Telescopic drill rod assembly and cement-soil mixing pile machine

Abstract

The utility model belongs to the technical field of constructional engineering, and particularly relates to a telescopic drill rod assembly and a cement mixing pile machine. The telescopic drill rod assembly comprises an outer drill rod, an inner core rod, a telescopic sleeve rod, a grouting unit and a driving device, and the outer drill rod is hollow; the inner core rod is rotationally connected into the outer drill rod, the inner core rod is hollow to form a grouting channel, an annular cavity is formed between the inner core rod and the outer drill rod, and an outer thread is arranged on the outer peripheral face, located in the cavity, of the inner core rod; the telescopic sleeve rod is connected between the inner core rod and the outer drill rod in a sleeved mode. The upper end of the telescopic sleeve rod is provided with an inner thread section matched with the outer thread in a sealed mode. The grouting unit is connected to the inner core rod extending out of the outer drill rod in a sealed and sleeved mode and communicates with the grouting channel. The output end of the driving device is in transmission connection with the end of the inner core rod. The utility model is used for solving the problems of limited space and inconvenience in transportation of the cement mixing pile.

Description

Technical Field

[0001] The utility model belongs to the technical field of construction engineering, and in particular relates to a telescopic drill rod assembly and a cement soil mixing pile machine. Background Art

[0002] There are many methods for treating soft soil foundations, among which cement soil mixing pile technology has been widely used in recent decades. Cement soil mixing pile technology uses cement as a curing agent, mechanically forces the curing agent and soil to be mixed, and then improves the strength of the reinforced soil through a series of physical and chemical reactions between the curing agent and the soil. The cement soil mixing pile method has the advantages of simple construction, high efficiency, and micro-vibration, and can effectively improve the bearing capacity and stability of soft soil foundations.

[0003] The reinforcement depth of cement-soil mixing piles is generally 3 to 15 meters (i.e., the pile length is 3 to 15 meters). In recent years, with the development of science and technology and the continuous improvement of construction standards, the reinforcement depth has also been increasing. According to statistics, the maximum reinforcement depth of cement-soil mixing piles is currently close to 30 meters, which means that the drill rod length of the cement-soil mixing pile machine is not less than 30 meters, and the pile frame height of the mixing pile machine is not less than 32 meters (generally with a surplus height of 2 to 3 meters). This depth increases the safety risks in the transportation, installation and disassembly of the mixing pile machine, and the construction management of the mixing piles exponentially; at the same time, in some areas with limited space, mixing piles cannot be constructed due to their pile frame height. Utility Model Content

[0004] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide a telescopic drill rod assembly for solving the problem of limited space and inconvenient transportation of cement soil mixing piles.

[0005] On the one hand, the technical solution of the utility model to solve the above technical problems is as follows: a telescopic drill rod assembly, comprising:

[0006] An outer drill rod, wherein the outer drill rod is hollow inside;

[0007] An inner core rod is rotatably connected to the outer drill rod, the inner core rod is hollow inside to form a grouting channel, an annular cavity is formed between the inner core rod and the outer drill rod, and an outer thread is arranged on the outer peripheral surface of the inner core rod located in the cavity;

[0008] A telescopic sleeve rod, the telescopic sleeve rod is sleeved between the inner core rod and the outer drill rod, and the upper end of the telescopic sleeve rod is provided with an internal thread section that is sealed and matched with the external thread;

[0009] The grouting unit is sealed and sleeved on the inner core rod extending out of the outer drill rod and is communicated with the grouting channel.

[0010] The output end of the driving device is connected to the end of the inner core rod through a flange.

[0011] Compared with the prior art, the above technical solution has the following beneficial effects:

[0012] In view of the above problem, a telescopic drill rod is provided. After the outer drill rod is driven by an external driving device to drill into position, the inner core rod is driven to rotate by the driving device. The telescopic sleeve can be further extended downward for drilling through the external thread and the internal thread section on the telescopic sleeve, so that the length of the drill rod is reduced to 1 / 2 of the original length, and the pile frame of the pile driver is lowered accordingly, which greatly reduces the safety risks of the equipment in transportation, installation and construction management. At the same time, the application of mixing piles is realized in some space-constrained areas, thereby greatly reducing the manufacturing cost of the mixing pile machine. Since the telescopic sleeve and the inner core rod are hollow to form a grouting channel, cement slurry can be injected through the grouting unit.

[0013] Based on the above technical solution, the embodiment of the present application can also be improved as follows:

[0014] It also includes a pressure-maintaining unit, which is sealed and sleeved on the outer drill rod and communicated with the cavity, and is used to inject or extract a pressure-maintaining medium into the cavity to maintain the pressure in the cavity within a target range.

[0015] A pressure-maintaining unit is used to inject gas into the cavity to maintain pressure, so as to prevent the injected cement slurry from entering the cavity through the gap in the internal thread section on the telescopic sleeve. When the telescopic sleeve moves downward, the pressure-maintaining unit injects, and when the telescopic sleeve moves upward, the pressure-maintaining unit extracts, so as to ensure that the cavity is always at a constant pressure.

[0016] A sealing ring is provided at the bottom of the inner core rod, and the sealing ring is sealed between the inner core rod and the telescopic sleeve rod.

[0017] The sealing ring can prevent cement slurry passing through the grouting channel from flowing into the threaded gap between the telescopic sleeve and the inner core rod. When the telescopic sleeve moves upward, it blocks the cement slurry adhering to the inner wall of the telescopic sleeve. At the same time, it can prevent the pressurized gas in the cavity from entering the grouting channel from the threaded gap between the inner core rod and the telescopic sleeve to a certain extent.

[0018] A communicating air passage is provided on the internal thread section, one end of the communicating air passage is communicated with the space between the sealing ring and the internal thread section, and the other end is communicated with the cavity.

[0019] The pressure-maintaining gas is introduced into the space between the internal thread section and the sealing ring through the connecting air passage, so that the space has a positive pressure, thereby improving the sealing effect of the sealing ring and preventing the slurry in the inner wall of the telescopic sleeve from mixing into the space above the sealing ring.

[0020] A limiting convex ring is arranged on the top of the outer drill rod, and a limiting groove which is sealed and matched with the limiting convex ring is arranged on the inner core rod, so as to limit the axial displacement of the inner core rod;

[0021] A limiting step is arranged at the bottom of the outer drill rod, and a limiting boss matched with the limiting step is arranged at the top of the telescopic sleeve rod.

[0022] It also includes an electric control unit, and a first sensor and a second sensor connected to the electric control unit, wherein the first sensor sends a first control signal after the outer drill rod sinks to the bottom to control the driving device to drive the inner core rod;

[0023] The second sensor is arranged on the limiting step, and the limiting boss sends out a second control signal after contacting the second sensor, so as to control the driving device to reversely drive the inner core rod.

[0024] The grouting unit comprises a grouting sleeve and a grouting pipe connected to the grouting sleeve. The inner core rod extending from the outer drill rod is circumferentially spaced with a plurality of grouting holes connected to the grouting channel. The grouting sleeve is sealed and covered on the outside of the grouting hole.

[0025] The pressure-maintaining unit comprises a pressure-maintaining sleeve and a conduit connected to the pressure-maintaining sleeve. The pressure-maintaining sleeve is sleeved on the outer drill rod via a sealing ring. The outer drill rod is circumferentially provided with a plurality of through holes connected to the interior of the pressure-maintaining sleeve.

[0026] The driving device comprises a driving motor and a conductive slip ring electrically connected to the driving motor, and an output end of the driving motor is connected to the inner core rod.

[0027] On the other hand, this embodiment also discloses a method for using a telescopic drill rod assembly, which comprises the following steps:

[0028] After the pile position is determined, the mixer clamps the telescopic drill rod assembly and stirs it down as a whole;

[0029] After the telescopic drill rod assembly descends to the bottom, the driving device is started by controlling the first control signal to drive the inner core rod to rotate, and the telescopic sleeve rod in the telescopic drill rod assembly is driven to stir and descend for the second time;

[0030] After the telescopic sleeve rod descends to the bottom, the driving device is controlled to reverse through the second control signal, driving the inner core rod to reverse and drive the telescopic sleeve rod to rise;

[0031] After the telescopic rod rises to the top, the entire telescopic drill rod assembly is lifted by the mixer;

[0032] Among them, during the secondary stirring and descending process of the telescopic sleeve, the pressure-maintaining unit is controlled to synchronously inject the pressure-maintaining medium, and the injection amount of the pressure-maintaining medium matches the descending speed of the telescopic sleeve to maintain the sealing of the cavity above the telescopic sleeve; during the ascending process of the telescopic sleeve, the pressure-maintaining unit is controlled to synchronously extract the pressure-maintaining medium, and the extraction amount of the pressure-maintaining medium matches the ascending speed of the telescopic sleeve to maintain the sealing in the cavity and prevent cement slurry from entering the cavity above the telescopic sleeve.

[0033] Finally, this embodiment also includes a cement soil mixing pile machine, which includes the above-mentioned telescopic drill rod assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a schematic diagram of the overall structure of the utility model.

[0036] Figure 2 for Figure 1 Enlarged structural diagram at A in the middle.

[0037] Figure 3 It is a schematic diagram of the telescopic sleeve rod in the utility model.

[0038] Figure 4 for Figure 1 Schematic diagram of the transverse cross-sectional structure at the middle internal thread section.

[0039] Reference numerals:

[0040] 1. External drill rod; 2. Internal drill rod; 3. Cavity; 4. External thread; 5. Telescopic sleeve; 6. Internal thread section;

[0041] 7. Grouting unit; 8. Pressure maintaining unit; 9. Driving device;

[0042] 701, grouting sleeve; 702, grouting pipe; 703, grouting hole;

[0043] 801, pressure-maintaining sleeve; 802, conduit; 803, through hole;

[0044] 901, driving motor;

[0045] 10. Sealing ring;

[0046] 11. Connecting airway; 12. Sub-cavity;

[0047] 13. Position limiting convex ring; 14. Position limiting groove;

[0048] 15. Limiting step; 16. Limiting boss;

[0049] 17. Flange. DETAILED DESCRIPTION

[0050] The following embodiments of the technical solution of the utility model are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the utility model, and are therefore only used as examples, and cannot be used to limit the protection scope of the utility model.

[0051] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by technicians in the field to which the utility model belongs.

[0052] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0053] In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present utility model, the meaning of "plurality" is more than two, unless otherwise clearly and specifically limited.

[0054] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0055] Example 1

[0056] like Figure 1-4 As shown, the utility model provides a telescopic drill rod assembly, which includes: an outer drill rod, an inner core rod, a telescopic sleeve rod, a grouting unit and a driving device. In this embodiment, the telescopic drill rod assembly is used in a pile driver for cement-soil mixing piles. The turntable in the pile driver is sleeved on the outside of the outer drill rod to drive the telescopic drill rod assembly to rotate as a whole.

[0057] The outer drill rod is hollow inside, and the outer contour of the outer drill rod is a square that matches the turntable.

[0058] The inner core rod is rotatably connected to the outer drill rod, located in the hollow channel of the outer drill rod, and is coaxially arranged with the outer drill rod. The inner core rod is hollow inside to form a grouting channel, and an annular cavity is formed between the inner core rod and the outer drill rod. The outer peripheral surface of the inner core rod located in the cavity is provided with an external thread, and a driving device is installed on the top of the inner core rod. The output end of the driving device is transmission-connected to the top of the inner core rod through a flange, and the inner core rod is driven to rotate by the driving device; the telescopic sleeve rod is sleeved between the inner core rod and the outer drill rod, and the upper end of the telescopic sleeve rod is provided with an internal thread section that is sealed and matched with the external thread. Specifically, the internal thread section is tightly spirally matched with the external thread on the inner core rod, and the internal thread section is tightly matched with the inner wall of the outer drill rod, so that it has a better sealing effect and minimizes air leakage in the cavity.

[0059] The grouting unit is sealed and sleeved on the inner core rod extending out of the outer drill rod and is communicated with the grouting channel. The grouting unit extracts external cement slurry and the like and injects it downward into the borehole through the hollow grouting channel of the inner core rod.

[0060] It also includes a pressure-maintaining unit, which is sealingly sleeved on the outer drill rod and connected to the cavity, and is used to inject or extract a pressure-maintaining medium into the cavity to maintain the pressure in the cavity within a target range. Specifically, the pressure-maintaining medium can be gas or water. When the telescopic sleeve moves downward, the pressure-maintaining unit injects the pressure-maintaining medium, and when the telescopic sleeve moves upward, the pressure-maintaining unit extracts the pressure-maintaining medium to ensure that the cavity is always at a constant pressure. The movement of the telescopic sleeve and the extraction and injection of the pressure-maintaining unit are realized synchronously, and the amount of pressure-maintaining medium injected or extracted can be calculated according to the volume and automatically controlled by configuring an external control device.

[0061] After the outer drill rod is driven by the external driving device to drill into place, the inner core rod is driven to rotate by the driving device, and the telescopic sleeve can be further extended downward for drilling through the external thread and the internal thread section on the telescopic sleeve. Since the telescopic sleeve and the inner core rod are hollow to form a grouting channel, cement slurry can be injected through the grouting unit. At the same time, the pressure maintaining unit is used to inject gas into the cavity to maintain the pressure, so as to prevent the injected cement slurry from entering the cavity through the gap in the internal thread section on the telescopic sleeve.

[0062] After the telescopic sleeve is extended, cement slurry passing through the grouting channel in the inner core rod is likely to contact the inner wall of the telescopic sleeve. Therefore, in order to prevent the cement slurry on the inner wall of the telescopic sleeve from contacting the external thread in the inner core rod when the telescopic sleeve moves upward, a sealing ring is provided at the bottom of the inner core rod, and the sealing ring is sealed between the inner core rod and the telescopic sleeve.

[0063] The sealing ring can prevent cement slurry passing through the grouting channel from flowing into the threaded gap between the telescopic sleeve and the inner core rod. When the telescopic sleeve moves upward, it blocks the cement slurry adhering to the inner wall of the telescopic sleeve. At the same time, it can prevent the pressurized gas in the cavity from entering the grouting channel from the threaded gap between the inner core rod and the telescopic sleeve to a certain extent.

[0064] A communicating air passage is provided on the internal thread section, one end of the communicating air passage is communicated with the space between the sealing ring and the internal thread section, and the other end is communicated with the cavity.

[0065] The space formed between the sealing ring and the internal thread segment is specifically a secondary cavity, which is specifically located in the space inside the telescopic sleeve rod, outside the inner core rod, and between the sealing ring and the internal thread segment.

[0066] The pressure-maintaining gas is introduced into the auxiliary cavity space between the internal thread section and the sealing ring through the connecting air channel, so that there is a positive pressure in the space, thereby improving the sealing effect of the sealing ring and preventing the slurry in the inner wall of the telescopic sleeve from mixing into the space above the sealing ring.

[0067] A limiting convex ring is arranged on the top of the outer drill rod, and a limiting groove which is sealed and matched with the limiting convex ring is arranged on the inner core rod, so as to limit the axial displacement of the inner core rod.

[0068] The limiting convex ring on the outer drill rod and the limiting groove on the inner core rod can prevent the inner core rod from moving up and down, playing a limiting role, and at the same time can ensure the stability of rotation. A sealed bearing is installed here to achieve a sealing effect, and realize the overall sealing of the cavity together with the internal thread section and sealing ring below.

[0069] A limiting step is arranged at the bottom of the outer drill rod, and a limiting boss matched with the limiting step is arranged at the top of the telescopic sleeve rod.

[0070] The cooperation of the limiting step and the limiting boss limits the downward limit position of the telescopic sleeve rod, thereby preventing the telescopic sleeve rod from slipping off the external thread of the inner core rod and falling off.

[0071] It also includes an electric control unit, and a first sensor and a second sensor connected to the electric control unit. The electric control unit can be implemented by a PLC or a single-chip microcomputer and a peripheral circuit, and is used for automatic control according to the collected signal. The first sensor and the second sensor are not shown in the figure. Specifically, the first sensor sends a first control signal after the outer drill rod sinks to the bottom to control the drive device to drive the inner core rod; the second sensor is arranged on the limit step, and the limit boss sends a second control signal after contacting the second sensor to control the drive device to reverse and drive the inner core rod

[0072] Through the first sensor, the second sensor and the electric control unit, the automatic control of the rotational descent and rotational retraction of the telescopic sleeve is realized, and the intelligent control is realized as a whole.

[0073] In this embodiment, the grouting unit includes a grouting sleeve and a grouting pipe connected to the grouting sleeve. The inner core rod extending from the outer drill rod is circumferentially spaced and provided with a plurality of grouting holes connected to the grouting channel. The grouting sleeve is sealed and covered on the outside of the grouting hole. The grouting sleeve is rotatably sleeved on the inner core rod. When the inner core rod rotates, it does not affect the injection of cement slurry or other slurries from the grouting hole. To ensure the sealing effect, the upper and lower ends of the grouting sleeve are sealed and connected by means of sealing bearings, sealing rings, etc.

[0074] Similarly, the pressure maintaining unit includes a pressure maintaining sleeve and a conduit connected to the pressure maintaining sleeve. The pressure maintaining sleeve is sleeved on the outer drill rod through a sealing ring, and the pressure maintaining sleeve is rotatably connected to the outer drill rod. Specifically, the cross-section of the connection between the outer drill rod and the pressure maintaining sleeve is circular, which is convenient for the rotation of the outer drill rod. A plurality of through holes connected to the interior of the pressure maintaining sleeve are opened circumferentially on the outer drill rod. In this embodiment, the pressure maintaining medium is realized by gas, which enters the cavity through the through hole, and part of the gas enters the sub-cavity through the connecting airway on the internal threaded section to enhance the sealing effect of the sealing ring.

[0075] In this embodiment, the driving device includes a driving motor and a conductive slip ring electrically connected to the driving motor. The output end of the driving motor is connected to the inner core rod. The conductive slip ring is not shown in the figure and is specifically arranged on the same axial line as the inner core rod. When the outer drill rod rotates as a whole, the driving motor rotates therewith. At this time, the conductive slip ring can achieve a better conductive effect during the rotation process.

[0076] Example 2

[0077] This embodiment discloses a method for using a telescopic drill rod assembly, wherein the telescopic drill rod assembly is the telescopic drill rod assembly in Embodiment 1, and the method for using the telescopic drill rod assembly comprises the following steps:

[0078] After the construction preparation is completed and the pile position is determined, the telescopic drill rod assembly is clamped by a mixer and stirred and lowered as a whole. The outer drill rod in the telescopic drill rod assembly is a square drill rod, which is clamped and driven to rotate and descend by the mechanism in the mixer;

[0079] After the telescopic drill rod assembly descends to the bottom, the first control signal is triggered, and the driving device is started by the first control signal to drive the inner core rod to rotate, and drive the telescopic sleeve rod in the telescopic drill rod assembly to stir and descend for the second time;

[0080] After the telescopic sleeve rod descends to the bottom, the second control signal is triggered, and the second control signal controls the driving device to reverse, driving the inner core rod to reverse, and driving the telescopic sleeve rod to rise;

[0081] After the telescopic sleeve rod rises to the top, the telescopic drill rod assembly is lifted by the mixer to be separated from the borehole as a whole.

[0082] During the secondary stirring and descending process of the telescopic sleeve, the pressure-maintaining unit is controlled to synchronously inject the pressure-maintaining medium, and the injection amount of the pressure-maintaining medium matches the descending speed of the telescopic sleeve to maintain the sealing of the cavity above the telescopic sleeve; during the ascending process of the telescopic sleeve, the pressure-maintaining unit is controlled to synchronously extract the pressure-maintaining medium, and the extraction amount of the pressure-maintaining medium matches the ascending speed of the telescopic sleeve to maintain the sealing in the cavity and prevent cement slurry from entering the cavity above the telescopic sleeve. The amount of pressure-maintaining medium extracted or injected is calibrated in advance by the electronic control unit according to the rotation speed, so that the cavity above the telescopic sleeve always maintains a positive pressure, so that the sealing effect of the cavity is better, and cement slurry in the inner core rod is prevented from entering the cavity.

[0083] Example 3

[0084] In the present embodiment, a cement-soil mixing pile machine is disclosed, which includes the telescopic drill rod assembly in Embodiment 1. The telescopic drill rod assembly is installed on the driving end of the cement-soil mixing pile machine, and is clamped on the outside of the telescopic drill rod assembly by a turntable or other device of the cement-soil mixing pile machine, driving the telescopic drill rod assembly to perform the first rotation. After it is in place, the telescopic sleeve rod therein is further rotated by the driving device.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A telescopic drill rod assembly, characterized in that: include: An outer drill rod, wherein the outer drill rod is hollow inside; An inner core rod is rotatably connected to the outer drill rod, the inner core rod is hollow inside to form a grouting channel, an annular cavity is formed between the inner core rod and the outer drill rod, and an outer thread is arranged on the outer peripheral surface of the inner core rod located in the cavity; A telescopic sleeve rod, the telescopic sleeve rod is sleeved between the inner core rod and the outer drill rod, and the upper end of the telescopic sleeve rod is provided with an internal thread section that is sealed and matched with the external thread; A grouting unit, which is sealed and sleeved on the inner core rod extending out of the outer drill rod and is communicated with the grouting channel; The output end of the driving device is connected to the end of the inner core rod through a flange.

2. The telescopic drill rod assembly according to claim 1, characterized in that: It also includes a pressure-maintaining unit, which is sealed and sleeved on the outer drill rod and communicated with the cavity, and is used to inject or extract a pressure-maintaining medium into the cavity to maintain the pressure in the cavity within a target range.

3. The telescopic drill rod assembly according to claim 2, characterized in that: A sealing ring is provided at the bottom of the inner core rod, and the sealing ring is sealed between the inner core rod and the telescopic sleeve rod.

4. The telescopic drill rod assembly according to claim 3, characterized in that: A communicating air passage is provided on the internal thread section, one end of the communicating air passage is communicated with the space between the sealing ring and the internal thread section, and the other end is communicated with the cavity.

5. The telescopic drill rod assembly according to claim 3, characterized in that: A limiting convex ring is arranged on the top of the outer drill rod, and a limiting groove which is sealed and matched with the limiting convex ring is arranged on the inner core rod, so as to limit the axial displacement of the inner core rod; A limiting step is arranged at the bottom of the outer drill rod, and a limiting boss matched with the limiting step is arranged at the top of the telescopic sleeve rod.

6. The telescopic drill rod assembly according to claim 5, characterized in that: It also includes an electric control unit, and a first sensor and a second sensor connected to the electric control unit, wherein the first sensor sends a first control signal after the outer drill rod sinks to the bottom to control the driving device to drive the inner core rod; The second sensor is arranged on the limiting step, and the limiting boss sends out a second control signal after contacting the second sensor, so as to control the driving device to reversely drive the inner core rod.

7. The telescopic drill rod assembly according to claim 2, characterized in that: The grouting unit comprises a grouting sleeve and a grouting pipe connected to the grouting sleeve, the inner core rod extending from the outer drill rod is provided with a plurality of grouting holes connected to the grouting channel at intervals in the circumferential direction, and the grouting sleeve is sealed and covered on the outside of the grouting hole; The pressure-maintaining unit comprises a pressure-maintaining sleeve and a conduit connected to the pressure-maintaining sleeve. The pressure-maintaining sleeve is sleeved on the outer drill rod via a sealing ring. The outer drill rod is circumferentially provided with a plurality of through holes connected to the interior of the pressure-maintaining sleeve.

8. The telescopic drill rod assembly according to claim 1, characterized in that: The driving device comprises a driving motor and a conductive slip ring electrically connected to the driving motor, and an output end of the driving motor is connected to the inner core rod.

9. A cement soil mixing pile machine, characterized in that: It comprises a telescopic drill rod assembly as described in any one of claims 1-8.

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