CN112049115A - Anti-seepage treatment method for deep foundation pit excavation of water-rich silt stratum - Google Patents

Anti-seepage treatment method for deep foundation pit excavation of water-rich silt stratum Download PDF

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Publication number
CN112049115A
CN112049115A CN202010839310.8A CN202010839310A CN112049115A CN 112049115 A CN112049115 A CN 112049115A CN 202010839310 A CN202010839310 A CN 202010839310A CN 112049115 A CN112049115 A CN 112049115A
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China
Prior art keywords
water
foundation pit
excavation
grouting
sand
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CN202010839310.8A
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Chinese (zh)
Inventor
夏明锬
邹春华
梅灿
龙华东
张志冰
周坤
李应姣
刘欣
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China Railway 11th Bureau Group Co Ltd
China Railway Construction Corp Ltd CRCC
China Railway 11th Bureau Group Urban Rail Engineering Co Ltd
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China Railway 11th Bureau Group Co Ltd
China Railway Construction Corp Ltd CRCC
China Railway 11th Bureau Group Urban Rail Engineering Co Ltd
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Priority to CN202010839310.8A priority Critical patent/CN112049115A/en
Publication of CN112049115A publication Critical patent/CN112049115A/en
Pending legal-status Critical Current

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    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00Excavations; Bordering of excavations; Making embankments
    • E02D17/02Foundation pits
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D19/00Keeping dry foundation sites or other areas in the ground
    • E02D19/06Restraining of underground water
    • E02D19/10Restraining of underground water by lowering level of ground water
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D19/00Keeping dry foundation sites or other areas in the ground
    • E02D19/06Restraining of underground water
    • E02D19/12Restraining of underground water by damming or interrupting the passage of underground water
    • E02D19/16Restraining of underground water by damming or interrupting the passage of underground water by placing or applying sealing substances
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D29/00Independent underground or underwater structures; Retaining walls
    • E02D29/16Arrangement or construction of joints in foundation structures

Abstract

The invention provides an anti-seepage treatment method for excavation of a deep foundation pit of a water-rich silt stratum. The treatment method comprises the following specific steps: firstly, adopting WSS grouting at the joint position of the diaphragm wall outside the foundation pit, then arranging precipitation wells outside the foundation pit to reduce the water pressure, placing a water pump in each precipitation well, carrying out manual exploration excavation from the second-layer earthwork excavation in the deep foundation pit, exploring the water leakage condition at the joint position of the diaphragm wall by adopting Luoyang shovel exploration excavation, and taking a blocking measure according to the water leakage condition; after confirming that all underground continuous wall seams of the manual excavation bin section have no water leakage situation, arranging a grouting platform at the edge of the foundation pit, and simultaneously arranging a plurality of sand material backfill windows at the outer side of the foundation pit, and in the mechanical excavation process of the foundation pit, performing emergency treatment by adopting grouting and concrete backfill modes when meeting the water leakage situation. The method avoids the risk of water gushing and sand gushing, achieves the effect of quickly and stably excavating the deep foundation pit of the subway to meet the bottom, shortens the construction period and saves the cost.

Description

Anti-seepage treatment method for deep foundation pit excavation of water-rich silt stratum
Technical Field
The invention belongs to the field of foundation pit construction, and particularly relates to an anti-seepage treatment method for excavation of a deep foundation pit in a water-rich silt stratum.
Background
The subway can quickly, safely and comfortably transport passengers with large flow, and has good social and economic benefits, so that the urban subway construction is developed rapidly in recent years. However, because the subway construction is carried out underground, the underground structure is greatly influenced by the hydrogeological environment, huge construction safety risks exist in the construction process of the subway civil engineering, the underground construction safety risks are easily influenced by water seepage of the underground enclosure structure, and particularly when the enclosure structure is an underground continuous wall, the hidden danger of water seepage at the joint is larger.
At present, in the subway construction process, foundation pit engineering risk control is mainly focused on water treatment, particularly deep foundation pits, once water leakage occurs in the foundation pits, water gushing and sand gushing channels can be formed, a large amount of water and soil loss outside the pits can be accompanied, and if the water and soil loss is not blocked in time, serious consequences can be generated. Particularly, when a deep foundation pit is excavated in a water-rich silt stratum, water gushing and sand gushing accidents are more easily caused, great influence is caused on surrounding buildings, pipelines and roads, if water gushing and sand gushing occur in the foundation pit, effective control cannot be achieved in a short time, once a water gushing and sand gushing channel is formed, ground collapse is caused, and the pipeline and the residential community are affected. How to prevent and treat the water seepage problem in the excavation process of the foundation pit during the construction is a difficult problem that the safety of the deep foundation pit must be overcome.
Most of the existing foundation pit seepage-proofing and leakage-stopping construction adopts a method of hole leading and grouting from the ground, the hole leading equipment and the grouting equipment have large volumes, and the working face of emergency rescue in a narrow ground of a subway foundation pit is not enough.
Disclosure of Invention
The invention provides a water-rich silt stratum deep foundation pit excavation anti-seepage treatment method aiming at the defects of the prior art, which can quickly and effectively control water leakage of a water-rich silt stratum deep foundation pit, avoid the risk of water gushing and sand gushing in the process of deep foundation pit excavation, achieve the effect of quickly and stably excavating a subway deep foundation pit to meet the foundation, shorten the construction period and save the cost.
In order to achieve the technical purpose, the invention provides an anti-seepage treatment method for excavation of a deep foundation pit of a water-rich silt stratum, which comprises the following specific steps of:
(1) adopting WSS grouting at the joint position of the diaphragm wall outside the foundation pit, wherein the grouting slurry adopts water glass-cement double-liquid slurry;
(2) after the WSS grouting is finished, arranging a precipitation well outside the foundation pit to reduce the water pressure, arranging a precipitation well 8-10 m outside the foundation pit, wherein the depth of the precipitation well is 20-22 m, placing a water pump in each precipitation well, and installing the water pump at a position 7-8 m below the ground; the potential hazards of water gushing and sand gushing occur in the excavation process of the foundation pit, a water pump in a precipitation well is immediately lowered to the bottom of the pit, and the water pressure difference between the inside and the outside of the pit and the emergency rescue pressure in the foundation pit are reduced;
(3) and (3) starting excavation from the second layer of earthwork in the deep foundation pit, before excavation of the foundation pit earthwork, carrying out artificial exploration excavation on the joint of the underground continuous wall of each bin, carrying out artificial exploration excavation on the joint of the underground continuous wall with the length multiplied by the width multiplied by 1.5m and the depth of 1.5 m-1.8 m, then carrying out exploration excavation on the joint of the underground continuous wall by adopting a Luoyang shovel with the depth of 2.0 m-2.5 m, exploring the water leakage condition of the joint of the underground continuous wall, and carrying out rapid water stop treatment according to the exploration condition.
(4) After confirming that the joints of all underground continuous walls of the manual excavation bin section have no water leakage situation, arranging a grouting platform at the edge of the foundation pit, arranging a grouting tool, and arranging grouting pipes along the long edge direction of the foundation pit, wherein the arrangement of the grouting pipes requires that the pipe connection grouting work is realized within 10min at any position during the excavation of the foundation pit; meanwhile, sand material backfill windows with the width of 0.5-0.6 m and the length of 0.8-1 m are arranged on the hardened pavement at the joint edge of each ground wall outside the foundation pit, and each sand material backfill window is blocked by steel plate quick-drying cement;
(5) after the construction in the step (4) is completed, carrying out excavation operation of a slope-releasing machine according to a foundation pit excavation scheme; in the mechanical excavation process of the foundation pit, when the water seepage condition occurs, a grouting pipe is connected within 10min for temporary grouting and plugging; when the collapse is met and emergency rescue is needed, a sand material backfill window is opened to carry out sand concrete backfill operation.
The further technical scheme of the invention is as follows: the rapid water stopping treatment process according to the exploration condition in the step (3) is as follows:
a. when seepage water appears in the ground wall seam, continuous wall seam position exists infiltration passageway: manually cleaning the positions of the defective joints of the ground wall at the first time, and plugging by using quick-drying cement clusters; or firstly adopting quick-drying cement for plugging, then adopting a steel plate for welding and plugging, then horizontally opening grouting holes at two sides of the water leakage position, penetrating the thickness of the underground diaphragm wall to the outer soil side of the foundation pit, embedding a galvanized grouting pipe with a ball valve, adopting a horizontal grouting technology to inject cement-water glass double-liquid slurry for plugging, finally adopting a WSS grouting technology at the outer side of the joint of the foundation pit diaphragm wall, and adopting the cement-water glass double-liquid slurry again for vertical grouting treatment, wherein the treatment depth is at least 2m below the foundation pit base;
b. when water gushing and sand gushing dangerous situations occur on the ground wall joint: b, paving cotton wool at the position of a soil body placed at the seam of the water burst wall, decompressing by adopting a water discharging pipe with a ball valve, repeatedly and alternately performing back pressure on the water burst sand burst opening by adopting sand bags and quilts, closing the ball valve of the water discharging pipe until the water burst sand burst amount reaches a controllable degree when a back pressure body consisting of the sand bags and the quilts reaches the radius of 2 m-2.5 m and the height of 1.6 m-1.8 m, and then performing horizontal double-liquid grouting and leakage blocking in the pit by adopting the horizontal grouting technology which is the same as the step a, wherein the WSS grouting technology performs vertical double-liquid grouting on the seam of the underground diaphragm wall outside the pit;
the invention has the following excellent technical scheme: the grouting slurry in the step (1), the step (3) and the step (5) adopts water glass-cement double-fluid slurry, and the cement slurry density is 1.51Kg/cm3The density of the water glass is 1.15Kg/cm3And the ratio of cement slurry to water glass slurry is 1: 1.
The further technical scheme of the invention is as follows: in the step a of the step (3), when the water seepage amount is small, a quick-drying cement cluster is adopted for plugging, when the quick-drying cement cluster is subjected to plugging, water gushing or water gushing and sand gushing occur, a galvanized pressure relief water pipe with a ball valve at one end is buried for pressure release, when the water pressure is released, the periphery of the galvanized pipe is plugged by the manually-mixed quick-drying cement cluster, and the ball valve is closed after the plugging is finished; and (c) when the water seepage amount in the step (3) a is large, firstly plugging by using quick-drying cement and then plugging by welding a steel plate.
The invention has the following excellent technical scheme: and (b) in the step (3), judging the width and depth of the defect of the seam of the water leakage ground wall, and when the seam of the ground wall is large and the risk of water and sand gushing exists, welding and plugging the quick-drying cement mass at the plugging position by adopting a steel plate, and plugging the welding seam by using quick-drying cement.
The invention has the following excellent technical scheme: and (c) taking the phi 80mm in the emergency material cage in the two foundation pits and the ball valve pressure relief water pipe with the length of 2.5m by the ball valve pressure relief water pipe in the step (3) b, arranging the two pressure relief pipelines in a splayed manner, placing one end of a ball-free valve on cotton wool of a water gushing and sand gushing port, and enabling one end of the ball valve to face towards the inner side of the foundation pit.
The invention has the following excellent technical scheme: and (c) in the step (3), two layers of sandbags and one layer of quilt are adopted to repeatedly and alternately carry out back pressure water burst and sand gushing.
The invention has the following excellent technical scheme: the grouting platform in the step (4) is arranged in the middle of a side access way of a foundation pit in a construction site, and the grouting tool comprises a small cement warehouse, a water glass warehouse, a double-liquid grouting machine and a slurry mixing barrel; and 2 grouting pipes of 130-160 m are respectively arranged on each side along the long side direction of the foundation pit.
The invention has the following excellent technical scheme: and (4) installing a pipeline signboard on the ground every 8-10 m along the peripheral pipeline of the foundation pit in the step (4), wherein the pipeline signboard is made of a stainless steel plate with the thickness of 150mm multiplied by 100mm, characters are engraved, and red paint is coated.
The invention has the beneficial effects that:
(1) the invention adopts the WSS grouting technology aiming at the position of the flexible joint of the diaphragm wall outside the foundation pit, and the water glass-cement double-liquid slurry (A, C slurry) is prepared by taking water glass and cement as main raw materials and adding quantitative water. The slurry has the characteristics of fast gelatinization, high consolidation strength and the like. After the silt layer is injected, the gaps among the sandy particles are filled with slurry to solidify the sandy particles, so that the sand layer is compacted, the cohesive force and the internal friction angle value of the soil layer are increased, and finally the purposes of quickly improving the underground soil body and forming a waterproof reinforcing body at the joint position of the continuous wall are achieved.
(2) The invention arranges the dewatering well outside the foundation pit, reduces the water pressure outside the pit by adopting the dewatering well outside the pit during the excavation of the foundation pit, the water pump is arranged at the position 7m below the ground, and the water pump in the dewatering well is immediately put down to the bottom of the pit once the hidden danger of water gushing and sand gushing occurs in the excavation process of the foundation pit, thereby reducing the water pressure difference inside and outside the pit and the emergency rescue pressure in the foundation pit.
(3) According to the method, the second-layer earthwork excavation is started in the foundation pit, the joint of the underground continuous wall of each bin is manually excavated before the earthwork excavation of the foundation pit, the water leakage situation of the joint position of the underground continuous wall is explored, emergency rescue and leakage stoppage measures can be performed according to different situations, and the problem of water gushing and sand gushing of the joint of the underground wall in the excavation process of the deep foundation pit is successfully solved.
(4) When mechanical excavation is carried out after the joint treatment of the continuous wall is finished, a fixed grouting platform and grouting equipment are arranged at the middle position of a side access way of a foundation pit in a construction site, so that the double-liquid grouting operation of connecting pipes can be realized within 10min at any position, and the grouting seepage prevention work can be carried out at any time; arranging a sand backfill window on a hardened pavement at each ground wall joint edge outside the foundation pit, wherein the backfill window can be opened to carry out sand concrete backfill operation and the like when emergency rescue is needed; and the signboard is arranged aiming at the pipeline, so that the pipeline is prevented from being damaged by mistake during construction and emergency rescue.
The invention adopts the WSS grouting and the pressure relief technology of the dewatering well to treat the underground diaphragm wall joint outside the foundation pit, and adopts the comprehensive treatment measures of manual groove digging in the foundation pit and quick-drying cement, plugging steel plates, horizontal injection of double-liquid slurry and the like at the position with water seepage hidden trouble. Research shows that by adopting the technology, the risk of water burst and sand gushing is avoided, the effect of quickly and stably excavating the subway deep foundation pit is achieved, the construction period is shortened, the cost is saved, and reference are provided for foundation pit excavation under similar geological conditions.
Drawings
FIG. 1 is a schematic view of the distribution of dewatering wells in the present invention;
FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;
FIG. 3 is a schematic view of excavation of a foundation pit according to the present invention;
FIG. 4 is a schematic view of the distribution of the sand backfill window of the present invention;
fig. 5 is a cross-sectional view of a sand backfill window.
In the figure: the method comprises the following steps of 1, a foundation pit, 2, a dewatering well, 3, a water pump, 4, an artificial pit, 5, a Luoyang shovel, 6, a sand backfill window, 7, a sealing steel plate, 8, quick-drying cement, 9, a hardened pavement, 10, an underground continuous wall and 11, and a foundation pit support.
Detailed Description
The invention is further illustrated by the following figures and examples. Fig. 1 to 5 are drawings of embodiments, which are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the embodiments of the present invention. The following claims presented in the drawings are specific to embodiments of the invention and are not intended to limit the scope of the claimed invention. 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.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "inner", "outer", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, or the orientations or positional relationships that the products of the present invention are conventionally placed in use, or the orientations or positional relationships that are conventionally understood by those skilled in the art, and are used for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the equipment or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
The invention is further explained by combining a specific embodiment, and the embodiment is arranged along the east-west direction of a Xingxing road aiming at a No. 4 subway line water transparent bridge station of a certain city. The station is an underground three-layer double-column three-span box-shaped frame structure standard station, the total clear length of the station is 157m, the buried depth of a station bottom plate is 23.7m, and the buried depth of a shield shaft section bottom plate is about 25.5 m. The main structure of the station adopts an open cut and direct construction method, and the standard section and the end well enclosure structure adopt underground continuous walls with the thickness of 1 m. Seven supports and one support replacement are arranged in the vertical direction of the standard section of the foundation pit and the shield well, wherein the first support and the fifth support are reinforced concrete supports, and the second support, the third support, the fourth support and the sixth support are phi 609 steel pipe supports.
The station open cut foundation pit engineering mainly relates to soil layers as follows: 1-1 miscellaneous fill, 2 plain fill, 2 sandy silt, 3 sandy silt, 2 sandy silt, 5 silt and 5 silt with silt, 6 sandy silt and silt, 7-1 sandy silt, 1 silt clay, 2 silt clay and silt sand, 3 sandy silt clay, 1 middle sand, 1 broken stone and clay, 21 completely weathered andesite, 21)2 strongly weathered andesite, (22)3-1 middle and upper weathered andesite, and 22)3-2 middle and lower weathered andesite. The station structure floor is basically located on the silty fine clay layer of the sixth 1. The surface water of the field is mainly a 150m middle river on the south side of the field, the surface width of the water river is 11-13 m, the water depth is 1-3 m, the water level elevation is 6.40m during exploration, and the water level and the flow of the river are mainly controlled by seasonal atmospheric precipitation. According to the water-containing medium, occurrence conditions, water physical properties and hydraulic characteristics of underground water, the types of the underground water of the field are mainly pore diving of the quaternary loose rock, pore pressure bearing water and bedrock fracture water.
In the construction project, I-steel joints are adopted at positions of non-shield tunnel portals, flexible joints are adopted at corresponding positions of shield tunnel portals, the joints of the underground continuous wall are the parts which are most prone to water leakage due to construction process reasons, meanwhile, due to the fact that construction processes are multiple, control of each link is related to the quality of the underground continuous wall, and problems of seam water leakage or wall body damage and the like often occur in engineering; in addition, the construction of the flexible joint diaphragm wall adopts a circular locking pipe type to process joint pouring concrete, adjacent sections are grooved after the locking pipe is pulled out after the pouring is finished, because the concrete of the finished groove section is directly contacted with mud, soil and sand, and because the pulling out of the locking pipe is carried out before final setting during initial setting, silt can be attached to the joints after the pulling out, the best effect cannot be achieved by brushing the wall at the later stage, a construction joint is bound to be arranged between two walls when the flexible joint concrete is poured, and unlike an I-shaped steel joint and a steel plate which are in water retaining, large or small water leakage is bound to be caused at the construction joint of a water-rich stratum; in addition, due to geological problems, the time for forming the groove by impacting is too long, the groove section collapses, and after groove forming is finished, wall brushing is not clean. The station foundation pit periphery is laid with electric power, gas, running water, communication, rainwater, sewage, gravity sewer pipe along the revival road, has six harmony sources and two residential districts of people's ampere yuan, if take place to gush water and gush sand dangerous situation in the foundation pit, can not obtain effective control in the short time, once form gush water and gush sand passageway, will accompany a large amount of off-pit soil and water losses, will lead to the fact the ground to cave in, reach pipeline and residential district safety. Aiming at the construction project, the worker adopts the anti-seepage treatment method for the deep foundation pit excavation of the water-rich silt stratum, and the specific treatment process is as follows:
(1) adopting WSS to inject at the position of the flexible joint of the diaphragm wall outside the foundation pitThe grouting reinforcement is implemented by adopting a grouting technology, wherein the grouting slurry adopts water glass-cement double-fluid slurry (A, C slurry) and takes water glass and cement as main raw materials, and the density of the cement slurry is 1.51Kg/cm3The density of the water glass is 1.15Kg/cm3And the ratio of cement slurry to water glass slurry is 1: 1. The slurry has the characteristics of fast gelatinization, high strength of a solidified body and the like, and after the silt layer is injected, the gaps among the sandy particles are filled with the slurry to solidify the sandy particles, so that the sand layer is compacted, the cohesion and the internal friction angle value of the soil layer are increased, and finally the purposes of quickly improving the underground soil body and forming a waterproof reinforced body at the joint position of the continuous wall are achieved.
(2) And the dewatering well outside the foundation pit reduces the water pressure, and is constructed after the WSS grouting is finished in order to prevent the damage of the dewatering well outside the pit caused by the WSS grouting. According to the underground water pumping test data, one precipitation well 2 is arranged at every 8m outside the foundation pit 1, the distribution of the precipitation wells is shown in figure 1, the depth of the precipitation well 2 is 22m, the precipitation well outside the pit is adopted to reduce the water pressure outside the pit during the excavation of the foundation pit, and as shown in figure 2, a water pump 3 is installed at a position 7m below the ground. The water pump 3 is connected with lifting mechanisms such as a winch fixed on the ground through a lifting steel wire rope, and once the potential hazard of water gushing and sand gushing occurs in the excavation process of the foundation pit, the water pump 3 in the dewatering well 2 is immediately lowered to the bottom of the well, so that the water pressure difference between the inside and the outside of the pit and the emergency rescue pressure in the foundation pit are reduced.
(3) The deep foundation pit adopts a manual exploration and excavation construction technology,
the excavation depth of each layer of earthwork in a foundation pit is about 4m, excavation starts from the second layer of earthwork in the foundation pit, before excavation of the earthwork of the foundation pit, excavation detection is carried out on a joint between two underground continuous walls, the excavation detection is divided into two steps, as shown in figure 3, artificial pit detection 4 with the length multiplied by the width multiplied by the depth of 1.5m multiplied by 0.8m multiplied by 1.5m is artificially excavated, then a Luoyang shovel 5 with the diameter of 100mm is adopted at the joint of the foundation pit to carry out excavation for 2.5m, the water leakage condition of the joint position of the underground continuous walls is explored, the Luoyang shovel excavation can prevent collapse risk caused by too deep pit detection, and the processing is carried out according to the exploration process, and the method:
a. and (4) no leakage condition, and mechanical excavation is carried out after all the ground wall joints of the bin are completely excavated.
b. There is obvious percolating water in the diaphragm wall seam, and infiltration passageway exists in diaphragm wall seam position:
firstly, manually cleaning the position of a defective joint of a ground wall at the first time, plugging by using a mixed quick-drying cement block, if the water pressure is higher, the quick-drying cement block is difficult to plug, burying a galvanized pressure relief water pipe with a ball valve at one end, when the water pressure is released, plugging the periphery of the galvanized pipe by using the manually mixed quick-drying cement block, and closing the ball valve after plugging; secondly, judging the width and the depth of the defect of the joint of the water leakage ground wall, if the hidden danger of the defect is large, adopting a steel plate for welding and plugging the quick-drying cement block, and plugging the welding joint by using quick-drying cement to prevent the quick-drying cement plugging block from falling off due to the factors of equipment collision, deformation and displacement of the underground continuous wall and the like in the excavation process of the foundation pit; thirdly, horizontally forming grouting holes on two sides of the water leakage position, penetrating the thickness of the underground diaphragm wall to the outer soil side of the foundation pit, embedding a galvanized grouting pipe with a ball valve, and injecting cement-water glass double-liquid slurry for plugging by adopting a horizontal grouting technology; fourthly, the WSS grouting technology is adopted at the outer side of the foundation pit for the joint of the underground diaphragm wall, and the cement-water glass double-liquid slurry is adopted again for vertical grouting treatment, wherein the treatment depth is 2m below the foundation pit base.
c. Treating water burst and sand burst dangerous cases: firstly, placing a soil body at the joint position of a water burst ground wall, paving a piece of cotton wool, taking two pressure relief water pipes with ball valves and with the length of 2.5m and phi 80mm in emergency material cages in a foundation pit, placing one end of each ball-free valve on the cotton wool at a water burst sand burst opening, enabling one end of each ball valve to face the inner side of the foundation pit, and arranging two pressure relief pipelines in a splayed manner; secondly, a sand bag filled in the foundation pit is adopted to carry out back pressure water burst and sand gushing opening, the pressure relief water pipe opening cannot be blocked, the sand bag is pressed against two layers and a cotton quilt is laid, and the steps are gradual; thirdly, the sandbag counter pressure body reaches radius 2m, highly about 1.8m, closes the pressure relief pipe ball valve, observes gushing water and gushing sand the condition, if gushing water and gushing sand and not being effectively controlled, then opens the pressure relief pipe ball valve, continues to adopt the sandbag increase counter pressure body volume, and the sand gushing volume reaches controllable degree until gushing water and gushing sand. And if water burst and sand burst are effectively controlled, adopting horizontal double-liquid grouting in the pit to stop leakage, and then carrying out vertical double-liquid grouting on the joint of the diaphragm wall by using the WSS technology outside the pit.
(3) And (3) carrying out mechanical excavation construction, namely after confirming that the joints of all underground continuous walls of the manual excavation bin section have no water leakage, carrying out slope-placing mechanical excavation operation according to a foundation pit excavation scheme, and realizing the purpose of rapid excavation along with excavation and support.
(4) Foundation pit excavation emergency safeguard measures:
a. a fixed grouting platform is arranged in the middle of a side access of a foundation pit in a construction site, and equipment such as a small cement warehouse, a water glass warehouse, a double-liquid grouting machine, a slurry mixing barrel and the like is arranged, so that a specially-assigned person can start up the machine for testing every day, and the reliability of the equipment performance is ensured. 2 grouting pipes of 150m are respectively arranged on each side along the long side direction of the foundation pit, and the requirement that the double-liquid grouting operation can be carried out on the connecting pipes within 10min at any position during the excavation of the foundation pit is required.
b. As shown in fig. 4, sand backfill windows 6 with the width of 0.5m and the length of 0.8m are arranged on the hardened pavement of each ground wall joint edge outside the foundation pit, each sand backfill window 6 is plugged by steel plates 7 and quick-drying cement 8, the surface rainwater is prevented from flowing backwards, if large seepage water occurs in the foundation pit, water and sand gushing accidents are caused, and when collapse and collapse occur outside the foundation pit due to a large amount of water and soil loss outside the foundation pit, the sand backfill windows 6 are opened to carry out backfill operations of sand concrete and the like.
c. The method comprises the steps of manufacturing 150mm multiplied by 100mm engraved characters on the stainless steel plate, marking red paint pipeline identification plates, and installing and binding the pipeline identification plates on the ground every 10m along the peripheral pipelines of the foundation pit, so that the pipeline is prevented from being damaged by errors during construction and emergency rescue.
In the embodiment, the risk and reason analysis of the hidden danger problem of water leakage caused by defects of the joint of the underground diaphragm wall of the silt composite stratum are carried out, and in the process of taking measures to solve the risk, a comprehensive subway deep foundation pit excavation technology comprising the steps of WSS grouting reinforcement and dewatering well measures outside the foundation pit, manual exploratory hole excavation and emergency rescue and leakage stoppage measures inside the foundation pit is formed, the problem of water gushing and sand gushing of the joint of the underground diaphragm wall in the excavation process of the deep foundation pit is successfully solved, and the construction of the main structure of the station is smoothly completed.
In summary, the present invention is described as an embodiment, but the present invention is not limited to the above embodiment, and any similar or identical means may be used to achieve the technical effects of the present invention, and all such means should fall within the protection scope of the present invention.

Claims (9)

1. An anti-seepage treatment method for excavation of deep foundation pits of water-rich silt formations is characterized by comprising the following specific steps:
(1) adopting WSS grouting at the joint position of the diaphragm wall outside the foundation pit, wherein the grouting slurry adopts water glass-cement double-liquid slurry;
(2) after the WSS grouting is finished, arranging a precipitation well outside the foundation pit to reduce the water pressure, arranging a precipitation well 8-10 m outside the foundation pit, wherein the depth of the precipitation well is 20-22 m, placing a water pump in each precipitation well, and installing the water pump at a position 7-8 m below the ground; the potential hazards of water gushing and sand gushing occur in the excavation process of the foundation pit, a water pump in a precipitation well is immediately lowered to the bottom of the pit, and the water pressure difference between the inside and the outside of the pit and the emergency rescue pressure in the foundation pit are reduced;
(3) the method comprises the following steps of starting excavation from the second layer of earthwork in a deep foundation pit, carrying out manual exploration excavation on the joint of the underground continuous wall of each bin before excavation of the earthwork of the foundation pit, carrying out manual exploration excavation on the joint of the underground continuous wall of each bin, carrying out artificial exploration excavation on the joint of the underground continuous wall of each bin with the length multiplied by the width multiplied by 1.5m multiplied by 0.8m and the depth of 1.5m to 1.8m, then carrying out exploration excavation on the joint of the underground continuous wall by adopting a Luoyang shovel with the depth;
(4) after confirming that the joints of all underground continuous walls of the manual excavation bin section have no water leakage situation, arranging a grouting platform at the edge of the foundation pit, arranging a grouting tool, and arranging grouting pipes along the long edge direction of the foundation pit, wherein the arrangement of the grouting pipes requires that the pipe connection grouting work is realized within 10min at any position during the excavation of the foundation pit; meanwhile, sand material backfill windows with the width of 0.5-0.6 m and the length of 0.8-1 m are arranged on the hardened pavement at the joint edge of each ground wall outside the foundation pit, and each sand material backfill window is blocked by steel plate quick-drying cement;
(5) after the construction in the step (4) is completed, carrying out excavation operation of a slope-releasing machine according to a foundation pit excavation scheme; in the mechanical excavation process of the foundation pit, when the water seepage condition occurs, a grouting pipe is connected within 10min for temporary grouting and plugging; when the collapse is met and emergency rescue is needed, a sand material backfill window is opened to carry out sand concrete backfill operation.
2. The method for anti-leakage treatment of deep foundation pit excavation in water-rich silt formation according to claim 1, wherein the rapid water-stopping treatment process according to the exploration condition in the step (3) is as follows:
a. when seepage water appears in the ground wall seam, continuous wall seam position exists infiltration passageway: manually cleaning the positions of the defective joints of the ground wall at the first time, and plugging by using quick-drying cement clusters; or firstly adopting quick-drying cement for plugging, then adopting a steel plate for welding and plugging, then horizontally opening grouting holes at two sides of the water leakage position, penetrating the thickness of the underground diaphragm wall to the outer soil side of the foundation pit, embedding a galvanized grouting pipe with a ball valve, adopting a horizontal grouting technology to inject cement-water glass double-liquid slurry for plugging, finally adopting a WSS grouting technology at the outer side of the joint of the foundation pit diaphragm wall, and adopting the cement-water glass double-liquid slurry again for vertical grouting treatment, wherein the treatment depth is at least 2m below the foundation pit base;
b. when water gushing and sand gushing dangerous situations occur on the ground wall joint: laying cotton wool at the position of a soil body placed at the seam of the water burst wall, releasing pressure by using a pressure releasing water pipe with a ball valve, repeatedly and alternately performing back pressure on the water burst sand burst opening by using sand bags and quilts, closing the ball valve of the pressure releasing pipe until the sand burst amount reaches a controllable degree when a back pressure body consisting of the sand bags and the quilts reaches a radius of 2 m-2.5 m and a height of 1.6 m-1.8 m, and then performing horizontal double-liquid grouting plugging in the pit by using the horizontal grouting technology the same as the step a, wherein the WSS grouting technology performs vertical double-liquid grouting on the seam of the underground diaphragm wall outside the pit.
3. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 1, characterized in that: the grouting platform in the step (4) is arranged in the middle of a side access way of a foundation pit in a construction site, and the grouting tool comprises a small cement warehouse, a water glass warehouse, a double-liquid grouting machine and a slurry mixing barrel; and 2 grouting pipes of 130-160 m are respectively arranged on each side along the long side direction of the foundation pit.
4. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 1, characterized in that: and (4) installing a pipeline signboard on the ground every 8-10 m along the peripheral pipeline of the foundation pit in the step (4), wherein the pipeline signboard is made of a stainless steel plate with the thickness of 150mm multiplied by 100mm, characters are engraved, and red paint is coated.
5. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 2, characterized in that: the grouting slurry in the step (1), the step (3) and the step (5) adopts water glass-cement double-fluid slurry, and the cement slurry density is 1.51Kg/cm3The density of the water glass is 1.15Kg/cm3And the ratio of cement slurry to water glass slurry is 1: 1.
6. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 2, characterized in that: in the step a of the step (3), when the water seepage amount is small, a quick-drying cement cluster is adopted for plugging, when the quick-drying cement cluster is subjected to plugging, water gushing or water gushing and sand gushing occur, a galvanized pressure relief water pipe with a ball valve at one end is buried for pressure release, when the water pressure is released, the periphery of the galvanized pipe is plugged by the manually-mixed quick-drying cement cluster, and the ball valve is closed after the plugging is finished; and (c) when the water seepage amount in the step (3) a is large, firstly plugging by using quick-drying cement and then plugging by welding a steel plate.
7. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 2, characterized in that: and (b) in the step (3), judging the width and depth of the defect of the seam of the water leakage ground wall, and when the seam of the ground wall is large and the risk of water and sand gushing exists, welding and plugging the quick-drying cement mass at the plugging position by adopting a steel plate, and plugging the welding seam by using quick-drying cement.
8. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 2, characterized in that: and (c) taking the phi 80mm in the emergency material cage in the two foundation pits and the ball valve pressure relief water pipe with the length of 2.5m by the ball valve pressure relief water pipe in the step (3) b, arranging the two pressure relief pipelines in a splayed manner, placing one end of a ball-free valve on cotton wool of a water gushing and sand gushing port, and enabling one end of the ball valve to face towards the inner side of the foundation pit.
9. The anti-leakage treatment method for the deep foundation pit excavation of the water-rich silt stratum according to claim 2, characterized in that: and (c) in the step (3), two layers of sandbags and one layer of quilt are adopted to repeatedly and alternately carry out back pressure water burst and sand gushing.
CN202010839310.8A 2020-08-19 2020-08-19 Anti-seepage treatment method for deep foundation pit excavation of water-rich silt stratum Pending CN112049115A (en)

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