CN109183804B - Foundation pit excavation mixed support prestress self-adaptive automatic compensation method - Google Patents
Foundation pit excavation mixed support prestress self-adaptive automatic compensation method Download PDFInfo
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- CN109183804B CN109183804B CN201810997658.2A CN201810997658A CN109183804B CN 109183804 B CN109183804 B CN 109183804B CN 201810997658 A CN201810997658 A CN 201810997658A CN 109183804 B CN109183804 B CN 109183804B
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- spring
- foundation pit
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- pipe sleeve
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
- E02D17/04—Bordering surfacing or stiffening the sides of foundation pits
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2250/00—Production methods
- E02D2250/0046—Production methods using prestressing techniques
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Abstract
The invention provides a self-adaptive automatic compensation device method for prestress of a mixed support for foundation pit excavation, which is characterized in that materials such as a high-strength spring, a high-strength screw rod, a high-strength nut, a steel pipe and the like are jointly used for forming the device, and the lost prestress in a steel support is automatically compensated by utilizing the principle that the spring generates elasticity opposite to the stress when the spring is compressed or stretched. The device simple structure facilitates the use, especially when carrying out the later stage to the steel shotcrete and demolish as long as utilize to screw up the nut and can easily demolish the spring compression. The method can ensure that the steel support is kept to have reliable prestress in the construction process, prevent the problem of stress relaxation of the steel support in later construction, ensure that the concrete support is constantly pressed when the mixed support is adopted, avoid tensile stress and prevent the concrete from being damaged by tension.
Description
Technical Field
The invention relates to a device for self-adaptive and automatic compensation of prestress of a mixed support for foundation pit excavation, belonging to the design part of foundation pit excavation support.
Background
In the excavation process of a foundation pit, particularly when deep excavation is carried out on the foundation pit and high-rise buildings or heavy building facilities exist around the foundation pit, the prestress in the supporting structure of the foundation pit can cause large loss in the excavation process of the foundation pit, and similar situations can be met by the supporting structure which is not specially processed in the past. This can not in time carry out effectual stress compensation's problem meticulously design the device to traditional bearing structure in can carry out timely automatic compensation to the stress that loses through high strength spring at the in-process of foundation ditch excavation, especially carry out the in-process that mixes the support because the elastic modulus of concrete is little than the steel shotcrete, and the deflection is not big, leads to the prestressing force loss among the steel shotcrete structure great even entering relaxed state. This problem is now solved by this automatic compensation device.
The steel shotcrete all needs recovery reuse among the supporting construction of foundation ditch, because the too big power in the steel shotcrete leads to not dismantling well when dismantling, can compress the spring in the device through this device, demolishs the steel shotcrete that just can relax.
Disclosure of Invention
In view of the above disadvantages of the prior art, the present invention is directed to solve the problem that the stress loss in the support structure cannot be compensated in time during the excavation of the foundation pit.
The invention provides a self-adaptive automatic compensation method and a device for mixed support prestress of foundation pit excavation, which can be used for solving the problem that the settlement and inclination degree of a foundation pit are increased because the stress in an upper-layer supporting structure begins to relax in the process of continuously wanting deep excavation of the foundation pit in the foundation pit construction process. The self-compensation can keep enough stress in the supporting structure to support the periphery of the foundation pit.
The specific implementation scheme of the invention is as follows:
a device for self-adaptive and automatic compensation of prestress of mixed support for excavation of a foundation pit. And (3) connecting the base with the high-strength screw and the steel pipe sleeve with an embedded component in the foundation pit wall, then inserting the spring sleeve with the spring and the screw hole into the steel pipe sleeve of the base, and installing the screw cap. The automatic compensation method is suitable for various supporting structures in foundation pit excavation.
A self-adaptive automatic compensation method for prestress of mixed support for excavation of a foundation pit. The method mainly uses materials such as a high-strength spring, a high-strength screw rod, a high-strength nut, a steel pipe and the like to jointly form the prestress compensation device, and the prestress compensation device automatically compensates the lost prestress in the steel support by utilizing the principle that the spring generates elastic force opposite to the stress when the spring is compressed or stretched. When the foundation pit excavation steel support is installed, the base of the outer steel pipe sleeve with the rigid strength screw rod is fixed in the embedded component, the high-strength spring is filled into the spring outer steel pipe sleeve with the screw hole, then the spring outer steel pipe sleeve with the screw hole is aligned with the outer steel pipe sleeve, the screw rod is inserted into the steel pipe sleeve of the base, and finally the high-strength nut is installed. The method is characterized by comprising the following steps:
the method comprises the following steps: a suitable high strength spring is selected.
The spring is selected in relation to the maximum horizontal displacement that the foundation pit will undergo, for example, the maximum depth H of the foundation pit is designed to correspond to the allowable inclination angle σ corresponding to the depth of the foundation pit in the relevant specification,
the allowable horizontal displacement of the top of the foundation pit is:
[S]＝H·σ (A)
assuming the spring compressible length is L:
L≥[S](B)
the maximum soil pressure P to which the steel support needs to be subjected can be calculated according to the passive pressure calculation methodmax：
Pmax＝KaγH (C)
In the formula: ka-lateral pressure coefficient of soil around foundation pit
Gamma-the gravity of the soil around the foundation pit
H-design depth of foundation pit
The maximum spring force that the spring can provide is F, assuming the hooke's modulus of the spring is k:
F＝k·L (D)
the spring must satisfy the following conditions in order to provide sufficient elastic force:
F≥Pmax(E)
the hooke's modulus of the spring and the compressible length of the spring can be determined from the above 5 equations.
Step two: high strength nuts and bolts (mainly in tension and compression of springs when the foundation pit bottom is inclined due to the diaphragm wall) are selected.
Permissible screw and nut degreest]The maximum elastic force F of the spring is required to be larger than the maximum elastic force F of the spring, and the tensile strength of the steel is determined in the design and manufacture process and can be selected according to relevant requirements.
Step three: and selecting the diameters of the spring steel pipe sleeve and the base steel pipe sleeve in the device according to the diameter of the steel support adopted in the current place.
Step four: the outer diameter of the spring can be determined according to the diameter of the selected spring steel tube sleeve. The natural length of the spring is more than 2 times of the length of the steel pipe sleeve.
In summary, according to the existing spring parameters: the hooke's modulus, natural length of the spring, the outer diameter of the spring, the compressibility of the spring, etc. may be customized to the particular spring gauge and type.
Step five: the installation can be carried out according to the design content of the component.
By adopting the method and the structure, the automatic compensation of the prestress in the supporting structure in the foundation pit excavation is realized, and the later-stage steel support dismantling operation is facilitated. Especially, when the steel support is dismantled in the later period, the steel support can be easily dismantled only by tightening the nut to compress the spring. The method can ensure that the steel support is kept to have reliable prestress in the construction process, prevent the problem of stress relaxation of the steel support in later construction, ensure that the concrete support is constantly pressed when the mixed support is adopted, avoid tensile stress and prevent the concrete from being damaged by tension.
The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit is simple and convenient, and the design reliability of the provided device is high.
Drawings
Fig. 1 is a schematic view of a three-dimensional overall structure of the device for self-adaptive and automatic compensation of prestress of mixed support for excavation of a foundation pit.
Fig. 2 is a base structure of the device for self-adaptive and automatic compensation of prestress of mixed support for excavation of foundation pit.
Fig. 3 is a spring sleeve structure of the device for self-adaptive and automatic compensation of prestress of mixed support for excavation of foundation pit.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
With reference to fig. 1, a device for self-adaptive and automatic compensation of pre-stress of a hybrid support for excavation of a foundation pit includes: high strength nut 1, outer steel pipe sleeve base 2, high strength screw rod 3, outer steel pipe sleeve 4, high strength spring 5, inlayer steel pipe sleeve 6, screw 7.
And (3) with reference to fig. 2, selecting the size of the high-strength screw according to the calculation requirement, welding the high-strength screw on the base, designing the diameter of the outer steel pipe sleeve according to the diameter of the on-site steel support, and enabling the inner diameter of the outer steel pipe sleeve to be the same as the size of the steel pipe in the steel support.
And (3) designing the outer diameter of the inner steel pipe sleeve according to the inner diameter of the outer steel pipe sleeve, wherein the thickness of the inner steel pipe can be determined according to the thickness of the outer steel pipe sleeve, and the corresponding spring is required to be customized and put into the inner steel pipe sleeve according to the calculation in the front of the foundation.
With reference to fig. 2 and 3, the screw of the device of fig. 2 is inserted through the corresponding screw hole of fig. 3, and the nut is screwed to form the device of fig. 1.
The self-adaptive automatic compensation method for the prestress of the mixed support for foundation pit excavation comprises the following steps:
the method comprises the following steps: a suitable high strength spring is selected.
The spring is selected in relation to the maximum horizontal displacement that the foundation pit will undergo, for example, the designed maximum depth of the foundation pit is H corresponding to the allowable inclination angle σ corresponding to the depth of the foundation pit in the relevant specification, in the embodiment, it is assumed that the designed maximum depth of the foundation pit is H20 m, and the allowable inclination angle σ is 0.01 ° (degree)
The allowable horizontal displacement of the top of the foundation pit is:
[S]＝H·σ (A)
assuming the spring compressible length is L:
L≥[S](B)
assuming that the compressible length L of the spring needs to be at least greater than 1.1mm, the compressible length of the spring can be selected according to actual field design, so as to determine the size of L.
The maximum soil pressure P to which the steel support needs to be subjected can be calculated according to the passive pressure calculation methodmax：
Pmax＝KaγH (C)
In the formula: ka-lateral pressure coefficient of soil around foundation pit
Gamma-the gravity of the soil around the foundation pit
H-design depth of foundation pit
The maximum soil pressure P to which the steel support needs to be subjected can be calculated according to the passive pressure calculation methodmax：
Lateral pressure coefficient K of soil around foundation pitaCan take 0.5, the heavy gamma of the soil around the foundation pit can take 18kN/m3：
Then P ismax＝KaγH＝0.5×18×20＝180KPa
The maximum spring force that the spring can provide is F, assuming the hooke's modulus of the spring is k (the hooke's modulus of the spring can be chosen reasonably according to design requirements), then:
F＝k·L (D)
the spring must satisfy the following conditions in order to provide sufficient elastic force:
F≥Pmax(E)
the hooke's modulus of the spring and the compressible length of the spring can be determined from the above 5 equations.
The maximum spring force that the spring can provide is F, and the spring must satisfy:
F≥Pmax＝180Kpa
step two: high strength nuts and bolts (mainly in tension and compression of springs when the foundation pit bottom is inclined due to the diaphragm wall) are selected.
Permissible screw and nut degreest]The maximum elastic force F of the spring is required to be larger than the maximum elastic force F of the spring, and the tensile strength of the steel is determined in the design and manufacture process and can be selected according to relevant requirements.
Step three: and selecting the diameters of the spring steel pipe sleeve and the base steel pipe sleeve in the device according to the diameter of the steel support adopted in the current place.
Step four: the outer diameter of the spring can be determined according to the diameter of the selected spring steel tube sleeve. The natural length of the spring is more than 2 times of the length of the steel pipe sleeve.
In summary, according to the existing spring parameters: the hooke's modulus, natural length of the spring, the outer diameter of the spring, the compressibility of the spring, etc. may be customized to the particular spring gauge and type.
Step five: the installation can be carried out according to the design content of the component.
The foregoing description of the embodiments of the invention has been presented in detail, and each embodiment herein is provided to provide a further understanding of the invention. It should be understood that the above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily made by those skilled in the art without substantially departing from the present invention are also included in the scope of the present invention.
Claims (7)
1. A self-adaptive automatic compensation method for prestress of a mixed support for foundation pit excavation is characterized in that a self-adaptive automatic compensation device for prestress of the mixed support for foundation pit excavation is used and comprises an outer layer steel pipe sleeve base, a high-strength screw rod, an outer layer steel pipe sleeve, a spring and an inner layer steel pipe sleeve, wherein the outer layer steel pipe sleeve base is connected with an embedded component in a foundation pit wall, and the inner layer steel pipe sleeve with the spring is inserted into the outer layer steel pipe sleeve of the outer layer steel pipe sleeve base;
when the foundation pit excavation steel support is installed, firstly fixing an outer layer steel pipe sleeve base with a high-strength screw rod in an embedded component, then loading a high-strength spring into an inner layer steel pipe sleeve with a screw hole, aligning the outer layer steel pipe sleeve and the screw rod together, inserting the screw rod into an outer layer steel pipe sleeve of the outer layer steel pipe sleeve base, and finally installing a high-strength nut;
characterized in that the method comprises the following steps:
the method comprises the following steps: selecting proper high-strength spring
The selection of the spring is related to the maximum horizontal displacement which can be generated by the foundation pit, the designed maximum depth of the foundation pit is H, the allowable inclination angle corresponding to the depth of the foundation pit in the relevant specification is sigma,
the allowable horizontal displacement of the top of the foundation pit is:
[S]＝H·σ (A)
assuming the spring compressible length is L:
L≥[S](B)
the maximum soil pressure P to which the steel support needs to be subjected can be calculated according to the passive pressure calculation methodmax：
Pmax＝KaγH (C)
In the formula: ka-lateral pressure coefficient of soil around foundation pit
Gamma-the gravity of the soil around the foundation pit
H-design depth of foundation pit
The maximum spring force that the spring can provide is F, assuming the hooke's modulus of the spring is k:
F＝k·L (D)
the spring must satisfy the following conditions in order to provide sufficient elastic force:
F≥Pmax(E)
determining the hooke coefficient of the spring and the compressible length of the spring according to the above 5 equations;
step two: selecting high-strength nut and screw
Permissible screw and nut degreest]The tensile strength of the steel is determined in the design and manufacture process, and the steel is selected according to related requirements;
step three: selecting the diameters of an inner layer steel pipe sleeve and an outer layer steel pipe sleeve in the device according to the diameter of a steel support adopted in the current place;
step four: determining the outer diameter of the spring according to the diameter of the selected inner steel pipe sleeve;
step five: the installation is carried out according to the design content of the component.
2. The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit as claimed in claim 1, wherein: the natural length of the spring is more than 2 times of the length of the inner steel tube sleeve.
3. The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit as claimed in claim 1, wherein: in the first step, according to the existing spring parameters: the hooke's modulus, natural length, outer diameter, and compressibility of the spring are customized to the relevant spring specifications and types.
4. The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit as claimed in claim 1, wherein: the inner layer steel pipe sleeve is provided with a screw hole, and the high-strength screw rod is inserted into the screw hole and fixed through a screw cap.
5. The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit as claimed in claim 1, wherein: the high-strength screw rods are multiple.
6. The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit as claimed in claim 1, wherein: the number of screw holes corresponds to the number of screw rods.
7. The method for self-adaptive automatic compensation of the prestress of the mixed support for excavation of the foundation pit as claimed in claim 1, wherein: the high-strength screws are uniformly distributed on the outer layer steel pipe sleeve base.
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| CN201810997658.2A CN109183804B (en) | 2018-08-29 | 2018-08-29 | Foundation pit excavation mixed support prestress self-adaptive automatic compensation method |
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| CN201810997658.2A CN109183804B (en) | 2018-08-29 | 2018-08-29 | Foundation pit excavation mixed support prestress self-adaptive automatic compensation method |
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| CN109183804B true CN109183804B (en) | 2020-08-21 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103244161A (en) * | 2013-05-23 | 2013-08-14 | 湖南科技大学 | Yielding type backing plate device |
| CN104929663A (en) * | 2015-06-05 | 2015-09-23 | 江苏中矿立兴能源科技有限公司 | Support mechanism capable of applying prestress, reducing pressure and unloading |
| CN204789130U (en) * | 2015-07-29 | 2015-11-18 | 三峡大学 | Multi -functional of hard and soft conversion can invariable load support |
| CN106285724A (en) * | 2016-10-14 | 2017-01-04 | 成都理工大学 | A kind of tunnel is by pressure type support system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080307721A1 (en) * | 2007-06-13 | 2008-12-18 | Jeffrey Todd Schultz | Anchoring Systems And Related Methods |
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- 2018-08-29 CN CN201810997658.2A patent/CN109183804B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103244161A (en) * | 2013-05-23 | 2013-08-14 | 湖南科技大学 | Yielding type backing plate device |
| CN104929663A (en) * | 2015-06-05 | 2015-09-23 | 江苏中矿立兴能源科技有限公司 | Support mechanism capable of applying prestress, reducing pressure and unloading |
| CN204789130U (en) * | 2015-07-29 | 2015-11-18 | 三峡大学 | Multi -functional of hard and soft conversion can invariable load support |
| CN106285724A (en) * | 2016-10-14 | 2017-01-04 | 成都理工大学 | A kind of tunnel is by pressure type support system |
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