Composite water stop enclosure structure for deep and large foundation pit in cities and towns

Abstract

The utility model provides a composite waterstop enclosure structure for a deep and large foundation pit in cities and towns, which relates to the technical field of foundation pit engineering construction and structurally comprises an underground diaphragm wall foundation pit enclosure structure formed by alternately connecting primary groove section underground diaphragm walls and secondary groove section underground diaphragm walls end to end. An H-shaped steel joint is arranged between the adjacent primary groove section underground diaphragm wall and secondary groove section underground diaphragm wall; the outer side of the underground diaphragm wall foundation pit support structure is provided with a three-axis cement soil mixing pile in the pit, and the inner side of the underground diaphragm wall foundation pit support structure is provided with a three-axis cement soil mixing pile in the pit. The three-shaft stirring piles, the high-pressure jet grouting piles and the asymmetric H-shaped steel heads are used for reinforcing and optimizing water stop of a traditional wall-supporting type foundation pit supporting structure, so that the water stop efficiency, the construction safety and the construction quality of the wall-supporting type foundation pit supporting structure are improved; the method is more suitable for construction of deep and large foundation pits in cities and towns in high-water-level strong karst areas close to important building environments.

Description

Technical Field

[0001] The utility model relates to the technical field of foundation pit engineering construction, in particular to a composite water-stopping enclosure structure for a deep and large foundation pit in a town. Background Art

[0002] With the acceleration of metropolitan construction, the application of urban underground space has received more and more attention. Subways, underground shopping malls, and underground parking lots are increasing day by day, and the scale of development is getting larger and larger. The requirements for deep foundation pit support technology are also getting higher and higher. The foundation pit is constantly developing in the direction of "deep, large and close", and new technologies, methods, and processes are constantly emerging. At present, the commonly used support methods are mainly divided into 5 categories, namely wall-support type (underground continuous wall + concrete support beam), pile-support type, pile-anchor type, composite soil nail support, and combined support. Among them, the wall-support type is more widely used in soft soil areas with poor geological conditions due to its advantages such as high rigidity, good integrity, and strong impermeability.

[0003] In order to adapt to different construction environments, a variety of new construction methods have emerged in the construction of underground continuous walls in wall-support support structures, mainly including the two-wall-in-one method, TRD method, CSM method, SMW method, WSP method, CRM method, TRUST method, and prefabrication method. The two-wall-in-one method combines the enclosure structure with the main structure, and is a form of enclosure structure that integrates enclosure, anti-seepage, load-bearing and basement structure exterior walls. It can reduce the amount of work and save resources to a certain extent, and has good economy, but it requires high construction technology. The TRD method and the CSM method respectively use advanced mechanical equipment such as chain saw cutting boxes and double-wheel milling machines to improve the underground continuous wall grooving process, which can form a more uniform wall with better water-stopping performance, but the operation efficiency is slow when encountering hard strata. The SMW method and the WSP method respectively insert H-shaped steel and steel pipe piles into the wall to improve the rigidity of the wall, and the construction quality at the joints is not easy to guarantee. The CRM method, the TRUST method, and the prefabrication method have explored the economy of underground continuous wall construction from the aspects of on-site use of wall materials, ultra-thin wall methods, and wall prefabrication, which are of great reference significance.

[0004] However, trenching, which is the core of foundation pit retaining structure construction, is still mostly done by traditional mud wall protection. In areas with developed caves and water-rich sandy strata, due to the large porosity and good permeability of the strata, a large amount of mud is easily lost, and mud skin is not easy to form, resulting in accidents such as trench wall instability and collapse. Conventional measures such as increasing mud density and viscosity can easily lead to difficulties in sinking steel cages and poor bite between concrete and steel bars. In addition, the use of large amounts of mud often causes environmental problems such as water pollution.

[0005] Therefore, in order to meet the needs of underground engineering construction with higher safety requirements, higher quality requirements, and higher environmental protection requirements in urban construction, it is of great practical and theoretical significance to study a composite water-stop retaining structure suitable for deep and large foundation pits in towns in strong karst areas with high water level sand layers.

[0006] The invention patent with publication number CN110528501A provides a water-stopping device for continuous wall joints in high-water-rich coastal areas. The horizontal reinforcement of the continuous wall and the vertical main reinforcement of the continuous wall are mechanically connected, and the steel flower pipe is tied and overlapped on the first wall steel cage; the galvanized iron sheet is installed on the outside of the I-shaped steel plate, the galvanized iron sheet and the pressure bar steel bar are spot welded, the I-shaped steel is welded to the first wall steel cage, the U-shaped stirrups and the horizontal reinforcement of the continuous wall are single-sided welded, the grouting pipe and the second wall steel cage are tied and overlapped, and the second wall steel cage is hoisted and embedded in the wing plate of the I-shaped steel plate; the sandbags are piled on the outside of the web of the I-shaped steel plate joint, and the lower filling height is the height of the underground continuous wall; its waterproof effect is ideal and can effectively prevent concrete bypass, and the setting of the steel flower pipe ensures the water-stopping effect at the joint. This technology does not involve technologies such as double-row three-axis mixing piles and high-pressure rotary spray piles, and is not the same as the key points of this research result. Utility Model Content

[0007] In view of the adverse geological conditions of high water level and strong karst development often faced in the construction of coastal cities in my country, conventional deep and large foundation pit retaining structures are difficult to simultaneously meet the increasingly high engineering safety requirements, quality requirements and environmental protection requirements in urban construction. The utility model provides a composite water-stop retaining structure for deep and large foundation pits in towns, the purpose of which is to ensure high-quality forming, safe construction and efficient construction of underground continuous walls, and to have stronger anti-seepage capabilities to make up for the deficiencies of existing technologies.

[0008] The utility model provides the following technical solutions to achieve the above objectives:

[0009] A composite water-stop retaining structure for deep and large urban foundation pits comprises an underground continuous wall foundation pit retaining structure formed by alternately connecting the underground continuous wall of a mother trench section and the underground continuous wall of a sub-trench section end to end; H-shaped steel joints are arranged between the underground continuous walls of adjacent mother trench sections and the underground continuous walls of the sub-trench sections; the outer side of the underground continuous wall foundation pit retaining structure is provided with triaxial cement-soil mixing piles driven outside the pit, and the inner side is provided with triaxial cement-soil mixing piles driven inside the pit.

[0010] Furthermore, the H-shaped steel joint is an asymmetric H-shaped steel joint in which one side of the main groove section is short and one side of the sub-groove section is long.

[0011] Furthermore, on the outside of the underground continuous wall foundation pit retaining structure, high-pressure rotary jet piles are arranged at the wall joints of the underground continuous wall of the main trench section and the underground continuous wall of the sub-trench section.

[0012] Furthermore, a mother trench section underground continuous wall steel cage is provided in the mother trench section underground continuous wall; a sub-trench section underground continuous wall steel cage is provided in the sub-trench section underground continuous wall.

[0013] Furthermore, the underground continuous wall steel cage of the mother trench section is connected to the H-shaped steel joint.

[0014] Beneficial Effects

[0015] Compared with the existing technology, the utility model uses three-axis mixing piles, high-pressure jet grouting piles, and asymmetric H-shaped steel heads to reinforce and optimize the water-stopping of the traditional wall-support type foundation pit support structure, thereby improving its water-stopping efficiency, construction safety, and construction quality, and is more suitable for the construction of deep and large foundation pits in cities and towns in high-water-level strong karst areas near important buildings and structures. It has the following beneficial effects:

[0016] 1. The utility model enhances the anti-seepage performance of the foundation pit water-stop curtain by arranging three-axis cement-soil mixing piles on both sides of the underground continuous wall groove section;

[0017] 2. The utility model extends the water seepage path of the weak points of the wall and improves the anti-seepage performance of the wall by adding H-shaped steel at the connection of the sub-groove section of the underground continuous wall, enhances the bite effect of the sub-groove section of the underground continuous wall, and improves the overall rigidity of the wall.

[0018] 3. The utility model strengthens the water-stopping performance of the water-stop curtain outside the pit at the undulating parts of the foundation line in the strong karst area by adding high-pressure rotary jet piles at the connection of the mother-and-child trough sections outside the underground continuous wall pit; and strengthens the anti-seepage performance of the weak points of the connection of the mother-and-child trough sections of the underground continuous wall.

[0019] 4. The utility model is used to pre-treat and reinforce the water-rich sandy soil layers on both sides of the retaining structure to prevent accidents such as instability and collapse of the trench wall, improve the construction efficiency and quality of the underground continuous wall, and ensure operation safety; reduce the disturbance of the underground continuous wall construction to the adjacent existing structures, and ensure the safe operation and use of surrounding buildings (structures) and equipment facilities; greatly reduce mud loss and groundwater pollution problems, and have good environmental and economic benefits.

[0020] 5. The utility model forms a three-layer water-stopping composite water-stopping retaining structure by arranging cement-soil mixing piles, adding H-shaped steels and adding high-pressure rotary jet piles on both sides of the underground continuous wall. The three-layer water-stopping technology complements each other and combines soft and hard technologies to block the water seepage path to the greatest extent, thereby improving the long-term water-stopping ability of the retaining structure and the safety of foundation pit use. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the utility model, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0022] Figure 1 It is a schematic diagram of the structure of the utility model;

[0023] Figure markings: 1-three-axis cement-soil mixing piles driven outside the pit, 2-three-axis cement-soil mixing piles in the pit, 3-underground continuous wall of the main trench section, 4-underground continuous wall of the sub-trench section, 5-underground continuous wall steel cage of the main trench section, 6-underground continuous wall steel cage of the sub-trench section, 7-H-shaped steel joint, 8-high-pressure rotary jet piles. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention.

[0025] It should be noted that in the present invention: the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the orientations or positional relationships shown in the accompanying drawings. These terms are mainly for better describing the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have specific orientations, or to be constructed and operated in specific orientations; the terms "installed", "set", "provided with", "connected", "connected", "sleeved" and the like should be understood in a broad sense; for example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements or components. In addition, some terms may be used to express other meanings in addition to indicating a direction or position relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in this utility model can be understood according to specific circumstances.

[0026] Example 1. A composite water-stopping enclosure structure for a deep and large foundation pit in a town, the structure of which is as follows: Figure 1 As shown, it includes an underground continuous wall foundation pit retaining structure formed by the underground continuous wall 3 of the mother trench section and the underground continuous wall 4 of the sub-trench section alternately connected end to end; H-shaped steel joints 7 are arranged between the adjacent underground continuous walls 3 of the mother trench section and the underground continuous walls 4 of the sub-trench section; the outer side of the underground continuous wall foundation pit retaining structure is provided with a three-axis cement-soil mixing pile 1 driven outside the pit, and the inner side is provided with a three-axis cement-soil mixing pile 2 driven inside the pit.

[0027] The H-shaped steel joint 7 is an asymmetric H-shaped steel joint with a short main groove section on one side and a long sub-groove section on the other side.

[0028] On the outside of the underground continuous wall foundation pit retaining structure, high-pressure rotary jet piles 8 are arranged at the wall joints of the underground continuous wall 3 of the main trench section and the underground continuous wall 4 of the sub-trench section.

[0029] The mother trench section underground continuous wall 3 is provided with a mother trench section underground continuous wall steel cage 5; the sub-trench section underground continuous wall 4 is provided with a sub-trench section underground continuous wall steel cage 6. The asymmetric H-shaped steel joints are located at both ends of the mother trench section underground continuous wall steel cage 5.

[0030] In the above technology, the three-axis cement soil mixing piles 1 driven outside the pit and the three-axis cement soil mixing piles 2 in the pit form double rows of three-axis cement soil mixing piles. The cement soil mixing piles are formed by mixing pure cement slurry with sand and soil layers. The construction process of cement soil mixing piles is designed according to geological conditions, groundwater conditions, and site conditions. The actual construction parameters are determined according to the results of the test piles. In order to take into account both the water-stopping effect and economy, the row of mixing piles outside the foundation pit is constructed by drilling one hole, and the row of mixing piles inside the foundation pit is constructed by interlocking to ensure the water-stop curtain effect, the safety of underground continuous wall construction, and the quality of trenching.

[0031] The asymmetric H-shaped steel joint is welded to both ends of the underground continuous wall steel cage 5 of the mother groove section to ensure that the mother and child groove sections are fully engaged to form a tongue and groove, thereby ensuring the overall rigidity and water-stopping effect of the connection between the mother and child groove sections of the underground continuous wall. The asymmetric type means that the flange plates of the H-shaped steel joints on both sides of the mother and child groove sections have different widths, with one side of the mother groove section being short and the other side of the child groove section being long, so as to ensure better drill bit guidance during the construction of the child groove section.

[0032] The high-pressure jet grouting pile 8 is arranged at the connection of the mother-and-child groove section outside the underground continuous wall pit. The high-pressure jet grouting pile selection should be constructed by single-tube method, double-tube method and triple-tube method according to the needs of the project. The construction process of high-pressure jet grouting pile should be designed according to geological conditions and groundwater conditions, and the construction parameters should be determined according to the results of the test piles. In order to further ensure the water-stopping effect, the high-pressure jet grouting pile should enter the slightly weathered rock for no less than 1 m to strengthen the water-stopping curtain outside the pit and the wall joint anti-seepage.

[0033] When the above-mentioned technology is implemented, first, the three-axis cement-soil mixing piles 1 driven outside the pit and the three-axis cement-soil mixing piles 2 in the pit are completed according to the design documents. The pile diameter, spacing and rock penetration depth of the three-axis cement-soil mixing piles 1 driven outside the pit and the three-axis cement-soil mixing piles 2 in the pit meet the size requirements of the specifications, and the row spacing meets the size requirements of the sub-trench section underground continuous wall 4 and the mother trench section underground continuous wall 3. The guide wall working surface of the sub-trench section underground continuous wall 4 and the mother trench section underground continuous wall 3 is excavated and the guide wall construction is completed. The foundation trench of the mother trench section underground continuous wall 3 is excavated, the mother trench section underground continuous wall steel cage 5 is manufactured and installed according to the design requirements, and H-shaped steel joints 7 are installed at both ends of the mother trench section underground continuous wall steel cage 5, the mother trench section underground continuous wall steel cage 5 is hoisted to the foundation trench, and the underwater concrete pouring of the mother trench section underground continuous wall 3 is completed. Excavate the foundation trench of the sub-trench section underground continuous wall 4, make and install the sub-trench section underground continuous wall steel cage 6 according to the design requirements, hoist the sub-trench section underground continuous wall steel cage 6 to the foundation trench, and complete the underwater concrete pouring of the sub-trench section underground continuous wall 4. After the construction of the sub-trench section underground continuous wall 4 and the mother trench section underground continuous wall 3 is completed, high-pressure rotary grouting piles 8 are constructed at the wall joints of the sub-trench section underground continuous wall 4 and the mother trench section underground continuous wall 3 outside the foundation pit. The pile diameter and rock penetration depth of the high-pressure rotary grouting piles 8 meet the design requirements. At this point, the construction of the composite water-stop retaining structure of the foundation pit is completed.

[0034] Embodiment 2. A composite water-stop enclosure structure for deep and large urban foundation pits. This embodiment is based on Embodiment 1, and the underground continuous wall 4 of the sub-trench section and the underground continuous wall 3 of the main trench section adopt a concrete internal support or a steel structure internal support system in the pit, and other principles are the same as those of Embodiment 1.

[0035] Embodiment 3. A composite water-stop enclosure structure for a deep and large foundation pit in a town. This embodiment is based on Embodiment 1, and the H-shaped steel joint 7 is made of welded steel plates.

[0036] Embodiment 4. A composite water-stopping retaining structure for deep and large foundation pits in towns. This embodiment is based on Embodiment 1. The three-axis cement-soil mixing piles 1 driven outside the pit and the three-axis cement-soil mixing piles 2 driven inside the pit can be double-axis according to actual geological conditions, or can be driven with or without driving with according to groundwater conditions. Other principles are similar to those of Embodiment 1.

[0037] Obviously, the above is only a part of the embodiments of the utility model, not all of the embodiments. The above embodiments are not used to limit the utility model. For those skilled in the art, the utility model can have various changes and variations. Any combination, modification, equivalent replacement, improvement and all other embodiments that can be made by ordinary technicians in the field within the spirit and principle of the utility model should be within the protection scope of the utility model.

Claims

1. A composite water-stopping enclosure structure for deep and large foundation pits in towns, characterized by: The invention comprises an underground continuous wall foundation pit retaining structure formed by alternately connecting the mother trench section underground continuous wall (3) and the sub-trench section underground continuous wall (4) end to end; H-shaped steel joints (7) are arranged between adjacent mother trench section underground continuous walls (3) and sub-trench section underground continuous walls (4); and the outer side of the underground continuous wall foundation pit retaining structure is provided with a pit outer casing triaxial cement soil mixing pile (1), and the inner side is provided with a pit inner triaxial cement soil mixing pile (2).

2. The composite water-stopping enclosure structure for deep and large foundation pits in towns according to claim 1 is characterized by: The H-shaped steel joint (7) is an asymmetric H-shaped steel joint with a short main groove section on one side and a long sub-groove section on the other side.

3. The composite water-stopping enclosure structure for deep and large foundation pits in towns according to claim 1 is characterized by: High-pressure jet grouting piles (8) are arranged at the wall joints of the main trench section underground continuous wall (3) and the sub-trench section underground continuous wall (4) on the outside of the underground continuous wall foundation pit retaining structure.

4. The composite water-stopping retaining structure for deep and large foundation pits in towns according to any one of claims 1 to 3, characterized in that: A main trench section underground continuous wall (3) is provided with a main trench section underground continuous wall reinforcement cage (5); and a sub-trench section underground continuous wall (4) is provided with a sub-trench section underground continuous wall reinforcement cage (6).

5. The composite water-stopping enclosure structure for deep and large foundation pits in towns according to claim 4 is characterized by: The underground continuous wall steel cage (5) of the mother trench section is connected to the H-shaped steel joint (7).

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