CN112064660A - Grading depressurization method for foundation pit - Google Patents
Grading depressurization method for foundation pit Download PDFInfo
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- CN112064660A CN112064660A CN202010929608.8A CN202010929608A CN112064660A CN 112064660 A CN112064660 A CN 112064660A CN 202010929608 A CN202010929608 A CN 202010929608A CN 112064660 A CN112064660 A CN 112064660A
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- pit
- depressurization
- ground wall
- well
- foundation pit
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/12—Restraining of underground water by damming or interrupting the passage of underground water
- E02D19/18—Restraining of underground water by damming or interrupting the passage of underground water by making use of sealing aprons, e.g. diaphragms made from bituminous or clay material
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D19/00—Keeping dry foundation sites or other areas in the ground
- E02D19/06—Restraining of underground water
- E02D19/10—Restraining of underground water by lowering level of ground water
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Paleontology (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
Abstract
The invention provides a foundation pit step-by-step depressurization method, which comprises the steps of depressurizing through a first-stage pit external depressurization well between a ground wall and a water-stop curtain adjacent to the ground wall, and then obtaining a first-stage confined water head and a second-stage confined water head in a region to be excavated in a region surrounded by the ground wall and the adjacent water-stop curtain, so as to reduce the height difference between the second-stage confined water head and the first-stage confined water head in the region to be excavated and further reduce the pressure of the ground wall. The invention can reduce the difference of the bearing water heads inside and outside the pit and protect the enclosure structure of the ultra-deep foundation pit; reducing the leakage risk of the ultra-deep foundation pit; and the safety factor of the construction operation in the foundation pit is increased. The invention can effectively control the depressurization range, ensure controllable sedimentation in each depressurization area, reduce the water head difference inside and outside the foundation pit ground wall and effectively ensure the construction safety of the deep foundation pit.
Description
Technical Field
The invention relates to a foundation pit grading depressurization method.
Background
Along with the development of urban underground space, the depth of the underground space is deeper and deeper, some underground structures are buried deeply into the underground layer-seventy-percent confined water layer, but the underground continuous wall serving as the enclosure structure has no good countermeasure, the leakage problem is inevitable in the construction process, and the weak point of the foundation pit enclosure structure and the subsequent excavation construction face great risks mainly due to the huge layer-seventy-percent confined water head difference.
Disclosure of Invention
The invention aims to provide a foundation pit grading depressurization method.
In order to solve the problems, the invention provides a foundation pit grading depressurization method, which comprises the following steps:
setting a depressurization well in a pit in an area to be excavated;
arranging a ground wall outside the area to be excavated, wherein the ground wall is inserted into a ninth pressure water layer;
arranging a waterproof curtain on the outer side of the ground wall, wherein the waterproof curtain is inserted into a seventh pressure-bearing water layer;
an out-pit depressurization well is arranged between the ground wall and the waterproof curtain;
and reducing the water level of the seventh layer of underground water in the area to be excavated by opening the in-pit depressurization well and the out-pit depressurization well.
Further, in the above method, the step of providing a waterproof curtain outside the floor wall includes:
2 or more than 2 waterproof curtains are arranged on the outer side of the ground wall at preset intervals;
set up outer decompression well in pit between ground wall and the waterproof curtain, include:
a first-stage pit outer pressure reduction well is arranged between the ground wall and a waterproof curtain adjacent to the ground wall;
and a second-stage pit outer depressurization well is arranged between every two adjacent waterproof curtains.
Further, in the above method, the lowering the water level of the seventh layer of groundwater in the area to be excavated by opening the in-pit depressurization well and the out-pit depressurization well includes:
and under a normal precipitation state, opening a first-stage pit external pressure reduction well between the ground wall and one water stop curtain adjacent to the ground wall, and simultaneously opening a pit internal pressure reduction well in the area to be excavated.
Further, in the above method, the lowering the water level of the seventh layer of groundwater in the area to be excavated by opening the in-pit depressurization well and the out-pit depressurization well includes:
and under an emergency precipitation state, opening one or more second-stage pit external pressure reduction wells between two adjacent waterproof curtains, simultaneously opening one-stage pit external pressure reduction wells between the ground wall and one adjacent waterproof curtain of the ground wall, and opening pit internal pressure reduction wells in the area to be excavated.
Further, in the above method, inserting the waterproof curtain into a seventh layer of the pressurized water layer, comprises:
and inserting the waterproof curtain into two thirds of the seventh pressure-bearing water layer.
Further, in the above method, after the waterproof curtain is installed outside the ground wall, the method further includes:
and reinforcing the waterproof curtain by adopting ultra-deep MJS and CSM cement soil mixing piles.
Compared with the prior art, after the pressure of a first-stage pit outer pressure reduction well between the adjacent waterproof curtains of the ground wall is reduced, a first-stage confined water head and a second-stage confined water head in the area to be excavated are obtained in the area surrounded by the ground wall and the adjacent waterproof curtains, so that the height difference between the second-stage confined water head and the first-stage confined water head in the area to be excavated is reduced, and the pressure of the ground wall is further reduced. The invention can reduce the difference of the bearing water heads inside and outside the pit and protect the enclosure structure of the ultra-deep foundation pit; reducing the leakage risk of the ultra-deep foundation pit; and the safety factor of the construction operation in the foundation pit is increased. The invention can effectively control the depressurization range, ensure controllable sedimentation in each depressurization area, reduce the water head difference inside and outside the foundation pit ground wall and effectively ensure the construction safety of the deep foundation pit.
Drawings
Fig. 1 is a schematic view of a foundation pit grading depressurization method according to an embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1, the present invention provides a method for reducing pressure of a foundation pit by stages, comprising:
step S1, arranging a depressurization well 1 in the pit in the area 2 to be excavated;
step S2, arranging a ground wall 3 on the outer side of the region 2 to be excavated, wherein the ground wall is inserted into a ninth confined water layer;
step S3, arranging a waterproof curtain 4 on the outer side of the floor wall 3, wherein the waterproof curtain is inserted into a seventh layer of pressure-bearing water layer;
step S4, arranging an out-pit depressurization well between the ground wall 3 and the waterproof curtain 4;
and step S5, reducing the water level of the seventh layer of underground water in the area to be excavated 2 by opening the in-pit depressurization well 1 and the out-pit depressurization well.
In the above, it is found through investigation that some engineering cases cause excessive settlement of surrounding strata due to improper pressure-reducing water, and the normal use of surrounding pipelines and building structures is seriously affected. Therefore, the inadequate induction of excess settlement of the surrounding formation by the reduced pressure water is also one of the important manifestations of the damage of the pressure water.
In order to ensure the safety of foundation pit earthwork excavation construction and reduce the leakage risk of the ultra-deep foundation pit when the foundation pit has an emergency leakage situation, the invention provides an off-pit graded pressure-bearing water pressure reduction construction method, which is used for protecting and navigating the foundation pit construction.
The water-stop curtain is arranged in the figure 1, after a first-stage pit outer pressure reducing well 5 between adjacent water-stop curtains of the ground wall is subjected to pressure reduction, a first-stage confined water head A and a second-stage confined water head B in an area surrounded by the ground wall and the adjacent water-stop curtain are obtained, so that the height difference between the second-stage confined water head B in the area to be excavated and the first-stage confined water head A is reduced, as shown in the figure 1, the height difference between the second-stage confined water head B and the first-stage confined water head A is H2, the height difference between the first-stage confined water head A and the previous-stage confined water head is H1, and the pressure of the ground wall is reduced. The invention can reduce the difference of the bearing water heads inside and outside the pit and protect the enclosure structure of the ultra-deep foundation pit; reducing the leakage risk of the ultra-deep foundation pit; and the safety factor of the construction operation in the foundation pit is increased. The invention can effectively control the depressurization range, ensure controllable sedimentation in each depressurization area, reduce the water head difference inside and outside the foundation pit ground wall and effectively ensure the construction safety of the deep foundation pit.
In an embodiment of the method for stepping down the pressure of the foundation pit, in step S3, the step of arranging a waterproof curtain on the outer side of the ground wall includes:
2 or more than 2 waterproof curtains 4 are arranged on the outer side of the ground wall 3 at preset intervals;
step S4, an out-pit depressurization well is arranged between the ground wall and the waterproof curtain, and the method comprises the following steps:
a first-stage pit outer pressure reduction well 5 is arranged between the ground wall and a waterproof curtain adjacent to the ground wall;
and a secondary pit external pressure reduction well (not shown) is arranged between each two adjacent waterproof curtains.
Here, only 1 waterproof curtain is arranged in fig. 1, and 1 or more waterproof curtains can be arranged at the side of the waterproof curtain far away from the ground wall, and after multi-stage depressurization is performed through a plurality of second-stage pit external depressurization wells between two adjacent waterproof curtains and a first-stage pit external depressurization well between the ground wall and the adjacent waterproof curtain, a first-stage confined water head a and a second-stage confined water head B in the area to be excavated are obtained in the area surrounded by the ground wall and the adjacent waterproof curtain, so that the height difference between the second-stage confined water head B in the area to be excavated and the first-stage confined water head a is further reduced, and further the pressure of the ground wall is reduced.
In an embodiment of the foundation pit grading depressurization method, in step S5, the step of opening the depressurization well in the pit and the depressurization well outside the pit to lower the water level of the seventh layer of groundwater in the area to be excavated includes:
and under a normal precipitation state, opening a first-stage pit external pressure reduction well between the ground wall and one water stop curtain adjacent to the ground wall, and simultaneously opening a pit internal pressure reduction well in the area to be excavated.
The construction method can be used for carrying out step-down construction according to the condition that whether leakage occurs in the foundation pit construction process or not, and is in a normal precipitation state when leakage does not occur, and is in an emergency precipitation state when leakage occurs and leakage can not be effectively blocked.
And under the normal precipitation state, opening the depressurization well in the pit and the depressurization well outside the first-stage pit, reducing the water level of the seventh layer of underground water in the excavation area of the foundation pit by 10.00-15.00m, and reducing the water level difference between the inside and the outside of the foundation pit wall.
In an embodiment of the foundation pit grading depressurization method, in step S5, the step of opening the depressurization well in the pit and the depressurization well outside the pit to lower the water level of the seventh layer of groundwater in the area to be excavated includes:
and under an emergency precipitation state, opening one or more second-stage pit external pressure reduction wells between two adjacent waterproof curtains, simultaneously opening one-stage pit external pressure reduction wells between the ground wall and one adjacent waterproof curtain of the ground wall, and opening pit internal pressure reduction wells in the area to be excavated.
In the emergency water lowering state, a second-level pit outer depressurization well and a first-level pit outer depressurization well outside the pit are opened simultaneously (the amount of opening the second-level pit outer depressurization is determined according to the productive water pumping test conclusion), the water level of the seventh layer around the foundation pit leakage point is lowered to be below the bottom plate surface, and after the water lowering is finished, the inner wall in the pit is subjected to leakage stoppage.
In an embodiment of the method for reducing the pressure of the foundation pit by stages, in step S3, inserting the waterproof curtain into the seventh layer of the confined water layer includes:
and inserting the waterproof curtain into two thirds of the seventh pressure-bearing water layer.
In an embodiment of the method for stepping down the pressure of the foundation pit, in step S3, after the waterproof curtain is arranged on the outer side of the ground wall, the method further includes:
and reinforcing the waterproof curtain by adopting ultra-deep MJS and CSM cement soil mixing piles.
The ultra-deep MJS jet flow pressure is 40MPa, and the effective reinforcing depth is 40-60 m; and the reinforcing depth of the CSM double-wheel milling deep-stirring equipment is 49 meters.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. A foundation pit grading depressurization method is characterized by comprising the following steps:
setting a depressurization well in a pit in an area to be excavated;
arranging a ground wall outside the area to be excavated, wherein the ground wall is inserted into a ninth pressure water layer;
arranging a waterproof curtain on the outer side of the ground wall, wherein the waterproof curtain is inserted into a seventh pressure-bearing water layer;
an out-pit depressurization well is arranged between the ground wall and the waterproof curtain;
and reducing the water level of the seventh layer of underground water in the area to be excavated by opening the in-pit depressurization well and the out-pit depressurization well.
2. The foundation pit graded depressurization method of claim 1, wherein the step of arranging a waterproof curtain outside the ground wall comprises:
2 or more than 2 waterproof curtains are arranged on the outer side of the ground wall at preset intervals;
set up outer decompression well in pit between ground wall and the waterproof curtain, include:
a first-stage pit outer pressure reduction well is arranged between the ground wall and a waterproof curtain adjacent to the ground wall;
and a second-stage pit outer depressurization well is arranged between every two adjacent waterproof curtains.
3. The foundation pit graded depressurization method according to claim 2, wherein the lowering of the water level of the seventh layer of groundwater in the area to be excavated by opening the in-pit depressurization well and the out-pit depressurization well comprises:
and under a normal precipitation state, opening a first-stage pit external pressure reduction well between the ground wall and one water stop curtain adjacent to the ground wall, and simultaneously opening a pit internal pressure reduction well in the area to be excavated.
4. The foundation pit graded depressurization method of claim 1, wherein the lowering of the water level of the seventh layer of groundwater in the area to be excavated by opening the in-pit depressurization well and the out-pit depressurization well comprises:
and under an emergency precipitation state, opening one or more second-stage pit external pressure reduction wells between two adjacent waterproof curtains, simultaneously opening one-stage pit external pressure reduction wells between the ground wall and one adjacent waterproof curtain of the ground wall, and opening pit internal pressure reduction wells in the area to be excavated.
5. The foundation pit staged depressurization method of claim 1, wherein inserting the waterproof curtain into a seventh layer of pressurized water comprises:
and inserting the waterproof curtain into two thirds of the seventh pressure-bearing water layer.
6. The method for stepping down the foundation pit according to claim 1, wherein after the waterproof curtain is arranged on the outer side of the foundation pit, the method further comprises the following steps:
and reinforcing the waterproof curtain by adopting ultra-deep MJS and CSM cement soil mixing piles.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010929608.8A CN112064660A (en) | 2020-09-07 | 2020-09-07 | Grading depressurization method for foundation pit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010929608.8A CN112064660A (en) | 2020-09-07 | 2020-09-07 | Grading depressurization method for foundation pit |
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| CN112064660A true CN112064660A (en) | 2020-12-11 |
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| CN202010929608.8A Pending CN112064660A (en) | 2020-09-07 | 2020-09-07 | Grading depressurization method for foundation pit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112593566A (en) * | 2020-11-24 | 2021-04-02 | 浙江二十冶建设有限公司 | Dewatering method for existing building deep foundation pit |
| CN113882410A (en) * | 2021-09-01 | 2022-01-04 | 武汉市政工程设计研究院有限责任公司 | Deep foundation pit underground water treatment structure and method |
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| CN109898534A (en) * | 2019-03-05 | 2019-06-18 | 东南大学 | A kind of more echelon Dewatering by pressure reduction control methods of high artesian stratum deep big foundation pit |
| CN209040135U (en) * | 2018-09-06 | 2019-06-28 | 中铁第一勘察设计院集团有限公司 | A kind of deep soft stratum combined type foundation pit Water outburst treatment construction |
| CN110777832A (en) * | 2019-11-08 | 2020-02-11 | 上海建工二建集团有限公司 | Waterproof curtain at end of underwater channel foundation pit along two sides of water |
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2020
- 2020-09-07 CN CN202010929608.8A patent/CN112064660A/en active Pending
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| CN209040135U (en) * | 2018-09-06 | 2019-06-28 | 中铁第一勘察设计院集团有限公司 | A kind of deep soft stratum combined type foundation pit Water outburst treatment construction |
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| CN109898534A (en) * | 2019-03-05 | 2019-06-18 | 东南大学 | A kind of more echelon Dewatering by pressure reduction control methods of high artesian stratum deep big foundation pit |
| CN110777832A (en) * | 2019-11-08 | 2020-02-11 | 上海建工二建集团有限公司 | Waterproof curtain at end of underwater channel foundation pit along two sides of water |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112593566A (en) * | 2020-11-24 | 2021-04-02 | 浙江二十冶建设有限公司 | Dewatering method for existing building deep foundation pit |
| CN113882410A (en) * | 2021-09-01 | 2022-01-04 | 武汉市政工程设计研究院有限责任公司 | Deep foundation pit underground water treatment structure and method |
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Application publication date: 20201211 |