A method for grading and escaping control of a screw conveyor for a shield cutting steel wall

Abstract

The application discloses a kind of shield cutting type steel ground wall spiral conveyer grading escape control method, comprising: in the wall grinding phase, the output torque upper limit of hydraulic motor is limited to the preset percentage of rated torque, to reserve the reserve torque consisting of the remaining percentage;When monitoring is stuck, under the condition that reserve torque is not called, the composite escape operation of alternating positive and negative rotation and axial reciprocating telescoping is executed;If the stuck is not removed, the output torque upper limit is released to the rated torque to call all reserve torque, and the composite escape operation is executed again under the condition of full torque.The application forms progressive levels from gentle release to strong escape by the grading limit and release of torque output, avoids the problem that steel fragments are further pressed and embedded to the locked deep place in the traditional method by always forcibly escaping with rated torque, and considers escape efficiency and equipment structure protection.

Description

Technical Field

[0001] This invention relates to the field of tunnel shield construction technology, and in particular to a graded slack-free control method for a screw conveyor used in shield tunneling for cutting steel diaphragm walls. Background Technology

[0002] With the increasing density of urban rail transit networks, the number of new tunnels passing under existing operating stations is growing. Direct tunneling using shield tunneling to cut through the reinforced concrete diaphragm walls of existing stations has become an advanced method replacing traditional mining methods for clearing obstacles, offering advantages such as simplified procedures and shorter construction periods. In such projects, the screw conveyor plays a crucial role in transporting the excavated soil from the soil bin to the downstream facilities; its continuous and stable operation is a fundamental prerequisite for the successful tunneling of the shield through the diaphragm wall.

[0003] When the object being cut is a diaphragm wall containing H-beam joints, the fragments formed after the steel section is cut by the cutter head are significantly different in shape, size, and rigidity from conventional steel bars or concrete fragments. These steel fragments are irregularly shaped sheets or strips and are not easily broken further by the helical blades. During transport within the screw conveyor cylinder, their movement is random. This randomness means that the steel fragments may unexpectedly interfere with the helical blades or cylinder wall at any time and at any location. Once the steel fragments wedge or bridge in the narrow gap between the helical blades and the cylinder wall, the rotational resistance of the helical shaft will increase sharply, and the conveying function will be lost.

[0004] To address the jamming problem of screw conveyors during slag discharge, various methods have been developed, including forward and reverse operation, axial extension and retraction, and manual cleaning of inspection ports. However, these methods are used independently as post-jamming measures, without a progressive logical connection based on the severity of the jamming. Under normal operating conditions without structural steel fragments, jamming is usually sporadic and mild, and operators can restore operation with a single measure. However, when structural steel fragments become the jamming medium, their geometric irregularity and high rigidity make the locking effect between them and the screw blades more stubborn, significantly reducing the effectiveness of single measures. At this point, operators face a dilemma: repeatedly attempting to untangle the material with the rated torque may cause the structural steel fragments to become more deeply embedded, worsening the jamming; abandoning mechanical untangling too early and resorting to manual clearing will result in frequent window opening operations, significantly reducing construction efficiency and increasing operational risks. Therefore, how to establish a systematic handling logic that balances extrication efficiency and equipment protection in the case of jamming caused by steel fragments has become a key technical bottleneck restricting the feasibility of shield tunneling projects that directly cut steel diaphragm walls. Summary of the Invention

[0005] In view of the above problems, a staged scrambling control method for screw conveyors used in shield tunneling steel diaphragm walls is proposed to overcome or at least partially solve these problems. Specifically: A method for staged slack-free control of a screw conveyor used in shield tunneling for cutting steel diaphragm walls, wherein the screw conveyor is driven by a hydraulic motor and equipped with a telescopic cylinder that drives the screw shaft to extend and retract axially, the method comprising: During the wall-grinding stage of the shield cutterhead cutting the diaphragm wall, the upper limit of the output torque of the hydraulic motor is limited to a preset percentage of its rated torque in order to reserve a reserve torque consisting of the remaining percentage of the rated torque. When jamming of the screw conveyor is detected, the first unblocking operation is performed. Without calling up the reserve torque, the hydraulic motor is controlled to alternately output positive and negative torque, and the telescopic cylinder is simultaneously controlled to drive the screw shaft to extend and retract axially. If the jamming is not relieved after the first escape operation, the second escape operation is performed. The upper limit of the hydraulic motor's output torque is released from the preset percentage to the rated torque to call up all the reserve torque. Under the condition of calling up the reserve torque, the alternating output of positive and negative torque and the axial extension and retraction of the screw shaft are performed again.

[0006] Optionally, the preset percentage is determined based on the ratio of the average steady-state operating torque of the screw conveyor before jamming occurs in the wall grinding stage to the rated torque of the hydraulic motor, so that the difference between the preset percentage and the average steady-state operating torque constitutes the normal available torque window in the wall grinding stage, and the reserve torque is superimposed on the normal available torque window.

[0007] Optionally, in the first escape operation, controlling the hydraulic motor to alternately output positive and negative torque is specifically as follows: within one alternation cycle, first control the hydraulic motor to output positive torque to drive the screw shaft to rotate positively for the first number of revolutions. After reaching the first number of revolutions, immediately switch the torque direction and control the hydraulic motor to output negative torque to drive the screw shaft to rotate negatively for the second number of revolutions. The first number of revolutions and the second number of revolutions are equal. The alternation cycle is repeated at least once.

[0008] Optionally, the first number of laps can be between 3 and 5 laps, and the second number of laps can be between 3 and 5 laps.

[0009] Optionally, in the first escape operation, controlling the telescopic cylinder to drive the spiral shaft to extend and retract along the axial direction specifically involves controlling the telescopic cylinder to drive the spiral shaft to move a preset distance from its initial axial position in the first direction, and immediately moving it in the opposite direction a preset distance after reaching the preset distance, and then moving it in the opposite direction a preset distance again after reaching the preset distance, so as to form a reciprocating motion around the initial axial position; wherein, the moving speed of the spiral shaft in the reciprocating motion does not exceed a preset speed threshold.

[0010] Optionally, the preset speed threshold is 10 mm / s.

[0011] Optionally, during the execution of the first and second escape operations, the tunnel boring machine remains in a suspended state to remove the tunnel boring machine's propulsion force from the force system of the screw conveyor; only when the torque and speed of the screw shaft are both monitored to return to the steady-state operating range of the wall grinding stage, and the duration exceeds the preset stable duration, it is determined that the jam has been released, and the tunnel boring machine resumes propulsion.

[0012] Optionally, the judgment condition for detecting jamming in the screw conveyor is as follows: the real-time torque value of the hydraulic motor increases by more than a preset torque increase threshold within a continuous first preset time period, and the real-time speed of the screw shaft is continuously lower than a preset speed lower limit threshold within a continuous second preset time period, and the increase in the real-time torque value is a non-pulse increment, so as to eliminate the torque pulse interference generated when the slag block passes through the screw blade instantaneously.

[0013] Optionally, if the jamming is still not resolved after the second unblocking operation, a third unblocking operation is performed. The third unblocking operation includes: stopping the rotation and extension of the screw shaft, injecting liquid polyurethane into the preset injection port at the bottom of the screw conveyor cylinder, with the injection amount being such that the liquid polyurethane forms a sealing body with a thickness not less than the preset sealing thickness in the space between the slag outlet gate of the screw conveyor and the bottom of the cylinder; maintaining stable internal pressure of the screw conveyor during the curing process of the liquid polyurethane; and opening the inspection port located downstream of the sealing body for manual clearing after curing.

[0014] Optionally, if the jamming is not resolved after the third escape operation, or if the pressure in the soil chamber continues to decrease during the period when the screw shaft stops rotating and the rate of decrease exceeds the preset rate threshold, the jamming location is determined to be the interface between the soil chamber and the screw conveyor, and the fourth escape operation is performed. The fourth escape operation includes: under normal pressure open conditions, the screw shaft section on the side of the soil chamber is retracted into the cylinder by the telescopic cylinder, so that an open space without the screw shaft section is occupied at the interface between the soil chamber and the cylinder, and personnel enter the soil chamber through the open space to manually clear the obstruction.

[0015] This invention limits the upper limit of the hydraulic motor's output torque to a preset percentage of the rated torque and reserves a reserve torque during the wall grinding stage. This creates a progressive hierarchy in the extrication operation after jamming: "extrication without using the reserve torque" and "extrication using all the reserve torque." In the first extrication operation, because the combined extrication action of forward and reverse rotation and axial extension is performed with a torque output below the rated value, the mechanical compressive force on the steel fragments is controlled at a low level. This avoids the risk of the steel fragments being further pressed into the deep gaps between the blades when forcibly extricated with the rated torque in traditional methods. When the first extrication operation fails, the release of the reserve torque allows the second extrication operation to apply a stronger loosening force to the jammed object under full torque conditions. At this time, the jammed object has not yet experienced load compression, and its locking state with the blades is still reversible, thereby increasing the success rate of the second extrication operation. This method integrates graded control of torque output with progressive logic of the detachment operation, so that the handling process of the specific working condition of stuck steel fragments has a clear hierarchy from gentle loosening to powerful detachment, taking into account both the detachment efficiency and the structural protection of the screw conveyor. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a graded slack-free control method for a screw conveyor used in shield tunneling steel diaphragm wall construction, provided by an embodiment of the present invention. Figure 2 This is a torque-time diagram of a graded entrapment control method provided in an embodiment of the present invention; Figure 3 This is a multi-level progressive escape decision logic diagram provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Reference Figures 1 to 3 This invention provides a method for graded scrambling control of a screw conveyor used in shield tunneling steel diaphragm wall cutting, which may specifically include: A method for staged slack-free control of a screw conveyor used in shield tunneling for cutting steel diaphragm walls, wherein the screw conveyor is driven by a hydraulic motor and equipped with a telescopic cylinder that drives the screw shaft to extend and retract axially, the method comprising: During the wall-grinding stage of the shield cutterhead cutting the diaphragm wall, the upper limit of the output torque of the hydraulic motor is limited to a preset percentage of its rated torque in order to reserve a reserve torque consisting of the remaining percentage of the rated torque. When jamming of the screw conveyor is detected, the first unblocking operation is performed. Without calling up the reserve torque, the hydraulic motor is controlled to alternately output positive and negative torque, and the telescopic cylinder is simultaneously controlled to drive the screw shaft to extend and retract axially. If the jamming is not relieved after the first escape operation, the second escape operation is performed. The upper limit of the hydraulic motor's output torque is released from the preset percentage to the rated torque to call up all the reserve torque. Under the condition of calling up the reserve torque, the alternating output of positive and negative torque and the axial extension and retraction of the screw shaft are performed again.

[0020] In actual engineering, during the wall-grinding stage of the shield tunneling machine cutting the steel diaphragm wall, the shield cutterhead rotates and cuts the diaphragm wall containing H-beam joints. The concrete strength grade of the diaphragm wall is C35, and the specifications of the H-beam joints are: web height 650mm, flange width 350mm, plate thickness 10mm, and steel material Q235B. The steel fragments produced by the cutterhead cutting are irregularly shaped flakes or strips, with a maximum size of several hundred millimeters. They enter the soil chamber through the cutterhead opening along with the reinforcing bars and concrete fragments. Foam solution and bentonite slurry are continuously injected into the soil chamber through injection pipelines to improve the slag. The volume ratio of foam concentrate to water in the foam solution is 2% to 3%, and the mass ratio of bentonite to water in the bentonite slurry is 8% to 12%. The improved slag is in a fluid plastic state, which is beneficial for the screw conveyor to discharge it.

[0021] In an embodiment of the invention, the screw conveyor is a shafted screw conveyor, driven by a hydraulic motor through a reducer to rotate the screw shaft. The hydraulic motor is a variable displacement slant-shaft piston motor, with a rated torque equal to the maximum torque that the motor can continuously output under rated working pressure. The reduction ratio of the reducer is determined based on the ratio of the rated speed of the hydraulic motor to the design speed of the screw shaft. The screw shaft is composed of multiple shaft sections connected by flanges, and the screw blades are welded and fixed along the spiral line of the outer edge of the screw shaft. The radial clearance between the outer edge of the screw blades and the inner wall of the cylinder is 5mm on one side. A 5mm thick wear-resistant layer is overlaid on the surface of the screw blades and the shaft, and the wear-resistant layer material is an iron-based wear-resistant alloy. The front section of the screw blades, namely the three blades near the soil chamber side, has multiple tungsten carbide wear-resistant alloy blocks welded around its periphery, with the alloy blocks spaced apart circumferentially along the outer edge of the blades.

[0022] The screw conveyor is also equipped with a telescopic cylinder to drive the screw shaft to extend and retract along its axial direction. The piston rod end of the telescopic cylinder is connected to the non-driving end of the screw shaft via a thrust bearing, and the cylinder body is fixed to the front bulkhead of the tunnel boring machine. The thrust bearing bears the axial force generated when the screw shaft rotates and decouples the rotational motion from the linear motion of the piston rod of the telescopic cylinder, so that the telescopic cylinder only bears the axial force and does not rotate with the screw shaft. The telescopic cylinder has a stroke of 800mm, is supplied with oil by an independent hydraulic circuit, and controls the extension and retraction direction through a three-position four-way solenoid directional valve and the extension and retraction speed through a speed control valve.

[0023] Before the wall-grinding operation begins, operators set the upper limit of the hydraulic motor's output torque on the control panel in the tunnel boring machine's main control room. The control panel communicates with the hydraulic pump's displacement controller via a CAN bus. The displacement controller adjusts the swashplate angle of the hydraulic pump according to the set upper limit torque value, thereby limiting the maximum pressure of the hydraulic oil output to the hydraulic motor and thus restricting the hydraulic motor's output torque to a preset percentage of its rated torque. This preset percentage is determined by the ratio of the average steady-state operating torque of the screw conveyor before jamming during the wall-grinding stage to the rated torque of the hydraulic motor. The average steady-state operating torque is obtained as follows: after the tunnel boring machine cutterhead begins cutting the diaphragm wall and before the first jamming event is detected, the control system continuously collects the real-time torque values ​​of the hydraulic motor at a set sampling frequency, forming a torque data sequence. The arithmetic mean of this torque data sequence is taken as the average steady-state operating torque. The torque value corresponding to the preset percentage is greater than the average steady-state operating torque; the difference between the two constitutes the normal available torque window during the wall-grinding stage, and the reserve torque is superimposed on this window.

[0024] During the wall-grinding stage, the tunnel boring machine (TBM) control system collects real-time data from the pressure sensor at the hydraulic motor inlet and the speed sensor at the auger shaft at a fixed sampling period. The pressure sensor's range is 1.5 times the rated working pressure of the hydraulic motor, and the speed sensor is a Hall effect sensor installed at the detection gear on the output shaft side of the reducer. The control system converts the pressure value into a torque value based on the hydraulic motor's displacement parameters to obtain the real-time torque value.

[0025] Upon detecting a jam, the control system automatically pauses the propulsion action of the tunnel boring machine's hydraulic cylinders and executes the first escape operation. This first escape operation is performed without utilizing reserve torque; that is, the upper limit of the hydraulic motor's output torque remains limited to a preset percentage of the rated torque. The core of this first escape operation is to synchronize the alternating forward and reverse rotation of the auger shaft with its axial reciprocating extension and retraction, and to perform a brief unloading at the moment of each torque direction change.

[0026] The specific execution method of alternating forward and reverse rotation is as follows: An alternation cycle is defined. Within this cycle, the control system first uses the hydraulic pump's displacement controller to output forward torque to drive the helical shaft to rotate forward a preset number of times. When the cumulative number of rotations reaches the set number, a torque direction switch is triggered. After the switch is triggered, the control system does not immediately establish reverse torque but first performs a brief unloading: the hydraulic motor's directional valve is moved from the forward working position to the floating position, connecting both the hydraulic motor's working port and return port to the oil tank simultaneously, placing the hydraulic motor in a floating state. At this time, the hydraulic motor is not constrained by the hydraulic pump's oil supply, and the helical shaft and hydraulic motor continue to rotate under inertia, draining the residual pressure oil in the working oil circuit into the oil tank. The pressure at the hydraulic motor's working port rapidly decreases within 0.1s to 0.2s. When the pressure sensor detects that the working port pressure has dropped to the corresponding preset unloading value, the control system switches the directional valve from the floating position to the reverse working position, the hydraulic pump resumes supplying oil to the hydraulic motor, establishing reverse torque, and driving the helical shaft to rotate in the opposite direction for the same number of times. After rotating in the reverse direction to the set number of revolutions, the torque direction switch is triggered again, repeating the above process of brief unloading before establishing positive torque. This cycle continues. The preset unloading value is 10% to 20% of the current torque limit, and the preset unloading duration is 0.3s to 0.5s.

[0027] The physical mechanism of brief unloading is as follows: Under the continuous compression of the spiral blades, the surface of the steel fragments forms a contact surface with the front face of the spiral blades. This contact surface bears both normal compressive force and tangential friction under torque. When the product of the normal force and the coefficient of friction—the maximum static friction—is greater than the driving force exerted by the spiral blades on the steel fragments along the tangential direction of the contact surface, the contact surface is in a frictional self-locking state, and the steel fragments cannot be pushed by the spiral blades. If unloading is not performed during torque direction switching and reverse loading is performed directly, the normal force on the contact surface remains at a high level. The tangential driving force of the reverse torque is opposite to that of the forward torque, and initially insufficient to overcome the remaining maximum static friction, the steel fragments do not displace. As the reverse torque continues to increase, the tangential driving force exceeds the maximum static friction, and the steel fragments suddenly slide, potentially entering a deeper position in the gap between the spiral blades and the cylinder wall, i.e., secondary jamming occurs. Brief unloading reduces the torque to a preset unloading value at the moment of switching, significantly decreasing the normal compressive force on the contact surface, allowing elastic deformation to recover, and lowering the normal force on the contact surface to a level insufficient to maintain the self-locking state, thus releasing the self-locking state. Under the low contact stress conditions after the self-locking state is released, the hydraulic motor begins to build up reverse torque, and the helical blades act on the steel fragments with a gradually increasing tangential driving force. The steel fragments are smoothly pushed out of the jammed position without being initially locked, achieving release.

[0028] Synchronous with the alternating forward and reverse rotation is the axial reciprocating extension and retraction of the screw shaft. The control telescopic cylinder drives the screw shaft from its initial axial position to move a preset distance towards the soil chamber side. Upon reaching this distance, the stroke sensor of the telescopic cylinder detects a position signal, triggering axial reversal, moving the screw shaft to move the same preset distance towards the slag outlet side. Upon reaching this preset distance, axial reversal is triggered again, and this cycle repeats. The duration of each axial reversal is controlled to at least partially overlap with the brief unloading period during torque direction switching. That is, the timing of the telescopic cylinder's reversing valve switching and the timing of the hydraulic motor's reversing valve switching to the floating position are coordinated by the control system, allowing the screw shaft to complete the axial movement direction change during the low contact stress period when the torque is unloaded. During this overlapping period, the contact force between the screw blades and the steel fragments is low, and the axial friction force that the telescopic cylinder needs to overcome to drive the screw shaft axial reversal is correspondingly reduced. Therefore, the peak load of the telescopic cylinder is lower than the axial reversal load under non-unloaded conditions.

[0029] After the first extrication operation is completed, the control system continues to monitor the torque and speed of the screw shaft. If, within the preset monitoring time, the torque and speed of the screw shaft both return to the steady-state operating range of the wall-grinding stage, and the duration exceeds the preset stabilization time, it is determined that the jam has been released, the control system automatically resumes the propulsion action of the shield tunneling cylinder, and the screw conveyor resumes normal slag discharge operation.

[0030] If, after the first escape operation is completed, the torque and speed of the auger shaft do not return to the steady-state operating range within the preset monitoring time, it is determined that the first escape operation failed to remove the jam, and the control system automatically enters the second escape operation. The second escape operation releases the upper limit of the hydraulic motor's output torque from a preset percentage to the rated torque, i.e., it calls up all the reserve torque. Specifically, the control system sends a command to the hydraulic pump's displacement controller, modifying the torque limit parameter of the displacement controller from the value corresponding to the preset percentage to the value corresponding to the rated torque. The swashplate angle of the hydraulic pump is adjusted accordingly, restoring the maximum pressure that the hydraulic pump can output to the hydraulic motor to the rated working pressure, and restoring the upper limit of the hydraulic motor's output torque to the rated torque. Under the condition of calling up all the reserve torque, the combination operation of alternating forward and reverse rotation and axial reciprocating extension is executed again, with a brief unloading performed each time the torque direction changes. During the second escape operation, the hydraulic motor can output a larger torque peak within the alternating cycle, and the driving force of the auger blades acting on the steel fragments is significantly increased. Meanwhile, since the reserve torque was not used in the first escape operation, the steel fragments were not overloaded and squeezed during the previous escape process, and the locking state was still reversible. Therefore, the increased escape torque in the second escape operation can effectively act on the stuck objects that have not yet been compressed and locked.

[0031] During the first and second escape operations, the tunnel boring machine's propulsion cylinders remain in a state of suspended oil supply, and the hydraulic locks of the propulsion cylinders remain closed. This removes the propulsion force from the screw conveyor's load-bearing system, preventing the propulsion force from being transmitted through the soil chamber to the screw conveyor inlet and exacerbating the jamming or interfering with the escape operation. The screw conveyor cylinder has multiple openable inspection ports spaced axially, and the muck outlet is equipped with a double-stage lower muck gate.

[0032] The preset percentage is determined based on the ratio of the average steady-state operating torque of the screw conveyor before jamming occurs in the wall grinding stage to the rated torque of the hydraulic motor. This ensures that the difference between the preset percentage and the average steady-state operating torque constitutes the normal available torque window in the wall grinding stage, and the reserve torque is superimposed on the normal available torque window.

[0033] In one or more embodiments of the present invention, in the first escape operation, controlling the hydraulic motor to alternately output positive torque and reverse torque specifically means: within one alternation cycle, first controlling the hydraulic motor to output positive torque to drive the spiral shaft to rotate positively for a first number of revolutions, and after reaching the first number of revolutions, immediately switching the torque direction and controlling the hydraulic motor to output reverse torque to drive the spiral shaft to rotate in the opposite direction for a second number of revolutions, the first number of revolutions and the second number of revolutions being equal, and the alternation cycle being repeated at least once.

[0034] The first escape operation involves the sequential management of alternating torque outputs by the hydraulic motor, which alternately outputs positive and negative torque. These alternating cycles are not simple repetitions but rather represent a progressive relationship in torque state. Before the first alternating cycle begins, the hydraulic motor's output torque is still limited to a preset percentage, and the reserve torque has not yet been utilized. Upon detecting a jamming signal, the control system records the real-time torque value of the hydraulic motor as the initial torque reference value for the escape operation, and then initiates the first alternating cycle.

[0035] During the forward rotation phase of the first alternating cycle, if the steel fragments are pushed out of the stuck position under the action of forward torque during the first number of forward rotations of the auger shaft, the rotational resistance of the auger shaft will decrease, the real-time torque value of the hydraulic motor will drop back to near the average steady-state operating torque, the speed will return to the design speed range, the control system will determine that the stuck position has been released, and will no longer execute the remaining unloading and reverse rotation steps in this alternating cycle, directly ending the first escape operation and resuming shield tunneling.

[0036] If the forward rotation phase of the first alternating cycle fails to loosen the steel fragments, a brief unloading is performed after the first revolution. During the process of establishing reverse torque after unloading, the direction of the helical blades acting on the steel fragments is opposite to that during forward rotation. After being pushed forward by the helical blades during the forward rotation phase, the front end of the steel fragment may have become embedded in the narrow gap between the helical blades and the cylinder wall, while the rear end is separated from the rear blades by a certain distance. Reverse rotation causes the helical blades to contact and apply thrust from the rear end of the steel fragment, pushing in the opposite direction to the original embedding direction, thereby pulling the steel fragment out of the gap.

[0037] If the jamming persists after the first alternating cycle, the control system enters the second alternating cycle. In the second alternating cycle, the initial conditions for forward rotation differ from the first: after the unloading and reverse rotation of the first cycle, the spatial orientation of the steel fragments within the cylinder has changed, and their contact points with the auger blades and cylinder wall may have shifted. The forward rotation in the second cycle applies force from the new contact position, creating torques in different directions on the steel fragments, increasing the likelihood of loosening. The alternating cycle can be repeated until the control system detects that the torque and speed have returned to the steady-state operating range, or automatically switches to the second unblocking operation after reaching the preset maximum number of repetitions. The preset maximum number of repetitions is typically set to three to five times to avoid prolonged ineffective operation under low torque conditions, which could affect construction efficiency.

[0038] In a preferred embodiment of the present invention, the first number of revolutions is in the range of 3 to 5 revolutions, and the second number of revolutions is in the range of 3 to 5 revolutions.

[0039] In the first escape operation, the first and second laps both range from 3 to 5 laps. This range is determined based on the following two constraints.

[0040] On the one hand, the continuous rotation of the helical shaft in a single direction imposes an upper limit on the accumulation of frictional heat between the steel fragments and the helical blades. When the hydraulic motor outputs positive or negative torque to drive the helical shaft to rotate in a single direction, if the steel fragments are stuck, the rake face of the helical blades and the surface of the steel fragments are in sliding frictional contact. Under the mixed lubrication conditions of bentonite slurry and foam solution, the coefficient of sliding friction is approximately 0.08 to 0.12. The frictional power is determined by the product of the normal force of the contact surface, the coefficient of friction, and the relative sliding speed. The frictional work is converted into heat, causing the local temperature of the contact surface to rise. When the number of rotations in one direction exceeds 5, the accumulated time of continuous friction on the contact surface may cause the local temperature to reach the tempering softening temperature range of the Q235B material of the steel fragments. The surface hardness of the material near the contact surface decreases, the tendency of adhesive wear increases, and the amount of material transferred from the surface of the steel fragments to the surface of the helical blades increases, i.e., adhesive wear occurs. Adhesive wear causes material transfer, which weakens the structural integrity of the steel fragments and increases the surface roughness of the screw blades. This increases the frictional resistance between the blades and the slag during subsequent slag discharge, which is detrimental to the long-term stable operation of the screw conveyor. Therefore, the upper limit of unidirectional rotation is set at 5 revolutions.

[0041] On the other hand, there is a lower limit constraint on the minimum stroke required for the helical blades to effectively loosen the steel fragments. During alternating forward and reverse rotations, the loosening of the steel fragments depends on the displacement gained during rotation in a single direction. The distance the steel fragments travel along the helical path per rotation corresponds to the lead of the helical blades. When there are fewer than three rotations in one direction, the cumulative displacement of the steel fragments along the helical path under the influence of the slag is small. Due to the combined effects of the plastic deformation buffering effect of the slag and the frictional force of the cylinder wall, the actual effective displacement of the steel fragments may be insufficient to disengage them from their original jammed position. When three rotations in one direction are achieved, the cumulative forward distance of the steel fragments has moved them at least as a whole through the length of a full pitch, completely disengaging them from the helical blades and cylinder wall surface at the initial jammed position, thus changing the geometric constraints of the jammed state. Simultaneously, the three cumulative rotations also allow sufficient time for the torque output of the hydraulic motor to stabilize in that direction, enabling the control system to obtain accurate torque data on the force state of the jammed object in that direction, providing reference information for subsequent unloading and reverse operation. Therefore, the lower limit for the number of rotations in one direction is set to 3.

[0042] Within the range of 3 to 5 revolutions, the accumulated frictional heat exerted by the helical blades on the steel fragments during each unidirectional rotation is controlled within the adhesive wear threshold. At the same time, the steel fragments obtain sufficient displacement to fully disengage from the stuck contact surface, and both constraints are satisfied.

[0043] The preset unloading value is 10% to 20% of the current torque limit. This range is determined by the pressure decay characteristics of the hydraulic system and the self-locking release conditions of the steel fragment contact surface. During unloading, the hydraulic motor's directional valve is in the floating position, the working oil circuit is connected to the oil tank, and the discharge rate of residual pressure oil is determined by the equivalent hydraulic resistance of the unloading circuit and the volume of the hydraulic motor's working chamber. For conventional shield tunnel screw conveyor hydraulic systems, the equivalent diameter of the unloading circuit is typically 10mm to 16mm, and the single-chamber volume of the hydraulic motor is determined by the displacement and swashplate angle. In the floating state, the time required for the pressure at the working port to decay from the pressure level corresponding to the current torque limit to 10% to 20% of that pressure level is approximately 0.15s to 0.25s. If the preset unloading value is set to 10% to 20% of the current torque limit, the time from the start of unloading to reaching the target unloading value is 0.15s to 0.25s. This time falls within the range of 0.1s to 0.3s required for the elastic recovery of the steel fragments. Due to the hysteresis effect of the hydraulic system, when the pressure sensor detects that the pressure has reached the preset unloading value, the actual stress level of the contact surface has already decreased further, and the normal force of the contact surface has dropped below the critical value that is insufficient to maintain the frictional self-locking state. If the preset unloading value is set to a higher proportion of the current torque limit, such as above 30%, the residual torque after unloading will still be large, the normal force of the contact surface will not be sufficiently reduced, the frictional self-locking state may not be completely broken, and the steel fragments will still be in a partially locked state when the reverse torque is established, resulting in a decrease in the escape effect. If the preset unloading value is set to a lower percentage of the current torque limit value, such as less than 5%, the unloading degree is too deep, the screw shaft almost completely stops rotating, and the slag inside the cylinder quickly settles and accumulates in the gap between the screw blades after losing agitation. When re-establishing torque, it is necessary to overcome the starting resistance of the slag after it has settled, and the unloading time is correspondingly extended, reducing the efficiency of the extrication operation.

[0044] The preset unloading time is 0.3s to 0.5s, determined by the measured data of the time required for elastic strain energy release, the pressure decay time of the unloading circuit, and the constraint of the soil settling time. After the unloading operation is triggered, the control system starts the timer simultaneously with the switching valve to the floating position. When the timer reaches the preset unloading time, regardless of whether the pressure sensor has detected a pressure drop to the preset unloading value, the control system forcibly ends the unloading state and switches the switching valve to the reverse working position to avoid the unloading time exceeding the safe range. The lower limit of 0.3s ensures that the pressure in the hydraulic motor working chamber has sufficiently decayed below the preset unloading value in most operating conditions, while the upper limit of 0.5s prevents the additional risks caused by soil settling and accumulation due to excessively long unloading times.

[0045] In one or more embodiments of the present invention, in the first escape operation, controlling the telescopic cylinder to drive the spiral shaft to extend and retract along the axial direction specifically involves controlling the telescopic cylinder to drive the spiral shaft to move a preset distance from its initial axial position in the first direction, and after reaching the preset distance, immediately moving it in the opposite direction by a preset distance, and after reaching the preset distance again, moving it in the opposite direction by a preset distance to form a reciprocating motion around the initial axial position; wherein, the moving speed of the spiral shaft in the reciprocating motion does not exceed a preset speed threshold.

[0046] In practical applications, determining the preset unloading time also involves the detectability of residual pressure decay in the hydraulic motor during floating. When the hydraulic motor's directional valve switches to the floating position, the pressure decay at the hydraulic motor's working port is not a linear process, but rather exhibits an exponential decay characteristic of being fast at first and then slowing down. In the initial 0.05s to 0.1s of unloading, the working port pressure rapidly drops from the pressure level corresponding to the current torque limit to 30% to 40% of that pressure level. During this stage, the pressure decay is mainly achieved by high-velocity oil leakage driven by the pressure difference between the hydraulic motor's working chamber and the oil tank. Afterward, the pressure decay rate gradually slows down, entering a slow decay stage dominated by internal leakage of the hydraulic motor and oil viscosity damping. If the preset unloading value is set to 10% of the current torque limit, under certain operating conditions, the time required for the pressure to decay from 15% to 10% may exceed 0.1s, causing the total unloading time to exceed the preset 0.5s upper limit. To avoid exceeding the unloading time limit, when the unloading duration reaches 0.5s and the pressure has not yet decreased to the preset unloading value, the control system forcibly terminates the unloading state and uses the torque value corresponding to the current actual pressure level as the starting point for establishing reverse torque, thus prioritizing the controllability of the operation sequence.

[0047] In one implementation, the interval between each brief unloading during alternating forward and reverse rotation is determined by the rotation duration of the first and second revolutions. During the wall grinding stage, the normal slag discharge speed of the auger shaft is typically 8 to 12 r / min. Using a median speed of 10 r / min, it takes 18 seconds for the auger shaft to rotate 3 times and 30 seconds for 5 rotations. This means the time interval between two adjacent brief unloadings is 18 to 30 seconds. During this interval, the auger blades continuously agitate the slag inside the cylinder, keeping the slag in a fluid state and preventing sedimentation and accumulation due to the auger shaft ceasing agitation. This time interval also allows the hydraulic system sufficient time to restore a stable oil supply after each unloading, preventing overshoot oscillations in the swashplate angle of the hydraulic pump and system pressure during the repressurization process after unloading.

[0048] In a preferred embodiment of the present invention, the preset speed threshold is 10 mm / s.

[0049] The speed threshold is determined based on the interaction characteristics between the spiral shaft driven by the telescopic cylinder and the slag inside the cylinder during axial movement. When the spiral shaft moves axially at a speed higher than 10 mm / s, the end face of the spiral blades rapidly compresses the slag along its axial movement path. The slag cannot be axially redistributed through the spiral channel of the spiral blades in a short time. The pore water pressure of the slag on the compression surface increases, the effective stress decreases, and the slag tends to liquefy locally. Local liquefaction weakens the lateral constraint force of the slag on the steel fragments. After losing the support of the slag, the steel fragments are more likely to overturn under the push of the spiral blades rather than be loosened by translation. The overturned steel fragments may re-embed themselves in the blade gaps in a more unfavorable posture. When the auger shaft moves axially at a speed not exceeding 10 mm / s, the slag has enough time to release stress and adjust its volume through the auger channel. The squeezing effect of the auger blades on the slag is limited to the rate range that the slag drainage and consolidation can absorb. During the movement, the steel fragments are always subject to continuous lateral constraints from the surrounding slag. The movement of the steel fragments is a translational sliding along the direction of the blade push, without overall overturning.

[0050] On the other hand, the 10mm / s speed threshold is also related to the inherent characteristics of the hydraulic circuit of the telescopic cylinder. The load force driving the axial movement of the telescopic cylinder's screw shaft includes the friction between the screw shaft and the slag inside the cylinder, the friction of the screw shaft bearings, and the additional resistance caused by the jamming of steel fragments. When the telescopic speed exceeds 10mm / s, the flow rate supplied to the telescopic cylinder by the hydraulic pump increases, and the pressure difference across the speed control valve in the hydraulic circuit rises. If the pressure difference of the speed control valve exceeds its rated stable working pressure difference range, the flow regulation accuracy of the speed control valve decreases, and the deviation between the actual telescopic speed and the set speed of the telescopic cylinder increases, potentially leading to speed overshoot. When the telescopic speed does not exceed 10mm / s, the speed control valve operates within the stable working pressure difference range, and the control accuracy of the telescopic speed remains within the allowable deviation range of the set value. In addition, the axial movement speed of the screw shaft also affects the accuracy of jamming judgment. When the screw shaft moves axially rapidly, the instantaneous fluctuation amplitude of the load pressure of the telescopic cylinder increases, which may be misjudged as abnormal torque by the jamming monitoring system, triggering unnecessary repeated triggering of extrication operations. The 10mm / s moving speed makes the load pressure change of the telescopic cylinder gradual, which is in line with the signal processing frequency band of the torque monitoring system.

[0051] In one or more embodiments of the present invention, during the execution of the first and second escape operations, the tunnel boring machine remains in a suspended advance state to remove the tunnel boring machine's propulsion force from the force system of the screw conveyor; only when the torque and speed of the screw shaft are both detected to have recovered to the steady-state operating range of the wall grinding stage, and the duration exceeds the preset stable duration, it is determined that the jam has been released, and the tunnel boring machine resumes its advance.

[0052] During the first and second extrication operations, the tunnel boring machine (TBM) remains suspended to remove the thrust from the screw conveyor's load-bearing system. The thrust is applied to the segment rings by the propulsion cylinders and transmitted through the shield body to the cutterhead and the soil chamber partition. During normal muck removal in the wall-grinding stage, the muck in the soil chamber is under pressure. A portion of the thrust is transmitted through the muck to the screw blades at the screw conveyor inlet, and this axial component of the transmitted force is superimposed on the screw conveyor's axial load-bearing system. When the screw conveyor jams, if the thrust is not released, the muck in the soil chamber remains under pressure, and the steel fragments at the screw conveyor inlet are continuously compressed by the axial thrust from the soil chamber side, maintaining a high level of contact stress between the steel fragments and the screw blades and cylinder wall. Under this high-stress condition, the forward and reverse rotation and axial reciprocating extension during the first extrication operation must simultaneously overcome the contact force caused by the jamming itself and the additional contact force caused by the thrust transmission. The effective effect of the extrication operation is partially offset by the additional contact force.

[0053] Pausing propulsion is achieved as follows: the control system sends a stop signal to the hydraulic circuit of the propulsion cylinder; the solenoid directional valve in the oil supply circuit of the propulsion cylinder switches to the closed position; the pressure oil supplied to the propulsion cylinder by the hydraulic pump is cut off; simultaneously, the hydraulic lock of the propulsion cylinder closes, locking the hydraulic oil in both chambers of the propulsion cylinder; and the piston rod of the propulsion cylinder remains in its current position and no longer extends. The shield propulsion force is reduced from the propulsion level before pausing to a residual level balanced only by the static friction between the shield and the surrounding soil; the excavated soil in the soil chamber is no longer subjected to the continuously increasing compression from the cutterhead propulsion face.

[0054] In the paused state, determining whether the torque and speed of the screw shaft have returned to the steady-state operating range of the wall-grinding stage is the core basis for judging whether the jam has been resolved. The steady-state operating range refers to the range of torque and speed maintained by the screw shaft during normal conveying of steel fragments and slag before the jamming event occurs in the wall-grinding stage. This range is defined by taking a statistical deviation width above and below the average steady-state operating torque as the center, and by taking a statistical deviation width above and below the design speed as the center, forming the normal operating range of the speed. The statistical deviation width is determined by multiplying the standard deviation of historical torque and speed data during normal slag discharge in the wall-grinding stage by a preset multiple.

[0055] After the first or second escape operation is completed, the control system continues to monitor torque and speed at a fixed sampling period. If the torque value falls back to the normal operating torque range and the speed value rises back to the normal operating speed range, timing begins. During timing, torque and speed must remain within their respective normal operating ranges and must not exceed these ranges again. When the duration reaches the preset stabilization time, the jamming is considered resolved. The preset stabilization time is set to prevent a situation where the steel fragment is temporarily pushed out of the jamming position during the escape operation, but due to its irregular shape, it flips over and gets stuck in a new position after the subsequent rotation of the helical blades, causing the torque and speed to deteriorate again after a brief recovery. The preset stabilization time is usually set to 10 to 15 seconds, which is longer than the time required for one rotation of the helical shaft, ensuring that the movement of the steel fragment over several pitches is observed to confirm that it has completely escaped the jamming sensitive area.

[0056] Once the jamming is determined to be resolved, the control system automatically resumes oil supply to the propulsion cylinders, and the tunnel boring machine resumes propulsion. If the torque or speed exceeds the limit again during the timing period, the timer is reset to zero, the control system determines that the jamming has not been resolved, and continues the current escape operation or proceeds to the next level of escape operation.

[0057] In one or more embodiments of the present invention, the judgment condition for detecting jamming of the screw conveyor is: the real-time torque value of the hydraulic motor increases by more than a preset torque increase threshold within a continuous first preset time period, and the real-time rotational speed of the screw shaft is continuously lower than a preset speed lower limit threshold within a continuous second preset time period, and the increase in the real-time torque value is a non-pulse increment, so as to eliminate the torque pulse interference generated when the slag block passes through the screw blade instantaneously.

[0058] The judgment condition for detecting jamming in the screw conveyor consists of three sub-conditions connected by a logical AND operation. All three sub-conditions must be met simultaneously for jamming to be determined.

[0059] The first sub-condition is that the increase in the real-time torque value of the hydraulic motor exceeds a preset torque increase threshold within a continuous first preset time period. The continuous first preset time period refers to a fixed time window calculated from the initial sampling point where the control system detects the start of the torque value increase; this time window is set to a length of 2 to 3 seconds. Within this time window, the control system records the real-time torque value one by one at a fixed sampling period, consistent with the main cycle of the control system, typically 50 to 100 ms. The increase in the real-time torque value refers to the difference between the torque value at the current sampling moment and the torque value at the start of the time window. The preset torque increase threshold is set to 50% to 80% of the steady-state operating torque average. The logic behind this threshold setting is as follows: during normal slag discharge, the steel fragments and slag flow under the propulsion of the spiral blades, and the instantaneous fluctuation of torque usually does not exceed 30% of the steady-state operating torque average; when a single steel fragment weaves between the spiral blades and the cylinder wall, the rotational resistance of the spiral shaft does not change instantaneously under the buffering effect of the slag, but gradually increases with the increase in wedging depth, and the increase in torque has a slope characteristic. The preset torque increase threshold is set to 50% to 80%, which is higher than the upper limit of the normal slag discharge torque fluctuation range, ensuring that only substantial jamming events exceeding the normal fluctuation range will trigger this sub-condition.

[0060] The second sub-condition is that the real-time rotational speed of the auger shaft remains below the preset lower speed threshold for a continuous second preset duration. The continuous second preset duration refers to a fixed time window calculated from the initial sampling point where the control system detects the beginning of the speed decrease; this time window is set to a length of 1 to 2 seconds, and the preset lower speed threshold is 20% to 30% of the auger shaft's design speed. This sub-condition requires the speed to remain below the lower threshold continuously, rather than dropping instantaneously. The purpose of setting the duration constraint is to exclude situations where the speed briefly decreases and then recovers within a sampling period due to the compression of the blades by a piece of slag passing instantaneously through the auger blades. When steel fragments become stuck, the rotational resistance of the auger shaft persists, and the driving force provided by the hydraulic motor under torque limitation is insufficient to overcome this resistance and maintain the design speed; therefore, the speed will remain below the lower threshold for a relatively long period.

[0061] The third sub-condition is that the real-time torque value increment is a non-pulse increment. The determination method for a non-pulse increment is as follows: within a continuous first preset time period, the absolute value of the difference between the torque value at each sampling point and the torque value at the previous sampling point is taken to obtain a torque fluctuation value sequence. Sampling points in the torque fluctuation value sequence that exceed a preset pulse determination threshold are marked as pulse points. The proportion of pulse points to the total number of sampling points in that time period is counted. If this proportion is lower than a preset proportion threshold, it is determined to be a non-pulse increment, and the sub-condition is met. The preset pulse determination threshold is set to 40% of the steady-state operating torque average, and the preset proportion threshold is set to 20%. When the steel fragments experience continuous jamming, the torque value shows a monotonically increasing trend of continuous rise or step-like rise, the torque fluctuation value between sampling points is small, and the pulse point proportion is less than 20%. When a torque pulse is generated instantaneously by a slag block passing through the spiral blade, the torque value rises sharply to a high value within a single sampling cycle and then quickly falls back. The torque fluctuation value exceeds the pulse determination threshold, and multiple pulse points appear densely, with the pulse point proportion exceeding 20%. This sub-condition is not met, and the jamming determination is prevented. When all three sub-conditions are met simultaneously, the stuck judgment logic outputs a true value, triggering the first escape operation.

[0062] In one or more embodiments of the present invention, if the jamming is still not resolved after the second unblocking operation, a third unblocking operation is performed; the third unblocking operation includes: stopping the rotation and extension of the screw shaft, injecting liquid polyurethane into a preset injection port at the bottom of the screw conveyor cylinder, the injection amount being such that the liquid polyurethane forms a sealing body with a thickness not less than the preset sealing thickness in the space between the slag outlet gate of the screw conveyor and the bottom of the cylinder; maintaining stable internal pressure of the screw conveyor during the curing process of the liquid polyurethane; and opening the inspection port located downstream of the sealing body for manual clearing after curing.

[0063] After the second escape operation is completed, the control system continuously monitors the torque and speed of the screw shaft within the preset monitoring time. If the torque value still does not fall back to the normal fluctuation range of the steady-state operating torque, or the speed value still does not rise back to the normal fluctuation range of the design speed, it is determined that the second escape operation has failed to remove the jam and the third escape operation is initiated.

[0064] After the third escape operation is initiated, the control system first issues a stop command, causing the hydraulic motor to stop outputting torque, the screw shaft to stop rotating, and the telescopic cylinder to stop its telescopic movement, keeping the screw shaft in its current axial position. After stopping rotation, the slag inside the screw conveyor cylinder gradually becomes still after losing the agitation of the screw blades, and the pressure transmission between the slag inside the cylinder and the slag in the soil chamber tends to reach a state of equilibrium.

[0065] After the auger shaft stops, liquid polyurethane is injected into a pre-designated injection port at the bottom of the auger conveyor cylinder. The pre-designated injection port is located at the bottom of the auger conveyor cylinder near the slag outlet, in the section between the slag outlet gate and the end of the cylinder. The pre-designated injection port is connected via pipeline to a grouting pump located on the trolley behind the tunnel boring machine. The grouting pump draws components A and B from the polyurethane raw material tank, mixes them in a specific ratio, and then transports them to the pre-designated injection port via pipeline. Component A of the liquid polyurethane is isocyanate, and component B is polyol, with a volume ratio of 1:1. After mixing, a polymerization reaction occurs. The initial viscosity at room temperature is 200 mPa·s to 300 mPa·s, and the flowable time (gel time) is 30 to 60 seconds.

[0066] During the injection process, the control system controls the grouting pump to inject liquid polyurethane into the bottom of the cylinder at a constant flow rate, set between 10L / min and 20L / min. The injection volume is determined by the liquid polyurethane forming a seal with a thickness not less than the preset sealing thickness within the enclosed space between the screw conveyor's slag outlet gate and the bottom of the cylinder. The preset sealing thickness is set between 300mm and 500mm. This enclosed space is defined by the inner wall surface of the bottom of the screw conveyor cylinder, the gate end face of the slag outlet gate, and the accumulation surface of residual slag inside the cylinder. After the liquid polyurethane is injected from the preset injection port at the bottom of the cylinder, it flows along the bottom of the cylinder under gravity and fills the low-lying areas of the enclosed space, causing the liquid level to gradually rise. The injection volume is controlled by the cumulative flow meter of the grouting pump. Injection stops when the cumulative injection volume reaches 1.2 times the theoretical volume calculated based on the cylinder's inner diameter and the preset sealing thickness. This coefficient is used to compensate for the seepage loss of liquid polyurethane in the gaps between the slag and the cylinder.

[0067] After injection stops, the liquid polyurethane begins to solidify inside the cylinder. The polymerization reaction continues, the polyurethane molecular chains grow and cross-link, and the volume expansion rate of the liquid polyurethane is 3% to 5%. The solidified polyurethane foam forms a tight seal. During the solidification process, the control system keeps the slag discharge gate of the screw conveyor closed. At the same time, it monitors the pressure changes inside the screw conveyor by monitoring the pressure data of the soil chamber. If the pressure rises abnormally, the control system releases the pressure by adjusting the opening of the slurry discharge valve on the soil chamber baffle, maintaining the internal pressure of the screw conveyor at the initial pressure level before solidification began.

[0068] After curing, the sealing body isolates the space on the slag discharge gate side of the screw conveyor from the space upstream of the cylinder, i.e., near the soil hopper, forming a water-stopping and soil-retaining barrier. At this point, the inspection port located downstream of the sealing body, i.e., on the slag discharge side, is opened. The inspection port is a flange-type opening on the cylinder, equipped with a sealing cover. When opening the inspection port, the operator first loosens the cover bolts and slowly opens the cover. Because the sealing body has isolated the slag and water pressure on the upstream side, no slag or muddy water will flow out after the inspection port is opened. The operator observes the inside of the cylinder through the inspection port to confirm the location of any stuck steel fragments. Using hydraulic shears or oxy-acetylene cutting tools, the steel fragments exceeding the gap between the screw blades are cut into smaller pieces that can be discharged by the screw conveyor, or the stuck object is directly removed using a pry bar and pliers. After manual clearing, the inspection port is closed and the sealing cover is retightened to restore the screw conveyor to a sealed state.

[0069] In one or more embodiments of the present invention, if the jamming is still not resolved after the third escape operation, or if the pressure in the soil chamber is determined to be continuously decreasing during the period when the screw shaft stops rotating and the rate of decrease exceeds a preset rate threshold based on the monitoring data of the soil chamber pressure sensor, the jamming location is determined to be the interface between the soil chamber and the screw conveyor, and a fourth escape operation is performed; the fourth escape operation includes: under normal pressure open conditions, the screw shaft section on the soil chamber side is retracted into the cylinder by the telescopic hydraulic cylinder, so that an open space without the screw shaft section is occupied at the interface between the soil chamber and the cylinder, and personnel enter the soil chamber through the open space to manually clear the obstruction.

[0070] The triggering conditions for the fourth escape operation include two scenarios.

[0071] The first scenario is that after the third escape operation is completed, the screw shaft still cannot resume normal rotation. That is, the real-time torque value of the hydraulic motor continues to exceed the upper limit of the normal fluctuation range of the steady-state operating torque, and the real-time speed of the screw shaft continues to be lower than the lower limit of the normal fluctuation range of the designed speed. It is determined that the manual obstacle removal performed through the inspection port in the third escape operation failed to remove the jam.

[0072] The second scenario involves determining, based on data from the soil pressure sensor, that the soil pressure in the soil chamber continuously decreases during the period when the auger shaft stops rotating, and the rate of decrease exceeds a preset threshold. The soil pressure sensor is installed on the front bulkhead of the tunnel boring machine, with its pressure-sensing surface in contact with the excavated soil inside the soil chamber, to monitor the soil pressure value in real time. After the auger shaft stops rotating, if there is no jamming at the interface between the soil chamber and the screw conveyor, the excavated soil inside the soil chamber is still supported by the excavated soil inside the cylinder at the inlet of the screw conveyor, and the soil pressure in the soil chamber remains relatively stable.

[0073] When the interface between the soil bin and the screw conveyor is completely blocked by steel fragments, the slag inside the screw conveyor cylinder is partially removed during the polyurethane injection and manual clearing process in the third unblocking operation. The supporting force of the slag inside the cylinder on the slag inside the soil bin is weakened. Under the action of the pressure inside the soil bin, the slag inside the soil bin shifts towards the cylinder. However, because the interface is blocked by steel fragments, the flow of slag is obstructed. The pressure in the soil bin does not drop instantaneously but decreases continuously, and the rate of decrease exceeds the preset rate threshold.

[0074] The preset rate threshold is set based on the natural fluctuation rate of the soil chamber pressure during normal slag discharge in the wall grinding stage. This natural fluctuation rate typically does not exceed 0.5 kPa / min, and the preset rate threshold is taken as 3 to 5 times this value, i.e., 1.5 kPa / min to 2.5 kPa / min. When the control system detects that the soil chamber pressure drop rate exceeds this threshold, the jamming location is determined to be the interface between the soil chamber and the screw conveyor. The fourth extrication operation is carried out under normal pressure opening conditions. The prerequisite for normal pressure opening is that the stratum at the location of the tunnel boring machine has undergone horizontal MJS reinforcement treatment, the 28-day unconfined compressive strength of the reinforced body is not less than 1.5 MPa, and the permeability coefficient is not greater than 1 × 10⁻ 7 The working face has self-stabilizing capabilities, with a pressure of m / s. Before opening the chamber, the pressure in the chamber is slowly released to atmospheric pressure through the ball valve on the chamber partition. During the release process, the pressure change in the chamber and the deformation data of the existing station structure are monitored. Once it is confirmed that there are no abnormalities, the chamber is opened.

[0075] In the fourth escape operation, the spiral shaft section on the soil chamber side is retracted into the cylinder by the telescopic hydraulic cylinder. The total telescopic stroke of the spiral shaft is 800mm. In the second escape operation, the axial reciprocating motion of the spiral shaft revolves around the initial axial position, with the piston rod of the telescopic hydraulic cylinder near the middle position within its stroke range. After entering the fourth escape operation, the control system sends a full retraction command to the telescopic hydraulic cylinder. The piston rod of the telescopic hydraulic cylinder retracts continuously at a speed of 5mm / s to 10mm / s. The piston rod drives the spiral shaft to move towards the slag outlet side through the thrust bearing, and the spiral shaft section on the soil chamber side retracts into the cylinder accordingly. When the piston rod retracts to the limit position of the telescopic hydraulic cylinder's stroke, the spiral shaft section on the soil chamber side has been completely retracted into the cylinder. After the retraction is completed, an open space without the spiral shaft section occupying it is formed at the interface between the soil chamber and the cylinder. The length of this space along the axial direction of the spiral shaft is equal to the distance the spiral shaft section retracts, and the radial dimension is the inner diameter of the cylinder. The open space directly connects the interior of the soil chamber with the interior of the cylinder, allowing workers to enter through the soil chamber and observe the situation of steel fragments stuck at the interface through this open space.

[0076] Workers use hydraulic shears or oxy-acetylene cutting tools to cut the steel fragments stuck at the interface into pieces smaller than the inner diameter of the cylinder. The cut pieces are then moved through an open space into the cylinder or soil chamber, and then manually transported or discharged via a screw conveyor after operation resumes. After the interface is cleared, the screw shaft is extended back to its designed position using a telescopic cylinder, the soil chamber door is closed, and the screw conveyor is restored to a sealed state.

[0077] This invention limits the upper limit of the hydraulic motor's output torque to a preset percentage of the rated torque and reserves a reserve torque during the wall grinding stage. This creates a progressive hierarchy in the extrication operation after jamming: "extrication without using the reserve torque" and "extrication using all the reserve torque." In the first extrication operation, because the combined extrication action of forward and reverse rotation and axial extension is performed with a torque output below the rated value, the mechanical compressive force on the steel fragments is controlled at a low level. This avoids the risk of the steel fragments being further pressed into the deep gaps between the blades when forcibly extricated with the rated torque in traditional methods. When the first extrication operation fails, the release of the reserve torque allows the second extrication operation to apply a stronger loosening force to the jammed object under full torque conditions. At this time, the jammed object has not yet experienced load compression, and its locking state with the blades is still reversible, thereby increasing the success rate of the second extrication operation. This method integrates graded control of torque output with progressive logic of the detachment operation, so that the handling process of the specific working condition of stuck steel fragments has a clear hierarchy from gentle loosening to powerful detachment, taking into account both the detachment efficiency and the structural protection of the screw conveyor.

[0078] The above provides a detailed description of a graded escaping control method for a screw conveyor used in shield tunneling steel diaphragm walls. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for graded slack-free control of a screw conveyor used in shield tunneling for cutting steel diaphragm walls, wherein the screw conveyor is driven by a hydraulic motor and equipped with a telescopic cylinder that drives the screw shaft to extend and retract axially, characterized in that... The method includes: During the wall-grinding stage of the shield cutterhead cutting the diaphragm wall, the upper limit of the output torque of the hydraulic motor is limited to a preset percentage of its rated torque in order to reserve a reserve torque consisting of the remaining percentage of the rated torque. When jamming of the screw conveyor is detected, the first unblocking operation is performed. Without calling the reserve torque, the hydraulic motor is controlled to alternately output positive and negative torque, and the telescopic cylinder is simultaneously controlled to drive the screw shaft to extend and retract axially. If the jamming is not relieved after the first escape operation, the second escape operation is performed, releasing the upper limit of the output torque of the hydraulic motor from the preset percentage to the rated torque to call up all the reserve torque, and under the condition of calling up the reserve torque, the operation of alternating output of positive and negative torque and the axial extension and retraction of the helical shaft is performed again.

2. The method according to claim 1, characterized in that, The preset percentage is determined based on the ratio of the average steady-state operating torque of the screw conveyor before jamming during the wall grinding stage to the rated torque of the hydraulic motor, so that the difference between the preset percentage and the average steady-state operating torque constitutes the normal available torque window during the wall grinding stage, and the reserve torque is superimposed on the normal available torque window.

3. The method according to claim 2, characterized in that, In the first escape operation, controlling the hydraulic motor to alternately output positive and negative torque specifically means: within one alternation cycle, first control the hydraulic motor to output positive torque to drive the spiral shaft to rotate positively for a first number of revolutions, and after reaching the first number of revolutions, immediately switch the torque direction and control the hydraulic motor to output negative torque to drive the spiral shaft to rotate negatively for a second number of revolutions. The first number of revolutions and the second number of revolutions are equal, and the alternation cycle is repeated at least once.

4. The method according to claim 3, characterized in that, The first number of laps ranges from 3 to 5 laps, and the second number of laps also ranges from 3 to 5 laps.

5. The method according to claim 4, characterized in that, In the first escape operation, controlling the telescopic cylinder to drive the spiral shaft to extend and retract along the axial direction specifically involves controlling the telescopic cylinder to drive the spiral shaft to move a preset distance from its initial axial position in the first direction, and immediately moving the preset distance in the opposite direction after reaching the preset distance, and then moving the preset distance in the opposite direction again after reaching the preset distance, so as to form a reciprocating motion around the initial axial position; wherein, the moving speed of the spiral shaft in the reciprocating motion does not exceed a preset speed threshold.

6. The method according to claim 5, characterized in that, The preset speed threshold is 10 mm / s.

7. The method according to claim 6, characterized in that, During the execution of the first and second escape operations, the tunnel boring machine remains in a suspended state to remove the tunnel boring machine's propulsion force from the force system of the screw conveyor; only when the torque and speed of the screw shaft are both detected to have returned to the steady-state operating range of the wall grinding stage, and the duration exceeds the preset stable duration, it is determined that the jam has been released, and the tunnel boring machine resumes propulsion.

8. The method according to claim 7, characterized in that, The judgment condition for detecting jamming in the screw conveyor is as follows: the real-time torque value of the hydraulic motor increases by more than a preset torque increase threshold within a continuous first preset time period, and the real-time rotational speed of the screw shaft remains below a preset lower speed threshold within a continuous second preset time period, and the increase in the real-time torque value is a non-pulse increment, so as to eliminate torque pulse interference generated when the slag block passes through the screw blade instantaneously.

9. The method according to any one of claims 1 to 8, characterized in that, If the jamming persists after the second unblocking operation, a third unblocking operation is performed. The third unblocking operation includes: stopping the rotation and extension of the screw shaft, injecting liquid polyurethane into a preset injection port at the bottom of the screw conveyor cylinder, with the injection amount being such that the liquid polyurethane forms a sealing body with a thickness not less than a preset sealing thickness in the space between the slag outlet gate of the screw conveyor and the bottom of the cylinder; maintaining stable internal pressure of the screw conveyor during the curing process of the liquid polyurethane; and opening the inspection port located downstream of the sealing body for manual clearing after curing.

10. The method according to claim 9, characterized in that, If the jamming is not resolved after the third escape operation, or if the pressure in the soil silo continues to decrease during the period when the screw shaft stops rotating and the rate of decrease exceeds a preset threshold, the jamming location is determined to be the interface between the soil silo and the screw conveyor, and the fourth escape operation is performed. The fourth escape operation includes: under normal pressure open conditions, the screw shaft section on the soil silo side is retracted into the cylinder by the telescopic cylinder, so that an open space without the screw shaft section is occupied at the interface between the soil silo and the cylinder, and personnel enter the soil silo through the open space to manually clear the obstruction.

Images