1、 Earth pressure balance shield tunneling (I) earth pressure balance tunneling characteristics earth pressure balance shield is to fill the excavated soil and sand into the soil bin between the excavation surface and the diaphragm, inject improved materials into it as needed, and use appropriate earth pressure to ensure the stability of the excavation surface.
In order to obtain the discharge volume suitable for the advance of the shield, the earth pressure and the excavated disc shall be measured, and the number of revolutions of the screw dumper and the advance speed of the shield shall be controlled to achieve a balanced state.
Generally, shield equipment adopts combined control mode.
(4) As the excavation surface exploration method to master the state of the excavation surface, like the earth pressure balance shield, it also uses mechanical penetration method or non-contact electromagnetic wave and ultrasonic investigation method.
（3） Waste volume management (1) in order to maintain the stability of the excavation surface while advancing smoothly, an appropriate amount of waste shall be discharged to maintain the balance between waste volume and advance volume.
When the ideal excavated state can not be achieved by adjusting the rotating speed of the screw conveyor, it can be adjusted by improving the plastic flow state of the residue.
(4) According to the engineering geological and hydrogeological conditions, the modifier shall be injected into the front of the cutterhead and the soil bin, and the residue shall be in the flow plastic state.
(2) The key to maintaining the stability of the excavation surface is to form a high-quality mud film on the excavation surface..
In addition, as waste, its state can change from semi-solid state to fluid state, and its properties are various.
In addition, it is necessary to confirm the foundation deformation, dumping state, cutter head torque and their changes caused by the propulsion, and correct the silo pressure in time during the propulsion.
The remaining mud after separation, plus water, clay, montmorillonite, tackifier, etc., shall be adjusted for relative density, concentration and viscosity, and then transported to the excavation surface for recycling.
For slurry pressurized shield construction, data are generally obtained from the flowmeter and densimeter set on the mud delivery pipe and mud discharge pipe, and the deviation flow and excavation dry sand volume are calculated to grasp the state of the excavation surface.
It is widely used in the field because of its simple application.
(2) The methods of waste volume management can be roughly divided into volume management method and weight management method.
（3） In order to maintain the stability of the excavation surface and smoothly promote the excavation, the amount of soil discharged and excavated shall be balanced during excavation.
Therefore, it is difficult to properly grasp the dumping volume.
Through the screw conveyor arranged through the diaphragm, the soil can be discharged while advancing.
The construction method uses the excavation equipment, excavation surface stabilization system and residue treatment equipment as a whole system.
Muck is transported to the ground by mud.
This method can also be used to infer the geological changes of surrounding rock.
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(2) The basic idea of pressure management of slurry silo is: as the upper limit value, the static earth pressure is used for the purpose of controlling the settlement of ground surface as much as possible; As the lower limit, active earth pressure is used to allow a small amount of settlement, but for the purpose of maintaining the stability of the excavation surface.
2) Good viscosity.
(1) Characteristics of improved slag soil: under the earth pressure balance mode, the slag soil shall have the following characteristics: 1) good plastic flow state.
Therefore, the deviation flow and excavated dry sand volume of the previous rings should be statistically calculated.
The method of calculating the number of residue trucks is a rough estimation.
(4) In the process of propulsion, the following methods are used to maintain the pressure of the silo: ① controlled by the number of revolutions of the screw dumper; ② Control the advancing speed of shield jack; ③ Combined control of the two.
On this basis, solid particles, gravels and sand are separated from the mud by mechanical treatment or other methods and discharged and transported away.
(5) Good management shall be implemented according to the construction conditions.
are added with solidified materials to form blocks (aggregates).
The mud transported to the ground uses a primary separation device to remove gravel, sand, etc; Silt, clay, etc.
(2) The basic idea of earth pressure management is: as the upper limit value, the static earth pressure is used for the purpose of controlling the settlement of the ground surface as much as possible; As the lower limit, a small amount of surface settlement can be allowed, but the active earth pressure can be used for the purpose of ensuring the stability of the excavation surface.
（4） Slurry treatment system and crushing technology in the silo (1) the excavated soil and sand are mixed in the slurry silo through the mixing wing and transported to the ground through the sludge discharge pipeline.
However, the gravity of surrounding rock will fluctuate during excavation, and the gravity of discharged slag will also change under the influence of factors such as the type, amount of additives or dumping mode.
As a volume management method, it is generally calculated by calculating the number of residue handling vehicles or from the number of revolutions of screw dumper.
During construction, soil and sand must be filled between the two excavation diaphragms and pressurized to meet the stability needs of the excavation surface.
(3) To master the stable state of the excavation surface, the water pressure gauge set on the diaphragm is generally used to confirm the mud water pressure in the mud tank.
The commonly used improvement materials are foam or bentonite slurry.
（2） Earth bunker pressure management (1) during the construction of earth pressure balance shield, in order to ensure the stability of the excavation surface, the pressure in the pressure chamber shall be properly maintained.
4) Low water permeability.
(2) According to the engineering geological and hydrogeological conditions of the tunnel, buried depth, line plane and slope, surface environment, construction monitoring results, shield posture and experience in the starting stage, the driving parameters such as shield cutterhead speed, driving speed and earth bin pressure shall be set.
Therefore, it is difficult to control the collapse of excavation surface or foundation settlement only according to the management of waste soil volume.
In general, if the pressure of the soil bin is insufficient, the risk of water gushing or collapse on the excavation surface will increase.
(2) when the residue can not meet these requirements, it is necessary to improve the muck by injecting improved materials into the cutterhead, the soil bin and the screw conveyor.
Generally, if the mud pressure is insufficient, the risk of collapse of the excavation surface will increase.
At the same time, the torque and thrust of the cutterhead shall be mastered, and the correct control management shall be carried out to prevent the loosening and damage of the excavation surface.
It is best to carry out the pressure management of pressure tank and the management of excavated soil volume at the same time.
2、 Slurry pressurized shield tunneling (I) characteristics of slurry pressurized tunneling in the process of slurry pressurized shield tunneling, while maintaining the stability of the excavation surface with slurry, it is excavated by mechanical excavation.
(3) To master the stable state of the excavation surface, the earth pressure gauge set on the diaphragm is generally used to determine the earth bin pressure.
(3) During the excavation, the Shield operation, the change of excavation parameters and the discharge of slag and soil shall be monitored and recorded, and the feedback shall be analyzed in time to adjust the excavation parameters and control the shield attitude.
3) Low internal friction.
However, both are used to detect the local porosity or cavity in front of or above the excavation face, so as to provide auxiliary information for judging the stable state of the excavation face.
If the pressure is too large, it will cause the increase of cutter head torque or thrust, resulting in the decrease of propulsion speed or ground uplift.
（5） Key points of earth pressure balance shield tunneling (1) the excavated muck shall fill the silo, the silo pressure formed by the muck shall be balanced with the water and soil pressure outside the cutterhead excavation surface, and the amount of waste soil shall be balanced with the amount of excavated soil.
If the pressure is too high, there will be the possibility of mud eruption and ground uplift.
The weight management method generally uses the weight of residue truck for acceptance.
The operation of the system shall fully consider the setting and management of such conditions as soil discharge volume, mud quality, excavation surface status, back wall grouting, mud delivery and discharge flow, mud discharge flow rate and so on (see Fig.
（4） The muck discharge of muck improved earth pressure balance shield must match the excavation volume of tunneling, so as to obtain a stable and appropriate support pressure value and make the TBM work in the best state.
（2） Mud sump pressure management (1) in the mud pressurized shield construction method, in order to ensure the stability of the excavation surface, it is necessary to set the mud pressure appropriately according to the soil and earth water pressure of the excavation surface.
