A method for controlling deformation of shield tunnels in close parallel with existing deep foundation pits

Abstract

A method for controlling deformation of an existing deep foundation pit paralleled by a shield tunnel at an ultra-close distance is provided. First, a servo steel support, a slag volume scanning device and a grouting bag are set up. Before the shield tunnel starts paralleling, a test section is established to control the soil bin pressure. When the shield tunnel is paralleled to the existing deep foundation pit, the excavation parameters are controlled, and the horizontal displacement is controlled by the grouting bag, the support axial force is adjusted by the support compensator to control the deformation, and the excavated volume is controlled by the slag volume scanning device. The method realizes active control of the deformation effect of the parallel deep foundation pit by controlling the excavation parameters, the servo support axial force control in the foundation pit, the bladder grouting control and the slag volume measurement control, ensuring that no large deformation and damage occurs. It has the characteristics of low cost, short construction period and good deformation control effect.

Description

Technical Field

[0001] The invention relates to the technical field of shield construction, and in particular to a method for controlling deformation of an existing deep foundation pit by a shield tunnel in ultra-close parallel operation. Background Art

[0002] When a shield tunnel is constructed in parallel with an existing deep foundation pit at a very close distance, the shield machine cuts through the rock and soil, causing great disturbance to the strata, which can easily have an adverse effect on the parallel deep foundation pit. In severe cases, it may cause the retaining structure of the adjacent existing deep foundation pit to become unstable, overturn, kick, and the pit bottom to bulge.

[0003] In the existing shield tunnels parallel to the existing deep foundation pit, the plane distance between the tunnel and the foundation pit is more than 2m or more than one time the hole diameter, and the ultra-close distance condition of 0.36m at the minimum is relatively rare. In order to control the adverse effects of parallel tunneling of shield machines on parallel deep foundation pits, the existing technology mainly adopts passive measures such as increasing steel support, length and stiffness of retaining structures and foundation reinforcement in the foundation pit. In the implementation process of the above-mentioned technology, the passive control measures in the foundation pit are costly to implement, the construction period is long, and the deformation effect of the existing deep foundation pit during the parallel tunneling construction of the shield machine cannot be reflected in time. In addition, the reinforcement effect of the stratum is difficult to guarantee, and it is difficult to achieve a good effect of controlling the deformation of the foundation pit. Moreover, the above-mentioned method is usually applied to conventional working conditions and is difficult to apply to the ultra-close distance parallel construction of existing deep foundation pits. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for controlling deformation of an existing deep foundation pit in ultra-close parallel to a shield tunnel. The method actively controls the deformation of the parallel deep foundation pits through excavation parameter control, servo support axial force control in the foundation pit, capsule grouting control and slag volume measurement control, ensuring that no large deformation or damage occurs. The method has the characteristics of low cost, short construction period and good deformation control effect.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for controlling deformation of an existing deep foundation pit in parallel with a shield tunnel at an ultra-close distance, characterized in that it includes the following steps:

[0006] 1) Servo steel supports are installed on the foundation pit retaining structure of the existing deep foundation pit, and support compensators are installed on the servo steel supports, and sensors are installed on the support compensators; a soil volume scanning device is installed in the tunnel; an inclinometer tube is installed between the tunnel and the existing deep foundation pit, and a grouting bag is set on the outside of the inclinometer tube;

[0007] 2) Before the shield machine starts to parallel the existing deep foundation pit, a test section is established and monitoring points are arranged on the side of the existing deep foundation pit to verify the influence of soil bin pressure and synchronous grouting pressure on the foundation pit retaining structure. When the shield machine cutterhead reaches the foundation pit retaining structure, the soil bin pressure should be controlled at 0.8-1.2 bar;

[0008] 3) When the shield machine is parallel to the existing deep foundation pit, the control excavation parameters are: soil bin pressure: 1.1-1.2 bar, excavation speed: 30-40 mm / min, cutter head speed: 1.5-1.8 rpm, cutter head torque: 2000-2500 KN•m, penetration: 15-25 mm / rad, thrust: 1600-1800 t, synchronous grouting volume: 5.5-6 m 3 ; Monitor the changes in the horizontal displacement of the soil through the inclinometer. If a large disturbance and horizontal displacement force occur, control the horizontal displacement by injecting grout into the grouting bag; monitor the support axial force through the sensor on the support compensator, and adjust the support axial force through the support compensator to control the deformation; scan the slag volume through the slag volume scanning device, compare the volume of the slag bucket before loading and the volume after loading, and accurately control the volume of slag unearthed.

[0009] As a further improvement of the present invention, it also includes a CNC pump station, a control center, an electric control cabinet, and a wireless communication device. The support compensator is a hydraulic jack. The support compensator is connected to the CNC pump station, the control center, the electric control cabinet, and the wireless communication device. When the sensor on the support compensator monitors that the support axial force is lost to the axial force data range of the design warning, the support compensator is controlled to compensate the support axial force in time. If the support axial force increases to a specific value, the support compensator is controlled to immediately reduce pressure and unload.

[0010] As a further improvement of the present invention, the length of the inclinometer tube covers the entire tunnel and 3m of the tunnel bottom, four grouting bags are arranged from bottom to top, covering the entire tunnel, a grouting pipe is installed on the ground, the grouting bag is connected to the grouting pipe on the ground, and grouting is injected into the grouting bag from bottom to top in four times.

[0011] As a further improvement of the present invention, in step 2), the monitoring points are arranged in sections of 3 m in length; when the cutter head of the shield machine reaches the foundation pit retaining structure, the soil bin pressure should be controlled at 1.0 bar.

[0012] As a further improvement of the present invention, the present invention further includes step 4) after the shield machine runs parallel to the existing deep foundation pit, when the pipe segment after the shield tail comes out reaches the foundation pit retaining structure, the shield machine continues to perform synchronous grouting, and the pressure at the pumping outlet is slightly greater than the water and soil pressure around the tunnel. The synchronous grouting pressure shall not be too high, and the grouting amount and grouting point are adjusted accordingly depending on the pressure value during grouting and the stratum deformation monitoring data, while ensuring that the upper and lower grouting ratio reaches 3:2, and the synchronous grouting speed matches the excavation speed.

[0013] The beneficial effects of the present invention are as follows: in the present invention, by controlling the excavation parameters, and then using capsule grouting to reduce disturbance and control horizontal displacement, using servo steel support to actively control the lateral deformation of the foundation pit in real time, and using the slag volume scanning device to accurately control the shield excavation, active control of the deformation influence of the parallel deep foundation pit is achieved, ensuring that no large deformation and damage occur, and good control effect, which can effectively ensure that the shield can be parallel to the existing deep foundation pit at an ultra-close distance, and there is no need to increase the support stiffness, increase the stiffness of the retaining structure, lengthen the length of the retaining structure, increase the buttress wall, strengthen the foundation and other measures, which can effectively shorten the construction period and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the construction scene of the present invention;

[0015] Marking description: Existing deep foundation pit 1, foundation pit retaining structure 2, servo steel support 3, support compensator 4, tunnel 5, slag volume scanning device 6, inclinometer tube 7, grouting bag 8. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0017] A method for controlling deformation of an existing deep foundation pit in parallel with a shield tunnel at an ultra-close distance, characterized by comprising the following steps:

[0018] Step 1) Figure 1 As shown, a servo steel support 3 is installed on the foundation pit retaining structure 2 of the existing deep foundation pit 1, and a support compensator 4 is installed on the servo steel support 3, and a sensor is installed on the support compensator 4; a slag volume scanning device 6 is installed in the tunnel 5; an inclinometer tube 7 is installed between the tunnel 5 and the existing deep foundation pit 1, and a grouting bag 8 is arranged outside the inclinometer tube 7. Among them, the support compensator 4 adopts a hydraulic jack, and the support axial force is applied to the foundation pit retaining structure 2 through the expansion and contraction of the hydraulic jack. The support compensator 4 is connected to the CNC pump station, the control center, the electric control cabinet, and the wireless communication device. The length of the inclinometer tube 7 covers the entire tunnel 5 and 3m at the bottom of the tunnel 5. There are four grouting bags 8 from bottom to top, covering the entire tunnel 5. A grouting pipe is installed on the ground, and the grouting bag 8 is connected to the grouting pipe on the ground.

[0019] Step 2) Before the shield machine starts to parallel the existing deep foundation pit, a test section is established, and monitoring points are arranged on the side of the existing deep foundation pit 1. The monitoring points are arranged in sections with a length of 3m each to verify the influence of the soil bin pressure and the synchronous grouting pressure on the foundation pit retaining structure 2. When the shield machine cutter head reaches the foundation pit retaining structure 2, the soil bin pressure on the soil bin partition should be controlled at 0.8-1.2 bar. In this embodiment, the soil bin pressure is controlled at 1.0 bar (hydrostatic head pressure).

[0020] Step 3) When the shield machine is parallel to the existing deep foundation pit, the control excavation parameters are: soil bin pressure: 1.1-1.2 bar, excavation speed: 30-40 mm / min, cutter head speed: 1.5-1.8 rpm, cutter head torque: 2000-2500 KN•m, penetration: 15-25 mm / rad, thrust: 1600-1800 t, synchronous grouting volume: 5.5-6 m 3 . The horizontal displacement changes of the soil are monitored by the inclinometer tube 7. If a large disturbance and horizontal displacement force occur, the horizontal displacement is controlled by injecting grout into the grouting bag 8, thereby avoiding excessive deformation or even damage of the foundation pit. When injecting grout into the grouting bag 8, it is injected four times from bottom to top. The support axial force is monitored by the sensor on the support compensator 4. When the support axial force loss is detected to the axial force data range of the design warning, the support compensator 4 is controlled to compensate the support axial force in time. If the support axial force increases to a specific value, the support compensator 4 is controlled to immediately decompress and unload, so as to realize dynamic adjustment of the axial force during shield excavation, so that the deformation meets the control requirements. The slag volume is scanned by the slag volume scanning device 6, and the volume of each slag vehicle can be displayed vividly. The volume of the slag bucket before loading is calculated by the rapid volume calculation method, and the volume after loading is obtained by repeating the above engineering calculation. The difference between the two volumes can intuitively show the specific status of the slag box, and it is reported to the staff for reference. Through this method, the accuracy error range of the slag volume results can be improved from ±20% to about ±5%. The high-precision slag volume results can help construction personnel accurately control the shield excavation.

[0021] Step 4) After the shield machine runs parallel to the existing deep foundation pit, when the segment after the shield tail comes out reaches the foundation pit retaining structure 2, the shield machine continues to perform synchronous grouting. The pressure at the pumping outlet is slightly greater than the water and soil pressure around the tunnel 5, and is initially taken as 0.2MPa. The synchronous grouting pressure must not be too high to prevent the retaining structure from being penetrated and causing deformation of the foundation pit. The grouting volume and grouting point are adjusted accordingly according to the pressure value during grouting and the stratum deformation monitoring data. At the same time, the upper and lower grouting ratio is ensured to reach 3:2, and the synchronous grouting speed is matched with the excavation speed. The grouting volume control table and the synchronous grouting material ratio table are as follows:

[0022] Table 1 Grouting volume control table

[0023]

[0024] Table 2 Synchronous grouting material ratio table

[0025] After all the above steps are completed, under the premise of ensuring the safety of the deep foundation pit, the shield machine can smoothly and parallelly carry out ultra-close deep foundation pits without increasing the support stiffness, increasing the stiffness of the retaining structure, lengthening the retaining structure, adding buttress walls, strengthening the foundation and other measures, thus saving time and cost for the project.

[0026] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention in any form. Any person with ordinary knowledge in the technical field may make partial changes or modifications to the technical contents disclosed in the present invention without departing from the scope of the technical features of the present invention, and the equivalent embodiments without departing from the technical features of the present invention are still within the scope of the technical features of the present invention.

Claims

1. A method for controlling deformation of an existing deep foundation pit in close parallel with a shield tunnel, characterized in that The following steps are involved: 1) Servo steel supports are installed on the foundation pit retaining structure of the existing deep foundation pit, and support compensators are installed on the servo steel supports, and sensors are installed on the support compensators; a soil volume scanning device is installed in the tunnel; an inclinometer tube is installed between the tunnel and the existing deep foundation pit, and a grouting bag is set between the inclinometer tube and the tunnel; 2) Before the shield machine starts to parallel the existing deep foundation pit, a test section is established and monitoring points are arranged on the side of the existing deep foundation pit to verify the influence of the soil bin pressure and the synchronous grouting pressure of the shield machine on the foundation pit retaining structure. When the shield machine cutterhead reaches the foundation pit retaining structure, the soil bin pressure is controlled at 0.8-1.2 bar; 3) When the shield machine is parallel to the existing deep foundation pit, the excavation parameters of the shield machine are controlled as follows: soil bin pressure: 1.1-1.2 bar, excavation speed: 30-40 mm / min, cutter head speed: 1.5-1.8 rpm, cutter head torque: 2000-2500 KN•m, penetration: 15-25 mm / rad, thrust: 1600-1800 t; the horizontal displacement change of the soil is monitored by the inclinometer tube. If a large disturbance and horizontal displacement occur, the horizontal displacement is controlled by injecting grout into the grouting bag; the support axial force is monitored by the sensor on the support compensator, and the support axial force is adjusted by the support compensator to control the deformation; the slag volume is scanned by the slag volume scanning device, and the volume of the slag bucket before loading and after loading are compared to accurately control the volume of the slag excavated.

2. The method for controlling deformation of an existing deep foundation pit in a shield tunnel at a very close distance according to claim 1, characterized in that: It also includes a CNC pump station, a control center, an electric control cabinet, and a wireless communication device. The support compensator is a hydraulic jack, which is connected to the CNC pump station, the control center, the electric control cabinet, and the wireless communication device. When the sensor on the support compensator detects that the support axial force is lost to the axial force data range of the design warning, the support compensator is controlled to compensate the support axial force in time. If the support axial force increases to a specific value, the support compensator is controlled to immediately reduce pressure and unload.

3. The method for controlling deformation of an existing deep foundation pit in a shield tunnel at a very close distance according to claim 1, characterized in that: The length of the inclinometer tube covers the entire tunnel and 3m below the tunnel. Four grouting bags are set from bottom to top, covering the entire tunnel. Grouting pipes are installed on the ground. The grouting bags are connected to the grouting pipes on the ground. Grouting is injected into the grouting bags in four times from bottom to top.

4. The method for controlling deformation of an existing deep foundation pit in a shield tunnel at an ultra-close distance according to claim 1, characterized in that: In step 2), when the shield machine cutterhead reaches the foundation pit retaining structure, the soil bin pressure is controlled at 1.0 bar.

5. The method for controlling deformation of an existing deep foundation pit in a shield tunnel at a very close distance according to claim 1, characterized in that: It also includes step 4) after the shield machine runs parallel to the existing deep foundation pit, when the pipe segment after the shield tail comes out reaches the foundation pit retaining structure, the shield machine continues to grouting, and the pressure at the pumping outlet is slightly greater than the water and soil pressure around the tunnel. The synchronous grouting pressure shall not be too high, and the grouting amount and grouting point shall be adjusted accordingly according to the pressure value during grouting and the stratum deformation monitoring data.

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