Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a rectangular push pipe counterforce device for a subway entrance/exit channel and a construction method, wherein a supporting system for steel leaning back is formed by an original entrance/exit structure and I-shaped steel inclined struts through an optimized structure, so that the push pipe counterforce device which is simple to install, firm, stable and high in bearing capacity is formed, and the stress deformation requirement of the counterforce device under high thrust is met.
The invention provides a construction method of a rectangular pipe jacking counterforce device for a subway entrance/exit channel, which comprises the following steps:
a pipe jacking starting bottom plate at the subway entrance and exit is constructed by plate descending to form a high-low span;
forming a back rest support of the reaction device at a high-low span position, and installing the back rest of the reaction device to enable the lower end of the back rest to abut against the support;
an inclined support is additionally arranged in the middle of the backrest, the upper end of the inclined support abuts against the back of the backrest, and the lower end of the inclined support is fixed on a bottom plate at a high span;
the jacking pipe applies acting force to the rear part by using a matched main jacking oil cylinder to carry out jacking construction of the jacking pipe;
and after the jacking construction of the jacking pipe is finished, removing the back rest and the inclined supports, and backfilling the back rest support formed by plate lowering construction to the designed elevation of the bottom plate.
The construction method is further improved in that before the installation of the back rest, a mark line is marked on the bottom plate in advance according to the jacking direction of the jacking pipe, the installation position of the back rest is positioned, and the installation direction of the back rest is perpendicular to the jacking direction.
The construction method is further improved in that the backrest is hoisted by a crane, the hoisting state is kept after the backrest falls down, the axis position and the verticality of the backrest are rechecked, the backrest is connected with the guide rail by bolts after the requirement of the jacking pipe is met, and a hoisting steel wire rope is loosened after the backrest is stable to finish the installation of the backrest.
The construction method is further improved in that 63C I-steel is adopted as the inclined support, and two ends of the I-steel are respectively connected with the rear rest and the embedded steel plate of the bottom plate.
The construction method is further improved in that the embedded steel plate of the bottom plate is additionally provided with quincuncial anchor bars which are anchored into the bottom plate.
The construction method is further improved in that during jacking construction of the jacking pipe, the backward deformation is monitored and measured, the monitoring frequency is 1 time/day, the monitoring items are backward displacement and inclination, the control value is accumulated displacement +/-5 mm, the change rate is +/-2 mm/day, the inclination rate is less than 0.2%, and a total station is adopted for monitoring.
The invention provides a rectangular pipe jacking counterforce device for a subway entrance/exit channel, which is characterized in that a pipe jacking starting bottom plate at the subway entrance/exit is constructed by adopting a descending plate to form a high-low span, a back support of the counterforce device is formed at the position of the high-low span, the counterforce device comprises a back support arranged in the support, the lower end of the back support is abutted against the support, an inclined support is additionally arranged in the middle of the back support, the upper end of the inclined support is abutted against the back of the back support, and the lower end of the inclined support is fixed on the bottom plate at the high span.
The device is further improved in that the inclined support is made of 63C I-steel, and two ends of the I-steel are respectively connected with the backrest and the embedded steel plate of the bottom plate.
The device is further improved in that the embedded steel plate of the bottom plate is additionally provided with quincuncial anchor bars which are anchored into the bottom plate.
The device of the invention is further improved in that the reclining is made of steel.
Due to the adoption of the technical scheme, the invention has the following technical effects:
1) the structure size is adjusted in a small range, and the structure itself is used as a part (support) of the counterforce device to replace the action of concrete against a wall (column);
2) i-shaped steel inclined struts are used for supporting and reinforcing, and are fast and simple to install;
3) the I-steel bracing is demolishd simply in the later stage, and repeatedly usable.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the elevation of the designed bottom plate surface of the original push pipe launching well is equal to the bottom plate surface of the entrance, the clearance is 5.27m, when the counterforce device is installed, the steel back 21 is not provided with supports at two ends for constraint, so that the steel back deformation cannot meet the requirement, and the supporting installation of the back is not facilitated. It is therefore necessary to add reinforced concrete walls 22 or reinforced concrete columns as supports for the steel recline.
In order to adjust the supporting and stress mode of the steel reclining, the original structure can be considered to be part of the support. Referring to fig. 2, the invention provides a construction method of a rectangular pipe jacking counterforce device for a subway entrance/exit channel, which mainly comprises the following steps:
firstly, a push pipe starting well bottom plate 10 at an entrance and an exit of a subway is constructed by plate descending, and a height span is formed by properly reducing the elevation of the bottom plate;
then, a backrest support A of the reaction device is formed at the high-low span position, and a backrest 11 of the reaction device is installed, so that the lower end of the backrest 11 is abutted against the support A, and the backrest 11 is convenient to stand;
then, considering that the span of the backrest 11 is too large, and in order to avoid the over-large deflection in the midspan, the inclined support 12 is additionally arranged in the middle of the backrest 11 to increase the overall rigidity of the counterforce device, the upper end of the inclined support 12 abuts against the back of the backrest 11, and the lower end of the inclined support 12 is fixed on the bottom plate 10 at the high span; the backrest 11 is made of steel, the inclined support 12 is made of 63C I-steel, and two ends of the I-steel are respectively connected with the backrest and the bottom plate embedded steel plate;
then, the jacking pipe applies acting force to the front part of the backrest 11 by using a matched main jacking oil cylinder (a jack 13) to carry out jacking construction of the jacking pipe, and the arrangement of the jack 13 is shown in figures 3 and 4;
and finally, after the jacking construction of the jacking pipe is completed, the backrest 11 and the inclined supports 12 are dismantled, the whole stress of the structure is not greatly influenced due to the small plate lowering amplitude, and the requirement of building design can be met by backfilling plain concrete after the plate is lowered, so that the construction method is more economic, simple and rapid compared with the method of re-constructing the concrete backrest support. Therefore, after the backrest 11 is removed, the design elevation from the backrest support A formed by the construction of backfilling the descending plate with plain concrete to the bottom plate 10 can be kept level with the bottom plate 10 with the original high span.
In summary, the construction process flow of the rectangular pipe jacking counterforce device construction method for the subway entrance/exit passage mainly comprises the following steps: optimized structure arrangement → analysis of support stress → erection of an I-shaped steel inclined strut → installation of steel reclining → monitoring of deformation of the jacking construction reclining.
The following is developed:
1) structurally optimised arrangement
The elevation of the designed bottom plate surface of the original push pipe starting well is equal to that of the bottom plate surface of the entrance and exit, the clearance is 5.27m, when the counterforce device is installed, the steel back rest two ends are not provided with supports for restraining, so that the steel back rest deformation cannot meet the requirement, and the supporting installation of the back rest is not facilitated. Therefore, reinforced concrete walls or reinforced concrete columns are required to be additionally arranged as supports for steel reclining.
In order to adjust the supporting and stress mode of the steel backrest, the original structure can be considered to be used as a part of the support, and the height of the bottom plate is properly reduced to form a support for the steel backrest at the high-low straddle position, so that the steel backrest can be conveniently erected. Because the plate lowering amplitude is not large, the whole stress of the structure is not greatly influenced, the requirement of building design can be met by backfilling plain concrete after the plate is lowered, and the plate lowering device is more economical, simple and quick compared with a rest support after concrete is rebuilt. Considering that the steel reclining span is too large, in order to avoid the over-large mid-span deflection, the I-steel inclined strut is additionally arranged in the middle part to increase the overall rigidity of the counterforce device.
2) Support force analysis
According to the design condition, the analysis is carried out according to the full load operation of 5 jacks 13 on each side, and the maximum output reaction force of each jack is 200t, as shown in fig. 3 and 4.
As shown in fig. 5, the i-steel diagonal brace adopts a frame structure in which the reaction device is regarded as being under the action of concentrated load, and a Q235 worker 63C diagonal brace is selected for force-bearing deformation analysis.
As shown in fig. 6 and 7, the main stress δ and the shear stress τ of the i-steel diagonal brace are both smaller than the bending strength and the shearing strength of the Q235 steel, and meet the requirements. The stress at the support is less than the strength f of the first-level fillet weldf wAnd meets the requirements. The maximum deflection of the counterforce is 840 multiplied by 10-6mm, the deflection requirement is recorded and read omega ═ H according to the design specification of the steel structureCAnd/1250, meeting the requirements.
3) Mounting steel back
Marking a mark line at the bottom plate in advance according to the jacking direction before the steel is installed at the back. The steel back rest is hoisted by adopting an 80t crane, after the steel back rest slowly falls down, the hoisting state is kept, the axis position and the verticality of the back rest are rechecked, the steel back rest is connected with the guide rail by adopting a bolt after the requirement of pipe jacking is met, a hoisting steel wire rope is loosened after the back rest is stable, and the installation process of the steel back rest is completed.
4) Erecting I-steel diagonal brace
According to design analysis, 63C I-steel can meet the requirement of 10000KN on stress deformation of the jacking pipe main jacking oil cylinder, and therefore the 63C I-steel is selected as a counter-force device for supporting. Two ends of the I-shaped steel are respectively connected with the steel backrest and the embedded steel plate of the bottom plate.
And cutting and processing the ground according to the length of the I-shaped steel according to a design drawing. The I-steel is hoisted to the lower part of the foundation pit through an 80t truck crane, after the I-steel inclined strut is erected by using a hoist, the bottom of the I-steel inclined strut is fully welded with an original bottom plate embedded steel plate 101 (with the size of 0.8m by 3.6m by 16mm), and the I-steel inclined strut is welded with the installed steel in a back-to-back mode. It should be noted that the pre-buried steel plate 101 is additionally provided with the C25, 150 x 150mm quincuncial arrangement anchor bars 102 to increase the pulling resistance of the steel plate, as shown in FIG. 8.
5) Jacking construction deformation monitoring
In order to ensure the construction quality of the jacking pipe and the safety of the counterforce device, the monitoring and measurement of the steel back-leaning deformation should be carried out in the jacking construction, the monitoring frequency is 1 time/day, the monitoring items are the steel back-leaning displacement and inclination, the control value is the accumulated displacement +/-5 mm, the change rate is +/-2 mm/day, the inclination rate is less than 0.2%, and the total station is adopted for monitoring. When the monitoring data is abnormal, the jacking is stopped to find out the reason, and the monitoring frequency is encrypted.
The invention also provides a rectangular push pipe counterforce device of the subway entrance/exit channel, which is used for realizing the construction method of the rectangular push pipe counterforce device of the subway entrance/exit channel, wherein a push pipe starting bottom plate at the entrance/exit of a subway is constructed by adopting a descending plate to form a high-low span, a back support A of the counterforce device is formed at the position of the high-low span, the counterforce device comprises a back support 11 arranged in the support, the lower end of the back part of the back support 11 is abutted against the support A, an inclined support 12 is additionally arranged in the middle part of the back support 11, the upper end of the inclined support 12 is abutted against the back part of the back support 11, and the lower end of the inclined support 12 is fixed on a bottom plate 10 at the high span, as shown in figure 2. The reclining device is characterized in that the reclining part 11 is preferably made of steel, the inclined support 12 is preferably made of 63C I-steel, and two ends of the I-steel are respectively connected with the reclining part 11 and the embedded steel plate 101 of the base plate 10. The plum blossom arrangement anchor bars 102 are additionally arranged on the embedded steel plate 101 of the bottom plate 10 and anchored into the bottom plate 10, so that the pulling resistance of the steel plate is increased.
In the rectangular pipe jacking counterforce device for the subway entrance/exit channel and the construction method, the size of the structure is adjusted in a small range, and the structure is also used as a part (support) of the counterforce device to replace the action of concrete on a back wall (column); i-shaped steel inclined struts are used for supporting and reinforcing, and are fast and simple to install; the I-steel bracing is demolishd simply in the later stage, and repeatedly usable. Furthermore, the reaction device is simple to install and dismantle, monitoring data of the reaction device are all within a required range in the jacking process, safety and reliability are achieved, and construction cost of jacking pipe reclining is reduced.
The parts not involved in the present invention are the same as or can be implemented by the prior art. Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.