1. Characteristics of spray anchor excavation (mining) method
【Formula】Compound lining new support, and the amount is greater than rigidity
The method adopts the first soft and then rigid composite lining and a new type of support structure system, the initial support is designed according to bearing all the basic loads, the secondary mold lining is used as a safety reserve, and the initial support and the secondary lining jointly bear the special load.
When the shallow buried excavation method is applied for design and construction, a variety of auxiliary construction methods are used at the same time to advance the pre-support to improve and strengthen the surrounding rock, and mobilize the self-supporting capacity of part of the surrounding rock; Different excavation methods are used to support and close the ring in time, so that it can act together with the surrounding rock to form a joint support system. In the construction process, monitoring and measurement, information feedback and optimized design are applied to achieve no collapse, less settlement and safe construction.
Compared with the new Austrian method, the shallow buried underground excavation method emphasizes the pre-support and pre-reinforcement of the formation. The structural stiffness of the shallow buried underground excavation method is relatively large, and the allowable deformation of the initial support is relatively small, which is conducive to reducing the disturbance to the formation and protecting the surrounding environment.
2. The spray anchor excavation (mine) method is applicable to the stratum
【Formula】Quaternary
Shallow burial and excavation technology is mostly used in Quaternary weak strata
3. Construction procedures of spraying anchor excavation (mining) method
【Formula】Pre-excavation of the second prison
(1) Formation pre-reinforcement and pre-support
In the construction of urban subway tunnels, unstable strata such as gravelly soil, sandy soil, cohesive soil or strongly weathered bedrock are often encountered. This kind of stratum has a short self-stabilization time in the process of tunnel excavation, and often the local stratum of the arch wall has begun to collapse before the initial support has had time to be applied or the shotcrete has not yet gained sufficient strength. Therefore, it is necessary to adopt the method of stratum pre-reinforcement and pre-support to improve the stability of the surrounding strata. The commonly used pre-reinforcement and pre-support methods are: advanced pre-grouting of small conduit, advanced deep hole grouting of excavation face and advanced support of pipe shed.
(2) Tunnel earthwork excavation
When the shallow buried excavation method is used for excavation operations, the selected excavation method and technological process should ensure that the disturbance to the formation is minimized, the self-supporting effect of the surrounding formation is improved and the surface settlement is reduced. According to different geological conditions and tunnel sections, different excavation methods are selected, but the general principle is: pre-support, pre-surface section, excavation section; A section of excavation, a section of support, and a section of closure into a ring.
(3) Initial support format
The initial support should be stiff and timely, and it must be constructed from top to bottom.
Among the many support forms, the steel arch anchor shotcrete support is the best support form to meet the above requirements.
(4) Secondary lining:
In the middle, it is necessary to confirm the basic stability of the initial supporting structure through deformation measurement, and the secondary lining construction can only be carried out after the acceptance of the waterproof structure construction, and the construction must be carried out from the bottom to the top, and the construction of the arch and the wall must never be allowed.
This is the main difference between the secondary lining construction and the general tunnel lining construction in the shallow buried underground excavation method. The cast-in-place reinforced concrete process and the use of mechanical equipment are basically the same as those of general tunnel lining construction.
The secondary lining template can adopt temporary wooden formwork or metal shaping formwork, and in more cases, the formwork trolley is used, because the cross-sectional size of the interval tunnel is basically unchanged, which is conducive to the use of formwork trolley, and accelerates the speed of formwork support and formwork. The formwork, wall frame and arch used in lining should be simple in style, easy to disassemble and assemble, smooth on the surface, and tight in joints. It should be checked on the model table before use; When reused, it should be inspected and refurbished at any time.
(5) Monitoring and measurement:
The use of monitoring and measurement information to guide the design and construction is an important part of the shallow buried underground excavation construction process.
If the measurement results prove to be not stable, monitoring should be continued; If the monitoring results prove that the support has a tendency to be unstable, it is necessary to determine the reinforcement plan through the design department in a timely manner.
Specific requirements and contents should be put forward in the design documents, and the cost of monitoring and measurement should be included in the project cost.
In the process of implementation, the construction unit shall have a special agency for implementation and management, and shall be controlled and led by the technical person in charge of the project. Experience has proved that vault settlement is a more intuitive and reliable basis for judging the control stability, and horizontal convergence and surface settlement are sometimes also important judgment bases. For metro tunnels, surface settlement measurement is particularly important.
4. Shallow buried underground excavation method
【Formula】The whole Taiwan ring is left in the middle hole on the side
Due to the different excavation methods, the construction of shallow buried underground excavation method can be divided into many specific construction methods, such as full section method, positive platform method, annular excavation reserved core soil method, unilateral wall guide pit method, double side wall guide pit method, middle partition wall method, cross middle partition wall, middle hole method, side hole method, column hole method, etc.
5. Full-section excavation method
【Formula】Suitable along the one, reduce disturbance and self-stability
(1) The full-section excavation method is suitable for tunnel construction with stable soil quality and small cross-section, and is suitable for manual excavation or small mechanical operation.
(2) The full-section excavation method adopts top-to-bottom excavation and molding, excavates along the contour, and advances the footage once according to the construction plan and carries out the initial support in time.
(3) The advantage of the full-section excavation method is that it can reduce the number of disturbances of the excavation to the surrounding rock, which is conducive to the formation of the natural bearing of the surrounding rock, and the process is simple; The disadvantage is that the geological conditions are strict, and the surrounding rock must have sufficient self-stabilization ability.
6. Step excavation method
【Formula】Appropriate face-to-face speed and long level
(1) The step excavation method is suitable for tunnel construction with good soil quality, as well as tunnels with weak surrounding rock and Quaternary sedimentary strata.
(2) The step excavation method divides the structural section into more than two parts, that is, it is divided into two working faces or several working faces up and down, and excavates step by step. According to the stratum conditions and mechanical supporting conditions, the step method can be divided into the positive step method and the middle partition step method. The positive step method can close the support earlier, which is conducive to controlling the structural deformation and the resulting ground settlement.
(3) The advantages of the step excavation method are that it has enough working space and fast construction speed, is flexible and changeable, and has strong applicability.
(4) Precautions for step excavation method:
1) The step method should determine the length of the excavation step according to the geology and the span of the excavation section, and the length of the soil tunnel step should not exceed 1 time of the tunnel width, and the step should not be more than 3 steps.
2) The length of a cycle of excavation, the stable rock mass should be determined according to the mechanical excavation capacity, and generally should not be greater than 4m; The length of a circular excavation in the soil layer and unstable rock mass should meet the requirements of the design documents.
7. Annular excavation reserved core soil method
【Formula】Optimal preset anchor for suitable shunts
(1) The annular excavation reserved core soil method is suitable for the construction of tunnels with general soil or weak surrounding rock and large cross-section that are easy to collapse. It is the most commonly used standard excavation method for shallow buried and underground excavation in urban Quaternary soft soil strata.
(2) In general, the section is divided into three parts: the annular arch, the upper core soil, and the lower step. According to the size of the section, the annular arch can be divided into several pieces for alternating excavation. The footage of annular excavation is 0.5~1.0m, which should not be too long. The length of the step should generally be controlled within 1D (D generally refers to the tunnel span).
(3) Construction operation process: use manual or single-arm roadheader to excavate the annular arch→ erect vertical steel support→ hang reinforcement mesh→ shotcrete. Under the protection of the initial support of the arch, in order to speed up the progress, it is advisable to use an excavator or a single-arm roadheader to excavate the core and the next step, and connect the long steel support and shotcrete and the bottom at any time. Depending on the deformation of the initial support or the construction sequence, arrange the secondary lining construction operation.
(4) The main advantages of the method:
1) Because the upper part of the excavation process is left with core soil to support the excavation face, the initial support of the arch can be built quickly and timely, so the stability of the excavation working face is good.
2) Like the step method, the core soil and the lower excavation are carried out under the protection of the initial support of the arch, and the construction safety is good. Compared with the ultra-short step method, the step length can be moderately lengthened to reduce the interference of the upper and lower step construction. Compared with the unilateral wall method, the degree of construction mechanization can be relatively improved, and the construction speed can be accelerated.
(5) Precautions:
1) Although the core soil enhances the stability of the excavation surface, the surrounding rock has to undergo many disturbances during the excavation, and there are many sections in the section, and the supporting structure forms a full section closure for a long time, which may increase the deformation of the surrounding rock. Therefore, it is often necessary to pre-support or pre-reinforce the excavation face and the rock mass in front of it in combination with auxiliary construction measures.
2) Because the arch excavation height is small, or the formation is soft and the anchor is not easy to form, so for the Quaternary stratum of the city, there is generally no or less anchor rod in the construction.
Yesterday 速记口诀5/16
1. Proximity construction management
Supervision of the special case
2. Causes of formation deformation
Pressure disturbance injection of groundwater
3. Formation deformation stage of shield construction
It is longer before and after the arrival
4. Influencing factors of stratum deformation
The ratio of soil cover to soil is the same as that of flood sand and viscosity reduction
5. Deformation control measures caused by unbalanced earth-water pressure on the shield excavation face
Speed regulation adds regulation characteristics, and cooperates with auxiliary construction
6. Control measures for deformation of surrounding rock during shield crossing
Attitude control is less suitable, drag reduction and less over-digging
7. Formation deformation control measures caused by shield tail prolapse
Timely filling of slurry
8. Deformation control measures for shield construction lining
Tighten fully to maintain the shape
9. Control measures for the decline of groundwater level caused by shield construction excavation or lining leakage
Segment group defense
10. Prediction and construction monitoring of formation deformation
The value is set by the meta-change supervision
11. Layout of shield construction stratum deformation monitoring points
The middle line and both sides, three in the same step
12. Shield construction stratum deformation monitoring project
The surface tunnel is changed, and the internal relay is transferred
13. Formation deformation monitoring method for shield construction
Vertical level flat guard edge, net 3 sensor pier in front of the photo
Three days ago, shorthand mantra 5/14
1. Segment assembly method
Choose to fight the top and tighten it
2. True circle retains meaning
Reduce sedimentation, keep sperm and speed up
3. Key points of segment assembly construction
Clear and control to prevent losses, spot check the empty push water
Seven days ago, shorthand mantra 5/10
1. Construction conditions of shield method
Homogeneous buried deep groundwater, cross-section affects sharp turns
2. Preparation for shield construction
Adjustment well excavation
3. Pre-construction investigation of shield tunneling
Electricity consumption in the underground environment
4. Technical preparation for shield construction
Graphic and textual shield survey
5. Selection of shield working well location and construction method
The vibration and noise alternate end is always, and the security economy affects the open digging well
6. The cross-sectional size of the shield working well is determined
Flat bottom, long and wide
7. Preparation before shield tunneling
Review the storage checklist
8. Basic requirements for construction site layout
According to the internal elimination equipment, the road warehouse yard line mixing pit
9. Layout of the shield construction site
Well prevention vertical transportation field, three stations and three roads
10. Shield construction facilities are set up
Mud charging pump machine room
11. Assembling and debugging of the shield
The plan reorganizes the ground load capacity and eliminates the special air commissioning
Two weeks agoShorthand mantra 5/3
1. The role of precipitation
Intercept seepage and stabilize the slope to prevent flow, and lift the shear pit to stabilize and reduce water power
2. Basis for the selection of engineering precipitation methods
Soil and water infiltration depth
3. Engineering precipitation method
Trap jet pipe latent infiltration
4. Collect water and drain it
Ditch well slope seepage pumping subsidence
5. Vacuum well point layout
The construction site is a deep water pit, and the main pump is far from the deep pipe into the soil
6. Vacuum well point and jet well point well formation method
Drilling and punching deep dilute filter seal
7. a tube well
The bottom of the pipe diameter slurry is made into a hole
8. Irrigation
The water drop needs to be protected, and the depth of the well is pressed at the top
9. Factors influencing the characteristics of groundwater seepage
Destination depth aquifer
10. The water separation (interception) curtain of the foundation pit and the precipitation inside and outside the pit are arranged
The inside and outside of the bottom pit, and the pressure in the pit in the layer is reduced
五周前速记口诀4/13
1. Requirements for waterproof base layer
Strong rough horizontal seam plus simulation test
2. Waterproof layer base treatment
Spray brush first corner, similar to the period of water to protect
3. Waterproofing membrane construction
Temperature ban perimeter protection, paving first partial, self-adhesive hot melt hose storage
4. Waterproof coating construction
Ammonia mud is dissolved in water, the ingredients should be coated 4, the joint head is finely reinforced 9, and the carcass is strong and stored
5. Waterproof layer protection measures
Prohibited people, moisture-proof, not allowed to operate or straight pile protection
6. General provisions for the acceptance of waterproof quality of bridge deck
The construction personnel self-inspection and evaluation, and the inspection was 10,537
7. Concrete base detection
The main control is rough level, the surface density is flat and dry, and the socket surface and cracks
8. Waterproof layer detection
The sampling material is now strong and thick, and there is generally no leakage of sealing, and the coil material is overlapped and particularly sticky shear
9. The temperature of asphalt concrete is detected
The roll is high and painted low 1270