CN109654295B - Temporary thrust block for elbow access point, construction method and design method thereof - Google Patents
Temporary thrust block for elbow access point, construction method and design method thereof Download PDFInfo
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- CN109654295B CN109654295B CN201811604611.1A CN201811604611A CN109654295B CN 109654295 B CN109654295 B CN 109654295B CN 201811604611 A CN201811604611 A CN 201811604611A CN 109654295 B CN109654295 B CN 109654295B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L1/00—Laying or reclaiming pipes; Repairing or joining pipes on or under water
- F16L1/024—Laying or reclaiming pipes on land, e.g. above the ground
- F16L1/028—Laying or reclaiming pipes on land, e.g. above the ground in the ground
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/46—Foundations for supply conduits or other canals
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L1/00—Laying or reclaiming pipes; Repairing or joining pipes on or under water
- F16L1/024—Laying or reclaiming pipes on land, e.g. above the ground
- F16L1/06—Accessories therefor, e.g. anchors
- F16L1/09—Accessories therefor, e.g. anchors for bringing two tubular members closer to each other
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Abstract
The invention provides a temporary thrust block for an elbow access point, a construction method and a design method thereof, wherein the temporary thrust block comprises a base, a first section steel and two second section steels are vertically pre-embedded on the upper surface of the base, the first section steel is positioned on the inner side of an elbow access point pipeline, the two second section steels are respectively and symmetrically arranged on the outer side of the elbow access point pipeline, the first section steel and the two second section steels are distributed in a triangular shape, and the elbow access point pipeline is positioned among the three section steels; the first connecting section steel is positioned above the elbow access point pipeline, and the second connecting section steel is positioned outside the middle of the elbow access point pipeline. The invention ensures the stress stability of the pipeline in the early stage, can maintain the integral stability of the subsequent ballast pouring, and saves the water-break time and space because of the temporary thrust structure constructed in advance.
Description
Technical Field
The invention relates to the technical field of pipeline relocation construction, in particular to a temporary thrust block for an elbow access point, a construction method and a design method thereof.
Background
For the municipal tap water pipeline, a thrust block (also called a ballast) with enough weight is required to be configured at the elbow part of the socket type pressure pipeline according to the pressure and the pipe diameter. The new construction, the line changing and the line expanding of the water pipe have the characteristics of large flow of the pipe, more influence on users, short window period of water cut-off construction, complex preparation work of excavation and cutting, high requirement on large-scale equipment management and the like, and the success of one time must be ensured. In particular to the engineering of changing straight lines into broken lines, the anti-thrust block of the access point cannot generate large displacement after the pipeline is pressurized by water, the socket joint cannot twist or deviate (the displacement is smaller than lcm), and the anti-thrust structure must be safe and reliable. For large-diameter pressure pipelines with 1200 legs and above, the design and the process of an access thrust scheme are the serious difficulties of the engineering construction. Most foreign design documents and construction instruction manuals of the structures are basic process designs, and the design and construction of thrust blocks of long-distance common pressure water transmission lines are performed at present in China, so that the research on access diversion thrust schemes under complex conditions is relatively less.
Disclosure of Invention
The invention aims at overcoming the defects of the prior art, and provides a temporary thrust block for an elbow access point, a construction method and a design method thereof, which ensure that the stress of a pipeline at the early stage is stable, and the overall stability of the subsequent ballast pouring can be maintained.
The invention provides an elbow access point temporary thrust block for a pressure pipeline relocation project, which comprises an embedded base below an elbow access point, wherein a first section steel and two second section steels are vertically embedded in the upper surface of the base, the first section steel is positioned at the inner side of the elbow access point pipeline, the two second section steels are respectively and symmetrically arranged at the outer side of the elbow access point pipeline, the first section steel and the two second section steels are distributed in a triangular shape, and the elbow access point pipeline is positioned among three section steels; the first connecting section steel is arranged above the elbow access point pipeline, and the second connecting section steel is arranged outside the middle part of the elbow access point pipeline; the three-dimensional steel is positioned at the outer side of a triangular structure formed by the first section steel and the two second section steels; the diagonal-bracing section steel is connected between the end part of the third section steel, which is close to the upper surface of the base, and the second connecting section steel.
In the technical scheme, the first section steel is positioned at the center of the elbow access point.
In the technical scheme, the third section steel is positioned on the angular bisector of the elbow access point.
In the technical scheme, the connecting line of the web plate of the second section steel and the center of the elbow access point coincides.
In the technical scheme, a saddle support is arranged between the two second section steel and the second connecting section steel and the elbow pipe body access point, and the arc surface of the saddle support is matched with the elbow access point pipeline outer wall.
In the technical scheme, the second section steel is parallel to a tangent line at the inflection point of the elbow access point pipeline.
In the technical scheme, inclined struts are arranged between two second section steels and the upper surface of the base at the outer side of the elbow access point pipeline, one ends of the inclined struts are welded on the second section steels which vertically correspond to each other, and the other ends of the inclined struts are welded on short section steels which are pre-buried on the surface of the outer side base in concrete so as to assist in supporting the second section steels.
The invention provides a design method of a temporary thrust block of an elbow access point for pressure pipeline relocation engineering, which is characterized by comprising the following steps:
firstly, making a plane position diagram of an elbow access point, and determining the position and size relation of a connecting elbow and an existing pipeline;
step two, judging the circle center position O of the elbow, and determining the circle center position as the mounting position H0 of the first section steel;
thirdly, an angular bisector of the elbow is made, and the installation position H1 of the third section steel is determined on the angular bisector at the outer side of the elbow;
determining the position of the first second section steel H2, ensuring that the second section steel is close to the existing pipeline, enabling the web direction to be tangential to the wall of the elbow to be constructed, enabling the included angle between the connecting line of the H2 and the circle center and the OH1 to be minimum, and facilitating the transmission of elbow pressure;
fifthly, taking an angular bisector as a base line to mirror OH2, determining an initial installation position H3 of the second section steel, and properly adjusting along the direction of OH3 until the wing plate contacts the existing pipeline when the H3 collides with the existing pipeline;
step six, according to a simplified calculation model of concentrated load in the middle of the cantilever beam, checking stress and deflection, determining the specification and the size of the section steel, finely adjusting the positions of H2 and H3, ensuring that the positions of the H2 and H3 and a newly-built pipeline are kept at 5-10cm, and reserving a welding space of a saddle support between the section steel and an elbow;
seventh, ensuring the size and the position of the concrete base and ensuring that the protective layer on the outer side of the profile steel is larger than 15cm;
eighth step, calculating the size and specification of the second connecting section steel, wherein the first connecting section steel is respectively arranged between the first section steel and the tops of the two second section steel, and the length of the first connecting section steel is not smaller than the interval between the tops of the first section steel and the second section steel; the second connecting section steel is arranged between the two second section steel, the tangential position of the inflection point of the elbow is determined as the installation position of the second connecting section steel, and a welding space of the saddle support is reserved between the second connecting section steel and the elbow;
and ninth, determining the size, specification and installation position of the diagonal-bracing section steel, wherein the diagonal-bracing section steel is positioned between the midpoint of the second connecting section steel and the bottom end of the third section steel exposed out of the base part.
In the technical scheme, the installation angles of the first section steel, the second section steel and the third section steel are perpendicular to the plane where the elbow pipeline is located, all the section steels are embedded in a concrete base designed at the bottom, and the base is integrally embedded in a non-disturbance rock-soil body at the lower part of the existing pipeline to form a resistance supporting system.
In the technical scheme, the installation angles of the second connecting section steel are parallel to the plane where the elbow pipeline is located.
In the technical scheme, the webs of the first section steel, the second section steel and the third section steel are arranged parallel to the pressure direction, the specification of the section steel is calculated according to the water pressure of the elbow access point, and each section steel can bear the total load of one half of the water pressure and meet the bending strength requirement and the deflection limiting value of 1cm at the saddle support.
In the technical scheme, the depth of the foundation pit is equal to the diameter D+0.3m of the pipeline, and when the foundation pit is a soil foundation, the anti-capsizing calculation requirement is also required to be met.
In the technical scheme, the embedded depth of the profile steel is not smaller than the diameter of the pipeline.
According to the technical scheme, the heights of the first section steel and the second section steel are calculated according to the height of the elbow and the water pressure of the elbow access point, wherein the embedded depth is not smaller than the diameter of the pipeline, and the exposed part is not smaller than the diameter of the pipeline plus 0.3m.
According to the technical scheme, the angle of the diagonal brace or the distance between the third section steel and the first section steel is determined according to the water pressure of the elbow access point, so that the sharp included angle between the diagonal brace and the plane where the elbow pipeline is located is smaller than 45 degrees.
According to the technical scheme, the curvature radius of the arc surface of the saddle support is determined according to the size of the elbow, so that the saddle support is effectively attached to the outer wall of the elbow.
The invention provides a construction method of an elbow access point thrust block for pressure pipeline relocation engineering, which comprises the following steps:
firstly, excavating a foundation pit below an elbow access point pipeline, and pouring a concrete cushion layer after cleaning;
secondly, reinforcing bars are arranged in the foundation pit to bind a reinforcement cage, and H-shaped steel is positioned and installed on the inner side and the outer side of an elbow access point;
thirdly, pouring concrete in the foundation pit to form a base and curing;
fourth, applying for water-break time, cutting the pipeline normally, assembling elbow and gasket
Fifthly, welding second connecting section steel between adjacent H-shaped steel, and diagonal bracing outside the second connecting section steel to enable a curve access point pipeline to be located in a steel portal formed by matching the H-shaped steel, the second connecting section steel and the diagonal bracing, welding a pipe wall backing plate and a wedge, and stabilizing an elbow;
sixthly, connecting the elbow and the pipeline, opening a valve to feed water after checking that the pipeline has water feeding conditions, and monitoring the deformation condition of the H-shaped steel structure to ensure stability;
and seventhly, continuously binding permanent thrust quick steel bars at the outer side of the elbow, and filling the die to finish the pouring construction of the permanent thrust block according to the design.
In the above technical scheme, the H shaped steel includes a first shaped steel and two second shaped steels, and wherein first shaped steel is located the inboard of elbow access point pipeline, and two second shaped steels symmetry respectively set up in the elbow access point pipeline outside, a first shaped steel and two second shaped steels are the triangle and distribute, and elbow access point pipeline is located between three shaped steels.
In the above technical scheme, the second connection shaped steel includes two first connection shaped steels, and two first connection shaped steels weld between the top of first shaped steel and the top of two second shaped steels, be provided with between two second shaped steels with the parallel second connection shaped steel of base upper surface, first connection shaped steel is located the top of elbow access point pipeline, and the second connection shaped steel is located elbow access point pipeline middle part outside.
In the technical scheme, the H-shaped steel further comprises a third section steel, and the third section steel is positioned on the outer side of the triangular structure formed by the first section steel and the two second section steels; the diagonal brace is connected between the end part of the third section steel, which is close to the upper surface of the base, and the second connecting section steel.
In the technical scheme, in the first step, the foundation pit is excavated and combined with geological conditions, and a digger, a rock drilling gun head or a roller bit is used for slotting, wherein the width of the foundation pit is larger than the diameter of a pipeline by 0.6m.
In the technical scheme, in the second step, the base needs to be poured at least 7 days before the line is changed and installed, the base is poured by adopting concrete with the mark of C20 and above, and the steel bars are ordinary ribbed binding steel bar cages with the diameter of 12 mm@150mm; the thickness of the protective layer is larger than 5cm, and the distance between the H-shaped steel stand column and the outer edge of the concrete is larger than 10cm.
In the technical scheme, in the fifth step, a saddle is inserted between the first section steel and the gaps between the two second section steels and the elbow, and the saddle is welded; the contact part between the saddle and the surface of the pipeline is protected by a rubber sheet with the thickness of 0.5 cm.
In the above technical scheme, in the sixth step, after all flange bolts at the joint of the elbow and the pipeline are installed, the place is cleaned, a spring displacement meter is installed at the top surface of the elbow bell and spigot, the spring displacement meter is adsorbed on the surface of the straight pipeline, the displacement probe is contacted with the elbow spigot ring, the position is adjusted to be stable, and the position is connected with a data acquisition device for monitoring the deformation condition of the H-shaped steel structure.
In the technical scheme, the first section steel is positioned at the center of the elbow access point; the third section steel is positioned on the angular bisector of the elbow access point.
In the technical scheme, the web plate of the second section steel coincides with the connecting line of the circle center of the elbow access point; the included angle between the two first connecting section steel is smaller than 90 degrees.
The invention solves the problems that under the restriction of complex underground pipelines common in municipal projects, enough working space and construction window period are not available, and the existing traditional design construction method has quality risks. By providing an in-situ cast-in-place concrete pre-buried section steel anti-thrust structure method, a process of quickly connecting the large-diameter nodular cast iron pressure pipeline elbow is formed, and the anti-thrust structure method is successfully applied to the water-break migration and change work of the municipal tap water main network for a plurality of times. Through pre-buried shaped steel support when pouring the base, the construction period of shaped steel steelframe and base need not to cut off water, only need cut off water during the old pipeline installation elbow of cutting changes, through shaped steel as temporary thrust device, just can operate the water-through in the construction period of permanent thrust piece. The analysis method for the stress and the structural safety of the steel structure is concise and quantifiable, and is beneficial to contractors to report project supervision engineers to obtain wholesale. Compared with the traditional precast concrete block assembling process or the early-strength concrete cast-in-situ process, the method has great advantages in safety, economy and construction convenience, and avoids hoisting operation with high risk and long time consumption. The invention greatly saves the shutdown time and the safety quality risk of water cut-off connection to water supply restoration, reduces the influence of water cut-off on users, and becomes a recommended construction method for water cut-off construction under similar complex conditions of the project of the inventor.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIGS. 2-7 are schematic diagrams of the design flow of the present invention;
FIG. 8 is a schematic view of the present invention after construction;
FIG. 9 is a schematic view of the construction status monitoring of the present invention;
FIG. 10 is a schematic view of a monitoring device installation;
FIG. 11 is a schematic view of the saddle support;
FIG. 12 is a schematic diagram of the operating mode in embodiment 2.
The device comprises a 1-elbow, a 21-first section steel, a 22-second section steel, a 23-third section steel, a 3-saddle support, a 4-foundation pit, a 5-first connecting section steel, a 6-second connecting section steel, a 7-diagonal section steel, an 8-permanent thrust block, a 9-new pipeline, a 10-groove, an 11-old pipeline, a 12-spring displacement meter, a 12.1-magnet base, a 12.2-lock catch, a 12.3-telescopic displacement needle, a 12.4-data collector and a 13-elbow socket ring.
Detailed Description
The invention will now be described in further detail with reference to the drawings and specific examples, which are given for clarity of understanding and are not to be construed as limiting the invention.
As shown in fig. 1, the invention provides a temporary thrust block for an elbow access point, which comprises a base positioned below the elbow 1 access point, wherein a first section steel 21 and two second section steels 22 are vertically embedded on the upper surface of the base, the first section steel 21 is positioned on the inner side of an elbow 1 access point pipeline, the two second section steels 22 are respectively symmetrically arranged on the outer side of the elbow 1 access point pipeline, the first section steel 21 and the two second section steels 22 are distributed in a triangular mode, and the elbow 1 access point pipeline is positioned among three section steels; a first connecting section steel 5 is welded between the top end of the first section steel 21 and the top ends of the two second section steels 22 respectively, a first connecting section steel 6 parallel to the upper surface of the base is arranged between the two second section steels 22, the first connecting section steel 5 is positioned above the elbow 1 access point pipeline, and the first connecting section steel 6 is positioned outside the middle of the elbow 1 access point pipeline; the novel steel structure comprises a base, and is characterized by further comprising third section steel 23 and diagonal section steel 7, wherein the third section steel 23 is vertically embedded in the upper surface of the base, and the third section steel 23 is positioned on the outer side of a triangular structure formed by the first section steel 21 and two second section steel 22; the diagonal-bracing section steel 7 is connected between the end of the third section steel 23 near the upper surface of the base and the first connecting section steel 6. The first section steel 21, the second section steel 22 and the first connecting section steel 5 form a triangular steel door frame structure, so that effective supporting force is provided for the elbow 1; the first connecting section steel 6 provides effective support at the inflection point of the elbow 1 through the third section steel 23 and the diagonal section steel 7. The steel structure provides temporary thrust for elbow 1.
The first section steel 21 is positioned at the center of the access point of the elbow 1, and plays a role in balancing the stress of the two second section steels and contributing to bending rigidity.
The third section steel 23 is positioned on an angular bisector of the access point of the elbow 1 and coincides with the thrust direction generated after the elbow receives water pressure.
The web of the second section steel 22 coincides with the connecting line of the center of the connecting point of the elbow 1, so that the bending resistance of the section steel is exerted to the maximum in the component force direction of the thrust.
The included angle between the two first connecting section steel 5 is smaller than 90 degrees.
And saddle supports 3 are arranged between the two second section steels 22 and the first connection section steel 6 as well as the pipe body access points of the elbow 1, and the arc surfaces of the saddle supports 3 are matched with the pipe outer walls of the access points of the elbow 1 to ensure that the stress of the outer walls of the elbow 1 is uniform. The cast iron pipe has insufficient ductility relative to the steel pipe and is easy to cause local damage, so saddle-shaped cushion protection is needed to be made at the contact point of the profile steel and the pipeline during the construction of the steel structure, and the stress of the contact point is dispersed.
The first connecting section steel 6 is parallel to a tangent line at the inflection point of the pipeline of the access point, so that the thrust generated by the elbow under the action of water pressure and the section steel 6 are positioned on the same plane, and no deflection force is generated.
And inclined struts are arranged between the first connecting section steel 6 and the upper surface of the base at the outer side of the elbow 1 access point pipeline. The diagonal bracing further strengthens the bending resistance of the whole steel structure system.
And the factors such as the water cut-off time cost, the material equipment cost, the construction safety and the like are comprehensively considered, and a pouring scheme after the pre-buried steel structure is recommended. Firstly, through measurement and check, the pre-buried section steel can avoid cutting points before water cut-off, and the pipe body can be accurately positioned and locked after the elbow 1 is installed. And cutting pipes, connecting, fixing and welding steel frames in normal construction, and performing integral pouring of the permanent stop blocks after all access works are completed. The scheme can ensure the stress stability of the pipeline in the early stage, can maintain the integral stability of the subsequent ballast pouring during the test operation, and simultaneously saves the water-break time and space because of the temporary thrust structure constructed in advance; the H-shaped steel is light in weight, the hoisting equipment is simple, the operation is convenient, and the follow-up existing pipeline removing work is not influenced.
The construction method of the elbow access point thrust block comprises the following steps:
firstly, excavating a foundation pit 4 below an access point pipeline of the elbow 1, wherein the depth of the foundation pit meets the embedded depth of supporting profile steel, the length and the width meet the thickness requirement of a protective layer on the outer side of the profile steel, and pouring a concrete cushion layer after cleaning; and the foundation pit 4 is excavated and combined with geological conditions, a digger, a rock drilling gun head or a roller bit head is used for slotting, and the width of the foundation pit 4 is larger than the diameter of a pipeline by 0.6m.
Secondly, reinforcing bars are arranged in the foundation pit 4 to bind a reinforcement cage, and H-shaped steel is positioned and installed on the inner side and the outer side of an access point of the elbow 1; the steel bars are selected from common ribbed binding steel bar cages with the diameter of 12 mm@150mm; the thickness of the protective layer is larger than 5cm, and the distance between the H-shaped steel upright posts and the outer edge of the mixed finger foundation pit 4 is larger than 10cm.
Thirdly, pouring concrete in the foundation pit 4 to form a base and curing; the base needs to be poured at least 7 days before the line is changed and installed, and the base is poured by adopting concrete with the labels of C20 and above.
And fourthly, applying for the water cut-off time of pipeline migration, cutting the pipeline normally, and assembling the elbow 1 and the gasket.
Fifthly, connecting the elbow and the pipeline, welding second connecting section steel between adjacent H-shaped steel, and diagonal bracing outside the second connecting section steel to enable the pipeline of the curve access point to be positioned in a steel portal formed by matching the H-shaped steel, the second connecting section steel and the diagonal bracing, welding a pipe wall backing plate and a wedge, and stabilizing the elbow 1; a saddle is inserted between the first section steel 21 and the gaps between the two second section steels 22 and the elbow 1 and welded; the contact part between the saddle and the surface of the pipeline is protected by a rubber sheet with the thickness of 0.5 cm.
Sixthly, connecting the elbow 1 with a pipeline, opening a valve to feed water after checking that the pipeline has water feeding conditions, and monitoring the deformation condition of the H-shaped steel structure to ensure stability; after all flange bolts at the joint of the elbow 1 and the pipeline are installed, a place is cleaned, a spring displacement meter 12 is installed at the top surface of a bell and spigot joint of the elbow 1, the spring displacement meter 12 is adsorbed on the surface of a straight pipe pipeline of a new pipeline and an old pipeline, a displacement probe is contacted with an elbow spigot ring 13, the position is adjusted to be stable, and the joint data acquisition device is used for monitoring the elbow spigot joint falling off and structural deformation conditions during test operation. The whole water-break line-changing project is installed from cutting to the condition that the valve opening water-passing time is less than 8 hours, the spring displacement meter 12 detects that the H-shaped steel structure is not obviously deformed, and the process requirements are completely met.
And seventhly, continuously binding permanent thrust quick steel bars at the outer side of the elbow 1, filling a die, and completing pouring construction of the permanent thrust block 8 according to the design, wherein the temporary section steel does not need to be removed, and pouring and wrapping the temporary section steel in the permanent thrust block.
In the technical scheme, the temporary thrust block is positioned below the existing pipeline, is embedded into a non-disturbance rock-soil body by adopting a cast-in-situ method, and is used for completing the temporary thrust structure for migration and modification in advance in the running state of the pipeline. The temporary thrust block consists of a concrete body embedded into a rock-soil body foundation and H-shaped steel embedded in the concrete, wherein the H-shaped steel comprises a first section steel 21 and two second section steels 22, the first section steel 21 is positioned on the inner side of an elbow 1 access point pipeline, the two second section steels 22 are symmetrically arranged on the outer side of the elbow 1 access point pipeline respectively, and the first section steel 21 and the two second section steels 22 are distributed in a triangular mode, and the elbow 1 access point pipeline is positioned among the three section steels.
The design method of the temporary thrust block of the elbow access point is characterized by comprising the following steps of:
firstly, making a plane position diagram of an access point of the elbow 1, and determining the position and size relation between the connecting elbow 1 and the existing pipeline;
step two, judging the circle center position O of the elbow 1, and determining the circle center position as the installation position H0 of the first section steel 21;
thirdly, an angular bisector of the elbow 1 is made, and the installation position H1 of the third section steel 23 is determined on the angular bisector of the outer side of the elbow 1;
determining the position of the first second section steel H2, ensuring that the second section steel is close to the existing pipeline, enabling the web direction to be tangential to the wall of the elbow to be constructed, enabling the included angle between the connecting line of the H2 and the circle center and the OH1 to be minimum, and facilitating the transmission of elbow pressure;
fifthly, taking an angular bisector as a base line to mirror OH2, determining an initial installation position H3 of the second section steel, and properly adjusting along the direction of OH3 until the wing plate contacts the existing pipeline when the H3 collides with the existing pipeline;
step six, according to a simplified calculation model of concentrated load in the middle of the cantilever beam, checking stress and deflection, determining the specification and the size of the section steel, finely adjusting the positions of H2 and H3, ensuring that the positions of the H2 and H3 and a newly-built pipeline are kept at 5-10cm, and reserving a welding space of a saddle support 3 between the section steel and the elbow 1;
seventh, calculating the size and specification of the second connecting section steel, wherein the first connecting section steel is respectively arranged between the first section steel 21 and the tops of the two second section steel 22, and the length of the first connecting section steel is not smaller than the interval between the tops of the first section steel 21 and the second section steel 22; the second connecting section steel is arranged between the third section steel 23 and the fourth section steel, the tangential position of the inflection point of the elbow 1 is determined as the installation position of the second connecting section steel, and a welding space of the saddle support 3 is reserved between the second connecting section steel and the elbow 1;
eighth step, determining the size, specification and installation position of the diagonal brace, wherein the diagonal brace is positioned between the key points of the second connecting section steel, namely the second section steel 22 is exposed out of the bottom end of the base part;
and ninth, ensuring the size and the position of the concrete base and ensuring that the protective layer on the outer side of the profile steel is larger than 15cm.
In the above technical scheme, the installation angles of the first section steel 21, the second section steel 22 and the third section steel 23 are all perpendicular to the plane where the elbow 1 pipeline is located. Each type of steel is embedded in a concrete base designed at the bottom, and the base is wholly embedded in a non-disturbance rock-soil body at the lower part of the existing pipeline to form a resistance supporting system.
In the technical scheme, the installation angles of the second connecting section steel are parallel to the plane where the elbow 1 pipeline is located.
In the technical scheme, the webs of the first section steel 21, the second section steel 22 and the third section steel 23 are arranged parallel to the pressure direction, the specification of the section steel is calculated according to the water pressure of the inlet point of the elbow 1, and each section steel can bear the total load of one half of the water pressure and meet the bending strength requirement and the deflection limiting value of 1cm at the saddle support.
According to the technical scheme, the depth of the foundation pit 4 is calculated to be equal to the diameter D+0.3m of the pipeline according to the water pressure of the access point of the elbow 1, and when the foundation pit is a soil foundation, the anti-capsizing calculation requirement is also required to be met.
In the technical scheme, the embedded depth of the section steel is not smaller than the diameter of the pipeline.
In the above technical scheme, the heights of the first section steel 21 and the second section steel 22 are calculated according to the height of the elbow 1 and the water pressure of the access point of the elbow 1, wherein the embedded depth is not smaller than the diameter of the pipeline, and the exposed part is not smaller than the diameter of the pipeline plus 0.3m.
In the technical scheme, the angle of the diagonal brace or the distance between the third section steel and the first section steel is determined according to the water pressure of the elbow access point, so that the acute included angle between the diagonal brace and the plane of the elbow pipeline is smaller than 45 DEG
In the technical scheme, the curvature radius of the arc surface of the saddle support 3 is determined according to the size of the elbow 1, so that the saddle support 3 is effectively attached to the outer wall of the elbow 1.
In the specific embodiment, according to the excavation form of the on-site trench 10 and the boundary of the foundation rock surface of the trench 10, the pouring base is designed to be completely embedded into the ultra-excavated trench 10, the height is 1.8m, and the concrete mass is 40m 3 . The three steel struts are designed, and the arrangement situation is shown in figure 3. The three section steel buttresses are in a regular triangle shape, one middle branching line of the three section steel buttresses forms 45 degrees with the pipeline, cutting connection during water cut-off is not affected, and resultant force of section steel resistance is in the main pressure direction. And finally, welding the connecting beam at the top of the section steel to form an integral support.
HW400X400xl3X21mmQ235H section steel is selected as the section steel, and the interface moment of inertia I= 66900cm in the direction perpendicular to the web. The welded diagonal braces are not included as additional security during installation. Because the whole concrete base is cast in situ and embedded into surrounding rock, the back wall is directly bonded with the rock body, the anti-slip and anti-overturning checking calculation can be omitted, and only the bending member checking calculation can be carried out.
The thrust structure calculation basic parameter table is shown in the following table:
the thrust of the elbow 1 is calculated according to the section compression force:
；
combining a section steel parameter table, checking the bending strength of the H-shaped steel according to a cantilever beam calculation formula under the action of concentrated load, and easily obtaining the maximum bending stress of the H-shaped steel upright post and the maximum deflection of a contact point, wherein the maximum bending stress and the maximum deflection are respectively as follows:
the method comprises the steps of carrying out a first treatment on the surface of the Less than the allowable stress 210 mpa=3.9 mm, < >>The method comprises the steps of carrying out a first treatment on the surface of the Meets the requirement that the displacement is less than 2 cm.
In embodiment 2, the foundation is considered to be cast-in-place concrete embedded in the bottom of the trench 10, constrained by the surrounding rock-soil body, and the overall slip and overturning are not considered. According to the cantilever beam strength and displacement under the action of concentrated load.
Typical examples take cantilever height h=1400 mm, pipe radius r=600 mm, section steel spacing b=1600 mm.
The concentrated force acting point is positioned in the middle of the section steel cantilever section and is 700mm away from the concrete.
The selection standard of the H-shaped steel materials is shown in the following table:
the geometric property standard of the section of the H-shaped steel is shown in the following table:
the calculation results of the thrust of the pipe intervention elbow 1 are shown in the following table:
because the three upright post section steels are mutually overlapped through connecting the steel beams, a statically indeterminate structure which is stressed together is formed to resist the pressure deformation together. The profile steel web plates are arranged parallel to the pressure direction, in order to facilitate calculation, the total water pressure is distributed according to an average principle, the profile steel behind each elbow 1 resists the total load of 1/2, and under the condition of small deformation of the profile steel upright post, the assumption can meet the precision requirement of engineering design.
The maximum bending stress is 155MPa, which is smaller than the design strength of 215MPa, the calculated safety coefficient Fs=215/100 >2, and the bending resistance of the structure is further improved by the third upright post on the inner side of the small radius of the elbow 1 and the designed diagonal bracing. The maximum deflection of the structure is about 1mm, which is far smaller than the requirement of 10mm of allowable displacement of the socket joint.
Similarly, the steel structure material selection conditions meeting the safety requirements can be calculated as follows:
what is not described in detail in this specification is prior art known to those skilled in the art.
Claims (7)
1. The utility model provides a temporary thrust piece of elbow access point which characterized in that: the embedded base is positioned below an elbow access point, a first section steel and two second section steels are vertically embedded in the upper surface of the base, the first section steel is positioned on the inner side of an elbow access point pipeline, the two second section steels are respectively and symmetrically arranged on the outer side of the elbow access point pipeline, the first section steel and the two second section steels are distributed in a triangular mode, and the elbow access point pipeline is positioned among the three section steels; the first connecting section steel is arranged above the elbow access point pipeline, and the second connecting section steel is arranged outside the middle part of the elbow access point pipeline; the three-dimensional steel is positioned at the outer side of a triangular structure formed by the first section steel and the two second section steels; the diagonal bracing section steel is connected between the end part of the third section steel, which is close to the upper surface of the base, and the second connecting section steel; the first section steel is positioned at the center of the elbow access point; the third section steel is positioned on an angular bisector of the elbow access point; the web of the second section steel coincides with the connecting line of the center of the elbow access point.
2. The temporary thrust block for the elbow access point according to claim 1, wherein saddle supports are arranged between the two second section steel and the second connecting section steel and the elbow pipe body access point, and the arc surfaces of the saddle supports are matched with the outer wall of the elbow access point pipeline.
3. A temporary stop for an elbow access point according to claim 1, wherein the second section steel is parallel to a tangent at the inflection point of the elbow access point conduit.
4. The temporary thrust block for the elbow access point according to claim 1, wherein diagonal braces are arranged between two second section steel and the upper surface of the base at the outer side of the elbow access point pipeline, one end of each diagonal brace is welded on the vertically corresponding second section steel, and the other end of each diagonal brace is welded on the short section steel embedded in the surface of the outer side base in the concrete so as to assist in supporting the second section steel.
5. The method for designing the temporary thrust block of the elbow access point according to claim 1, comprising the following steps:
firstly, making a plane position diagram of an elbow access point, and determining the position and size relation of a connecting elbow and an existing pipeline;
step two, judging the circle center position O of the elbow, and determining the circle center position as the mounting position H0 of the first section steel;
thirdly, an angular bisector of the elbow is made, and the installation position H1 of the third section steel is determined on the angular bisector at the outer side of the elbow;
determining the position of the first second section steel H2, ensuring that the second section steel is close to the existing pipeline, enabling the web direction to be tangential to the wall of the elbow to be constructed, enabling the included angle between the connecting line of the H2 and the circle center and the OH1 to be minimum, and facilitating the transmission of elbow pressure;
fifthly, taking an angular bisector as a base line to mirror OH2, determining an initial installation position H3 of the second section steel, and properly adjusting along the direction of OH3 until the wing plate contacts the existing pipeline when the H3 collides with the existing pipeline;
step six, according to a simplified calculation model of concentrated load in the middle of the cantilever beam, checking stress and deflection, determining the specification and the size of the section steel, finely adjusting the positions of H2 and H3, ensuring that the positions of the H2 and H3 and a newly-built pipeline are kept at 5-10cm, and reserving a welding space of a saddle support between the section steel and an elbow;
seventh, ensuring the size and the position of the concrete base and ensuring that the protective layer on the outer side of the profile steel is larger than 15cm;
eighth step, calculating the size and specification of the second connecting section steel, wherein the first connecting section steel is respectively arranged between the first section steel and the tops of the two second section steel, and the length of the first connecting section steel is not smaller than the interval between the tops of the first section steel and the second section steel; the second connecting section steel is arranged between the two second section steel, the tangential position of the inflection point of the elbow is determined as the installation position of the second connecting section steel, and a welding space of the saddle support is reserved between the second connecting section steel and the elbow;
and ninth, determining the size, specification and installation position of the diagonal-bracing section steel, wherein the diagonal-bracing section steel is positioned between the midpoint of the second connecting section steel and the bottom end of the third section steel exposed out of the base part.
6. The construction method of the temporary thrust block for the elbow access point according to claim 1, comprising the following steps:
firstly, excavating a foundation pit below an elbow access point pipeline, and pouring a concrete cushion layer after cleaning;
secondly, reinforcing bars are arranged in the foundation pit to bind a reinforcement cage, and H-shaped steel is positioned and installed on the inner side and the outer side of an elbow access point;
thirdly, pouring concrete in the foundation pit to form a base and curing;
fourthly, applying for the water cut-off time of pipeline migration, cutting the pipeline normally, and assembling an elbow and a gasket;
fifthly, welding a second connecting section steel between the connecting elbow and the new pipeline as well as between the old pipelines and the adjacent H-shaped steel, arranging an inclined strut on the outer side of the second connecting section steel, enabling the pipeline of a curve access point to be positioned in a steel portal formed by matching the H-shaped steel, the second connecting section steel and the inclined strut, welding a pipe wall backing plate and a wedge, and stabilizing the elbow;
sixthly, connecting the elbow and the pipeline, opening a valve to feed water after checking that the pipeline has water feeding conditions, and monitoring the deformation condition of the H-shaped steel structure to ensure stability;
and seventhly, continuously binding permanent thrust quick steel bars at the outer side of the elbow, and filling the die, and completing the casting construction of the permanent thrust block according to the design, wherein the temporary section steel does not need to be removed, and the casting is wrapped in the permanent thrust block.
7. The construction method of the temporary thrust block for the elbow access point according to claim 6, wherein in the sixth step, after all flange bolts at the joint of the elbow and the pipeline are installed, a place is cleaned, a spring displacement meter is installed at the top surface of the elbow bell and spigot, the spring displacement meter is adsorbed on the surface of a straight pipe of a new pipeline and an old pipeline, a displacement probe is contacted with an elbow spigot ring, the position is adjusted to be stable, and the joint data acquisition device is used for monitoring the elbow spigot falling and structural deformation conditions during test operation.
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| CN113346401B (en) * | 2020-09-30 | 2021-12-14 | 中国建筑第二工程局有限公司 | Precise positioning device for tail end of deep pipeline and construction method thereof |
| CN113202974B (en) * | 2021-06-01 | 2022-05-03 | 中铁四局集团有限公司 | Overlap-connection method for long-distance nodular cast iron pipeline subsection construction |
| CN113431958A (en) * | 2021-06-17 | 2021-09-24 | 国家能源聊城发电有限公司 | Pipeline anchor block arrangement method |
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