CN211973508U - A deep foundation pit support and anti-seepage system for coastal karst strata - Google Patents

Abstract

The utility model discloses a deep foundation pit support and seepage prevention system in coastal karst strata, which comprises a support structure, a karst cave treatment structure and a horizontal water-stop curtain. For crown beams and inner supports, the drilled occlusal piles are arranged around the foundation pit and form a closed anti-seepage body; the horizontal water-stop curtain is arranged just below the bottom of the foundation pit. The karst cave treatment measures of the utility model can prevent the risk of rapid development of the karst cave under the action of groundwater, and improve the ability of the foundation to resist local karst collapse. The combined support system of the drilled occlusal pile and the inner support of the utility model not only has a good support effect, but also has a small deformation capacity of the support structure, and does not need to be supplemented with waterproof measures such as a water-stop curtain. The horizontal water-stop curtain of the utility model uses grouting to perform water-stop treatment on the bottom area of the foundation pit, which can effectively cut off the effective passage of karst fissure water at the bottom of the pit, and completely solve the problem of water gushing at the bottom of the pit.

Description

A deep foundation pit support and anti-seepage system for coastal karst strata

technical field

The utility model relates to the technical field of foundation pit engineering, in particular to a deep foundation pit support and anti-seepage system for coastal karst strata.

Background technique

The coastal karst stratum belongs to the complex hydrogeological conditions, and has high requirements for the support and anti-seepage ability of the foundation pit project. Karst is a general term for various surface and underground dissolution phenomena formed by chemical erosion, disintegration, mechanical damage, transportation and deposition of soluble rock layers (carbonates, sulfates, halogen salts, etc.) by surface water and groundwater. With the prosperity and development of my country's economy, various construction projects have sprung up like mushrooms after a rain. Geotechnical engineering occupies a very important position in various civil engineering. As far as the geotechnical engineering of coastal karst strata is concerned, due to the abundant fissure water in coastal karst strata, during the excavation of deep foundation pits (excavation depths of more than 5m), the side walls and the bottom of foundation pits are both Faced with serious karst fissure water problems, corresponding water-stopping measures are essential. If the conventional foundation pit pile-anchor support structure is adopted, even if the vertical water-stop curtain is added, the side wall seepage cannot be completely avoided, and the water leakage at the bottom of the pit cannot be dealt with at all. Other forms of support structures also face similar difficulties. Similar to the support form of the underground diaphragm wall, the cost is higher. At present, there are few construction examples of deep foundation pits in karst development areas at home and abroad, and there is no mature technical experience to follow. It is imperative to explore effective deep foundation pit treatment methods for coastal karst formations.

Utility model content

The purpose of the utility model is to overcome the water seepage problem of the foundation pit engineering in the coastal karst stratum, and provide a deep foundation pit support and anti-seepage system for the coastal karst stratum that can effectively solve the serious water seepage problem during the excavation of the deep foundation pit of the coastal karst stratum.

The technical scheme adopted to realize the purpose of the present utility model is as follows:

A deep foundation pit support and anti-seepage system in coastal karst strata, comprising a support structure, a karst cave treatment structure and a horizontal water-stop curtain, the support structure includes a drilled occlusal pile and a crown beam, and the drilled hole The occlusal piles are arranged around the foundation pit and form a closed impermeable body, and the top of the drilled occlusal piles is provided with a crown beam; the karst cave treatment structure is located below the periphery of the foundation pit and the bottom of the foundation pit; the horizontal stop The water curtain is set just below the bottom of the foundation pit;

The drilled occlusal pile is composed of a reinforced concrete cast pile and a plain concrete cast pile, and the reinforced concrete cast pile is embedded between the plain concrete cast piles.

Further, waist beams are arranged on the inner side of the bored occlusal pile, and inner supports are arranged between the waist beams on the left and right sides, and the inner supports are reinforced concrete beams or steel beams.

Further, the karst cave treatment structure is located within a range of 5m from the periphery of the foundation pit and within 10m from the bottom of the foundation pit.

Further, the cave treatment structure includes a semi-filled cave treatment body, an unfilled cave treatment body, and a flow-plastic soft plastic cohesive soil fully filled cave treatment body.

Further, the drilled occlusal pile and the crown beam are fixedly connected by casting.

Further, the borehole diameter of the bored bite pile is 800-1200mm.

Further, the waist beam and the drilled occlusal pile are fixedly connected by planting reinforcement, and the waist beam and the inner support are fixedly connected by welding.

Further, the distance between the inner supports is less than 4m.

Further, the semi-filled karst cave treatment body is gravel, crushed stone, flow plastic soft plastic clay and cement water glass concrete; the unfilled karst cave treatment body is sand gravel, crushed stone and cement water glass mixture. Condensate; the flow-plastic soft-plastic cohesive soil fully filled karst cave treatment body is a flow-plastic soft plastic cohesive soil and cement water glass concrete.

Further, the thickness of the horizontal water-stop curtain is greater than 3m.

Compared with the prior art, the beneficial effects of the present utility model are as follows:

1. The karst cave treatment measures of the present utility model can prevent the risk of rapid development of the karst cave under the action of groundwater, avoid the risk of collapse of the supporting structure during construction and the risk of sudden surge of the foundation pit under the action of high-head karst confined water, and improve the performance of the karst cave. The ability of the foundation to resist local karst collapse.

2. The combined support system of the drilled occlusal pile and the inner support of the present invention not only has a good supporting effect and a small deformation capacity of the supporting structure, but also does not need to be supplemented with waterproof measures such as a water-stop curtain, and the side walls of the foundation pit rarely appear. water seepage. Compared with other enclosure structures (such as underground diaphragm walls, etc.) that meet the same engineering requirements, it has obvious advantages in comprehensive economic benefits:

①The reinforcement ratio is low. Drilled occlusal piles are usually arranged in a spaced arrangement of reinforced concrete piles and plain concrete piles, which greatly reduces the reinforcement ratio of the supporting structure. ② Stronger impermeability. Drilled occlusal piles are constructed continuously, and there is no construction joint between the piles, and the construction joints at the sub-section joints of the underground diaphragm wall are often the weak link of anti-seepage; ③ The construction is flexible, because the construction of the drilled occlusal piles can be turned according to needs. Change line, so it is more suitable for the construction of some plane and changeable geometric figures or foundation pits with various arcs. ④Using a full casing drilling rig, in the construction process, there is always an advanced steel casing wall, so there is no need for mud wall protection, thus saving the cost of mud production, use and waste slurry treatment. ⑤ The reaming (filling) coefficient is small, because there is always a steel casing to protect the wall during the construction process, which completely avoids the collapse of the hole wall, thereby reducing the reaming (filling) coefficient and reducing the amount of concrete pouring.

3. The horizontal water-stop curtain of the present utility model uses grouting to perform water-stop treatment on the bottom area of the foundation pit, which can effectively cut off the effective passage of karst fissure water at the bottom of the pit, and completely solve the problem of water gushing at the bottom of the pit.

4. The water glass used in the present invention is a commonly used grouting material. The water glass itself has strong cohesive force, strong acid corrosion resistance, and can enter the capillary pores. After hardening, the pores of the material are blocked to prevent its penetration. effect. Water glass slurry has the characteristics of short gel time, good injectability and controllability. The cement water glass slurry is used as the grouting material, which reduces the setting time of the cement slurry, prevents the cement slurry from being eroded by groundwater and is not easy to consolidate, and can significantly improve the water-cutting and anti-seepage performance of the horizontal water-stop curtain.

5. The horizontal water-stop curtain and the drilled occlusal piles together form a water-proof and anti-seepage system, so that the side wall of the foundation pit and the bottom of the foundation pit form a good closed body. The water-stop curtain can play a better supporting role, so that the soil around the foundation pit has less influence on the stability of the foundation pit.

Description of drawings

Figure 1 is a schematic cross-sectional view of the foundation pit support and anti-seepage system during the construction of drilled occlusal piles.

Figure 2 is a schematic cross-sectional view of the foundation pit support and anti-seepage system during the construction of the horizontal water-stop curtain.

Figure 3 is a schematic cross-sectional view of the foundation pit support and seepage prevention system during foundation pit excavation.

FIG. 4 is a plan view of FIG. 3 .

Figure 5 is a schematic cross-sectional view of a bored bite pile.

In the picture: 1. Ground, 2. Drilled occlusal pile, 3. Bottom of foundation pit, 4. Horizontal water-stop curtain, 5. Internal support, 6. Waist beam, 7. Crown beam, 8. Karst cave treatment structure, 9 , Grouting hole, 21, plain concrete pouring pile, 22, reinforced concrete pouring pile.

Detailed ways

The present utility model will be further described in detail below through the accompanying drawings and embodiments, but the protection scope of the present utility model is not limited to the above-mentioned contents.

As shown in Figures 1-5, a deep foundation pit support and seepage prevention system in coastal karst strata includes a support structure, a karst cave treatment structure 8 and a horizontal water-stop curtain 4. The support structure includes a borehole occlusion Pile 2, waist beam 6, crown beam 7 and inner support 5, described bored occlusal pile 2 is arranged around the foundation pit and forms a closed impermeable body, the top of the bored occlusal pile 2 is provided with crown beam 7, The inner side of the bored occlusal pile 2 is provided with a waist beam 6, and an inner support 5 is provided between the waist beams 6 on the left and right sides; the cave treatment structure 8 is located below the periphery of the foundation pit and the bottom 3 of the foundation pit; the horizontal direction The water-stop curtain 4 is arranged directly below the bottom 3 of the foundation pit;

The drilled clinching pile 2 is composed of a reinforced concrete cast pile 22 and a plain concrete cast pile 21 , and the reinforced concrete cast pile 22 is embedded between the plain concrete cast piles 21 .

Further, the inner support 5 is a reinforced concrete beam or a steel beam.

Further, the karst cave treatment structure 8 is located within 5m of the periphery of the foundation pit and within 10m of the bottom 3 of the foundation pit.

Further, the cave treatment structure 8 includes a semi-filled cave treatment body, an unfilled cave treatment body, and a flow-plastic soft plastic cohesive soil fully filled cave treatment body.

Further, the drilled occlusal pile 2 and the crown beam 7 are fixedly connected by casting.

Further, the diameter of the bore hole of the drilled bite pile 2 is 800-1200mm.

Further, the waist beam 6 and the drilled occlusal pile 2 are fixedly connected by planting reinforcement, and the waist beam 6 and the inner support 5 are fixedly connected by welding.

Further, the distance between the inner supports 5 is less than 4m.

Further, the semi-filled karst cave treatment body is gravel, crushed stone, flow plastic soft plastic clay and cement water glass concrete; the unfilled karst cave treatment body is sand gravel, crushed stone and cement water glass mixture. Condensate; the flow-plastic soft-plastic cohesive soil fully filled karst cave treatment body is a flow-plastic soft plastic cohesive soil and cement water glass concrete.

Further, the thickness of the horizontal water-stop curtain 4 is greater than 3m.

The construction method of the present utility model comprises the following steps:

A. The red line of the land for measuring and releasing, complete the setting of the construction enclosure, and proceed to the foundation pit construction after the site is leveled;

B. In order to ensure the safety of the foundation pit, the karst cave is treated within 10m below the bottom 3 of the foundation pit and within 5m around the foundation pit; the treatment method includes the following steps:

B1. For semi-filled karst caves, first fill with gravel and gravel, and then grouting cement water glass slurry through grouting hole 9 to form a semi-filled karst cave treatment body;

B2. For unfilled karst caves, first fill with gravel and gravel, and then grouting cement water glass slurry through grouting hole 9 to form an unfilled karst cave treatment body;

B3. For fully filled karst caves, directly grouting cement water glass slurry through the grouting hole 9 to form a fully filled karst cave treatment body;

C. Make a solid construction guide groove in advance according to the position of the drilled occlusal pile 2 in the design drawing, use the measuring instrument to locate the 2 pile points of the drilled occlusal pile, select the corresponding drilling equipment, construct the first batch of drilling, The first batch of boreholes is poured with plain concrete to form plain concrete cast piles 21;

D. 60±2 hours after the first batch of perforated concrete is poured, that is, before the initial setting of the concrete, the construction of the second batch of drilling is carried out between the two holes of the first batch of drilling, and the drilling is completed after the drilling is completed. Reinforced cages are poured into concrete to form reinforced concrete pouring piles 22, and the reinforced concrete pouring piles 22 are embedded between the plain concrete pouring piles 21 to form drilled occlusal piles 2;

E, after the construction of the bored occlusal pile 2 is completed and the surrounding of the foundation pit is closed by the bored occlusal pile 2, start the construction of the pile top crown beam 7;

F. Prepare cement water glass slurry according to the design ratio, first prepare the cement slurry, and then add water glass; the water-cement mass ratio of the cement slurry is 0.75-1, and the amount of water glass added is 2% of the quality of the cement slurry -4%;

G. The horizontal water-stop curtain 4 is formed by grouting through the grouting hole 9 at the position just below the bottom 3 of the foundation pit, and it is ensured that the supporting force of the water-retaining water at the lower part of the horizontal water-stop curtain 4 is not greater than that of the horizontal water-stop curtain 4 above earth pressure;

H. Start excavating the foundation pit in layers from the ground 1, and erect the waist beam 6 and the inner support 5 in time;

1. After the foundation pit is excavated to the design elevation, the bottom 3 of the foundation pit is manually leveled, and then the gravel cushion and C15 concrete cushion are constructed according to the design requirements, and the cushion is leveled according to the design requirements.

The present invention is not limited to this embodiment, and any equivalent concepts or changes within the technical scope disclosed by the present invention are included in the protection scope of the present invention.

Claims (10)

1. A deep foundation pit supporting anti-seepage system for a coastal karst stratum is characterized in that: the construction method comprises a supporting structure, a karst cave treatment structure (8) and a horizontal waterproof curtain (4), wherein the supporting structure comprises drilling secant piles (2) and a crown beam (7), the drilling secant piles (2) are arranged around a foundation pit and form a closed anti-seepage body, and the crown beam (7) is arranged at the top of the drilling secant piles (2); the karst cave treatment structure (8) is positioned at the periphery of the foundation pit and below the bottom (3) of the foundation pit; the horizontal waterproof curtain (4) is arranged right below the bottom (3) of the foundation pit;

the drilling secant pile (2) is composed of reinforced concrete cast piles (22) and plain concrete cast piles (21), and the reinforced concrete cast piles (22) are embedded between the plain concrete cast piles (21).

2. The system of claim 1, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the inner side of the drilling secant pile (2) is provided with a waist beam (6), an inner support (5) is arranged between the waist beams on the left side and the right side, and the inner support (5) is a reinforced concrete beam or a steel beam.

3. The system of claim 1, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the karst cave treatment structure (8) is positioned within the range of 5m of the periphery of the foundation pit and within the range of 10m of the bottom (3) of the foundation pit.

4. The system of claim 1, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the karst cave processing structure (8) comprises a half-filled karst cave processing body, a non-filled karst cave processing body and a flow-plastic soft-plastic sticky soil full-filled karst cave processing body.

5. The system of claim 1, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the drilling secant pile (2) is fixedly connected with the crown beam (7) in a pouring mode.

6. The system of claim 1, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the drilling diameter of the drilling occlusive pile (2) is 800-1200 mm.

7. The system of claim 2, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum, and comprises: the wale (6) is fixedly connected with the drilling secant pile (2) in a bar planting mode, and the wale (6) is fixedly connected with the inner support (5) in a welding mode.

8. The system of claim 2, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum, and comprises: the distance between the inner supports (5) is less than 4 m.

9. The system of claim 4, wherein the system is used for preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the semi-filling karst cave treatment body is gravel, broken stone, flow plastic soft plastic sticky soil and cement water glass concrete; the filling-free karst cave treatment body is gravel, broken stone and cement water glass concrete; the fluid-plastic soft-plastic cohesive soil full-filling karst cave treatment body is a fluid-plastic soft-plastic cohesive soil and cement water glass concrete body.

10. The system of claim 1, wherein the system is used for supporting and preventing seepage of deep foundation pits of the coastal karst stratum and comprises: the thickness of the horizontal waterproof curtain (4) is more than 3 m.

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