Multi-stage wing-shaped cement-soil mixing pile without support excavation and supporting device and construction method thereof

Abstract

The application discloses a multi-stage wing-shaped cement-soil mixing pile support-free excavation supporting device and a construction method thereof, which comprises outer partition walls, arched retaining walls, structure column walls, rib walls, inner partition walls and T-shaped retaining walls composed of cement-soil mixing piles. The outer partition walls are used for partitioning the side slope, the different partitioned filling loads are transmitted to the structure column walls through the arched retaining walls, the rib walls are introduced to transit to the next stage of foundation pits, and are connected with the inner partition walls. Finally, the lateral load is diffused to the ground soil through the T-shaped retaining walls. The wall bodies are closely connected to form a whole, the support-free and green excavation in the slope area is realized, the wing-shaped cement-soil mixing pile support-free excavation system is proposed, the variable cross-section cement-soil mixing piles are overlapped to form an arch, the wall body load is reduced through partitioned excavation, the graded excavation is further realized through the connecting wall, the overall stability of the foundation pit is ensured, and the excavation efficiency is improved and the construction operation area is expanded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit engineering excavation, in particular to a multi-stage wing-shaped cement-soil mixing pile support-free excavation supporting device and a construction method thereof. BACKGROUND

[0002] China is widely distributed in mountainous and hilly areas, and is a mountainous country, so it is often necessary to build structures on slopes or on slopes. The slope area foundation pit excavation often faces difficulties such as limited working surface, difficulty in laying horizontal steel support or concrete support, and the like, which leads to limited foundation pit excavation depth and cannot effectively guarantee construction safety.

[0003] Cement-soil mixing pile refers to the physical and chemical reaction of cement, soil and additives under the action of a mixer, which hardens the soil to improve the strength of the foundation. Cement-soil mixing pile belongs to flexible pile, has strong deformation coordination ability with soil, and can effectively avoid pile foundation bearing capacity surplus and save engineering cost. How to apply cement-soil mixing pile to soft soil area deep foundation pit excavation or slope area foundation pit excavation and realize support-free support is a problem to be solved. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the problems in the prior art, the present application is proposed.

[0006] Therefore, the technical problem to be solved by the present application is to overcome the deficiency and defect that deep foundation pit excavation cannot be realized due to the difficulty in setting supports in slope areas, and to effectively solve the limited working surface of large-area foundation pit excavation in soft soil areas.

[0007] To solve the above technical problems, the present application provides the following technical solutions: a multi-stage wing-shaped cement-soil mixing pile support-free excavation construction method, comprising the following steps:

[0008] Set the plane layout form and size of each wing-shaped cement-soil mixing pile according to site conditions and design requirements;

[0009] Calculate the excavation depth and excavation stages of each stage of foundation pit according to the excavation depth of foundation pit, and further determine the insertion depth, lap width and pile diameter of the outer partition wall, arched retaining wall, inner partition wall, structural column wall and T-shaped retaining wall according to the stratum conditions;

[0010] Determine the cement grade, solidifying agent, additive variety and mixing amount, and mixing method according to the engineering properties of the foundation soil.

[0011] The pile mixer is positioned, pile construction parameters are set, and a multi-stage wing-shaped cement-soil mixing pile support-free excavation support system is constructed in the order of an outer partition wall, an arch-shaped retaining wall of a first-stage foundation pit, a structural column wall of the first-stage foundation pit, a rib wall of the first-stage foundation pit, an inner partition wall of a second-stage foundation pit, an arch-shaped retaining wall of the second-stage foundation pit, a structural column wall of the second-stage foundation pit, a rib wall of the second-stage foundation pit, an inner partition wall of a final-stage foundation pit, and a T-shaped retaining wall, until the design elevation.

[0012] The application further provides a multi-stage wing-shaped cement-soil mixing pile support-free excavation support device, which comprises an outer partition wall;

[0013] An arch-shaped retaining wall is arranged on one side of the outer partition wall and used for supporting lateral loads of filling of the multi-stage foundation pit.

[0014] A structural column wall is used as an arch foot and plays a role in structure, connection and support.

[0015] A rib wall is arranged between the outer partition wall and the structural column wall and plays a transition role.

[0016] An inner partition wall is connected with the rib wall and used for connection and transition of the arch-shaped retaining wall of the first-stage foundation pit and above.

[0017] A T-shaped retaining wall is connected with the rib wall, arranged at the bottom of the final-stage foundation pit, and used for transferring loads to the bottom of the foundation pit and diffusing the loads to the foundation soil.

[0018] The structural column wall is arranged at the joint position of the arch-shaped retaining wall and the inner partition wall or the outer partition wall.

[0019] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile support-free excavation support device, the outer partition wall, the arch-shaped retaining wall, the structural column wall, the rib wall, the inner partition wall and the T-shaped retaining wall are all composed of cement-soil mixing piles.

[0020] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile support-free excavation support device, the outer partition wall is arranged outside the first-stage foundation pit, the outer partition wall is a vertical wall, used for dividing the filling area outside the foundation pit and transferring loads, and passes through the adjacent confined aquifer downward.

[0021] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile support-free excavation support device, the arch-shaped retaining wall is a circular arc arch-shaped wall, used for supporting filling of the multi-stage foundation pit and passing through the nearby confined aquifer downward.

[0022] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile without support excavation and support device, the construction column wall and the cement-soil mixing pile near the construction column wall are inserted with an I-shaped steel in a length direction, the overall rigidity of the structure is improved, and the top elevation of the rib wall is higher than the elevation corresponding to the half excavation depth of the foundation pit at the stage.

[0023] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile without support excavation and support device, the construction column wall and the cement-soil mixing pile near the construction column wall are inserted with an I-shaped steel in a length direction, the overall rigidity of the structure is improved, and the top elevation of the rib wall is higher than the elevation corresponding to the half excavation depth of the foundation pit at the stage.

[0024] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile without support excavation and support device, the construction column wall and the cement-soil mixing pile near the construction column wall are inserted with an I-shaped steel in a length direction, the overall rigidity of the structure is improved, and the top elevation of the rib wall is higher than the elevation corresponding to the half excavation depth of the foundation pit at the stage.

[0025] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile without support excavation and support device, the construction column wall and the cement-soil mixing pile near the construction column wall are inserted with an I-shaped steel in a length direction, the overall rigidity of the structure is improved, and the top elevation of the rib wall is higher than the elevation corresponding to the half excavation depth of the foundation pit at the stage.

[0026] As a preferred scheme of the multi-stage wing-shaped cement-soil mixing pile without support excavation and support device, the construction column wall and the cement-soil mixing pile near the construction column wall are inserted with an I-shaped steel in a length direction, the overall rigidity of the structure is improved, and the top elevation of the rib wall is higher than the elevation corresponding to the half excavation depth of the foundation pit at the stage.

[0027] The present application solves the technical problems of the long-existing inability to perform deep foundation pit excavation in a slope area and the limited working area of an existing large-area foundation pit, and through the wing-shaped cement-soil mixing pile without support excavation system, the variable cross-section cement-soil mixing pile is overlapped to form an arch shape, the load borne by the wall is reduced through zoned excavation, and the overall stability of the foundation pit is ensured through the connection wall to improve the excavation efficiency and expand the working area. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0029] Figure 1 It is a schematic diagram of the present application.

[0030] Figure 2 It is a partial schematic diagram of the present application.

[0031] Figure 3 A schematic diagram of a slope of the present application.

[0032] Figure 4 A schematic diagram of a whole top view of the present application.

[0033] Figure 5 A schematic diagram of a mixing pile lap of the present application.

[0034] Figure 6 A schematic diagram of an arch-shaped retaining wall of the present application.

[0035] Figure 7 A schematic diagram of a T-shaped retaining wall of the present application.

[0036] Figure 8 A schematic diagram of a pin-shaped mixing pile of the present application.

[0037] Figure 9 A schematic diagram of a middle mixing pile of the present application.

[0038] Figure 10 A schematic diagram of a top mixing pile of the present application. DETAILED DESCRIPTION

[0039] In order to make the above objectives, features and advantages of the present application more obvious and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0040] In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the concept of the present application, therefore, the present application is not limited to the specific embodiments disclosed below.

[0041] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. The "in one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0042] Embodiment 1

[0043] Reference Figures 1-3 For the first embodiment of the present application, the embodiment provides a multi-stage wing-shaped cement-soil mixing pile without support excavation support device, which comprises an outer partition wall 100, an arch-shaped retaining wall 200, a structural column wall 300, a rib wall 400 and an inner partition wall 500.

[0044] Further, the arched retaining wall 200 is arranged on one side of the outer partition wall 100, used to support the lateral load of the multi-stage foundation pit filling, the structural column wall 300 is used as the arch foot, and plays a role of construction, connection and support, the rib wall 400 is arranged between the outer partition wall 100 and the structural column wall 300, mainly plays a transition role, avoids stress concentration phenomenon, the inner partition wall 500 is connected with the rib wall 400, used for the connection and transition of the arched retaining wall 200 of the first-stage and above foundation pit, the T-shaped retaining wall 600 is connected with the rib wall 400, arranged at the bottom of the last-stage foundation pit, can transfer the load to the pit bottom and diffuse to the foundation soil, and enhances the structural stability.

[0045] It should be pointed out that the structural column wall 300 is arranged at the joint position of the arched retaining wall 200 and the inner partition wall 500 or the outer partition wall 100.

[0046] In summary, the slope is divided by the outer partition wall 100, the filling load of different partitions is transmitted to the structural column wall 300 through the arched retaining wall 200, the rib wall 400 is introduced to transition to the next-stage foundation pit, and is connected with the inner partition wall 500; finally, the lateral load is diffused to the foundation soil through the T-shaped retaining wall 600, the wall bodies are closely connected, form a whole, and realize the non-support and green excavation in the slope area.

[0047] Embodiment 2

[0048] Reference Figures 1-10 This embodiment is based on the previous embodiment.

[0049] Specifically, the outer partition wall 100, the arched retaining wall 200, the structural column wall 300, the rib wall 400, the inner partition wall 500 and the T-shaped retaining wall 600 are all composed of cement-soil mixing piles S.

[0050] Further, the outer partition wall 100 is located outside the first-stage foundation pit, the outer partition wall 100 is a vertical wall, used to divide the filling outside the pit, and passes through the adjacent confined aquifer downward.

[0051] Further, the arched retaining wall 200 is a circular arc, used to support the filling of the multi-stage foundation pit, passes through the adjacent confined aquifer downward, the structural column wall 300 and the cement-soil mixing piles S nearby must be inserted into the I-shaped steel in length, improving the overall rigidity of the structure, the rib wall 400 has a pile top elevation higher than the corresponding elevation of 1 / 2 excavation depth of the level foundation pit, and has a wall bottom elevation consistent with the inner partition wall, the inner partition wall 500 satisfies that the embedded depth is not less than 1.0he, and passes through the adjacent confined aquifer downward.

[0052] Further, the geometric size and embedded depth of the T-shaped retaining wall 600 are consistent with the inner partition wall 500 in the last-stage foundation pit, the T-shaped retaining wall 600 can be arranged separately, ensuring that the upper load and wall thrust are transferred to the soil in the last-stage foundation pit.

[0053] Preferably, as shown in Table 1:

[0054]

[0055] Table 1

[0056] The width b0 of the outer partition wall 100 should be greater than or equal to the single-width geometric width w of the arched retaining wall 200, and the width w of the arched retaining wall 200 is 1 / n of the total length L of the foundation pit excavation, and when L / n is greater than 5m, w=5m.

[0057] Preferably, the cement-soil mixing pile S is provided with a double variable cross-section according to the stratum distribution, the diameter d of the unexpanded pile body S-1 should be greater than 0.5m, the overlapping width of adjacent cement-soil mixing piles S should be greater than 0.2m, the pile spacing should be greater than 0.8m, and the ratio D / d of the diameter of the expanded pile body S-1 to the diameter of the unexpanded pile body S-2 is between 1.5 and 2.5.

[0058] Multi-stage wing-shaped cement-soil mixing pile unsupported excavation construction method:

[0059] According to the site conditions and design requirements, the planar layout form and size of each wing-shaped cement-soil mixing pile are set;

[0060] According to the excavation depth of the foundation pit, the excavation depth and the excavation number of each stage of the foundation pit are calculated, and further according to the stratum conditions, the insertion depth, the overlapping width and the pile diameter of the outer partition wall 100, the arched retaining wall 200, the inner partition wall 500, the structural column wall 300 and the T-shaped retaining wall 600 are determined;

[0061] According to the engineering properties of the foundation soil body, the cement grade, the solidifying agent, the variety and dosage of the additive and the mixing method are determined;

[0062] The pile machine is positioned, the pile machine construction parameters are set, and the multi-stage wing-shaped cement-soil mixing pile unsupported excavation support system is constructed in the order of the outer partition wall, the arched retaining wall of the first-stage foundation pit, the structural column wall of the first-stage foundation pit, the rib wall of the first-stage foundation pit, the inner partition wall of the second-stage foundation pit, the arched retaining wall of the second-stage foundation pit, the structural column wall of the second-stage foundation pit, the rib wall of the second-stage foundation pit, the inner partition wall of the last-stage foundation pit, and the T-shaped retaining wall, until the design elevation.

[0063] In summary, by designing and limiting the size of each type of retaining wall and setting the corresponding variable cross-section cement-soil mixing pile according to different soil layers, the multi-stage wing-shaped cement-soil mixing pile unsupported excavation support is realized.

[0064] Example 3

[0065] Reference Figures 1-10 , this example is based on the previous example, and illustrates a multi-stage wing-shaped cement-soil mixing pile unsupported excavation construction method.

[0066] If the upper part of the soft soil area is a medium compressive soil layer, corresponding to the phreatic layer, the buried depth of the confined aquifer is 8 m, the thickness is about 1 m, and the weak permeable layer is 9 m, the thickness is about 2 m, the silt soil, the soil water content is high, and the temporary slope deep foundation pit excavation is needed. The excavation width B is 10 m, the excavation length L is 15 m, and the excavation depth He is 10 m. Because the excavation depth of the foundation pit is large and it is not easy to use internal support or anchor rod for reinforcement, a multi-stage wing-shaped cement-soil mixing pile support system without support is selected.

[0067] The support system is mainly composed of outer partition wall 100, inner partition wall 500, arched retaining wall 200, structural column wall 300, T-shaped retaining wall 600 and rib wall 400. Among them: the outer partition wall 100 of the multi-stage wing-shaped cement-soil mixing pile support system without support is located outside the first foundation pit, the arched retaining wall 200 is used to support the outer filling soil or the transition platform filling soil of the multi-stage foundation pit, the inner partition wall 500 is used to connect and transition the arched retaining wall 200 of the first and above foundation pit, the structural column wall 300 is arranged at the joint position of the arched retaining wall 200 and the rib wall 400, the rib wall 400 is arranged between the outer partition wall 100 or the inner partition wall 500 and the structural column wall 300, and the T-shaped retaining wall 600 is located at the bottom of the last stage foundation pit. The spatial position and plane arrangement of the cement-soil mixing pile support system without support are shown in Figure 2 and Figure 3 .

[0068] Further, the outer partition wall 100 is arranged as a vertical wall, and the outer filling soil is processed in sections. The geometric width w of each arched retaining wall 200 is 5 m, and the width b0 of the outer partition wall 100 is 5 m.

[0069] The insertion ratio of the outer partition wall 100 is set to 2.0, and it has passed through the adjacent confined aquifer.

[0070] Further, the arched retaining wall 200 is arranged as a circular arc arched shape, the radian is π / 2, the arch height is 2.5 m, the insertion ratio is 1.2, and it has passed through the nearby confined aquifer.

[0071] Further, the insertion ratio of the inner partition wall 500 is set to 6.0 m and it has passed through the nearby confined aquifer.

[0072] Further, the structural column wall 300 and the steel bar embedded in the mixing pile near it are improved to improve the overall stiffness of the structure.

[0073] Further, the number of mixing piles of the rib wall 400 is set to 5, and the pile top elevation of the rib wall 400 corresponds to the elevation corresponding to 1 / 3 of the excavation depth of the level foundation pit.

[0074] Further, the embedded depth of the T-shaped retaining wall 600 is 6.0 m, each T-shaped retaining wall 600 is separately arranged, and the width is 4.0 m.

[0075] Further, the multi-stage wing-shaped cement-soil mixing pile without support excavation support system adopts layered excavation, and the excavation depth of each stage and the lateral spacing of adjacent partition walls are both 5.0 m.

[0076] Further, when n is a non-integer, n is taken as n+1 for calculation, and the excavation depth of each stage of the foundation pit is recalculated as he=He / (n+1).

[0077] Specifically, the multi-stage wing-shaped cement-soil mixing pile without support excavation support system has two stages, i.e., two-layered excavation.

[0078] Further, the multi-stage wing-shaped cement-soil mixing pile without support excavation support system has a foundation pit platform width b of 5 m, and an arch-shaped retaining wall 200 width w of 5 m.

[0079] Further, the multi-stage wing-shaped cement-soil mixing pile without support excavation support system sets bidirectional variable cross-section mixing piles according to the stratum distribution, and the unexpanded pile body S-2 has a diameter d of 0.8 m, the adjacent mixing piles have a lap width of 0.4 m, the pile spacing is 1.2 m, and the expanded pile body S-1 has a diameter D of 1.2 m.

[0080] According to the slope gradient and the plan size of the foundation pit excavation, three arch-shaped cement-soil mixing pile retaining walls 200 are set, the arch-shaped diameter is 5 m, the arc length is 7.85 m, the lap width is 0.4 m, and the single-stage foundation pit platform width is 5 m.

[0081] The foundation pit is excavated in two stages, and the stratum is covered by a confined water-bearing layer 7 and a soft interlayer, the outer partition wall 100, the inner partition wall 500, the rib wall 400, the arch-shaped retaining wall 200, and the T-shaped wall 600 are inserted through the confined water-bearing layer 8 and expanded in the soft soil layer depth range, and the pile diameter ratio is set to 1.5.

[0082] According to the engineering properties of the foundation soil body, the dry spraying method is used due to the high water content of the soil body, the lime cement type inorganic solidifying agent is selected, and the cement strength grade is 52.5R.

[0083] The mixing pile machine is positioned, the pile machine construction parameters are set, the multi-stage wing-shaped cement-soil mixing pile without support excavation support system is constructed in the order of the outer partition wall, the first-stage foundation pit arch-shaped retaining wall, the first-stage foundation pit rib wall, the first-stage foundation pit inner partition wall, the second-stage foundation pit arch-shaped retaining wall, the second-stage foundation pit rib wall, the second-stage foundation pit inner partition wall, and the T-shaped retaining wall, until the design elevation is reached.

[0084] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A multi-stage wing-shaped cement-soil mixing pile without support excavation and support device, characterized in that: Comprising An outer partition wall (100); An arched retaining wall (200) arranged on one side of the outer partition wall (100) for supporting the lateral load of the multi-stage foundation pit filling; A construction column wall (300) serving as an arch foot for construction, connection and support; A rib wall (400) arranged between the outer partition wall (100) and the construction column wall (300) for transition; An inner partition wall (500) connected with the rib wall (400) for connection and transition of the arched retaining wall (200) of the first-stage and above foundation pit; A T-shaped retaining wall (600) connected with the rib wall (400) and arranged at the bottom of the last-stage foundation pit for transferring the load to the bottom of the pit and diffusing to the foundation soil; The construction column wall (300) is arranged at the joint position of the arched retaining wall (200) and the inner partition wall (500) or the outer partition wall (100), The outer partition wall (100), the arched retaining wall (200), the construction column wall (300), the rib wall (400), the inner partition wall (500) and the T-shaped retaining wall (600) are all composed of cement-soil mixing piles (S), the outer partition wall (100) is located outside the first-stage foundation pit, the outer partition wall (100) is a vertical wall for dividing the filling area outside the pit and transferring the load, and it penetrates the adjacent confined aquifer downward.

2. The multi-stage wing-shaped cement-soil mixing pile without support excavation and support device according to claim 1, characterized in that: The arched retaining wall (200) is a circular arc-shaped wall for supporting the filling of the multi-stage foundation pit and penetrating the adjacent confined aquifer downward.

3. The multi-stage wing-shaped soil-cement mixing pile without support excavation and support device according to claim 2, characterized in that: The construction column wall (300) and the cement-soil mixing piles (S) near it must be inserted into an I-shaped steel throughout the length, and the exposed height of the rib wall (400) is higher than the elevation corresponding to half of the excavation depth of the foundation pit at the level.

4. The multi-stage wing-shaped soil-cement mixing pile without support excavation and support device according to claim 3, characterized in that: The inner partition wall (500) penetrates the adjacent confined aquifer downward.

5. The multi-stage wing-shaped cement-soil mixing pile without support excavation and support device according to claim 4, characterized in that: The geometric size and embedding depth of the T-shaped retaining wall (600) are consistent with those of the inner partition wall (500) in the last-stage foundation pit, and the T-shaped retaining wall (600) can be arranged separately to ensure that the load of the upper stage and the wall thrust are transferred to the soil inside the last-stage foundation pit.

6. The multi-stage wing-shaped soil-cement mixing pile without support excavation and support device according to claim 5, characterized in that: The width b0 of the outer partition wall (100) should be greater than or equal to the geometric width w of a single span of the arched retaining wall (200), and the width w of the arched retaining wall (200) is in proportional relationship with the total length L of the foundation pit excavation.

7. The multi-stage wing-shaped soil-cement mixing pile without support excavation and support device according to claim 6, characterized in that: The cement-soil mixing piles (S) are provided with a double-direction variable cross-section according to the stratum distribution, and the ratio of the diameter D of the enlarged pile body (S-1) to the diameter d of the un-enlarged pile body (S-2) is determined by the stratum properties.

8. A multi-stage wing-shaped cement-soil mixing pile without support excavation construction method, characterized in that: The multi-stage wing-shaped cement-soil mixing pile un-bracing excavation support device according to any one of claims 1-7, and The planar layout form and size of each wing-shaped cement-soil mixing pile are set according to the site conditions and design requirements; The excavation depth and excavation stage number of each stage of foundation pit are calculated according to the excavation depth of the foundation pit, and the insertion depth, overlapping width and pile diameter of the outer partition wall, arched retaining wall, inner partition wall, construction column wall and T-shaped retaining wall are further determined according to the stratum conditions; The cement grade, solidifying agent, variety and dosage of admixture and mixing method are determined according to the engineering properties of the foundation soil body. The pile mixer is positioned, pile mixer construction parameters are set, and multi-stage wing-shaped cement-soil mixing pile open excavation support systems are constructed in the order of external partition wall, first-stage foundation pit arched retaining wall, first-stage foundation pit structure column wall, first-stage foundation pit rib wall, second-stage foundation pit internal partition wall, second-stage foundation pit arched retaining wall, second-stage foundation pit structure column wall, second-stage foundation pit rib wall, last-stage foundation pit internal partition wall, and T-shaped retaining wall, until the design elevation.

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