Judgment method for shield machine cutting pile foundation in soft soil

Abstract

The present invention relates to a judgment method for shield machine cutting pile foundation in soft soil strata, comprising: setting an excavation path of the shield machine in the soft soil stratum, and determining the reinforced concrete pile foundation existing on the excavation path of the shield machine; observing the change characteristics of the shield machine cutter head torque and the cutter head motor current curve, so that during the excavation process of the shield machine, whether the shield machine cutter head begins to contact the pile foundation and whether the shield machine cutter head has separated from the pile foundation is correctly and reasonably judged, and construction parameters are timely and reasonably adjusted according to the judgment, so that the shield machine can safely and efficiently complete the construction of cutting the pile foundation.

Description

Technical Field

[0001] The invention relates to a shield machine excavation construction method in a tunnel engineering, in particular to a judgment method for shield cutting pile foundation in a soft soil layer. Background Art

[0002] When the shield machine is excavating in the soft soil layer, since the soft soil geology is relatively uniform, the shield machine can use a low cutter head speed and a fast advancement speed for excavation construction. When the shield machine is cutting the pile foundation, since the strength of the reinforced concrete pile foundation is much greater than that of the soft soil, it is necessary to use construction parameters different from those for soft soil excavation. By using a high cutter head speed and a slow advancement speed, the penetration of the cutter into the pile foundation can be greatly reduced, so that the cutter can cut and grind the pile foundation slowly to fully cut and crush the pile body. At the same time, it also avoids the excessive impact force of the pile body on the cutter, causing damage to the cutter, and excessive torsion angle of the shield machine, and reduces the adverse effects of pile cutting construction on the structure of the building above the pile foundation, improving construction efficiency and saving construction costs.

[0003] Therefore, a judgment method for shield cutting pile foundation in soft soil strata is needed to comprehensively judge whether the shield machine cutter head has begun to contact the pile foundation and whether the shield machine cutter head has completely detached from the pile foundation, so as to timely and reasonably adjust the construction parameters, avoid damage to the shield machine itself and adverse effects on the surrounding environment, etc., improve construction efficiency and save construction costs. Summary of the invention

[0004] The purpose of the present invention is to address the shortcomings of the existing shield cutting pile foundation construction technology in soft soil strata, and to provide a judgment method for shield machine cutting pile foundations in soft soil strata, so as to accurately judge whether the shield machine cutter head begins to contact the pile foundation and whether it is completely separated from the pile foundation. The method steps are simple and easy to understand. After accurate judgment, the shield construction parameters can be adjusted in time and reasonably, thereby improving the shield construction efficiency, saving construction costs, and reducing adverse effects on the surrounding environment.

[0005] To achieve the above object, the technical solution of the present invention is: a method for judging whether a shield machine cuts a pile foundation in a soft soil layer, comprising:

[0006] Step 1: Set the tunneling path of the shield machine;

[0007] Step 2, determine the reinforced concrete pile foundation existing on the tunneling path of the shield machine;

[0008] Step 3: Start the shield machine to excavate, observe the cutter head torque, the amplitude of the cutter head motor current curve, and the frequency change characteristics, and determine whether the shield machine cutter head begins to contact the pile foundation;

[0009] Step 4: If the shield machine cutter head has begun to contact the pile foundation, immediately adjust the shield construction parameters to the state of cutting the pile foundation;

[0010] Step 5: Continue to observe the cutter head torque, the amplitude of the cutter head motor current curve, and the frequency change characteristics to determine whether the shield machine cutter head is completely separated from the pile foundation;

[0011] Step 6: If the cutter head of the shield machine has completely separated from the pile foundation, adjust the shield construction parameters to the normal soft soil excavation state.

[0012] Furthermore, the specific method for setting the tunneling path of the shield machine is: by adjusting the shield posture, the shield machine is made to tunnel along the designed center line, and the error range of the shield posture does not exceed ±50mm of the designed value.

[0013] Furthermore, the specific method for determining the reinforced concrete pile foundation existing on the shield machine excavation path is: determining the reinforced concrete pile foundation invading the shield machine excavation range, and the shield machine excavates forward to cut and crush the reinforced concrete pile foundation.

[0014] Furthermore, the shield machine and cutterhead torque and cutterhead motor current curves are curves displayed in a graphical form on the monitoring server interface after the data acquisition system in the shield machine monitoring and management system processes and analyzes the collected cutterhead torque and cutterhead motor current data.

[0015] Furthermore, the amplitude and frequency change characteristics of the shield machine cutter head torque and cutter head motor current curve are the amplitude of the curve fluctuation and the speed of the curve fluctuation frequency change.

[0016] Furthermore, when the shield machine cutterhead begins to contact the pile foundation, the shield machine cutterhead torque curve shows the characteristics of gradually increasing amplitude and gradually increasing frequency, and at the same time, the cutterhead motor current curve also shows the characteristics of gradually increasing amplitude and gradually increasing frequency.

[0017] Furthermore, when the shield machine cutterhead is completely separated from the pile foundation, the amplitude and frequency of the shield machine cutterhead torque curve return to a relatively gentle state for normal soft soil excavation, and the amplitude and frequency of the cutterhead motor current curve also return to a relatively gentle state for normal soft soil excavation.

[0018] Furthermore, the specific method of adjusting the shield construction parameters to the state of cutting the pile foundation is: before the shield machine cuts the pile foundation, it is advanced by 1 ring, i.e. 1.2m, and the propulsion speed of the shield machine is reduced to 10-20mm / min, and the cutter head speed is maintained at 0.8rpm. When the cutter head of the shield machine begins to contact the pile foundation, the propulsion speed of the shield machine is further reduced to no more than 5mm / min, and the cutter head speed is increased to 1.0rpm.

[0019] The beneficial effects of the present invention are:

[0020] The present invention determines the reinforced concrete pile foundation on the shield machine's excavation path by setting the shield machine's excavation path in the soft soil layer; observes the change characteristics of the shield machine's cutter head torque and the cutter head motor current curve, so that during the shield machine's excavation process, it is possible to correctly and reasonably judge whether the shield machine's cutter head begins to contact the pile foundation and whether the shield machine's cutter head has separated from the pile foundation, and timely and reasonably adjusts the construction parameters according to the judgment, so that the shield machine can safely and efficiently complete the pile foundation cutting construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A cross-sectional view of the relative position relationship between the shield machine cutter head and the pile foundation for judging the method of shield machine cutting pile foundation in soft soil layer;

[0022] Figure 2 A longitudinal section diagram of the relative position relationship between the shield machine cutter head and the pile foundation for judging the method of shield machine cutting pile foundation in soft soil layer;

[0023] Figure 3 The cutter head torque and cutter head motor current curve of normal soft soil excavation for judging the shield machine cutting pile foundation in soft soil layer;

[0024] Figure 4 A cutter head torque and cutter head motor current curve diagram for judging the method of cutting pile foundation by a shield machine in soft soil strata when starting to cut pile foundation in soft soil;

[0025] Figure 5 The figure is a flow chart of the method for judging the shield machine cutting pile foundation in soft soil strata. DETAILED DESCRIPTION

[0026] The present invention provides a method for judging the shield machine cutting pile foundation in soft soil strata. The method is used to judge whether the shield machine cutter disc begins to contact the pile foundation and whether the shield machine cutter disc is completely separated from the pile foundation when the shield machine cuts the pile foundation, so as to facilitate timely and reasonable adjustment of construction parameters, better complete the construction of cutting the pile foundation, and protect the shield machine itself and the buildings above the pile foundation. In order to make the purpose and technical solution of the present invention clearer,

[0027] The following is combined with Figures 1 to 5 The present invention is used to describe the method for judging the pile foundation cut by a shield machine in a soft soil layer.

[0028] The cutter torque of the shield machine is a passive construction parameter. It is constantly changing due to the influence of the uniformity of the excavated soil layer, the propulsion speed, and the amount of excavated soil from the screw machine. However, it directly affects the force on the cutter tool and the deformation of the pile foundation being cut, and is an important control parameter for pile cutting construction. However, when the cutter torque is used as the basis for judging the cutting of pile foundations, since its value is generally large, and the change in resistance is relatively small when the tool first contacts the pile foundation, the value of the cutter torque does not change much at the beginning, making it difficult to make a timely judgment. Therefore, we introduced the current curve of the cutter motor, which changes more sensitively, and used the fluctuation characteristics of the current curve of a single cutter motor as auxiliary evidence to make a more timely and accurate judgment.

[0029] like Figure 3 As shown in the figure, when the shield machine is excavating in the soft soil layer, due to the relatively uniform soft soil geology, the shield machine cutterhead is subjected to relatively balanced forces, and the curves of the cutterhead torque and the cutterhead motor current are also relatively gentle.

[0030] like Figure 1 , 2 As shown, due to the characteristics of underground tunnel engineering, when the shield machine excavates forward along the design center line, it basically has a certain slope in the vertical direction, and the pile foundation of the building is generally constructed vertically downward using a reinforced concrete structure. Therefore, when the shield machine cuts the pile foundation, there is usually an angle of less than 90° between the shield machine and the pile foundation in the vertical direction. When the shield machine cuts the pile foundation, the tool on the edge of the cutter head 1 contacts the pile foundation 2 first, followed by the tool on the panel, and finally the tool in the center of the cutter head.

[0031] When the cutterhead speed is set to a fixed level, when the tool cuts the pile foundation, the pile foundation made of reinforced concrete is much harder than soft soil, which will produce greater resistance to the rotation of the cutterhead. In order to overcome the resistance, the cutterhead drive motor of the shield machine will also increase its output power accordingly. At the same time, due to the fixed spacing between the cutters on the cutterhead of the shield machine, as the cutterhead rotates, when the pile foundation contacts the cutter, the cutterhead torque will increase, and when the pile foundation is between the cutters, the cutterhead torque will decrease, which will cause the cutterhead torque and cutterhead motor current curves to fluctuate significantly with a certain regularity. As more and more cutters come into contact with the pile body, more resistance is added, and the fluctuation amplitude of the cutterhead torque and cutterhead motor current curves will gradually increase, such as Figure 4 As shown, the peak height of the curve is affected by the cut pile foundation material and has an upper limit.

[0032] According to the distribution characteristics of the shield machine cutterhead tools, the pile foundation is mainly cut by the leading cutter. Each leading cutter has a fixed trajectory line. The trajectory lines of the shield machine cutterhead tools are numbered in the order from the center of the cutterhead to the edge of the cutterhead, respectively L 1 , L 2 ...L i , and their corresponding trajectory radii are R1 , R 2 ……R i , the number of tools on each trajectory line is N 1 、N 2 ...N i , the tool center angle on each trajectory line is α 1 , α 2 ...α i , where α<180°.

[0033] Assume that the reinforced concrete pile foundation intrudes into the entire section of the tunnel. When the shield machine cuts the pile foundation, the angle between the cutterhead and the pile foundation is β, the cutterhead speed is 1.0rpm, and the height of the leading cutter on the cutterhead is consistent. At the same time, the slight time difference between the cutters on the same radial line of the shield machine cutterhead when cutting the pile foundation is ignored.

[0034] Phase 1: From L i The leading knife on the trajectory line starts to touch the pile foundation and ends at L 1 The leading cutter on the track line touches the pile foundation. In this stage, the cutter head rotates once per minute, and each leading cutter on the track line cuts the pile once per minute. i Taking the cutting of pile foundation by the leading cutter on the trajectory line as an example, the fluctuation frequency variation characteristics of the cutter head torque and cutter head motor current curve in stage one are explained.

[0035] L i The leading cutter on the track line starts cutting the pile foundation. The cutter head rotates once a minute. Each leading cutter on the track line cuts the pile once a minute. That is, the cutter head rotates once, and the number of times the cutter cuts the pile foundation is N. i The cutter head torque and cutter head motor current curve fluctuation frequency V generated by each circle of the trajectory tool cutting the pile foundation i =N i times / min, and the intervals between the peaks of the curves are ……and The sum of the interval times is 1 minute.

[0036] In this stage, the center of the shield machine cutterhead has not yet cut into the pile body, and the leading cutter on the cutterhead can only cut the upper part of the pile body. Therefore, each leading cutter cuts the pile body once per minute, but the tool trajectory line that contacts the pile foundation is L i Gradually superimposed to L 1 , the number of cutters contacting the pile foundation gradually increases, causing the fluctuation frequency of the cutter head torque and the cutter head motor current curve to gradually accelerate. However, it should be noted that according to the distribution characteristics of the cutter head cutters, the centers of the cutters on different trajectory lines are located on the same radial line or on different radial lines in the radial direction. Therefore, the acceleration of the curve fluctuation frequency is not a 1+1=2 relationship, but a 1+1≥1 relationship.

[0037] Phase 2: From L 1 The leading cutter on the trajectory line can cut the pile body below the center of the cutter head to L i The leading cutter on the track line can cut the pile body below the center of the cutter head. In this stage, the cutter head rotates once every 1 minute, and each leading cutter on the track line cuts the pile once every 0.5 minutes. 1 Taking the cutting of pile foundation by the leading cutter on the trajectory line as an example, the fluctuation frequency variation characteristics of the cutter head torque and cutter head motor current curve in the second stage are explained.

[0038] L 1 The leading cutter on the track line can cut the upper and lower parts of the pile. The cutter head rotates once per minute. Each leading cutter on the track line cuts the pile once every 0.5 minutes. That is, the number of times the cutter head rotates once is 2N. 1 The cutter head torque and cutter head motor current curve fluctuation frequency V generated by each circle of the trajectory tool cutting the pile foundation 1 =2N 1 times / min, the interval between curve peaks is ……and The interval time is 0.5min.

[0039] At the end of this stage, the shield machine cutterhead completely cuts into the pile body, and each leading cutter on the cutterhead cuts the pile body once every 0.5 minutes. 1 The trajectory line gradually overlaps to L i Therefore, at the same stage 1, and on its basis, the fluctuation frequency of the cutter head torque and cutter head motor current curve will be further accelerated, and at L i The leading cutter on the trajectory line can reach its fastest speed when it cuts to the lower half of the pile body.

[0040] Therefore, in the initial stage of shield machine pile cutting, the fluctuation frequency of the cutter head torque and cutter head motor current curve will gradually accelerate and i The leading cutter on the track line (outermost side of the cutter disc) can cut the pile below the center of the cutter disc to achieve the fastest speed. Figure 4 shown.

[0041] Similarly, when the cutter is separated from the pile body, the change characteristics of the cutter head torque and the cutter head motor current curve show opposite changes until they change to a relatively gentle state of soft soil excavation, at which time the shield machine cutter head is completely separated from the pile foundation.

[0042] The present invention mainly judges whether the shield machine cutter head begins to contact the pile foundation and whether it is completely separated from the pile foundation by observing the change characteristics of the shield machine cutter head torque and the cutter head motor current curve. If it is found that the shield machine cutter head torque and the cutter head motor current curve show a gradually increasing amplitude and a gradually increasing vibration frequency, the shield machine cutter head has begun to contact the pile foundation, and the construction parameters are immediately adjusted to the pile foundation cutting state; if it is found that the shield machine cutter head torque and the cutter head motor current curve amplitude gradually decreases, and the vibration frequency gradually slows down until it is basically flat, the shield machine cutter head has completely separated from the pile foundation, and the construction parameters are adjusted to the soft soil excavation state.

[0043] like Figure 5 As shown, the method for judging whether a shield machine cuts a pile foundation in a soft soil layer according to the present invention comprises:

[0044] 1) Set the tunneling path of the shield machine;

[0045] 2) Determine the reinforced concrete pile foundations on the tunneling path of the shield machine;

[0046] 3) Start the shield machine to excavate, observe the cutter head torque, the amplitude of the cutter head motor current curve, and the frequency change characteristics, and determine whether the shield machine cutter head begins to contact the pile foundation;

[0047] 4) If the shield machine cutter head torque and cutter head motor current curves show a gradually increasing amplitude and a gradually increasing frequency, it is judged that the shield machine cutter head has begun to contact the pile foundation, and the shield construction parameters are immediately adjusted to the state of cutting the pile foundation;

[0048] 5) Before the shield machine cuts the pile foundation, reduce the shield machine's propulsion speed to 10-20 mm / min 1 ring (1.2 m) in advance, and maintain the cutter head speed at 0.8 rpm. When the shield machine's cutter head begins to contact the pile foundation, further reduce the shield machine's propulsion speed to no more than 5 mm / min, and increase the cutter head speed to 1.0 rpm.

[0049] 6) Continue to observe the cutter head torque, amplitude and frequency change characteristics of the cutter head motor current curve to determine whether the shield machine cutter head is completely separated from the pile foundation;

[0050] 7) If the shield machine cutter head torque and cutter head motor current curves show a gradually decreasing amplitude and a gradually decreasing frequency until they reach a smooth state of normal soft soil excavation, it is judged that the shield machine cutter head has completely separated from the pile foundation, and the shield construction parameters are adjusted to the normal soft soil excavation state.

[0051] Effect test of the method for judging whether a shield machine cuts a pile foundation in a soft soil layer according to the present invention:

[0052] The above method is used to determine whether the shield machine cutter head begins to contact the pile foundation and whether the shield machine cutter head is completely separated from the pile foundation, and timely and reasonable construction parameter adjustments are made. From the perspective of structural settlement of underground structures, about 30 days after the cutting of the pile foundation is completed, the maximum structural settlement is +3.22mm, and the maximum horizontal displacement is -1.9mm; from the perspective of shield machine protection, after the cutting of the pile foundation is completed, the shield machine equipment is comprehensively inspected, and the overall condition is good without any abnormalities. After the shield machine is received, the cutter head tool is observed, and the tool has basically no abnormal damage.

[0053] The present invention is described in detail above with reference to the accompanying drawings. A person skilled in the art can make various variations of the present invention according to the above description. Therefore, some details in the embodiments should not be construed as limiting the present invention. The scope of protection of the present invention shall be defined by the scope of the attached claims.

Claims

1. A method for judging whether a shield machine cuts a pile foundation in a soft soil layer, characterized in that: The following steps are involved: Step 1: Set the tunneling path of the shield machine; Step 2, determine the reinforced concrete pile foundation existing on the tunneling path of the shield machine; Step 3, start the shield machine to excavate, observe the amplitude and frequency change characteristics of the cutter head torque and the cutter head motor current curve, and judge whether the shield machine cutter head begins to contact the pile foundation; the amplitude and frequency change characteristics of the shield machine cutter head torque and the cutter head motor current curve are the amplitude of the curve fluctuation and the speed of the curve fluctuation frequency change; when the shield machine cutter head begins to contact the pile foundation, the shield machine cutter head torque curve shows the characteristics of gradually expanding amplitude and gradually accelerating frequency, and at the same time, the cutter head motor current curve also shows the characteristics of gradually expanding amplitude and gradually accelerating frequency; Step 4: If the shield machine cutter head has begun to contact the pile foundation, immediately adjust the shield construction parameters to the state of cutting the pile foundation; Step 5: Continue to observe the cutter head torque, the amplitude of the cutter head motor current curve, and the frequency change characteristics to determine whether the shield machine cutter head is completely separated from the pile foundation; Step 6: If the shield machine cutterhead has completely separated from the pile foundation, adjust the shield construction parameters to the normal soft soil excavation state; The cutter head torque and cutter head motor current curves of the shield machine are curves displayed in the form of graphs on the monitoring server interface after the cutter head torque and cutter head motor current data collected are processed and analyzed by the data acquisition system in the shield machine monitoring and management system; the specific method of adjusting the shield construction parameters to the pile foundation cutting state is: before the shield machine cuts the pile foundation, one ring in advance, that is, 1.2m, the shield machine propulsion speed is reduced to 10-20mm / min, the cutter head speed is maintained at 0.8rpm, and when the shield machine cutter head begins to contact the pile foundation, the shield machine propulsion speed is further reduced to no more than 5mm / min, and the cutter head speed is increased to 1.0rpm.

2. The method for determining whether a shield machine cuts a pile foundation in a soft soil layer according to claim 1, characterized in that: The specific method for setting the tunneling path of the shield machine is: by adjusting the shield posture, the shield machine is made to tunnel along the designed center line, and the error range of the shield posture does not exceed ±50mm of the designed value.

3. The method for determining whether a shield machine cuts a pile foundation in a soft soil layer according to claim 1, characterized in that: The specific method for determining the reinforced concrete pile foundation existing on the shield machine excavation path is: determining the reinforced concrete pile foundation invading the shield machine excavation range, and the shield machine excavates forward to cut and crush the reinforced concrete pile foundation.

4. The method for determining whether a shield machine cuts a pile foundation in a soft soil layer according to claim 1, characterized in that: When the shield machine cutterhead is completely separated from the pile foundation, the amplitude and frequency of the shield machine cutterhead torque curve return to a relatively gentle state of normal soft soil layer excavation, and the amplitude and frequency of the cutterhead motor current curve also return to a relatively gentle state of normal soft soil layer excavation.

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