A method for single-sided formwork construction of ultra-large volume concrete with high and low spans

Abstract

This invention relates to a method for single-sided formwork construction of ultra-large volume concrete spans with varying elevations. The method includes the following steps: Step 1: Excavation and slope setting of the earthwork for the high and low spans; Step 2: Binding of steel mesh and installation of soil nails on the slope; Step 3: Shotcrete protection of the slope; Step 4: Base treatment and leveling of the slope; Step 5: Waterproofing layer construction; Step 6: Waterproofing protective layer construction; Step 7: Reinforcement binding of the raft foundation; Step 8: Pouring of concrete for the lower span raft foundation; Step 9: Single-sided formwork for the ultra-large "inverted triangle" concrete section of the high and low spans; Step 10: Pouring of the raft foundation concrete; Step 11: Curing; Step 12: Temperature measurement and monitoring. This invention solves the problems of waterproofing protection for raft foundations with varying elevations and the challenges of single-sided formwork for ultra-large volume concrete spans, reducing construction costs and saving construction time.

Description

Technical Field

[0001] This invention relates to the field of civil engineering, specifically to a method for single-sided formwork construction of ultra-large volume concrete with high and low spans. Background Technology

[0002] Because the height difference of traditional high and low span raft foundations is small, simple supports can meet the on-site construction requirements. However, if the height difference between the high and low spans is large, the connection between the high and low spans forms an "inverted triangle" of ultra-large volume concrete, which poses a construction challenge. The usual practice is to pre-embed channel steel when pouring the concrete of the low span first. The channel steel is used as a single-sided formwork support point to support the "inverted triangle" formwork. This has disadvantages, such as the pre-embedded channel steel creating weak points for leakage, increasing project costs, and being detrimental to energy conservation and material conservation requirements. Summary of the Invention

[0003] This invention aims to overcome the shortcomings of the prior art and provide a method for single-sided formwork construction of ultra-large volume concrete with high and low spans, solving the problems of waterproof protection of raft foundations with high and low spans and single-sided formwork of ultra-large volume concrete.

[0004] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0005] A method for single-sided formwork construction of ultra-large volume concrete with high and low spans, characterized by comprising the following steps:

[0006] Step 1: Excavation of earthwork with slope protection at different elevations;

[0007] Step 2: Tie the steel mesh on the slope and install soil nails;

[0008] Step 3: Shotcrete protection of the slope surface;

[0009] Step 4: Apply plaster and level the sloping surface as a base layer.

[0010] Step 5: Waterproofing layer construction;

[0011] Step Six: Apply the waterproof protective layer;

[0012] Step 7: Binding of raft foundation reinforcement;

[0013] Step 8: Pouring concrete for the low-span raft slab;

[0014] Step Nine: Single-sided formwork support for the large concrete cross-section of the "inverted triangle" with varying heights and depths;

[0015] Step 10: Pouring the raft foundation concrete to "close" it;

[0016] Step 11: Maintenance;

[0017] Step 12: Temperature measurement and monitoring.

[0018] The method for single-sided formwork construction of ultra-large volume concrete with high and low spans is characterized by:

[0019] Step 1: First, excavate the earthwork at the high and low cross-section section. Excavate according to the required ratio in the drawings and slope the slope to ensure the position of the upper and lower lines, the flatness of the slope line, and the slope. Then, manually trim the slope.

[0020] In step two, the slope support adopts a soil nailing wall support system with a slope ratio of 1:0.5. The soil nails are arranged in a rectangular pattern, with each row of soil nails having a length and longitudinal and transverse spacing of 2m. The soil nail hole diameter is 100mm, the inclination angle is 10°, and the reinforced soil nail rods are made of 1φ20 threaded steel. Cement grout is injected under normal pressure with a grout strength of M20, and at least two groutings are added. A ∅6@200×200 steel mesh is hung in the middle, and 1φ16 transverse reinforcing bar is welded to the outside and connected to all soil nail heads. The panel is made of fine stone concrete sprayed on site with a concrete strength grade of C20 and a thickness of 100mm. The concrete protection surface at the top of the slope extends 800mm outward.

[0021] In step three, the panel is made of fine aggregate concrete sprayed on site. The concrete strength grade is C20, the thickness is 100mm, and the concrete protection surface at the top of the slope extends 800mm outward.

[0022] In step four, after the slope surface is sprayed, the slope surface is leveled using M7.5 cement mortar, and after plastering, it is smoothed to achieve the requirement of full waterproof adhesion.

[0023] In step five,

[0024] 1. The entire waterproof substrate should be kept dry. Generally, the moisture content of the substrate should not exceed 9%. The ambient temperature for laying the waterproof membrane should not be lower than -10℃ for hot-melt construction of SBS modified bitumen waterproof membrane.

[0025] 2. Apply cold primer: Apply the primer and use a long-handled brush to apply the cold primer to the clean and dry base surface. For complex areas, use a paint brush. Ensure that there are no white gaps and apply evenly. Allow it to dry for more than 4 hours until it is no longer sticky to the feet before proceeding to the next step.

[0026] 3. Additional layer construction: Apply additional layer treatment to all internal and external corners with angles less than 135º, such as the corners of high and low spans and the junctions between the facade wall and the plane. The width of the additional layer shall not be less than 500mm.

[0027] 4. Roll material laying: When laying large areas, the person holding the blowtorch should stand in front of the roll material and aim the blowtorch at the junction of the roll material and the substrate. At the same time, heat the roll material and the substrate. The blowtorch head should be 50-100mm away from the roll material surface and at a 60º angle to the substrate. The full adhesion method should be used for construction in this area.

[0028] 5. Construction of roll material lap joints: Before hot-melt bonding of lap joints, melt the release layer on the surface of the next roll material with a blowtorch. The worker holding the blowtorch moves backward along the lap line with a trowel as a baffle. The blowtorch flame moves with the baffle. The blowtorch should be close to the baffle and about 50-100mm away from the roll material.

[0029] 6. The overlap width of the roll material should not be less than 100mm. The edge of the overlap should be filled with hot-melt modified asphalt. Then, use a blowtorch to evenly heat-melt the roll material overlap and smooth the edge with a small trowel. When laying the second layer of roll material, its overlap must be staggered from the overlap of the first layer by half the roll material width. Arrange the construction time for bonding the two layers of roll material properly and do not leave too long an interval, so as to avoid the first layer of roll material being contaminated with dust, which will affect the bonding effect of the two layers.

[0030] In step six, a pre-applied self-adhesive waterproof membrane is used to replace the traditional waterproof protective layer;

[0031] In step seven, the raft foundation reinforcement is tied in the order of first the lower span and then the higher span. The slope reinforcement is laid out on site according to the slope ratio to ensure that the angle and bending position of the reinforcement are correct. The reinforcement connection is optimized to ensure that the connection is made on both sides of the high and low spans. Continuous reinforcement is used on the slope.

[0032] In step eight, C35 concrete is used to pour the raft foundation and the slope with varying elevation. The concrete in this area is poured in two stages. The first stage is poured to the top elevation of the low-span raft foundation, and the second stage is poured to the 800mm high guide wall at the slope. The interval between the two stages is controlled within 2 hours. Three-section water-stop bolts are pre-embedded in the guide wall. The requirements for the water-stop steel plate are the same as those for the basement exterior wall.

[0033] In step nine,

[0034] 1. Before pouring the raft foundation in the low zone, first pre-embed 4 rows of 1m long steel pipes, buried at a depth of 400mm, with 600mm exposed above the top surface of the raft foundation. Arrange them along the variable cross section. The first row of steel pipes is 400mm from the edge of the variable cross section, the second row is 1400mm from the edge of the variable cross section, the third row is 2300mm from the edge of the variable cross section, and the fourth row is 3000mm from the edge of the variable cross section. They are arranged at 1000mm intervals parallel to the length direction of the variable cross section.

[0035] 2. Formwork construction requirements:

[0036] Template selection: 15mm thick film-coated wooden template;

[0037] Main keel: Φ48 double steel pipe, horizontally set. The initial main keel is fixed by the screws embedded in the guide wall. The second main keel is 400mm high from the bottom raft top, and the upper main keel spacing is 400mm.

[0038] Secondary joists: 40mm×90mm timber, vertically installed, spaced 150mm apart;

[0039] Screw: φ14 screw, vertical spacing 400mm, horizontal spacing 400mm;

[0040] 3. Template support settings:

[0041] All support systems use a ring-lock frame structure;

[0042] Double-row frame system: The double-row frame uprights above the top surface of the low zone raft slab are connected to the pre-embedded short uprights by fasteners. The longitudinal and transverse spacing of the uprights is 1m and the step distance is 1.5m. The top three water-stop tie rods are welded to the upper and lower double-layer horizontal reinforcement of the high zone raft slab. Other height ranges are reinforced by diagonal supports.

[0043] Diagonal bracing system: The diagonal bracing is set at a vertical spacing of 0.8m and crosses each other. The bottom of the diagonal bracing is connected to the pre-embedded third and fourth rows of short steel pipes. The top is set with U-shaped brackets and is tightly pressed against the main keel of the formwork. When the diagonal bracing passes through the double-row frame, the diagonal bracing is connected to the inner and outer rows of uprights with fasteners. Five diagonal bracings are set on each facade. The top of each diagonal bracing is supported on the main keel with a U-shaped bracket.

[0044] In step ten,

[0045] 1. Adopt layered pouring to ensure that the upper layer of concrete is poured before the lower layer of concrete has initially set.

[0046] 2. Perform a second vibration on the concrete before its initial setting.

[0047] 3. Control cracks;

[0048] The curing method for step eleven is the heat preservation method, and the concrete curing time shall not be less than 14 days;

[0049] In step twelve,

[0050] 1. Monitoring content and early warning indicators

[0051] During the concrete pouring and curing process, the monitoring content includes monitoring time, instantaneous temperature of concrete hydration heat, internal surface temperature difference, temperature drop rate and atmospheric temperature; when the temperature difference between the concrete surface point and the center point reaches 25℃ after the concrete pouring is completed, or when the temperature drop rate of the measuring point reaches -2.0℃ / day, an alert will be issued.

[0052] 2. For large-volume concrete construction, the temperature at which the concrete is poured into the formwork and the ambient temperature must be recorded. The temperature difference between the inside and outside of the concrete measuring points should not be less than 4 times per day after the concrete is poured.

[0053] 3. Each temperature monitoring point must be equipped with surface, bottom, and center temperature measuring points along the thickness direction of the concrete pouring body, and the spacing between other measuring points shall not exceed 600mm; the surface temperature of the concrete pouring body is the temperature 50mm inside the concrete surface; the bottom temperature is the temperature 50mm above the bottom surface of the concrete pouring body.

[0054] 4. Temperature measurement should begin from the time the concrete is poured into the formwork until it reaches its final set; measure the temperature every 4 hours from day 1 to day 4; measure the temperature every 8 hours from day 5 to day 7; and measure the temperature every 12 hours from day 7 until the end of the measurement period. For each temperature measurement, record and calculate the temperature rise / fall and temperature difference at each measurement point. Stop measuring the temperature when the temperature difference between the inner 40mm-100mm radius of the concrete surface and the ambient temperature is less than 20 degrees Celsius.

[0055] 5. Before installation, the temperature testing wire must be soaked in water at a depth of 1m for 24 hours without damage. The installation position of the temperature testing wire joint must be accurate and firmly fixed, and it should be insulated from the structural steel bars and the metal body of the fixing frame. The lead wires of the temperature testing wire should be arranged in a centralized manner and protected. The area around the temperature testing wire should also be protected. During the concrete pouring process, the temperature testing wire and lead wire should not be directly impacted when the material is poured. The vibrator should not touch the temperature testing element and lead wire.

[0056] 6. Handling large temperature differences:

[0057] (1) The temperature difference between the inner and outer surfaces should not exceed 25°C. Once the temperature difference between the inner and outer surfaces is found to be close to or exceeds 25°C, decisive measures should be taken (increase the covering thickness) to ensure that the temperature difference between the inner and outer surfaces is controlled within 25°C.

[0058] (2) When the temperature difference between the inside and outside of the concrete and the cooling rate exceed the temperature control index, spare plastic film and geotextile should be added in time. If necessary, burlap sacks can be purchased in an emergency to enhance the insulation performance.

[0059] (3) When the temperature difference between the surface temperature and the ambient temperature is greater than 20°C, and the air temperature is too low, use iodine tungsten lamps to increase the ambient temperature. When the air temperature is too high and the concrete surface temperature is too low, increase the thickness of the geotextile.

[0060] 7. Deformation monitoring:

[0061] The monitoring items include: deformation of the diagonal bracing keel, deformation of the positioning support point, deformation of the verticality of the upright, and overall horizontal displacement of the support frame;

[0062] Monitoring points are placed at the corners, at the points of greatest deformation in the high and low spans, and at the center of the perimeter.

[0063] The beneficial effects of this invention are: it changes the construction method for waterproofing protection and support of ultra-large volume concrete with varying heights and spans, reduces construction costs, saves construction time, standardizes and rationalizes construction, and helps solve quality problems such as cracking in ultra-large volume concrete.

[0064] This is beneficial for the construction of a foundation slab with a height difference of one layer due to design, geology, and other limitations, forming an "inverted triangle" super-large cross-section concrete, and ensuring quality and safety control throughout the entire process from the construction of the waterproof protective layer to the completion of the "closing" pouring of the high and low span concrete. Attached Figure Description

[0065] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0066] Figure 1 This is a schematic diagram of the variable cross-section in step nine. Detailed Implementation

[0067] A method for single-sided formwork construction of ultra-large volume concrete with high and low spans includes the following steps:

[0068] Step 1: Excavation of earthwork with slope protection at different elevations

[0069] First, earthwork excavation is carried out at the high and low span section with varying cross sections. The slope is set according to the excavation ratio required by the drawings to ensure the position of the upper and lower lines, the flatness of the slope line, and the slope. The slope is then manually trimmed.

[0070] Step 2: Binding the steel mesh on the slope and installing soil nails

[0071] The slope support adopts a soil nailing wall support system with a slope ratio of 1:0.5. The soil nails (anchors) are arranged in a rectangular pattern, with each row of soil nails (anchors) having a length and a longitudinal and transverse spacing of 2m. The soil nail hole diameter is 100mm, the inclination angle is 10°, and the reinforced soil nail rod is made of 1φ20 threaded steel. Cement grout is injected under normal pressure with a grout strength of M20, and at least two grouting sessions are performed. A ∅6@200×200 steel mesh is hung in the middle, and an external 1φ16 transverse reinforcing bar is welded and connected to all soil nail heads. The panel is made of fine aggregate concrete sprayed on site with a concrete strength grade of C20 and a thickness of 100mm. The concrete revetment at the top of the slope extends 800mm beyond the surface.

[0072] Step 3: Shotcrete slope protection

[0073] The panel is made of fine aggregate concrete sprayed on site, with a concrete strength grade of C20 and a thickness of 100mm. The concrete revetment at the top of the slope extends 800mm outward.

[0074] Step 4: Base treatment and leveling of the sloping surface with plaster.

[0075] After the slope surface is sprayed, the slope surface is leveled with M7.5 cement mortar, and after the plastering is completed, it is smoothed to achieve the requirement of full waterproof adhesion.

[0076] Step 5: Waterproofing layer construction

[0077] 1. The entire waterproof substrate should be kept dry, generally requiring a moisture content of no more than 9%. Laying waterproof membrane is strictly prohibited in rainy, snowy, or windy conditions of force 5 or higher. The ambient temperature for hot-melt application of SBS modified bitumen waterproof membrane should not be lower than -10℃.

[0078] 2. Apply cold primer: Apply the primer. Use a long-handled brush to apply the cold primer to the clean, dry substrate surface. For complex areas, use a paint brush. Ensure no bare spots and apply evenly. Allow to dry for at least 4 hours until it is no longer sticky to the touch before proceeding to the next step.

[0079] 3. Additional layer construction: For all internal and external corners with angles less than 135º, such as the high and low spans and the junctions between the facade walls and the plane, an additional layer shall be applied. The width of the additional layer shall not be less than 500mm.

[0080] 5. Roll Material Laying: When laying large areas, the person holding the blowtorch should stand in front of the roll material, aiming the blowtorch at the junction of the roll material and the substrate, simultaneously heating both the roll material and the substrate. The blowtorch head should be kept 50-100mm away from the roll material surface and at a 60º angle to the substrate. This area should be constructed using the full-adhesion method.

[0081] 6. Construction of roll material overlap joints

[0082] Before hot-melting the lap joint, the release layer on the surface of the next layer of roll material is melted with a blowtorch. Specifically, the worker holding the blowtorch moves along the lap joint with a trowel as a baffle, and the blowtorch flame moves with the baffle. The blowtorch should be close to the baffle and about 50 to 100 mm away from the roll material.

[0083] 7. The overlap width of the roll material should not be less than 100mm. The edges of the overlap should be wide enough to allow hot-melt modified asphalt to overflow. Then, use a blowtorch to evenly heat-melt the roll material overlap and smooth the edges with a small trowel. When laying the second layer of roll material, its overlap must be staggered from the first layer's overlap by half the roll width. Schedule the bonding time between the two layers of roll material carefully; do not allow too long an interval, as dust contamination on the first layer may affect the bonding effect.

[0084] Step Six: Waterproof Protective Layer Construction

[0085] Due to the steep slope and smooth surface of the waterproof membrane, traditional mortar / fine aggregate concrete application methods lack adhesion, easily leading to common quality problems such as detachment, cracking, and hollow areas. To address this critical issue, the project replaced the traditional waterproof protective layer with pre-applied self-adhesive waterproof membrane. Self-adhesive waterproof membranes offer the following advantages: 1. Excellent waterproofing performance; one layer is sufficient to meet Class I waterproofing requirements; 2. High strength and resistance to damage, providing better resistance to trampling and mud / sand contamination; 3. Better adaptability to base settlement. Building settlement is unavoidable, even within permissible limits, posing significant challenges to the waterproofing layer. High-polymer adhesive waterproof membranes bond firmly to the concrete structure, unaffected by building settlement. 4. Effectively shortens the construction period and reduces project costs. The polymer self-adhesive waterproof membrane has low requirements for the substrate conditions during construction; the moisture content of the substrate has little impact on the waterproofing process. No leveling layer, isolation layer, or protective layer is needed, reducing earthwork excavation and thus effectively shortening the construction period and reducing project costs. 5. Safe and environmentally friendly: No substrate treatment agent or open flame operation is required during construction, avoiding potential hazards and saving resources. 6. Less affected by constraints; even if the project is being constructed in winter, this area is not affected by low temperatures.

[0086] Step 7: Binding of raft foundation reinforcement

[0087] The raft foundation reinforcement is tied in the order of first the lower span and then the higher span. The slope reinforcement is laid out on site according to the slope ratio to ensure that the angle and bending position of the reinforcement are correct. The reinforcement connection is optimized to ensure that there is a connection on both sides of the high and low spans. Continuous reinforcement is used on the slope.

[0088] Step 8: Pouring Concrete for Low-Span Raft Slab

[0089] C35 concrete was used for pouring the raft foundation and the slope with elevation changes. The admixtures and winter construction measures met the relevant requirements. The concrete in this area was poured in two stages. The first pour was made up to the top elevation of the lower raft foundation, and the second pour was made up to the 800mm high guide wall at the slope. The interval between the two pours was controlled within 2 hours. Three-section water-stop bolts were pre-embedded in the guide wall (with the bottom formwork fixed by a single-sided formwork support). The requirements for the water-stop steel plate were the same as those for the basement exterior walls.

[0090] Step Nine: Single-sided formwork for the large concrete cross-section of the "inverted triangle" with varying heights and depths.

[0091] like Figure 1As shown: 1. Before pouring the raft foundation in the low zone, first pre-embed 4 rows of 1m long steel pipes, buried at a depth of 400mm, with 600mm exposed above the top surface of the raft foundation. Arrange them along the variable cross section. The first row of steel pipes is 400mm from the edge of the variable cross section, the second row is 1400mm from the edge of the variable cross section, the third row is 2300mm from the edge of the variable cross section, and the fourth row is 3000mm from the edge of the variable cross section. They are arranged at 1000mm intervals parallel to the length direction of the variable cross section.

[0092] 2. Formwork Construction Requirements

[0093] Template selection: 15mm thick film-coated wooden template.

[0094] Main keel: Φ48 double steel pipe, horizontally set. The initial main keel is fixed by the screws embedded in the guide wall. The second main keel is 400mm high from the bottom raft top, and the upper main keel spacing is 400mm.

[0095] Secondary joists: 40mm×90mm timber, vertically installed, spaced 150mm apart.

[0096] Screw: φ14 screw, vertical spacing 400mm, horizontal spacing 400mm.

[0097] 3. Template support settings

[0098] All support systems use a ring-lock frame structure;

[0099] Double-row frame system: The double-row frame uprights above the top surface of the low-level raft slab are connected to the pre-embedded short uprights via fasteners. The longitudinal and transverse spacing of the uprights is 1m, and the step distance is 1.5m. The top three water-stop tie rods are welded to the upper and lower double-layer horizontal reinforcement of the high-level raft slab. Other height ranges are reinforced with diagonal supports.

[0100] Diagonal bracing system: The diagonal braces are set at 0.8m vertical spacing and cross each other. The bottom of the diagonal brace is connected to the pre-embedded third and fourth rows of short steel pipes. The top is equipped with a U-shaped bracket and is tightly pressed against the main keel of the formwork. When the diagonal brace passes through the double-row scaffold, the diagonal brace is connected to the inner and outer rows of uprights with fasteners (this diagonal brace also serves as the outrigger of the double-row scaffold). Five diagonal braces are set on each facade. The top of each diagonal brace is supported by a U-shaped bracket on the main keel (the adjustment is made according to the height of the main keel of the formwork).

[0101] Step 10: Pouring the raft foundation concrete to "close" it

[0102] 1. To ensure the integrity of the structure and the continuity of construction, layered pouring shall be adopted. The upper layer of concrete should be poured before the lower layer has initially set. Depending on the integrity requirements, structural size, reinforcement density, and concrete supply, three pouring methods may be selected: full layering, segmented layering, and inclined layering.

[0103] 2. Before the concrete sets, the concrete is vibrated a second time to remove the water and voids formed under the coarse aggregate and horizontal steel bars due to bleeding. This helps to improve the bond between the concrete and the steel bars, prevent cracks caused by concrete settling, reduce internal micro-cracks, increase the density of the concrete, and improve the compressive strength of the concrete, thereby improving its crack resistance.

[0104] 3. Crack control measures:

[0105] 3.1 Low-heat slag cement should be given priority in concrete preparation, and retarders should be used appropriately.

[0106] 3.2 While ensuring the design strength grade of concrete, appropriately reduce the water-cement ratio and reduce the amount of cement used;

[0107] 3.3 Reduce the concrete pouring temperature, control the temperature difference between the inside and outside of the concrete, and reduce the mixing water temperature;

[0108] 3.4 Cover the concrete with insulation and moisture-retaining materials in a timely manner;

[0109] Step Eleven: Maintenance

[0110] The curing method is thermal insulation. In order to ensure that the newly poured concrete has suitable hardening conditions and to prevent cracks from forming in the early stage due to drying shrinkage, after the large volume of concrete is poured, although the concrete is covered in the order of pouring, the curing time shall not be less than 14 days.

[0111] Step Twelve: Temperature Measurement and Monitoring

[0112] 1. Purpose of temperature measurement

[0113] During the construction of large-volume concrete foundations, the accumulation and conduction of heat from cement hydration creates an unstable temperature field within the concrete. As the concrete ages, its internal temperature undergoes a rise and fall, leading to temperature differences at various points within the concrete. Under the influence of internal and external constraints, stress is generated within the concrete. When this tensile stress exceeds the concrete's tensile strength, cracks will form. To prevent excessive internal and external temperature differences during foundation concrete pouring from causing harmful cracks, temperature change monitoring is necessary.

[0114] 2. Monitoring content and early warning indicators

[0115] During the concrete pouring and curing process, monitoring should include monitoring time, instantaneous temperature of concrete hydration heat, internal surface temperature difference, temperature drop rate, and ambient temperature. When the temperature difference between the concrete surface point and the center point (internal surface temperature difference) reaches 25℃ after the concrete pouring is completed, or when the temperature drop rate at the measuring point reaches -2.0℃ / day, a written report should be submitted with a key note to issue a warning.

[0116] 3. For large-volume concrete construction, the temperature at which the concrete is poured into the formwork must be recorded (the temperature at which the concrete is poured into the formwork must be measured no less than twice per shift), the ambient temperature, and the temperature difference between the inside and outside of the concrete measuring points should be recorded no less than four times per day after the concrete is poured.

[0117] 4. Each temperature monitoring point must include surface, bottom, and center temperature measuring points along the thickness of the concrete pouring. The spacing between other measuring points should not exceed 600mm. The surface temperature of the concrete pouring is the temperature 50mm inside the surface of the concrete; the bottom temperature is the temperature 50mm above the bottom surface of the concrete pouring.

[0118] 5. Temperature measurement should begin from the time the concrete is poured into the formwork until it reaches its final set. Take measurements every 4 hours for days 1-4. Take measurements every 8 hours for days 5-7. Take measurements every 12 hours from day 7 until the end of the measurement period. Record and calculate the temperature rise / fall and temperature difference at each measurement point. Stop measuring when the temperature difference between the inner 40mm-100mm radius of the concrete surface and the ambient temperature is less than 20 degrees Celsius.

[0119] 6. Before installation, the temperature testing leads must be soaked in water at a depth of 1 meter for 24 hours without damage. The installation position of the temperature testing lead joints must be accurate and secure, and they should be insulated from the structural steel reinforcement and the metal body of the fixing frame. The lead wires of the temperature testing leads should be centrally arranged and protected. The area around the temperature testing leads should also be protected. During concrete pouring, the temperature testing leads and lead wires must not be directly impacted when pouring concrete, and the vibrator must not touch the temperature measuring element and lead wires.

[0120] 7. Handling large temperature differences

[0121] (1) The temperature difference between the inner and outer surfaces should not exceed 25°C. If the temperature difference between the inner and outer surfaces is found to be close to or exceeds 25°C, decisive measures should be taken (increase the covering thickness) to ensure that the temperature difference between the inner and outer surfaces is controlled within 25°C.

[0122] (2) When the temperature difference between the inside and outside of the concrete and the cooling rate exceed the temperature control index, spare plastic film and geotextile should be added in time. If necessary, burlap sacks can be purchased in an emergency to enhance the insulation performance.

[0123] (3) When the temperature difference between the surface temperature and the ambient temperature is greater than 20°C, and the air temperature is too low, use iodine tungsten lamps to increase the ambient temperature. When the air temperature is too high and the concrete surface temperature is too low, increase the thickness of the geotextile.

[0124] 8. Deformation monitoring

[0125] (1) Monitoring items

[0126] Settlement, displacement and deformation of the support structure.

[0127] (1) Layout of measuring points

[0128] The monitoring items include: deformation of the diagonal bracing keel, deformation of the positioning support point, deformation of the verticality of the upright, and overall horizontal displacement of the support frame.

[0129] (3) Layout of monitoring points

[0130] Monitoring points should be placed at the corners, at the points of greatest deformation such as the height difference between the spans, and at the center of the perimeter. The monitoring points should be stable, reliable, and clearly visible.

Claims

1. A construction method for high-low cross super large volume concrete single side formwork, characterized in that It comprises the following steps: Step one: high and low span earthwork slope excavation; Step two: slope surface steel mesh binding, soil nailing placement; Step three: slope surface shotcrete slope protection; Step four: slope surface base treatment plastering and leveling; Step five: waterproof layer construction; Step six: waterproof protective layer construction; Step seven: raft reinforcement binding; Step eight: low span raft concrete pouring; Step nine: high and low span "inverted triangle" super large concrete section single side formwork; Step ten: raft concrete "closing" pouring; Step eleven: maintenance; Step twelve: temperature measurement and monitoring; In step one, first excavate the high and low span variable cross-section part, excavate according to the drawing requirement excavation ratio, slope, ensure the upper line, lower line position and slope line flatness and slope, and manually trim the slope; In step two, the slope support adopts soil nailing wall support system, the slope ratio is 1:0.5, the soil nailing is arranged in a rectangular shape, the length and longitudinal and transverse spacing of each row of soil nailing are 2m, the soil nailing hole diameter is 100mm, the inclination angle is 10°, the steel soil nailing rod body adopts 1φ20 screw steel, the slurry is normal pressure grouting cement slurry, the slurry strength is M20, and at least twice slurry supplement is performed, the middle is hung ∅6@200×200 steel mesh, the outer part is welded with 1φ16 transverse reinforcing bars and connected with all soil nailing heads, the surface plate is formed by on-site shotcrete, the concrete strength grade is C20, the thickness is 100mm, and the slope top concrete cover is extended by 800mm; In step three, the surface plate is formed by on-site shotcrete, the concrete strength grade is C20, the thickness is 100mm, and the slope top concrete cover is extended by 800mm; In step four, after the slope surface is sprayed, M7.5 cement mortar is used for leveling construction treatment on the slope surface, and after the plastering is completed, pressure polishing treatment is performed, so as to achieve the waterproof full adhesion requirement; In step five, 1. The entire waterproof base should be kept dry, the ambient temperature for laying the waterproof roll should be above -10℃, and the SBS modified asphalt waterproof roll should be hot-melt constructed; 2. Cold primer oil is brushed: cold primer oil is brushed on the clean and dry base surface with a long handle brush, and the complex parts are brushed with a paintbrush, which requires no white exposure, uniform brushing, and drying for more than 4h until it is not sticky to the feet, and then the next process can be performed; 3. Additional layer construction: additional layer treatment is performed on the high and low span shadow and sun corner parts with all angles less than 135º, the vertical plane intersection, and the additional layer width is not less than 500mm; 4. Roll laying: when laying a large area, the person holding the torch should stand in front of the roll laying, aim the torch at the intersection of the roll and the base, heat the roll and the base at the same time, the torch head should be kept at a distance of 50-100mm from the roll surface, and the torch should be at an angle of 60º with the base; 5. Roll lap joint construction: before hot-melt bonding lap joint, the isolation layer on the surface of the next layer of roll is melted with a torch, the worker holding the torch moves the trowel as a baffle along the lap joint line, the torch flame moves together with the baffle, and the torch should be close to the baffle, at a distance of 50-100mm from the roll; 6. The overlap width of the roll material should not be less than 100mm. The edge of the overlap should be filled with hot-melt modified asphalt. Then, use a blowtorch to evenly heat-melt the roll material overlap and smooth the edge with a small trowel. When laying the second layer of roll material, its overlap must be staggered from the overlap of the first layer by half the roll material width. Arrange the construction time for bonding the two layers of roll material properly and do not leave too long an interval, so as to avoid the first layer of roll material being contaminated with dust, which will affect the bonding effect of the two layers. In step six, a pre-applied self-adhesive waterproof membrane is used to replace the traditional waterproof protective layer; In step seven, the raft foundation reinforcement is tied in the order of first the lower span and then the higher span. The slope reinforcement is laid out on site according to the slope ratio to ensure that the angle and bending position of the reinforcement are correct. The reinforcement connection is optimized to ensure that the connection is made on both sides of the high and low spans. Continuous reinforcement is used on the slope. In step eight, C35 concrete is used to pour the raft foundation and the slope with varying elevation. The concrete in this area is poured in two stages. The first stage is poured to the top elevation of the low-span raft foundation, and the second stage is poured to the 800mm high guide wall at the slope. The interval between the two stages is controlled within 2 hours. Three-section water-stop bolts are pre-embedded in the guide wall. The requirements for the water-stop steel plate are the same as those for the basement exterior wall. In step nine, 1. Before pouring the raft foundation in the low zone, first pre-embed 4 rows of 1m long steel pipes, buried at a depth of 400mm, with 600mm exposed above the top surface of the raft foundation. Arrange them along the variable cross section. The first row of steel pipes is 400mm from the edge of the variable cross section, the second row is 1400mm from the edge of the variable cross section, the third row is 2300mm from the edge of the variable cross section, and the fourth row is 3000mm from the edge of the variable cross section. They are arranged at 1000mm intervals parallel to the length direction of the variable cross section.

2. Formwork construction requirements: Template selection: 15mm thick film-coated wooden template; Main keel: Φ48 double steel pipe, horizontally set. The initial main keel is fixed by the screws embedded in the guide wall. The second main keel is 400mm high from the bottom raft top, and the upper main keel spacing is 400mm. Secondary joists: 40mm×90mm timber, vertically installed, spaced 150mm apart; Screw: φ14 screw, vertical spacing 400mm, horizontal spacing 400mm; 3. Template support settings: All support systems use a ring-lock frame structure; Double-row frame system: The double-row frame uprights above the top surface of the low zone raft slab are connected to the pre-embedded short uprights by fasteners. The longitudinal and transverse spacing of the uprights is 1m and the step distance is 1.5m. The top three water-stop tie rods are welded to the upper and lower double-layer horizontal reinforcement of the high zone raft slab. Other height ranges are reinforced by diagonal supports. Diagonal bracing system: The diagonal bracing is set at a vertical spacing of 0.8m and crosses each other. The bottom of the diagonal bracing is connected to the pre-embedded third and fourth rows of short steel pipes. The top is set with U-shaped brackets and is tightly pressed against the main keel of the formwork. When the diagonal bracing passes through the double-row frame, the diagonal bracing is connected to the inner and outer rows of uprights with fasteners. Five diagonal bracings are set on each facade. The top of each diagonal bracing is supported on the main keel with a U-shaped bracket. In step ten, 1. Adopt layered pouring to ensure that the upper layer of concrete is poured before the lower layer of concrete has initially set.

2. Perform a second vibration on the concrete before its initial setting.

3. Control cracks; The curing method of step eleven is insulation method, and the concrete curing time shall not be less than 14 days; In step twelve, 1. Monitoring content and early warning indicators During the pouring and solidification of concrete, the monitoring content includes monitoring time, concrete hydration heat temperature, inner and outer temperature difference, temperature drop rate and atmospheric temperature; when the temperature difference between the surface point temperature and the center point temperature of the concrete after pouring reaches 25℃ or the temperature drop rate of the temperature measuring point reaches -2.0℃ / day, an alarm is given; 2. Mass concrete construction requires recording the mold temperature and environmental temperature, and the concrete measuring point inner and outer temperature difference shall not be less than 4 times per diel; 3. Each temperature monitoring point must be arranged along the thickness direction of the concrete pouring body, and the outer surface, bottom and center temperature measuring points must be arranged, and the remaining measuring points shall not be more than 600mm apart; the outer surface temperature of the concrete pouring body is the temperature at 50mm inside the outer surface of the concrete; the bottom temperature is the temperature at 50mm above the bottom surface of the concrete pouring body; 4. Temperature measurement starts from the time when the concrete enters the mold to the final setting; temperature measurement is carried out once every 4 hours from the 1st to the 4th day; temperature measurement is carried out once every 8 hours from the 5th to the 7th day; temperature measurement is carried out once every 12 hours from the 7th day to the end of temperature measurement; the rise and fall values and temperature difference values of each temperature measuring point shall be recorded and calculated every time the concrete is measured; when the temperature difference between the temperature at 40mm-100mm inside the surface and the environmental temperature is less than 20 degrees, stop temperature measurement; 5. Before the temperature test lead is installed, it must be soaked under water 1m away for 24 hours without damage; the temperature measuring lead joint installation position must be accurate, fixed firmly, and insulated from the structure steel and the metal body of the fixing frame; the temperature measuring lead outgoing line shall be concentrated and protected; the temperature measuring lead shall also be protected, and the temperature measuring lead and the outgoing line shall not be directly impacted by the material during the pouring process, and the vibrator shall not touch the temperature measuring element and the outgoing line; 6. Treatment when the temperature difference is large: (1) The inner and outer temperature difference shall not exceed 25℃, and once the inner and outer temperature difference is close to or exceeds 25℃, decisive measures shall be taken, including increasing the covering thickness to ensure that the inner and outer temperature difference is controlled within 25℃; (2) When the concrete inner and outer temperature difference and the temperature drop rate exceed the temperature control indicators, the spare plastic film and geotextile shall be covered in time, and the burlap shall be purchased in emergency to enhance the insulation performance; (3) When the surface temperature and atmospheric temperature, the temperature difference is greater than 20℃, the air temperature is too low, the iodine tungsten lamp is used to increase the atmospheric temperature, and when the air temperature is too high and the concrete surface temperature is too low, the thickness of the geotextile is increased; 7. Deformation monitoring: The monitoring items include: deformation of diagonal bracing keel rod, deformation of positioning support point, deformation of vertical rod verticality, overall horizontal displacement of support; The monitoring points are arranged at the deformation maximum positions of the corners, high and low spans and the center positions around.

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