Underground engineering foundation pit retaining wall

Abstract

The application discloses an underground engineering foundation pit retaining wall, which comprises at least two rows of multiple-row supporting structures; the multiple-row supporting structure comprises at least two special cross-section profile steels, the special cross-section profile steel comprises a web and flanges located on both sides of the web, one side flange or both side flanges are fixedly provided with a mortise and tenon connecting piece, the special cross-section profile steels are connected with adjacent special cross-section profile steels through the mortise and tenon connecting pieces, and each row of multiple-row supporting structures and the original soil or the treated reinforced soil located therebetween jointly form the underground engineering foundation pit retaining wall. In the application, the multiple-row special cross-section profile steels in the foundation pit retaining wall jointly deform and bear stress, so that the mechanical properties and the deformation resistance of the foundation pit retaining wall are improved, the cantilever depth of the cantilever supporting system is significantly increased, or the number of supporting channels of the pile supporting system of the foundation pit retaining wall is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underground engineering foundation pit retaining, in particular to a kind of underground engineering foundation pit retaining wall. BACKGROUND

[0002] In the underground engineering foundation pit retaining system, the section of profile steel is simple, has good mechanical properties, and as the component member of the temporary engineering of foundation pit, it can be recycled and used repeatedly after the use of foundation pit, has good economy, so it is widely used in underground engineering. But the mechanical properties of single-row profile steel are limited, when the depth of foundation pit increases gradually, it can only increase the number of support channels to meet the force and deformation requirements of retaining structure. Even so, due to the limit of the ultimate performance index of single-row profile steel section, the maximum applicable depth of foundation pit excavation generally does not exceed 13 meters.

[0003] The section of profile steel commonly used in conventional foundation pit retaining body is too simple. If the retaining body uses two or more rows of ordinary profile steel, the ordinary profile steel cannot bear the horizontal deformation as a whole due to the ineffective connection between them, so the domestic profile steel retaining body basically uses single-row profile steel, and the use of multiple rows of profile steel in parallel has not been found in actual engineering. SUMMARY

[0004] The present application provides a kind of underground engineering foundation pit retaining wall, inserts multiple rows of support and retaining structure in the soil outside the foundation pit, the multiple rows of support and retaining structure includes multiple profile steels connected by insertion, and the multiple rows of support and retaining structure and the soil form a combined foundation pit retaining wall, which can effectively increase the cantilever depth of cantilever support system or reduce the number of support channels of pile support system, reduce the number of temporary support of foundation pit, improve the safety of engineering, speed up the construction progress, reduce the cost of engineering, and produce good economic and social benefits.

[0005] In order to achieve the above purpose, the present application provides a kind of underground engineering foundation pit retaining wall, which includes at least two rows of multiple rows of support and retaining structure, the multiple rows of support and retaining structure includes at least two profile steels, the profile steel includes a web and flanges on both sides of the web, one side of the flange or both sides of the flange is fixedly provided with a mortise and tenon joint, and the profile steel is connected with the adjacent profile steel by insertion through the mortise and tenon joint. Each row of multiple rows of support and retaining structure and the original soil or the reinforced soil between them form an underground engineering foundation pit retaining wall.

[0006] Preferably, the underground engineering foundation pit retaining wall further includes a single-row support and retaining structure, and the single-row support and retaining structure includes a conventional profile steel.

[0007] Preferably, the single-row support and retaining structure can be not arranged or arranged at intervals with the multiple rows of support and retaining structure along the longitudinal direction of the foundation pit according to needs.

[0008] Preferably, the special cross-section steel mortise and tenon joint comprises a tenon and a mortise.

[0009] Preferably, the special cross-section steel is provided with a mortise or a tenon on one side flange.

[0010] Preferably, the special cross-section steel is provided with a mortise and / or a tenon on each side flange.

[0011] Preferably, the mortise comprises two mortise side plates, a mortise notch and a mortise cavity, one end of the mortise side plate is fixed on the flange of the special cross-section steel, the other end of the two mortise side plates forms the mortise notch, and the two mortise side plates and the flange of the special cross-section steel form the mortise cavity; the width of the mortise cavity is greater than the width of the mortise notch.

[0012] Preferably, the tenon comprises a tenon neck and a tenon head, one end of the tenon neck is fixed on the flange of the special cross-section steel, the tenon head is fixed on the other end of the tenon neck, and the cross-section width of the tenon head is greater than the width of the tenon neck.

[0013] Preferably, the shape of the mortise cavity matches the shape of the tenon head, the minimum width of the mortise notch is greater than the width of the corresponding tenon neck and less than the width of the tenon head, the size of the mortise cavity is greater than the size of the tenon head, so as to facilitate the smooth insertion of the tenon into the mortise and realize the effective connection of the tenon and the mortise.

[0014] Preferably, the tenon and / or the mortise are fixed on the flange of the special cross-section steel in a full-length or segmented manner.

[0015] Preferably, the mortise and tenon joint at the top end of the special cross-section steel in the innermost row and the outermost row of the multi-row support structure is partially disconnected to form a notch for placing a top ring beam.

[0016] The present application has the following advantages:

[0017] The present application adds a groove and tenon connecting piece on the flange of a profile steel, thereby forming a special cross-section profile steel with convenient and safe and reliable insertion and extraction, and with an insertion groove and tenon arranged along the longitudinal direction (Z axis) of the profile steel. The insertion groove and tenon of adjacent special cross-section profile steels are longitudinally engaged to form a plurality of rows of support and blocking structures. At least two rows of the plurality of rows of support and blocking structures and the original soil or the reinforced soil after treatment located therebetween jointly form an underground engineering enclosure wall with a plurality of rows of inserted profile steels. The plurality of rows of special cross-section profile steels in the enclosure wall jointly deform and bear stress, thereby improving the mechanical properties and deformation resistance of the foundation pit enclosure wall, significantly increasing the cantilever depth of a cantilever support system or effectively reducing the support channel number of the foundation pit enclosure wall of a pile support system, and the special cross-section profile steels can be extracted and recycled multiple times after the foundation pit is used, thereby producing good economic and social benefits under the condition of ensuring engineering safety. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A plan view of a foundation pit enclosure wall with a plurality of rows of support and blocking structures provided in an embodiment of the present application;

[0019] Figure 2 A cross-sectional view of a foundation pit enclosure wall with a single row of support and blocking structures in a plurality of rows of support and blocking structures provided in an embodiment of the present application;

[0020] Figure 3 A plan view of a foundation pit enclosure wall with a plurality of rows of support and blocking structures and a single row of support and blocking structures provided in an embodiment of the present application;

[0021] Figure 4 A plan view of a foundation pit enclosure wall with a plurality of rows of support and blocking structures and a single row of support and blocking structures provided in an embodiment of the present application;

[0022] Figure 5 A plan view of a foundation pit enclosure wall with a plurality of rows of support and blocking structures and a single row of support and blocking structures provided in an embodiment of the present application;

[0023] Figure 6 A schematic view of a special cross-section profile steel with an insertion groove provided on only one side provided in an embodiment of the present application;

[0024] Figure 7 A schematic view of a special cross-section profile steel with an insertion tenon provided on only one side provided in an embodiment of the present application;

[0025] Figure 8 A schematic view of a special cross-section profile steel with an insertion groove provided on one side and an insertion tenon provided on the other end provided in an embodiment of the present application;

[0026] Figure 9 A schematic view of a "T"-shaped insertion groove and a "T"-shaped insertion tenon before connection provided in an embodiment of the present application;

[0027] Figure 10 A schematic view of the connection between the T-shaped slot and the T-shaped tenon provided in the embodiments of the present application;

[0028] Figure 11 A schematic view of the connection between the polygonal slot and the polygonal tenon provided in the embodiments of the present application;

[0029] Figure 12 A schematic view of the connection between the polygonal slot and the polygonal tenon provided in the embodiments of the present application;

[0030] Figure 13 A schematic view of the connection between the circular slot and the circular tenon provided in the embodiments of the present application;

[0031] Figure 14 A schematic view of the connection between the circular slot and the circular tenon provided in the embodiments of the present application. DETAILED DESCRIPTION

[0032] The underground engineering foundation pit retaining wall provided by the present application is further described in detail below in combination with the accompanying drawings and specific embodiments. The advantages and features of the present application will be more apparent according to the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and all use non-precise ratios, only for the purpose of facilitating and clearly assisting in the description of the embodiments of the present application.

[0033] The present application provides an underground engineering foundation pit retaining wall, comprising: at least two columns of multiple rows of supporting structures;

[0034] Each column of the multiple rows of supporting structures contains at least two special cross-section profile steels; the special cross-section profile steel contains a web and flanges on both sides of the web, one side flange or both side flanges are fixedly provided with a slot-and-tenon connecting piece, and the special cross-section profile steel is connected with the adjacent special cross-section profile steel through the slot-and-tenon connecting piece to form two or more rows of effectively connected profile steel members;

[0035] Each column of the multiple rows of supporting structures and the original soil or the treated and reinforced soil therebetween jointly form the underground engineering foundation pit retaining wall.

[0036] The number of columns of the multiple rows of supporting structures, the column spacing t, the number of rows of the special cross-section profile steels of each column of the multiple rows of supporting structures, and the row spacing S are determined according to the depth of the underground engineering foundation pit and the surrounding conditions. As shown in Figure 1 The multiple rows of supporting structures 2 containing multiple rows of special cross-section profile steels 3 are densely arranged with a column spacing t, and each row of special cross-section profile steels 3 is connected through the slot-and-tenon connecting pieces fixedly arranged on the flanges. As shown in Figure 2The single-row multi-row support structure 2 is shown in the cross-sectional view of the foundation pit retaining wall, the multi-row support structure 2 comprises a plurality of rows of effective connection special section steel 3, the top end of the special section steel 3 is higher than the foundation pit ground level, the rest is located in the soil, and the bottom end is lower than the bottom of the foundation pit, the flange of the special section steel is provided with a slot and tenon connector, the slot and tenon connector of the top end of the special section steel of the innermost row and the outermost row of the multi-row support structure 2 is partially disconnected to form a notch 4, which is used for placing a top ring beam 8, and the integrity of the multi-column support structure in the foundation pit retaining wall is enhanced.

[0037] The underground engineering foundation pit retaining wall further comprises a single-row support structure, the single-row support structure is located in the soil, the top end of the single-row support structure is higher than the foundation pit ground level, and the bottom end is lower than the bottom of the foundation pit. The single-row support structure 5 is a single-row H-shaped steel member, which is arranged according to the needs along the longitudinal direction of the foundation pit and is spaced apart from the multi-row support structure 2. As shown in Figure 3 As shown in Figure 4 As shown in Figure 5 As shown in

[0038] The special section steel structure 3 is divided into five types according to the slot and tenon connector provided on the flanges on both sides of the web 9: special section steel with a slot 6 provided on one side of the flange, special section steel with a tenon 7 provided on one side of the flange, special section steel with a slot 6 provided on both sides of the flange, special section steel with a tenon 7 provided on both sides of the flange, and special section steel with a slot 6 provided on one side of the flange and a tenon 7 provided on the other side of the flange.

[0039] As shown in Figure 6 As shown in the schematic view of the special section steel 3 with a slot 6 provided on one side of the flange on both sides of the web 9, the special section steel 3 is provided with a slot 6 on one side of the flange of the web 9; the slot 6 comprises two slot side plates 601, a slot notch 602 and a slot inner cavity 603, one end of the two slot side plates 601 is fixed on the flange of the special section steel 3, the other end forms the slot notch 602, the two slot side plates 601 and the flange of the special section steel 3 form the slot inner cavity 603, and the width of the slot inner cavity 603 is greater than the width of the slot notch 602; the Z-axis is defined along the longitudinal direction of the steel in the plane of the web of the special section steel 3, the Y-axis is defined along the width direction of the web, and the X-axis is defined perpendicular to the web to establish a rectangular coordinate.

[0040] As shown in Figure 7The special section steel 3 is shown in the figure, one side of the flange of the web 9 is provided with the mortise 7, the mortise 7 includes the mortise neck 701 and the mortise head 702, one end of the mortise neck 701 is fixed on the flange of the special section steel 3, the other end of the mortise neck 701 is fixedly connected with the mortise head 702, the cross-sectional width of the mortise head 702 is greater than the width of the mortise neck 701; the special section steel 3 is defined as that the Z axis is along the longitudinal direction of the steel in the plane of the web, the Y axis is along the width direction of the web, and the X axis is perpendicular to the web to establish a rectangular coordinate.

[0041] As shown in the figure, Figure 8 The special section steel 3 is shown in the figure, one side of the flange of the web 9 is provided with the mortise 7, the mortise 7 includes the mortise neck 701 and the mortise head 702, one end of the mortise neck 701 is fixed on the flange of the special section steel 3, the other end of the mortise neck 701 is fixedly connected with the mortise head 702, the cross-sectional width of the mortise head 702 is greater than the width of the mortise neck 701; the special section steel 3 is defined as that the Z axis is along the longitudinal direction of the steel in the plane of the web, the Y axis is along the width direction of the web, and the X axis is perpendicular to the web to establish a rectangular coordinate.

[0042] The two special section steels 3 connected with each other are inserted along the Z axis by the mortises 7 or the mortises 6 arranged on the flanges respectively, to form the multi-row supporting and blocking structure 2 which are effectively connected by mutual engagement.

[0043] The shape of the mortise inner cavity 603 matches the shape of the mortise head 702, the minimum width of the mortise slot 602 should be greater than the width of the corresponding mortise neck 701 and less than the width of the mortise head 702, the mortise inner cavity 603 should be greater than the size of the mortise head 702, so as to facilitate the mortise 7 to be smoothly inserted into the mortise 6 to realize the effective connection of the two special section steels 3. The shape of the mortise inner cavity 603 can be "T" shape, polygon or circle, and the shape of the mortise head 702 corresponds to "T" shape, polygon and circle.

[0044] As shown in the figure, Figure 9 , Figure 10The "T" shaped slot 6 and the "T" shaped tenon 7 are connected respectively, and the front and back schematic diagrams are shown in the figure. The "T" shaped slot includes two "L" shaped slot side plates 601, a slot notch 602 and a slot inner cavity 603. One end of the two "L" shaped slot side plates 601 is fixed on the flange of the special cross-section profiled steel 3, and the fixed connection part is chamfered with a circular arc or a broken line. The other end of the two "L" shaped slot side plates 601 forms the slot notch 602. The two "L" shaped slot side plates 601 and the flange of the special cross-section profiled steel 3 form the "T" shaped slot inner cavity 603. The "T" shaped tenon includes a tenon neck 701 and a tenon head 702. One end of the tenon neck 701 is fixed on the flange of the special cross-section profiled steel 3, and the fixed connection part is chamfered with a circular arc or a broken line. The other end of the tenon neck 701 is fixedly connected with the tenon head 702, and the fixed connection part is chamfered with a circular arc or a broken line. The size of the slot inner cavity 603 is larger than that of the tenon head 702. The width of the slot notch 602 is larger than that of the tenon neck 701, and the width of the tenon head 702 is larger than that of the slot notch 602.

[0045] As Figure 11 , Figure 12 The front and back schematic diagrams of the polygonal slot 6 and the polygonal tenon 7 are shown in the figure. The polygonal slot includes two right trapezoidal slot side plates 601, a slot notch 602 and a slot inner cavity 603. One end of the two right trapezoidal slot side plates 601 is fixed on the flange of the special cross-section profiled steel 3, and the fixed connection part is chamfered with a circular arc or a broken line. The other end of the two trapezoidal slot side plates 601 forms the slot notch 602. The two right trapezoidal slot side plates 601 and the flange of the special cross-section profiled steel 3 form the polygonal slot inner cavity 603. The polygonal tenon 7 includes a tenon neck 701 and a polygonal tenon head 702. One end of the tenon neck 701 is fixed on the flange of the special cross-section profiled steel 3, and the fixed connection part is chamfered with a circular arc or a broken line. The other end of the tenon neck 701 is fixedly connected with the tenon head 702, and the fixed connection part is chamfered with a circular arc or a broken line. The size of the slot inner cavity 603 is larger than that of the tenon head 702. The width of the slot notch 602 is larger than that of the tenon neck 701, and the width of the tenon head 702 is larger than that of the slot notch 602.

[0046] As Figure 13 , Figure 14The front and rear schematic views of the circular slot 6 and the circular tenon 7 are respectively shown, the circular slot includes two "half circle" shaped slot side plates 601, a slot notch 602 and a slot inner cavity 603, one end of the two "half circle" shaped slot side plates 601 is fixed on the flange of the special cross-section profiled steel 3, the fixed connection part is chamfered with a circular arc or a broken line, the other end of the two "half circle" shaped slot side plates 601 forms the slot notch 602, and the two "half circle" shaped slot side plates 601 and the flange of the special cross-section profiled steel 3 form the circular slot inner cavity 603. The circular tenon 7 includes a tenon neck 701 and a circular tenon head 702, one end of the tenon neck 701 is fixed on the flange of the special cross-section profiled steel 3, the fixed connection part is chamfered with a circular arc or a broken line, the other end of the tenon neck 701 is fixedly connected with the tenon head 702, and the fixed connection part is chamfered with a circular arc or a broken line. The size of the slot inner cavity 603 is greater than that of the tenon head 702, the width of the slot notch 602 is greater than that of the tenon neck 701, and the width of the tenon head 702 is greater than that of the slot notch 602.

[0047] Embodiments of the present application are:

[0048] In the case that the single-column multi-row supporting and blocking structure 2 only includes two rows of special cross-section profiled steels 3, the single-side flanges of the two rows of special cross-section profiled steels 3 are provided with groove and tenon connecting pieces; during the construction of the foundation pit support wall, the soil 1 outside the foundation pit excavation contour is subjected to conventional mechanical stirring (such as stirring pile, rotary jet pile, etc.), then the first special cross-section profiled steel 3 adjacent to the inner boundary line of the foundation pit support wall is pressed into the soil 1, then the groove 6 or the tenon 7 of the groove and tenon connecting piece of the second special cross-section profiled steel 3 is inserted along the tenon 7 or the groove 6 of the first special cross-section profiled steel 3 in the longitudinal direction, the effective connection of the two rows of special cross-section profiled steels 3 is realized by the biting effect of the tenon 7 and the groove 6, so as to increase the overall rigidity of the multi-row supporting and blocking structure 2 in the web direction (Y direction), and the construction of the single-column multi-row supporting and blocking structure 2 is completed. After the construction of the multi-row supporting and blocking structure 2 of other columns is sequentially completed, the groove notch 4 of the groove and tenon connecting piece of the special cross-section profiled steel in each multi-row supporting and blocking structure 2 is used to bind the steel bars and pour the top ring beam 8, so as to enhance the integrity of the multi-row supporting and blocking structure between different columns of the foundation pit support wall.

[0049] In the case that the single-row multi-row bracing structure 2 contains three special cross-section section steels 3, the innermost row and the outermost row of the special cross-section section steels 3 of the multi-row bracing structure 2 are provided with the groove-and-tenon connectors on one side of the flange, and the rest of the special cross-section section steels 3 are provided with the groove-and-tenon connectors on both sides of the flange. During the construction of the foundation pit retaining wall, the soil 1 outside the foundation pit excavation contour is mechanically stirred (such as stirring pile, rotary jet pile, etc.) in a conventional manner. Then, the first special cross-section section steel 3 adjacent to the inner edge line of the foundation pit retaining wall is pressed into the soil 1, and then the insertion groove 6 or the insertion tenon 7 of the groove-and-tenon connector of the second special cross-section section steel 3 is inserted longitudinally along the insertion tenon 7 or the insertion groove 6 of the first special cross-section section steel 3, and finally the insertion groove 6 or the insertion tenon 7 of the groove-and-tenon connector of the third special cross-section section steel 3 is inserted longitudinally along the insertion tenon 7 or the insertion groove 6 of the second special cross-section section steel 3. The effective connection of the two rows of special cross-section section steels 3 is realized by the biting effect of the insertion tenon 7 and the insertion groove 6, thereby increasing the overall stiffness of the multi-row bracing structure 2 in the web direction (Y direction), and the construction of the single-row multi-row bracing structure 2 is completed. After the construction of the multi-row bracing structure 2 of the other rows is completed in turn, the groove-and-tenon connector groove 4 of the special cross-section section steel in each multi-row bracing structure 2 is used to bind the steel bars and pour the top ring beam 8, thereby enhancing the integrity of the multi-row bracing structure between different rows of the foundation pit retaining wall.

[0050] In the case that the single-row multi-row bracing structure 2 contains three special cross-section section steels 3, the innermost row and the outermost row of the special cross-section section steels 3 of the multi-row bracing structure 2 are provided with the groove-and-tenon connectors on one side of the flange, and the rest of the special cross-section section steels 3 are provided with the groove-and-tenon connectors on both sides of the flange. During the construction of the foundation pit retaining wall, the soil 1 outside the foundation pit excavation contour is mechanically stirred (such as stirring pile, rotary jet pile, etc.) in a conventional manner. Then, the first special cross-section section steel 3 adjacent to the inner edge line of the foundation pit retaining wall is pressed into the soil 1, and then the insertion groove 6 or the insertion tenon 7 of the groove-and-tenon connector of the second special cross-section section steel 3 is inserted longitudinally along the insertion tenon 7 or the insertion groove 6 of the first special cross-section section steel 3, and finally the insertion groove 6 or the insertion tenon 7 of the groove-and-tenon connector of the third special cross-section section steel 3 is inserted longitudinally along the insertion tenon 7 or the insertion groove 6 of the second special cross-section section steel 3. The effective connection of the two rows of special cross-section section steels 3 is realized by the biting effect of the insertion tenon 7 and the insertion groove 6, thereby increasing the overall stiffness of the multi-row bracing structure 2 in the web direction (Y direction), and the construction of the single-row multi-row bracing structure 2 is completed. After the construction of the multi-row bracing structure 2 of the other rows is completed in turn, the groove-and-tenon connector groove 4 of the special cross-section section steel in each multi-row bracing structure 2 is used to bind the steel bars and pour the top ring beam 8, thereby enhancing the integrity of the multi-row bracing structure between different rows of the foundation pit retaining wall.

[0051] The present application adds groove and tenon connecting pieces on the flange of the profile steel, thereby forming special cross-section profile steel with convenient and safe and reliable insertion and extraction, and with insertion groove and tenon arranged along the longitudinal direction (Z axis) of the profile steel, the insertion tenon and the insertion groove of the adjacent special cross-section profile steel are longitudinally engaged to form multiple-row supporting and blocking structure, at least two columns of multiple-row supporting and blocking structure and the original soil or the reinforced soil after treatment located therebetween jointly form underground engineering enclosure wall with multiple-row inserted profile steel, and according to the specific conditions of the foundation pit, single-row supporting and blocking structure can be arranged at intervals between the multiple-row supporting and blocking structure, thereby improving the mechanical properties and deformation resistance of the foundation pit enclosure wall, significantly increasing the cantilever depth of the cantilever supporting system or effectively reducing the support channel number of the pile supporting system foundation pit enclosure wall, the special cross-section profile steel can be pulled out and recycled multiple times after the use of the foundation pit, and better economic and social benefits can be generated under the condition of ensuring the safety of the project.

[0052] Although the present application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as limiting the present application. After reading the above description, various modifications and alternatives of the present application will be apparent to those skilled in the art. Therefore, the scope of protection of the present application should be defined by the appended claims.

Claims

1. An underground engineering foundation pit retaining wall, characterized by, The invention relates to a kind of underground engineering foundation pit retaining wall structure, which comprises at least two rows of multi-row bracing structures, the multi-row bracing structure comprises at least two special section steels, the special section steel comprises a web and flanges on both sides of the web, one side flange or both side flanges are fixedly provided with a mortise and tenon connector, the special section steel is connected with adjacent special section steel by mortise and tenon connector; each row of multi-row bracing structure and the soil body between them form a kind of underground engineering foundation pit retaining wall structure together. At least one row of single-row bracing structure, the single-row bracing structure comprises a conventional steel, which is arranged between the multi-row bracing structures according to the engineering needs. The mortise and tenon connector at the top end of the innermost row and the outermost row of the special section steel in the multi-row bracing structure is partially disconnected to form a notch for placing a top ring beam to reinforce the multi-row bracing structure.

2. A retaining wall for an excavation according to claim 1, wherein, The mortise and tenon connector of the special section steel comprises a tenon and a mortise.

3. A retaining wall for a foundation pit of an underground work according to claim 2, wherein The special section steel is fixedly provided with a mortise or a tenon on one side flange.

4. A retaining wall for a foundation pit of an underground work according to claim 2, wherein The special section steel is fixedly provided with a mortise and / or a tenon on both side flanges.

5. A retaining wall for a foundation pit of an underground work according to claim 2, wherein The mortise comprises two mortise side plates, a mortise notch and a mortise inner cavity, one end of the mortise side plate is fixed on the flange of the special section steel, the other end of the two mortise side plates forms a mortise notch, and the mortise inner cavity is formed by the two mortise side plates and the flange of the special section steel; the width of the mortise inner cavity is greater than the width of the mortise notch.

6. A retaining wall for a foundation pit of an underground work according to claim 2, wherein The tenon comprises a tenon neck and a tenon head, one end of the tenon neck is fixed on the flange of the special section steel, and the tenon head is fixed on the other end of the tenon neck; the cross-sectional width of the tenon head is greater than the width of the tenon neck.

7. A retaining wall for a foundation pit of an underground work according to claim 5 or 6, wherein The shape of the mortise inner cavity matches the shape of the tenon head, the minimum width of the mortise notch is greater than the width of the corresponding tenon neck and less than the width of the tenon head, and the size of the mortise inner cavity is greater than the size of the tenon head, so that the tenon can be smoothly inserted into the mortise to achieve effective connection of the mortise and the tenon.

8. The retaining wall for a foundation pit of an underground structure according to claim 2, wherein The tenon and / or the mortise are fixed on the flange of the special section steel in a full-length or segmented manner.

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