Summary of tunnel construction technical work
Since the beginning of the 20th year, he has been involved in the project department. He has mainly participated in surveying and tunnel construction work. He is mainly responsible for tunnel construction excavation and initial technical support. Now he will give a brief introduction to the tunnel project. This project is a convenient communication route between the Guogao Railway and the Changsong Expressway. The total length of the whole line is about 36.132 kilometers. The entire line is set up with the Longchang Expressway connecting the Daohu Hub Interchange. It is divided into four sections by the white sand. The total length of the a1 section is 9 kilometers, including one tunnel, which is separated by double holes. The total length is 1087.5 meters, the left line is 1075 meters long, the maximum depth is 117 meters, the right line is 1100 meters long, and the maximum depth is 117 meters. The tunnel area belongs to the structure-erosion and erosion low mountainous landscape, the surface layer is mostly the Quaternary residual slope soil, the late Yanshanian granite and its weathering layer, the surrounding rock grade is grade v, the stability of the cave roof and side wall is poor, and the groundwater is mainly weathered. The pore-fracture water and the structure-fracture water in the bedrock are not corrosive to concrete. There are six fault layers across the tunnel axis in the tunnel area, which have certain influence on the stability of the tunnel and the surrounding rock level. I have participated in surveying and tunnel construction. In general, I have some deep understanding of tunnel construction, so I will make an overall evaluation of tunnel construction.
1. Construction plan:
The tunnel structure is designed according to the new Austrian law principle. It is constructed by ordinary drilling and blasting method. The v-level surrounding rock section with poor geological conditions in the portal section is excavated by cd method. The construction support adopts composite support, with bolts and steel arches. , wet-sprayed concrete, steel mesh, steel frame and anchor joint support, and supplemented by large pipe shed or small pipe and other advanced support. The reinforced concrete lining of the shallow buried section of the hole should be applied in time. Construction auxiliary measures shall be constructed before excavation.
During construction, the left and right guide pits should be opened in the longitudinal direction of not less than 2d, and the vertical distance of the upper and lower steps of the guide pit should be less than 5m, and the longitudinal distance should be adjusted according to the measurement results to ensure the safe and smooth construction of the tunnel. .
Temporary side wall demolition shall be carried out after the internal force of the temporary support and the deformation of the surrounding rock are basically stable. Each time the steel support spacing is not more than 2 times, the measurement data of the deformation within the hole shall be closely monitored during the demolition process. If there is a sudden change, the dismantling shall be stopped immediately. If necessary, measures may be taken to locally strengthen the initial support.
Strengthen relevant monitoring and ventilation during the construction process.
2. Excavation of the cavern:
The tunnel entrance and exit is poorly geological, and the tunnel entrance should be selected for construction during the dry season. When constructing a hole, a reasonable construction method must be selected. The order of the hole must be strictly controlled. It is strictly forbidden to excavate the large brush slope. After completing the arching and the advanced pipe shed, the main body of the Myeongdong lining construction should be carried out immediately. It must be timely protected, and the import and export combined with the relevant construction assistance measures to form a hole.
The v-level surrounding rock should be excavated by mechanical excavation or controlled blasting, and the face should be timely and necessary. In actual and row drilling and blasting operations, the midline, horizontal line and section profile of the excavation section shall be determined before drilling and blasting, the position of the blasthole shall be marked, and inspection and recording shall be carried out after drilling the hole to ensure the safety of drilling and blasting. When excavating the excavator, the appropriate type of machine should be selected according to the strength of the surrounding rock. When excavating the excavator, the site should be leveled to clear the accumulated water and create a good operating environment. When excavating, pay close attention to the stability of the excavation surface. And try to reduce over-excavation. The tunnel construction should be staked out to ensure the accuracy. The length and direction of the tunnel should be calculated according to the coordinates of each main control point during construction, and the line should be laid according to the ground. In order to ensure that the bottom of the tunnel is excavated according to the longitudinal slope shown in the design drawings and meets the correct staking of the lining, a leveling point should be set every 50 meters in the hole.
The length of each excavation cycle should not be greater than 1.5 times the distance between the steel supports or anchors.
Tunnel excavation must strictly control under-excavation and minimize over-excavation. Mechanical excavation must be used for controlled blasting techniques such as smooth blasting, microseismic blasting and pre-cracking blasting. During the blasting, the excavation footage and charge should be strictly controlled, and the blasting wave speed should be controlled to avoid the adverse impact of blasting vibration on the houses in the residential area around the tunnel site.
3. Initial support:
After the blasting of surrounding rock at all levels, the initial sneeze shall be applied in time to close the exposed surface of the surrounding rock.
The thickness of the initial spray shall not be less than 4 cm. Immediately after the initial spray, steel arches, steel meshes, anchors, etc. shall be installed, and then sprayed to the initial thickness of the design; the inverted arch shall be applied in time to form a closed loop as soon as possible.
Wet spray technology should be adopted for all shotcrete, and dry spray should not be used to ensure the quality of shotcrete.
Before spraying the concrete, flush the dust and debris from the rock wall with water or high pressure air duct.
The spraying operation should be carried out in layers of appropriate thickness, and the subsequent spraying should be carried out after the final layer of concrete has been set. If the final setting is more than 1 hour and the surface is covered with dust, it should be cleaned. When the rock face has a large concave ridge, it should be combined with the initial spray to level.
After the sprayed concrete is finally condensed for 2 hours, it should be sprayed and cured, and the curing time is generally not less than 7 days.
At the temporary arch of the excavation, the spray should be full.
The steel arches should be placed on the vertical plane in the direction of the midline according to the midline, horizontal, tunnel section and reserved settlement, and strive to be neat, and the rock face should be as close as possible. The gap between the steel frame and the surrounding rock must be filled with shotcrete and compacted. When the gap is too large, the block should be tightened in time;
Measures to prevent subsidence and subsidence should be taken according to geological conditions. The scum under the arch of the support must be removed. When the formation is soft, a pad or padding beam should be added and applied as a lock anchor. The shot should be full at the excavation.
The longitudinal connection between the steel frames should be firm and integral. The anchor and the backing plate should be vertical and in full contact with the spray jaws, the nuts must be tightened.
4. Construction drainage and structural drainage:
Before the tunnel construction, the ground drainage system of the cave roof and the opening should be done in time according to the design requirements to prevent the infiltration and erosion of the surface water.
Before the tunnel construction, the ground of the tunnel section shall be cleaned, and the ditch shall be diverted to close the water and the ground shall not be accumulated. The potholes, pits, etc. for exploration shall be backfilled with clay and laminated.
When the outer road of the tunnel is downhill in the tunnel, the subside of the road should be reversed and drained to the outside of the road. It is advisable to set a horizontal intercepting facility at a distance of 5 meters to intercept the surface water into the cave. Mechanical drainage must be taken when draining the slope in the cave.
When the structure is used for drainage and drainage, the surface of the shotcrete should be flat, and the uneven ratio of the unevenness should be no more than 1/6. The sharp protrusions such as steel bars should be cut and ground to avoid breaking the waterproof layer. The eva waterproofing membrane has a lap width of 10 cm and is double-slit welded by an automatic walking heat sealing machine. Each weld shall be inspected for air tightness at an inflation pressure of 0.15 mPa and maintained at a constant pressure for not less than 2 minutes. The weld strength is not lower than the parent strength.
The cross-sectional shape, size, position and depth of the drainage and the slope should meet the design requirements. The drain fitting should be tightly sealed and must not be loose.
During construction, the side and vertical and horizontal drain pipes should be kept from crushing and clogging; when the concrete on the side ditch is poured, isolation measures should be taken to prevent the cement slurry from infiltrating and causing the drainage ditch to block and ensure the smooth drainage system.
Longitudinal construction joints are made of water-swellable water-stopping glue, which should be constructed in strict accordance with the product description and construction process requirements. Before the construction, use the wire brush to remove the sand and concrete slag from the construction surface. After the construction, confirm that there is no gap between the concrete and the water-stopping glue. If there is a gap, use a trowel to smooth it. It takes about 24 hours from the construction of the water stop glue to the surface hardening. After the surface of the water stop glue is hardened and the touch is dry, the concrete can be continuously poured. Do not soak the water-stopping glue in the construction.
5. When the secondary lining secondary lining concrete is poured, the construction organization management should be strengthened, the concrete shrinkage ratio should be selected, and the template trolley with sufficient rigidity should be used to minimize the gap between the second lining and the initial branch; when the secondary lining strength is reached Only 90% of the design strength can be demoulded.
The concrete pouring adopts the pumping and pouring process to mechanically vibrate and compact. Before pumping, the cement slurry mixed according to the design mix ratio or the concrete lubrication pipe prepared by halving the aggregate should be used. The height, order and direction of each layer should be determined according to factors such as mixing capacity, transportation distance, filling speed, temperature inside the cave and vibration. In order to prevent the displacement of the trolley caused by excessive pressure deviation on both sides during pouring, the height difference of the perfusion surface on both sides should be controlled within 50cm, and the casting speed should be controlled reasonably.
During the construction process, the pump should be continuously operated and pumped continuously for construction. It is advisable to avoid “cold seam” caused by stoppage. When the intermittent time exceeds the specification requirements, it should be treated according to the construction joint.
When the concrete is poured to the working window 50cm, before the working window is closed, the residue of the mortar and other materials near the window should be cleaned, the release agent should be applied, and the mold release agent should be closed to prevent the unevenness or even leakage of the surface of the window. Pulp phenomenon.
The anti-arc part below the arch line of the tunnel lining is a difficult part of the pouring operation. The rafting performance, slump and tamping method should be effectively controlled to reduce the bubbles in the arc and effectively improve the surface quality of the lining.
The top cover is connected to the conveying pipe by a top mold center top sealer, and the top cover is gradually pressed. When the observation hole on the stop plate has a slurry overflow, the mark is completed.
The demoulding is controlled according to the construction specifications using the strength achieved by the last plate capping test piece. When the external load is not tolerated, the strength of the concrete should be 5mpa or the surface and edges of the concrete should not be damaged when the mold is removed and can be subjected to self-weight. When the lining is applied in advance and subjected to surrounding rock pressure, it should be carried out according to the specifications. .
Before the mold is removed, the outer surface of the formwork is rinsed with water. After the mold is removed, the surface of the concrete is sprayed with high-pressure water to reduce the heat of hydration, and the curing period is not less than 14 days. The tunnel construction adopts new technology, new structure, new materials and new equipment. The v-level surrounding rock system anchor adopts the hollow anchor of the forward and reverse circulation combined grouting technology, which can adapt well to the up-and-down-down stalk body. Grouting; longitudinal construction joints are water-swellable water-stopping glue, which is a water-swellable single-liquid sealant. After hardening, it becomes a rubber elastomer with good recovery. It expands in water volume, fills voids, and has good water stopping effect. It overcomes the current situation. Waterstops are prone to aging and inconvenient construction. The above is a combination of field work experience and theory to briefly explain and summarize the tunnel construction technology, and more advocate the application of new technologies, new processes, new materials, abolish the old and backward construction technology, and have a very good construction schedule and construction quality. Great improvement.
1. Construction plan:
The tunnel structure is designed according to the new Austrian law principle. It is constructed by ordinary drilling and blasting method. The v-level surrounding rock section with poor geological conditions in the portal section is excavated by cd method. The construction support adopts composite support, with bolts and steel arches. , wet-sprayed concrete, steel mesh, steel frame and anchor joint support, and supplemented by large pipe shed or small pipe and other advanced support. The reinforced concrete lining of the shallow buried section of the hole should be applied in time. Construction auxiliary measures shall be constructed before excavation.
During construction, the left and right guide pits should be opened in the longitudinal direction of not less than 2d, and the vertical distance of the upper and lower steps of the guide pit should be less than 5m, and the longitudinal distance should be adjusted according to the measurement results to ensure the safe and smooth construction of the tunnel. .
Temporary side wall demolition shall be carried out after the internal force of the temporary support and the deformation of the surrounding rock are basically stable. Each time the steel support spacing is not more than 2 times, the measurement data of the deformation within the hole shall be closely monitored during the demolition process. If there is a sudden change, the dismantling shall be stopped immediately. If necessary, measures may be taken to locally strengthen the initial support.
Strengthen relevant monitoring and ventilation during the construction process.
2. Excavation of the cavern:
The tunnel entrance and exit is poorly geological, and the tunnel entrance should be selected for construction during the dry season. When constructing a hole, a reasonable construction method must be selected. The order of the hole must be strictly controlled. It is strictly forbidden to excavate the large brush slope. After completing the arching and the advanced pipe shed, the main body of the Myeongdong lining construction should be carried out immediately. It must be timely protected, and the import and export combined with the relevant construction assistance measures to form a hole.
The v-level surrounding rock should be excavated by mechanical excavation or controlled blasting, and the face should be timely and necessary. In actual and row drilling and blasting operations, the midline, horizontal line and section profile of the excavation section shall be determined before drilling and blasting, the position of the blasthole shall be marked, and inspection and recording shall be carried out after drilling the hole to ensure the safety of drilling and blasting. When excavating the excavator, the appropriate type of machine should be selected according to the strength of the surrounding rock. When excavating the excavator, the site should be leveled to clear the accumulated water and create a good operating environment. When excavating, pay close attention to the stability of the excavation surface. And try to reduce over-excavation. The tunnel construction should be staked out to ensure the accuracy. The length and direction of the tunnel should be calculated according to the coordinates of each main control point during construction, and the line should be laid according to the ground. In order to ensure that the bottom of the tunnel is excavated according to the longitudinal slope shown in the design drawings and meets the correct staking of the lining, a leveling point should be set every 50 meters in the hole.
The length of each excavation cycle should not be greater than 1.5 times the distance between the steel supports or anchors.
Tunnel excavation must strictly control under-excavation and minimize over-excavation. Mechanical excavation must be used for controlled blasting techniques such as smooth blasting, microseismic blasting and pre-cracking blasting. During the blasting, the excavation footage and charge should be strictly controlled, and the blasting wave speed should be controlled to avoid the adverse impact of blasting vibration on the houses in the residential area around the tunnel site.
3. Initial support:
After the blasting of surrounding rock at all levels, the initial sneeze shall be applied in time to close the exposed surface of the surrounding rock.
The thickness of the initial spray shall not be less than 4 cm. Immediately after the initial spray, steel arches, steel meshes, anchors, etc. shall be installed, and then sprayed to the initial thickness of the design; the inverted arch shall be applied in time to form a closed loop as soon as possible.
Wet spray technology should be adopted for all shotcrete, and dry spray should not be used to ensure the quality of shotcrete.
Before spraying the concrete, flush the dust and debris from the rock wall with water or high pressure air duct.
The spraying operation should be carried out in layers of appropriate thickness, and the subsequent spraying should be carried out after the final layer of concrete has been set. If the final setting is more than 1 hour and the surface is covered with dust, it should be cleaned. When the rock face has a large concave ridge, it should be combined with the initial spray to level.
After the sprayed concrete is finally condensed for 2 hours, it should be sprayed and cured, and the curing time is generally not less than 7 days.
At the temporary arch of the excavation, the spray should be full.
The steel arches should be placed on the vertical plane in the direction of the midline according to the midline, horizontal, tunnel section and reserved settlement, and strive to be neat, and the rock face should be as close as possible. The gap between the steel frame and the surrounding rock must be filled with shotcrete and compacted. When the gap is too large, the block should be tightened in time;
Measures to prevent subsidence and subsidence should be taken according to geological conditions. The scum under the arch of the support must be removed. When the formation is soft, a pad or padding beam should be added and applied as a lock anchor. The shot should be full at the excavation.
The longitudinal connection between the steel frames should be firm and integral. The anchor and the backing plate should be vertical and in full contact with the spray jaws, the nuts must be tightened.
4. Construction drainage and structural drainage:
Before the tunnel construction, the ground drainage system of the cave roof and the opening should be done in time according to the design requirements to prevent the infiltration and erosion of the surface water.
Before the tunnel construction, the ground of the tunnel section shall be cleaned, and the ditch shall be diverted to close the water and the ground shall not be accumulated. The potholes, pits, etc. for exploration shall be backfilled with clay and laminated.
When the outer road of the tunnel is downhill in the tunnel, the subside of the road should be reversed and drained to the outside of the road. It is advisable to set a horizontal intercepting facility at a distance of 5 meters to intercept the surface water into the cave. Mechanical drainage must be taken when draining the slope in the cave.
When the structure is used for drainage and drainage, the surface of the shotcrete should be flat, and the uneven ratio of the unevenness should be no more than 1/6. The sharp protrusions such as steel bars should be cut and ground to avoid breaking the waterproof layer. The eva waterproofing membrane has a lap width of 10 cm and is double-slit welded by an automatic walking heat sealing machine. Each weld shall be inspected for air tightness at an inflation pressure of 0.15 mPa and maintained at a constant pressure for not less than 2 minutes. The weld strength is not lower than the parent strength.
The cross-sectional shape, size, position and depth of the drainage and the slope should meet the design requirements. The drain fitting should be tightly sealed and must not be loose.
During construction, the side and vertical and horizontal drain pipes should be kept from crushing and clogging; when the concrete on the side ditch is poured, isolation measures should be taken to prevent the cement slurry from infiltrating and causing the drainage ditch to block and ensure the smooth drainage system.
Longitudinal construction joints are made of water-swellable water-stopping glue, which should be constructed in strict accordance with the product description and construction process requirements. Before the construction, use the wire brush to remove the sand and concrete slag from the construction surface. After the construction, confirm that there is no gap between the concrete and the water-stopping glue. If there is a gap, use a trowel to smooth it. It takes about 24 hours from the construction of the water stop glue to the surface hardening. After the surface of the water stop glue is hardened and the touch is dry, the concrete can be continuously poured. Do not soak the water-stopping glue in the construction.
5. When the secondary lining secondary lining concrete is poured, the construction organization management should be strengthened, the concrete shrinkage ratio should be selected, and the template trolley with sufficient rigidity should be used to minimize the gap between the second lining and the initial branch; when the secondary lining strength is reached Only 90% of the design strength can be demoulded.
The concrete pouring adopts the pumping and pouring process to mechanically vibrate and compact. Before pumping, the cement slurry mixed according to the design mix ratio or the concrete lubrication pipe prepared by halving the aggregate should be used. The height, order and direction of each layer should be determined according to factors such as mixing capacity, transportation distance, filling speed, temperature inside the cave and vibration. In order to prevent the displacement of the trolley caused by excessive pressure deviation on both sides during pouring, the height difference of the perfusion surface on both sides should be controlled within 50cm, and the casting speed should be controlled reasonably.
During the construction process, the pump should be continuously operated and pumped continuously for construction. It is advisable to avoid “cold seam” caused by stoppage. When the intermittent time exceeds the specification requirements, it should be treated according to the construction joint.
When the concrete is poured to the working window 50cm, before the working window is closed, the residue of the mortar and other materials near the window should be cleaned, the release agent should be applied, and the mold release agent should be closed to prevent the unevenness or even leakage of the surface of the window. Pulp phenomenon.
The anti-arc part below the arch line of the tunnel lining is a difficult part of the pouring operation. The rafting performance, slump and tamping method should be effectively controlled to reduce the bubbles in the arc and effectively improve the surface quality of the lining.
The top cover is connected to the conveying pipe by a top mold center top sealer, and the top cover is gradually pressed. When the observation hole on the stop plate has a slurry overflow, the mark is completed.
The demoulding is controlled according to the construction specifications using the strength achieved by the last plate capping test piece. When the external load is not tolerated, the strength of the concrete should be 5mpa or the surface and edges of the concrete should not be damaged when the mold is removed and can be subjected to self-weight. When the lining is applied in advance and subjected to surrounding rock pressure, it should be carried out according to the specifications. .
Before the mold is removed, the outer surface of the formwork is rinsed with water. After the mold is removed, the surface of the concrete is sprayed with high-pressure water to reduce the heat of hydration, and the curing period is not less than 14 days. The tunnel construction adopts new technology, new structure, new materials and new equipment. The v-level surrounding rock system anchor adopts the hollow anchor of the forward and reverse circulation combined grouting technology, which can adapt well to the up-and-down-down stalk body. Grouting; longitudinal construction joints are water-swellable water-stopping glue, which is a water-swellable single-liquid sealant. After hardening, it becomes a rubber elastomer with good recovery. It expands in water volume, fills voids, and has good water stopping effect. It overcomes the current situation. Waterstops are prone to aging and inconvenient construction. The above is a combination of field work experience and theory to briefly explain and summarize the tunnel construction technology, and more advocate the application of new technologies, new processes, new materials, abolish the old and backward construction technology, and have a very good construction schedule and construction quality. Great improvement.
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