Fine-grain tailing sand soil layer exploration drilling hole-forming control method

Abstract

The invention provides a fine-grain tailing sand soil layer exploration drilling hole forming control method. The control method mainly aims at control in the drilling exploration process of a soil layer formed by accumulation of fine-grain tailing sandy soil, and specifically comprises the steps that before the water level is initially seen, dry drilling is carried out, a casing pipe is adopted for wall protection after water breakthrough, and after water level observation is stable, slurry is adopted for wall protection drilling; when the particle size components of the deposits mainly comprise tail silt and tail silt, common bentonite slurry is adopted for slurry retaining wall drilling; when the particle size components of the deposits mainly comprise tail silty clay and tail clay, the slurry protecting wall adopts Keel chemical slurry; in the drilling process, the drilling speed is not higher than 285-295 r / min for accumulation bodies with the hole depth within 60 m; drilling is conducted on an accumulation body with the depth of 60-120 m at the low speed of 142 r / min, and the bit pressure is adjusted in real time. Through selection of wall protection modes with different particle sizes and quantitative control of key operation procedures, the drilling and coring efficiency can be greatly improved, and in-hole accidents and the production cost are reduced.

Description

Technical Field

[0001] The invention relates to the field of mine tailings dump exploration, in particular to a hole formation control method in fine-grained tailings sand layer exploration drilling. Background Art

[0002] In recent years, with the rapid development of the national economy, the demand for mineral products has increased, the scale of mining development has become larger and larger, and the mining and selection particle size has become finer and finer, resulting in a large amount of fine-grained solid waste being dumped in the reservoir area. In order to grasp and verify its stability, according to the mine safety management regulations, regular dam exploration and evaluation are required.

[0003] Existing geological exploration methods primarily rely on drilling, using a drill rig to drill holes and obtain physical parameters of the subsurface rock formations for geological analysis and exploration results. Due to the complex sedimentary characteristics of the deposits, poor regularity of sand and soil interlayers, heavy intergranular material, generally poor consolidation, and high water content that is easily disturbed, drilling exploration in tailings reservoir areas is more difficult than in general fluvial sedimentary areas. Drilling exploration typically relies on personnel experience and operational skills. However, engineering practice has shown that when the deposit thickness exceeds 30m, inadequate drilling process control and improper wall protection methods can easily lead to borehole wall shrinkage and collapse. Beyond 60m, the risk of rod burial and drill bit jamming is more likely. Beyond 100m, footage is difficult or there is a risk of "wasted holes," causing significant challenges for on-site operations, especially in deep hole sections beyond 60m. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a method for controlling drilling and hole formation in the exploration of fine-grained tailings sand layers. The control method can greatly improve the efficiency of drilling and coring, reduce in-hole accidents and production costs, and effectively alleviate the current situation of lack of rules and regulations in fine-grained deep hole exploration in the field of mine tailings ponds, through the selection of wall protection methods with different particle sizes and quantitative control of key operating procedures. The method has extremely strong practicality.

[0005] In order to achieve the above technical objectives, the present invention provides a method for controlling drilling and hole formation in fine-grained tailings sand layer exploration. The control method mainly controls the drilling exploration process of a soil layer formed by accumulation of fine-grained tailings sand, and is particularly suitable for fine-grained, powdery, and colloid tailings sand with a particle size between 0.075 mm and less. The method specifically comprises the following steps:

[0006] S1. Once the drilling rig is in place and ready, begin drilling. Before the initial water level is reached, dry drill with the rig. After water is reached, use casing to protect the borehole. Extend the casing 1-3 meters below the initial water level. After 25-35 minutes, observe the stable water level. The total depth of the casing should not exceed 65 meters to avoid excessive friction and difficulty in removing it at the end of the hole.

[0007] S2. After observing the stable water level, switch to slurry wall drilling. When the deposit's particle size composition is primarily tailing silt sand and tailing silt soil, slurry wall drilling uses ordinary bentonite mud. Ordinary bentonite mud is prepared using bentonite powder, a relatively abundant calcium-based bentonite. When the deposit's particle size composition is primarily tailing silt clay and tailing clay, slurry wall drilling uses CLEAR chemical mud. CLEAR chemical mud can be purchased as a finished product or prepared from purchased CLEAR chemical mud powder. CLEAR chemical mud has a high molecular weight and strong adsorption and bonding capacity, allowing drill cuttings to settle quickly. Compared to bentonite mud, it is more suitable for wall protection in clay layers.

[0008] S3. During the drilling process, for Grade III and lower accumulations within a depth of 60m, the drilling speed shall not exceed 285-295 r / min (gear 2). For Grade II and higher accumulations at a depth of 60-120m, the drilling speed shall be low, at 142 r / min (gear 1). The vertical axis feed drilling pressure at each depth shall be calculated and applied according to formula ① and adjusted in real time: P = 0.0095 rh - 0.07L ①, Where: P-bit pressure, unit KPa; r-tailings layer density, unit KN / m 3 ;h-drilling depth, unit: m; L-drill pipe length, unit: m;

[0009] S4. During the drilling process, when the hole depth is less than 60m, core sampling and in-situ testing shall be carried out at intervals of 1.50m, with each drilling not exceeding 1.5m. When the hole depth is greater than 60m, core sampling and in-situ testing shall be carried out at intervals of 3m, with each drilling not exceeding 1.0m.

[0010] S5. If there is leakage during the drilling process, stop the machine immediately and lift the drill. Pour enough air-dried clay balls into the hole and compact them by reversing the drill bit to seal the leakage before drilling again. The diameter of the air-dried clay balls can be 20mm.

[0011] A further technical solution of the present invention: The amount of air-dried clay balls in step S5 is calculated according to the following formula: G=KrAh②, In the above formula, G is the amount of air-dried clay balls, in kg; r is the density of air-dried clay balls, in kN / m 3 ; A-drilling area, unit m 2 ; h-the length of the plugging section in each round, in m; K-the backfill coefficient.

[0012] A preferred technical solution of the present invention: the fine-grained tailings sand in step S1 refers to tailings fine sand, tailings silt sand, tailings silt soil and tailings silty clay with a discharged sediment particle size of 0.075 mm or less.

[0013] The preferred technical solution of the present invention is: when ordinary bentonite slurry is used in step S2, when the drilling depth is within 60m, the slurry concentration is 75-100Kg / m 3 , add 0.50-1.0kg hydroxypropyl methylcellulose and 1.75-3.0kg soda ash at the same time; when the drilling depth is greater than 60m and less than 120m, the mud concentration is 125-150kg / m 3 At the same time, 1.25-1.5 kg of hydroxypropyl methylcellulose and 3.5-4.25 kg of soda ash are added per cubic meter of mud. The amount of hydroxypropyl methylcellulose and soda ash added is controlled to control the slurry pH value to be not less than 8, the viscosity to be not less than 21, and the sediment at the bottom of the hole to be not more than 15 cm. The hydroxypropyl methylcellulose is cold water instant soluble. When the viscosity of the bentonite slurry is low, it can quickly increase the viscosity of the bentonite slurry and reduce water loss. The soda ash (caustic soda) has the function of adjusting the pH value, enhancing dispersibility and improving fluidity.

[0014] When using Kelier chemical mud in step S2, the mud is prepared using Kelier chemical mud powder, wherein the concentration of Kelier chemical mud powder is 0.30~0.40Kg / m 3 , and add 0.20-0.30 kg of caustic soda per cubic meter of mud to adjust the pH value, control the slurry pH value to be not less than 9, the viscosity to be not less than 19, and the sediment at the bottom of the hole to be no more than 10 cm.

[0015] The preferred technical solution of the present invention is: in step S4, ensure that the thickness of the scum at the bottom of the hole is not greater than 10 cm, and when coring, use a split-type ring knife sand collector to coring.

[0016] The preferred technical solution of the present invention is as follows: the drilling and hole-forming equipment is an XY-150 or XY-200 high-speed hydraulic drilling rig, the base of which is equipped with two S1105 high-efficiency diesel engines to ensure sufficient power output of the traction and rotation systems; the drill rod specification is Ф50x6.5mm, which has a larger transmission torque than the general Φ42mm drill rod, reducing the risk of rod falling off; the high-speed hydraulic drilling rig frame has two types: crawler type and tripod type, of which the crawler type frame is suitable for the dam area, and the tripod type is more suitable for the beach facing the water area due to its light weight; the diameter of the wall casing is selected in combination with the borehole diameter as Ф127mm, Ф108mm, and Ф89mm, and two or three diameters are reasonably matched according to the water level burial depth; the bottom 1 to 3m section of the wall casing is set in the form of a flower pipe, and adopts 150 to 200g / m 2 Wrapped in non-woven geotextile, the water level can be continuously monitored by an electronic water level gauge.

[0017] The preferred technical solution of the present invention is: when calculating the drilling pressure during the early hole exploration, the tailings layer weight is taken in combination with the existing reports. When there is no reference data, the tailings layer weights of various states are taken as follows: the tailings layer weight in the loose state is 16kN / m 3 , slightly dense state takes 17kN / m 3 , medium density state takes 18.5kN / m 3 , dense state takes 20kN / m 3 , tail silty clay takes 18.5kN / m 3 ; The pore pressure will be adjusted after the actual weight of each layer is determined through field tests.

[0018] The preferred technical solution of the present invention is as follows: during the drilling process, the drill should be drilled to the bottom each time without pausing in between. If the drill encounters resistance during drilling, it should not be released suddenly. If the drill is stuck, it should not be pulled hard. Instead, it should be lowered according to the upper resistance and lifted according to the lower resistance, and the stuck should be released by rotating in the up and down directions.

[0019] The preferred technical solution of the present invention is as follows: during the drilling process, the drum is lifted at a speed of 0.5 to 1.0 m / s when the drill is pulled out, and when the core tube is lifted to the hole mouth, it is quickly supported to prevent negative pressure from forming at the bottom of the drill tool.

[0020] The preferred technical solution of the present invention is that the density r of the air-dried clay ball used for plugging is 1.45×10 3 kg / m 3 , the backfill coefficient K is taken as 2.0.

[0021] The water used to prepare the slurry in the present invention can be the production circulating water used in the mining area after being treated by a recovery pump station, and it only needs to meet the standards for fluoride, sulfide, thallium, lead, chromium and the like; the specific gravity of the slurry is tested by a hydrometer, the viscosity is measured by a Marsh funnel meter, the pH value is tested by a test paper, and the sediment thickness is measured by a pendulum measurement method.

[0022] The present invention has the following effects:

[0023] During the drilling process, the present invention utilizes different slurry wall protection methods based on different backfill layers to enhance the wall protection effect. Different rotation speeds are used based on different hole depths to prevent significant vibration of the machine body due to high-speed rotation, which would cause excessive disturbance of the rock and soil surrounding the hole wall. This ensures that the tailings sand and soil are moderately cut, minimizing the disturbance of the hole wall soil. Furthermore, the drilling pressure at each depth is calculated and adjusted in real time based on the drilling depth to avoid problems such as hole collapse caused by excessive drilling pressure. By selecting different particle size wall protection methods and quantitatively controlling key operational procedures, the present invention can significantly improve drilling and coring efficiency, reduce in-hole accidents and production costs, and effectively alleviate the current situation of a lack of on-site regulations for fine-grained deephole exploration in the field of mine tailings ponds. The invention is highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the construction process of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below with reference to specific embodiments. The technical solutions presented in the following embodiments are specific embodiments of the present invention and are not intended to limit the scope of the invention as claimed. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0026] In the following embodiments, the drilling equipment is an XY-150 or XY-200 high-speed hydraulic drill, with a drill rod specification of Ф50x6.5mm; the casing diameter is selected in combination with the borehole diameter as Ф127mm, Ф108mm, or Ф89mm, and two or three diameters are reasonably matched according to the water level burial depth; the bottom 1-3m section of the wall casing is set in a flower tube form and adopts 150-200g / m 2 Wrapped with non-woven geotextile. When pulling out the drill, the drum should be hoisted at a speed of 0.5 to 1.0 m / s. When the core tube reaches the hole, it should be quickly supported to prevent negative pressure from forming at the bottom of the drill tool.

[0027] In the following embodiments, the vertical axis drilling pressure at each depth is calculated and applied according to formula ① and adjusted in real time: P = 0.0095rh - 0.07L ①, Where: P-bit pressure, unit KPa; r-tailings layer density, unit KN / m 3 ;h-drilling depth, unit: m; L-drill pipe length, unit: m;

[0028] The input amount of air-dried clay balls is calculated according to the following formula: G=KrAh②, In the above formula, G is the amount of air-dried clay balls, in kg; r is the density of air-dried clay balls, in kN / m 3 ; A-drilling area, unit m 2 ; h-the length of the plugging section in each round, in m; K-the backfill coefficient.

[0029] Implementation 1: For the Z9# hole of a reservoir dam, the drilling area is mainly composed of tailing silt sand and tailing silt soil, and the designed hole depth is 60.0m. During the drilling process, the method of the present invention is used to control the drilling of the Z9# hole. The details are as follows:

[0030] S1. The drilling rig is positioned and the hole is opened. First, the drilling speed is controlled at 285 (295) r / min (gear 2) to prevent the high-speed rotating machine body from vibrating and causing the sand and soil in the hole wall to collapse. The drilling pressure is calculated using the above formula ① and applied in combination with the bottom hole pressure indicator according to the middle scale or the whole scale. Since the dial scale value is an integer and the decimal is difficult to read, it is generally read according to the middle scale value or the whole scale value for easy control on site (the final actual value in the following embodiments is taken according to this rule). The calculation results and the actual drilling pressure values ​​are shown in Table 1 below. The advance per round is controlled at an interval of 1.50m, and the drilling speed is controlled at 1.0m / s.

[0031] Table 1 shows the drilling pressure at different hole depths below 10m in the first drilling operation.

[0032]

[0033] S2. When the water level was first seen at 9.2 m, a single layer of 127 mm diameter casing was installed as the wall protection. The casing was 10.5 m long, with a decorative pipe at the bottom 1.0 m. After standing for 30 minutes, the stable water level was observed.

[0034] S3. After observing the stable water level, continue drilling with ordinary bentonite mud wall protection; the initial mud concentration is based on previous experience and is 50 kg / m 3 At the same time, add soda ash 1Kg / m 3 Configuration, the effect is not good, there is a serious sedimentation phenomenon that requires repeated hole washing, change to bentonite powder 75Kg / m 3 , soda ash 2Kg / m 3 At the same time, add 0.5g / m 3 After the drilling depth reaches 30m, the sand content of the mud in the hole gradually increases. In order to ensure the quality of sampling and testing at 1.5m intervals and avoid the hole collapse caused by long-term operation in the hole, the mud concentration is 100Kg / m of bentonite powder. 3 , soda ash 3.0Kg / m 3 , Hydroxypropyl methylcellulose 1.0kg / m 3 After adjustment, the slurry return was normal. 57.4 m passed through the tailings layer and entered the lower natural soil layer. The drilling speed was controlled at 285 (295) r / min (2nd gear) throughout the entire process. The drilling pressure was calculated using the above formula ① and applied in combination with the bottom hole pressure indicator according to the middle scale or full scale reading. Since the dial scale values ​​are integers and decimals are difficult to read, the middle scale value or full scale value is generally read on site for easy control (the final actual values ​​in the following embodiments are all taken according to this rule). The calculation results and actual drilling pressure values ​​are shown in Table 2 below. The drilling speed was controlled at 1.0 m / s.

[0035] Table 2 shows the drilling pressure at different hole depths from 10 to 60 m in Example 1

[0036]

[0037] The performance of the above-mentioned wall protection slurry was tested, and its index test is shown in Table 3 below.

[0038] Table 3 Performance indicators of the wall protection mud in Example 1

[0039]

[0040] S4. Use air-dried clay balls to seal any minor leakage in the upper part. The amount of clay balls used is calculated according to the above formula ②. The calculation results are shown in Table 4 below:

[0041] Table 4 shows the clay ball backfill dosage in Example 1

[0042]

[0043] Example 2: Hole Z14# of a dam in a certain reservoir area is mainly composed of tailing silt sand and tailing silt soil, with a designed hole depth of 95m. During the drilling process, the method of the present invention is used to control the drilling of hole Z9#, which is as follows:

[0044] S1. Drilling rig in place, drilling. The process before the initial water level is the same as step S1 of embodiment 1.

[0045] The water level was first seen at S2.12.6m. Casing was used for wall drilling. A single layer of Ø127mm casing was installed as wall protection. The casing was 13.5m long and the bottom 1m was a flower pipe. After standing for 30 minutes, the stable water level was observed.

[0046] S3. After observing the stable water level, continue drilling with bentonite slurry wall protection. The process for the 13-65m depth section is the same as step 3 of S1 in Example 1. After 65m, in order to ensure the sampling and testing quality of 1.0m return and avoid the occurrence of hole collapse in the low-speed drilling hole, the slurry concentration is 125Kg / m of bentonite powder. 3 , soda ash 4Kg / m 3 , Hydroxypropyl methylcellulose 1.25kg / m 3 Adjustments were made, and the slurry return was normal. At 94.3 m, the tailings layer was penetrated and the underlying natural soil layer was entered. The drilling speed was controlled at 142 r / min (gear 1) throughout the entire process. The weight on bit was estimated using formula ①, as shown in Table 5. The actual applied value was obtained using the bottom hole pressure indicator and applied according to the rules in Example 1. The drill pull-up speed was controlled at 0.5 m / s. Mud performance indicators were tested and shown in Table 6.

[0047] Table 5: WOB of different hole depths from 60m to 95m in the second implementation

[0048]

[0049] Table 6 Performance indicators of the medium wall protection mud in implementation 2

[0050]

[0051] S4. Promptly seal any abnormal depth of upper slurry. Apply Formula ② to estimate the amount of clay balls to be used and add according to Table 7.

[0052] Table 7 shows the clay ball backfill dosage in Example 2

[0053]

[0054] Implementation 3: Hole Z19# in a reservoir sedimentary beach is mainly composed of interbedded tailing silt sand, tailing silt soil and tailing silty clay, with a designed hole depth of 31m. During the drilling process, the method of the present invention was used to control the drilling of hole Z9#, as follows:

[0055] S1. Position the drilling rig (trip-type) and drill the hole. Before the initial water level is reached, maintain a drilling speed of 142 r / min (gear 1). Calculate the weight on bit using formula ① and apply the actual applied value based on the bottom hole pressure indicator. The actual value is determined according to the rules in Example 1. The calculated and actual pressure values ​​are shown in Table 7. The actual values ​​are also determined according to the rules in Example 1. Control the drill pull-up speed to 0.5 m / s. Each pass is spaced 1.50 m apart, and the drill pull-up speed is controlled at 1.0 m / s.

[0056] Table 7: WOB of different hole depths from 1m to 5m in the third implementation

[0057]

[0058] When the water level was first seen at S2.3.2m, casing was used for wall drilling. A single layer of Ø127mm casing was installed as wall protection. The casing was 4.5m long and the bottom 1.5m was a flower pipe. After standing for 60 minutes, the stable water level was observed.

[0059] S3. Stabilize the water level observation hand and continue drilling with Kelier chemical mud wall protection. Initially, according to the instruction manual, the Kelier chemical mud dry powder is 0.1Kg / m 3 , soda ash is 0.05Kg / m 3 When added to water, the wall protection effect is not obvious compared with bentonite slurry, and there is a slight shrinkage hole and drill bit phenomenon. The dry powder is adjusted to 0.35Kg / m 3 , soda ash is 0.25Kg / m 3The subsequent advance was smooth, and at 30.3 m, the tailings layer was penetrated and the underlying natural soil layer was entered. The drilling speed was controlled at 142 r / min (level 1) throughout the entire process. The drilling pressure was calculated using formula (1) and applied based on the actual applied value obtained from the bottom hole pressure indicator. The actual pressure was determined according to the rules in Example 1. The calculated and actual pressure values ​​are shown in Table 8. The drilling speed was controlled at 1.0 m / s. Mud performance indicators are shown in Table 9.

[0060] Table 8: WOB of different hole depths from 5m to 30m in the third implementation

[0061]

[0062] Table 9 Performance indicators of the medium wall protection mud in implementation three

[0063]

[0064] Through the operations of the three examples described above, it can be seen that, compared to existing operations, the new process, with comprehensive control, reduces the drilling time for 60m deep holes from 6-8.5 days to 3-3.5 days. This overcomes the difficulty of drilling deep holes from 60-120m, significantly reducing the high costs and risks of drilling buried deep holes. This process has been tested and applied in multiple fine-grained tailings sand layer exploration projects in tailings ponds in Hubei and Jiangxi, demonstrating strong practical results.

[0065] In the above three embodiments, different mud wall protection methods are used according to different filling layers during the drilling process. By selecting wall protection methods with different particle sizes and quantitatively controlling key operating procedures, the drilling and coring efficiency is greatly improved and accidents in the hole are reduced.

Claims

1. A method for controlling drilling and forming holes in a fine-grained tailings sand layer, characterized by: The control method is mainly used to control the drilling exploration process of the soil layer formed by the accumulation of fine-grained tailings sand, and specifically includes the following steps: S1. Once the drilling rig is in place and ready, begin drilling. Before the initial water level is reached, dry drill with the rig. After water is reached, use casing to protect the borehole. Extend the casing 1-3 meters below the initial water level. After 25-35 minutes of stabilization, observe the stable water level. S2. After observing the stable water level, switch to slurry wall drilling. When the particle size composition of the deposit is mainly tailing silt sand and tailing silt soil, use ordinary bentonite mud for slurry wall drilling. When the particle size composition of the deposit is mainly tailing silt clay and tailing clay, use Kelier chemical mud for slurry wall drilling. S3. During the drilling process, for Grade III and lower accumulations within a depth of 60m, the drilling speed shall not exceed 285-295 r / min. For Grade II and higher accumulations at a depth of 60-120m, the drilling speed shall be low, at 142 r / min. The vertical axis feed drilling pressure at each depth shall be calculated and applied according to formula ① and adjusted in real time: P=0.0095 rh-0.07L ① Where: P-bit pressure, unit KPa; r-tailings layer density, unit KN / m 3 ; h-drilling depth, unit: m; L-drill pipe length, unit: m; S4. During the drilling process, when the hole depth is less than 60m, core sampling and in-situ testing shall be carried out at intervals of 1.50m, with each drilling not exceeding 1.5m. When the hole depth is greater than 60m, core sampling and in-situ testing shall be carried out at intervals of 3m, with each drilling not exceeding 1.0m. S5. During the drilling process, if there is leakage, stop the machine immediately and lift the drill, then pour enough air-dried clay balls into the hole, compact them and seal the leakage by reversing the drill bit before continuing drilling.

2. The method for controlling the drilling of fine-grained tailings sand layers according to claim 1, wherein: The input amount of air-dried clay balls in step S5 is calculated according to the following formula: G=KrAh ② In the above formula, G is the amount of air-dried clay balls, in kg; r is the density of air-dried clay balls, in kN / m 3 ; A-drilling area, unit m 2 ; h-the length of the plugging section in each round, in m; K-the backfill coefficient.

3. The method for controlling the drilling of fine-grained tailings sand layer exploration according to claim 1, characterized in that: The fine-grained tailings sand and soil in step S1 refers to the discharged sediment particle size of tailings fine sand, tailings silt sand, tailings silt soil and tailings silty clay with a discharge size of 0.075 mm or less.

4. The method for controlling hole formation in exploration drilling of fine-grained tailings sand layer according to claim 1, characterized in that: When ordinary bentonite slurry is used in step S2, the slurry concentration is 75-100 kg / m when the drilling depth is within 60 m. 3 At the same time, add 0.50-1.0kg hydroxypropyl methylcellulose and 1.75-3.0kg soda ash per cubic meter of mud; when the drilling depth is greater than 60m and less than 120m, the mud concentration is 125-150kg / m 3 , at the same time add 1.25-1.5kg hydroxypropyl methylcellulose and 3.5-4.25kg soda ash; the amount of hydroxypropyl methylcellulose and soda ash added should control the slurry pH value to be not less than 8, the viscosity to be not less than 21, and the sediment at the bottom of the hole to be no more than 15cm; When using Kelier chemical mud in step S2, the mud is prepared using Kelier chemical mud powder, wherein the concentration of Kelier chemical mud powder is 0.30~0.40Kg / m 3 , and add 0.20-0.30 kg of caustic soda per cubic meter of mud to adjust the pH value, control the slurry pH value to be not less than 9, the viscosity to be not less than 19, and the sediment at the bottom of the hole to be no more than 10 cm.

5. The method for controlling drilling and hole formation in fine-grained tailings sand layer exploration according to claim 1, characterized in that: In step S4, ensure that the thickness of the scum at the bottom of the hole is no more than 10 cm. When coring, use a split-type ring knife sand collector to coring.

6. The method for controlling drilling and hole formation in fine-grained tailings sand layer exploration according to claim 1, characterized in that: The drilling equipment is XY-150 or XY-200 high-speed hydraulic drilling rig, with a drill rod specification of Ф50x6.5mm; the casing diameter is selected according to the drill hole diameter as Ф127mm, Ф108mm, or Ф89mm, and two or three diameters are reasonably matched according to the water level depth; the bottom 1-3m section of the wall casing is set in the form of a flower pipe, and adopts 150-200g / m 2 Non-woven geotextile wrap.

7. The method for controlling hole formation in exploration drilling of fine-grained tailings sand layer according to claim 1, characterized in that: When calculating drilling pressure during early hole exploration, the tailings layer weight is taken in combination with existing reports. When there is no reference data, the tailings layer weights of various states are taken as follows: The tailings layer weight in loose state is 16kN / m 3 , slightly dense state takes 17kN / m 3 , medium density state takes 18.5kN / m 3 , dense state takes 20kN / m 3 , tail silty clay takes 18.5kN / m 3 ; The pore pressure will be adjusted after the actual weight of each layer is determined through field tests.

8. The method for controlling hole formation in exploration drilling of fine-grained tailings sand layer according to claim 1, characterized in that: During the drilling process, drill to the bottom each time without pausing. If the drill encounters resistance during drilling, do not release it suddenly. If the drill gets stuck, do not pull it hard. Instead, lower the upper resistance and lift the lower resistance, and move it up and down to release the jam.

9. The method for controlling hole formation in exploration drilling of fine-grained tailings sand layer according to claim 1, characterized in that: During the drilling process, the drum lifting speed is 0.5-1.0 m / s when pulling out the drill. When the core tube is lifted to the hole mouth, it is quickly supported to prevent negative pressure from forming at the bottom of the drill tool.

10. The method for controlling hole formation in exploration drilling of fine-grained tailings sand layer according to claim 2, characterized in that: The density r of the air-dried clay ball used for plugging leaks is 1.45×10 3 kg / m 3 , the backfill coefficient K is taken as 2.0.

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