral density of the drill rod; the energy ratio is the ratio of the integral area of ​​the power spectral density in the low-frequency band to the integral area of ​​the power spectral density in the vibration spectrum.

[0032] Specifically, the monitoring cycle per unit frequency is 10 seconds.

[0033] Specifically, capillary water is the water that rises from the groundwater through the capillary action of the soil.

[0034] As will be understood by those skilled in the art, the passive rise of capillary water and its principle are conventional techniques well known to them, and therefore will not be elaborated upon here.

[0035] Optionally, the preset energy percentage can be selected from [25%, 40%].

[0036] Preferably, the preset energy percentage in the preferred embodiment is 30%.

[0037] Specifically, the vibration spectrum of the drill rod during the drilling test is obtained by a triaxial vibration acceleration sensor set at the top of the drill rod.

[0038] Specifically, under the conditions of railway construction, when the ambient temperature is in the range of 28℃ to 33℃, the passive upward rate of capillary water increases by 0.2 mm / h for every 1℃ increase in ambient temperature.

[0039] As will be understood by those skilled in the art, the capillary passive rise rate is calculated based on the ambient temperature and the moisture content of the first soil layer. The calculation method of the capillary passive rise rate is a conventional technique well known to those skilled in the art, so the calculation method of the capillary passive rise rate will not be described in detail here.

[0040] Specifically, the low-frequency band is the frequency range in the vibration spectrum where the vibration frequency is less than the first preset vibration frequency.

[0041] Optionally, the first preset vibration frequency can be selected within the range of [15Hz, 25Hz].

[0042] Preferably, the first preset vibration frequency is 20Hz.

[0043] Specifically, the drilling angle is the acute angle formed by the drilling rod 1 and the horizontal surface 8.

[0044] Specifically, the drilling angle is adjusted by controlling the acute angle between the drill rod and the horizontal surface of the ground using a tracked down-the-hole drill rig.

[0045] As will be understood by those skilled in the art, the operating principle and process of tracked down-the-hole drills are conventional technical means well known to those skilled in the art, and therefore the operating principle and process of tracked down-the-hole drills will not be described in detail here.

[0046] Specifically, the drilling angle is negatively correlated with the energy ratio.

[0047] In practice, when the energy percentage is less than 2% of the preset energy percentage, the drilling angle is adjusted to 96% of the current drilling angle. When the energy percentage exceeds 2% of the preset energy percentage, the drilling angle is reduced by 1° for every 1% exceeding 2%. In a specific embodiment, the current energy percentage is 34% and the current drilling angle is 25°. The reduced drilling angle is 25° × 96% - (2% / 1%) × 1° = 22°.

[0048] In practice, this invention involves drilling and testing the sand layer above the Quaternary strata, specifically the first soil layer. Since the actual drilling and sampling environment for the Quaternary strata was an outdoor railway construction site, the removal of vegetation and exposure of the surface due to construction activities reduced surface albedo and transpiration cooling, leading to an increase in surface temperature. Furthermore, soil compaction, such as by transport or construction vehicles, reduced porosity and created cracks below the surface. The combined heat transfer from transport and construction vehicles further amplified the evaporation effect, accelerating water migration to the surface via capillary action. Therefore, by obtaining the vibration spectrum of the drill rod during the drilling process, the invention characterizes how increased surface evaporation under elevated ambient temperature leads to a faster passive rise rate of capillary water from groundwater, resulting in increased moisture content in the sand layer. The low frequencies in the vibration spectrum... The energy percentage of a segment characterizes the softening degree and water content change of the sand layer. When the energy percentage is greater than the preset energy percentage, it indicates that the sand layer has softened due to the increase in water content. The mechanical abrupt change at the interface between the sand layer and the clay layer below it shifts upward earlier, that is, the mechanical abrupt change at the interface between the first soil layer and the second soil layer shifts upward earlier. Due to its low permeability, the clay layer exhibits a lag effect in softening time due to water absorption and expansion. Therefore, a soft-hard interface is formed between the first soil layer and the second soil layer. If the drive device of the drill rod at this time... Misjudging the softened sand layer as a drill rod jamming issue and increasing drilling intensity can lead to localized compaction of the clay layer and uneven distribution of soil adhering to the drill bit. Consequently, uneven mass distribution occurs during rotating sampling in the Quaternary strata, causing resonance. Therefore, by reducing the acute angle between the drill rod and the horizontal surface, the mechanical transition at the interface between the first and second soil layers is further smoothed, avoiding vertical impact on the softened sand layer. This suppresses vibration sources, prevents stress concentration points from forming in the softened sand layer, and further improves the stability of directional sampling drilling in the Quaternary strata.

[0049] Please see Figure 4 The diagram shows a flowchart illustrating the determination of drilling intensity in a closed-loop Quaternary strata directional sampling drilling method for environmental protection, as described in an embodiment of the present invention. The determination of drilling intensity based on the maximum temperature value of the drill rod within the first soil layer includes: Obtain the temperature value at the temperature sampling point on the drill rod within the first soil layer; The temperature value at the temperature sampling point with the highest temperature value among all temperature sampling points is determined as the maximum temperature value; If the maximum temperature value is greater than the preset temperature value, it is determined that the friction of the drill rod in the first soil layer has increased abnormally, and the drilling intensity is reduced.

[0050] Specifically, the drilling intensity is adjusted by controlling the hydraulic feed cylinder through a PLC integrated on the tracked down-the-hole drill rig.

[0051] As will be understood by those skilled in the art, the operating principle and process of the hydraulic feed cylinder are conventional technical means well known to them, and therefore the operating principle and process of the hydraulic feed cylinder will not be described in detail here.

[0052] Specifically, the drilling intensity is negatively correlated with the maximum temperature value.

[0053] Optionally, the preset temperature value can be selected within a range of [60℃, 75℃].

[0054] Preferably, the preset temperature value in the preferred embodiment is 65°C.

[0055] Specifically, the temperature value of the drill rod is obtained by a resistance temperature detector installed on the drill rod.

[0056] In practice, when the maximum temperature value is within 2°C of the preset temperature value, the drilling intensity is adjusted to 95% of the current drilling intensity. When the maximum temperature value exceeds the preset temperature value by more than 2°C, the drilling intensity is reduced by 1N for every 1°C exceeding 2°C. In a specific embodiment, the current maximum temperature value is 68°C, the current drilling intensity is 5.50kN, and the reduced drilling intensity is 5.50kN×95%-(1°C / 1°C)×1N=5.224kN. When the calculated drilling intensity has more than three decimal places, it is rounded to three decimal places.

[0057] In practice, this invention determines the drilling intensity based on the maximum temperature value of the drill rod within the first soil layer. This maximum temperature value represents the sand layer losing water due to the mechanical energy of the drill rod being converted into heat during drilling, which reduces the cohesion between sand particles. This leads to an abnormal increase in friction between the rear end of the drill rod and the sand layer during drilling, and the dry sand particles are more easily embedded in the microcracks on the drill rod surface, further increasing friction. When this maximum temperature value exceeds a preset temperature value, it indicates that the increased friction leads to increased frictional power consumption at the rear end of the drill rod and the sand layer, manifested as an abnormal temperature rise at this contact surface. Therefore, by reducing the drilling intensity, the normal pressure of sand particles intruding into the drill rod surface is reduced, weakening the mechanical meshing effect and further compensating for the water loss caused by the conversion of mechanical energy into heat during drilling. Furthermore, by reducing the drilling intensity, a buffer window is provided for the temperature rise of the drill rod, improving the stability of the drilling process.

[0058] Specifically, the amount of sand carried on the bottom lip surface is the product of the area of ​​the bottom lip surface, the drilling distance of the first soil layer on the drilling trajectory, and the sand grain adhesion fitting conversion coefficient.

[0059] Specifically, the sand grain adhesion fitting conversion coefficient is the mass of sand grains adhering to a unit contact area on the bottom lip surface when drilling a unit drilling distance in the sand layer. The unit of the sand grain adhesion fitting conversion coefficient is... .

[0060] Optionally, the selectable range of the sand grain adhesion fitting conversion coefficient is: .

[0061] Preferably, the preferred embodiment of the sand particle adhesion fitting conversion coefficient is as follows: .

[0062] In a specific embodiment, the bottom lip surface area of ​​the current drill pipe is 19.6. The drilling distance for the first soil layer along the drilling trajectory was 2.7m, and the sand grain adhesion fitting conversion coefficient was... The calculated amount of sand on the bottom lip surface is .

[0063] Specifically, determining the rotation speed of the drill rod based on the amount of sand on the bottom lip surface and the vibration frequency of the drill rod within the second soil layer includes: If the amount of sand on the bottom lip surface is greater than the preset amount of sand, and the vibration frequency is greater than the first preset vibration frequency but less than the second preset vibration frequency, then it is determined that the attached sand particles on the drill rod undergo an electrochemical reaction with the second soil layer, resulting in an impact on the stability of the drilling that does not meet the requirements, and the rotation speed of the drill rod is increased.

[0064] Optionally, the preset sand content can be selected within the range of [4g, 8g]; the second preset vibration frequency can be selected within the range of [22Hz, 30Hz]. Preferably, the preset amount of sand is 6g, and the preset vibration frequency is 28Hz.

[0065] Specifically, the rotation speed of the drill rod is positively correlated with the amount of sand carried on the bottom lip surface.

[0066] Specifically, the rotation speed of the drill rod is adjusted by a variable hydraulic motor on a tracked down-the-hole drill rig.

[0067] As will be understood by those skilled in the art, the operating principle and process of a variable hydraulic motor are conventional technical means well known to them, and therefore the operating principle and process of a variable hydraulic motor will not be described in detail here.

[0068] In practice, when the amount of sand on the lip surface exceeds the preset amount by less than 0.2g, the rotation speed is adjusted to 1.1 times the current rotation speed. When the amount of sand on the lip surface exceeds the preset amount by more than 0.2g, the rotation speed is increased by 1rpm for every 0.1g exceeding 0.2g. In a specific embodiment, the current vibration frequency is 22Hz, the amount of sand on the lip surface is 6.35g, and the current rotation speed is 150rpm. The increased rotation speed is 150rpm×1.1+(0.15g / 0.1g)×1rpm=165.15rpm. When the calculated rotation speed has more than one decimal place, it is rounded to the nearest integer, i.e., 165rpm.

[0069] In practice, this invention calculates the amount of sand carried on the bottom lip surface based on the area of ​​the bottom lip of the drill rod and the drilling distance of the first soil layer along the drilling trajectory. The product of the bottom lip surface area, the drilling distance of the first soil layer along the drilling trajectory, and the sand grain adhesion fitting conversion coefficient is determined as the amount of sand carried on the bottom lip surface. The sand grain adhesion fitting conversion coefficient is the mass of sand grains adhering to a unit contact area of ​​the bottom lip surface when drilling a unit drilling distance in the sand layer. When this amount of sand carried on the bottom lip surface is greater than a preset amount, it indicates that the drilling rod has penetrated... When softening the sand layer, high-purity quartz sand particles adhere to the bottom lip of the drill rod. As the bottom lip penetrates the underlying clay layer, the quartz sand particles embed themselves into the surface of the relatively soft clay minerals under drilling pressure. Due to the high water content of the clay layer, the surface of the quartz sand particles is weakly acidic in the moist clay environment, while the surface of clay minerals, such as montmorillonite, is weakly alkaline. A microscopic pH gradient field is formed at the interface between the two. Under the catalysis of moisture and mechanical pressure, a local dissolution and reprecipitation reaction occurs at the interface. Aluminosilicates in quartz and clay minerals form an amorphous aluminum silicate gel at the interface. This gel has instantaneous adhesion capabilities. When the drill rod rotates, the gel causes strong adhesion between quartz sand grains and clay. When the rotational torque accumulates to exceed the gel strength, the adhesion point breaks, and the drill rod resistance decreases. As rotation continues, new gel is formed at the interface, creating a periodic nonlinear rotational resistance fluctuation. If the frequency of this fluctuation is close to or matches the natural frequency of the drill rod, it will trigger structural resonance, manifested as resonant vibration of the drill rod, which will reduce the directional accuracy of the drilling trajectory. Therefore, by increasing the rotational speed of the drill rod, the excitation frequency of the nonlinear rotational resistance fluctuation process is changed, making the excitation frequency far away from the natural frequency of the drill rod, thus destroying the resonance condition. Furthermore, the shear force provided by the increased rotational speed is used to destroy the gel in the early stage of gel formation, inhibiting the gel from reaching the level of generating strong adhesion, and further improving the accuracy of closed-loop Quaternary strata directional drilling sampling.

[0070] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for environmental protection, comprising a closed fourth formation oriented sampling drilling method, characterized in that, The method comprises: drilling and testing a first soil layer above a quaternary stratum through a drilling rod; obtaining a vibration frequency spectrum of the drilling rod in a unit frequency monitoring period during the drilling and testing; determining a drilling angle according to an energy proportion of a low frequency band in the vibration frequency spectrum; continuing the drilling and testing according to the drilling angle, and determining a drilling intensity based on a maximum temperature value of the drilling rod in the first soil layer; continuing the drilling and testing according to the drilling intensity, and calculating a bottom lip surface sand amount based on a bottom lip surface area of the drilling rod and a drilling distance of the first soil layer on a drilling track; determining a rotating speed of the drilling rod according to the bottom lip surface sand amount and a vibration frequency of the drilling rod in a second soil layer; controlling the drilling rod to complete actual drilling sampling of the quaternary stratum according to the drilling angle, the drilling intensity and the rotating speed, wherein the second soil layer is soil between the first soil layer and the quaternary stratum.

2. The sealed quaternary formation coring method for environmental protection of claim 1, wherein, The method of determining the drilling angle according to the energy proportion of the low frequency band in the vibration frequency spectrum comprises: comparing the energy proportion of the low frequency band in the vibration frequency spectrum in the unit frequency monitoring period with a preset energy proportion; if the energy proportion is greater than the preset energy proportion, determining that the influence on the interface mechanics due to passive upward migration of capillary water of underground water does not meet the requirements, and reducing the drilling angle. The horizontal axis of the vibration frequency spectrum is the vibration frequency of the drilling rod, and the vertical axis is the power spectral density of the drilling rod; the energy proportion is a ratio of the integral area of the power spectral density of the low frequency band to the integral area of the power spectral density in the vibration frequency spectrum.

3. The sealed quaternary formation coring method for environmental protection of claim 2, wherein, The low frequency band is a frequency interval in which the vibration frequency is less than a first preset vibration frequency in the vibration frequency spectrum.

4. The method for environmental protection according to claim 3, wherein, The drilling angle is an acute angle included between the drilling rod and a horizontal plane of the ground.

5. The method for environmental protection according to claim 4, wherein, The drilling angle and the energy proportion are in a negative correlation.

6. The method for environmental protection according to claim 5, wherein, The method of determining the drilling intensity based on the maximum temperature value of the drilling rod in the first soil layer comprises: obtaining a temperature value at a temperature sampling point on the drilling rod in the first soil layer; determining the temperature value at the temperature sampling point with the maximum temperature value among all temperature sampling points as the maximum temperature value; if the maximum temperature value is greater than a preset temperature value, determining that the friction of the drilling rod in the first soil layer is abnormally increased, and reducing the drilling intensity.

7. The sealed quaternary formation coring method for environmental protection of claim 6, wherein, The drilling intensity and the maximum temperature value are in a negative correlation.

8. The sealed quaternary formation coring method for environmental protection of claim 7, wherein, The bottom lip surface sand amount is a product of the bottom lip surface area, the drilling distance of the first soil layer on the drilling track and a sand particle adhesion fitting conversion coefficient.

9. The sealed quaternary formation coring method for environmental protection of claim 8, wherein, The method of determining the rotating speed of the drilling rod according to the bottom lip surface sand amount and the vibration frequency of the drilling rod in the second soil layer comprises: if the bottom lip surface sand amount is greater than a preset sand amount, and the vibration frequency is greater than a first preset vibration frequency and less than a second preset vibration frequency, determining that the attached sand particles on the drilling rod and the second soil layer have an electrochemical reaction, which causes the influence on the stability of the drilling to not meet the requirements, and increasing the rotating speed of the drilling rod.

10. The sealed quaternary formation coring method for environmental protection of claim 9, wherein, The rotating speed of the drilling rod and the bottom lip surface sand amount are in a positive correlation.

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