Self-stable supporting structure for deep foundation pit

Abstract

The application discloses a self-stabilizing supporting structure for deep foundation pit, which is composed of at least one row of retaining piles, a pressing top plate fixedly arranged on the top of the retaining piles and a diagonal brace, the diagonal brace is fixedly connected with the retaining piles and / or the pressing top plate; the diagonal brace is composed of a front diagonal brace and a rear diagonal brace, and a plurality of self-stabilizing reinforcing members are fixedly arranged on the rear diagonal brace or the retaining piles away from the center of the foundation pit; the self-stabilizing reinforcing member is an auxiliary diagonal brace fixedly connected to the surface of the rear diagonal brace away from the center of the foundation pit, the size of the auxiliary diagonal brace is smaller than that of the rear diagonal brace, and the auxiliary diagonal brace and the rear diagonal brace form an included angle of 90-120 degrees; the pressing top plate is made of 20cm-thick reinforced concrete, and the steel bars in the pressing top plate are made of HPB300-grade steel bars and HRB400-grade steel bars; the self-stabilizing reinforcing members are arranged on the outer side of the rear diagonal brace or the retaining piles, the self-stabilizing reinforcing members effectively utilize the dead weight of the soil above the self-stabilizing reinforcing members of the supporting structure when the supporting structure has a tendency to rotate, prevent the deflection of the supporting structure, have the effect of resisting overturning and the effect of strengthening self-stabilization.

Description

TECHNICAL FIELD

[0001] The present application relates to a self-stable supporting structure for deep foundation pit. BACKGROUND

[0002] The urbanization process in China is becoming more and more significant, and the contradiction between supply and demand of urban space capacity is increasingly prominent. The development of underground space inevitably involves foundation pit engineering. Traditional foundation pit supporting technology in soft soil area uses a large amount of reinforced concrete structure, and the installation of support causes narrow construction space, inconvenience of earth excavation, leading to prolonged construction period. The removal of support causes a large amount of construction waste, and the cutting or blasting produces noise and dust, which pollutes the surrounding environment.

[0003] The self-stable foundation pit supporting structure technology is also known as SKY STAR technology. The technology uses steel members instead of traditional reinforced concrete support, realizes vertical excavation and recycling of steel members, effectively reduces the engineering cost while ensuring the safety of the foundation pit, greatly improves the earth excavation efficiency, significantly shortens the construction period, and can be widely used for foundation pits with a depth of 12m or less.

[0004] In the paper "Research on Foundation Pit Excavation Based on Self-stable Steel Support Foundation Pit Support Structure" published in Railway Construction Technology 2022 (02), article number 10094539 (2022) 02013705, Wang Jian-sheng mentioned that the three steel support ultimate bearing capacities of the support mode combining double-row enclosure piles with double-row grouting steel pipe supports all reached 1100kN; the surface subsidence amplitude of the adjacent building measurement point was smaller using the self-stable steel support foundation pit support structure; the time-space effect existed in the influence of foundation pit excavation on the surface subsidence of the surrounding area, and under the condition of high groundwater level, the surrounding buildings close to the foundation pit were significantly affected by the foundation pit excavation. However, the self-stability effect still needs to be strengthened, and as the excavation of the foundation pit deepens, the soil around the support and support structure enclosure piles continues to decrease, and the support structure will have a tendency to rotate around its bottom end into the foundation pit, i.e., a tendency to overturn. Patent CN116335150A: Construction method of self-stable foundation pit support structure, steps: 1) set double-row support piles, and set inclined braces in the foundation pit at the top of the double-row support piles; 2) pour the double-row pile support pile top ring beam, connecting beam and pressure top plate, and fix the first inclined brace; 3) excavate downward to the second inclined brace, and at the intersection of the inclined brace of the outer row support pile and the inner row pile, construct a concrete ring beam to fix the second inclined brace; 4) continue to excavate downward, repeat the above steps to the foundation bottom, and immediately pour a reinforced cushion layer on the foundation bottom side facing the pit to fix all the inclined braces; 5) construct the basement structure of the bottom plate, set a water stop steel plate at the position where the inclined brace penetrates the bottom plate and the exterior wall of the basement to prevent water leakage, and cut off the steel pipe that intrudes into the exterior wall of the basement after the basement emerges from the ground and is backfilled. The use of the present invention can avoid the problems of weak overall stiffness of single-row support pile structure using single inclined brace, and at the same time, the use of double-row piles can improve the overall stiffness and stability of the enclosure, and reduce the deformation of the foundation pit. However, the self-stability effect is not strong enough, and as the excavation of the foundation pit deepens, the soil around the support and support structure enclosure piles continues to decrease, and the support structure will have a tendency to rotate around its bottom end into the foundation pit. SUMMARY

[0005] The purpose of the present application is to overcome the defects in the prior art and provide a deep foundation pit self-stable support structure. By setting a self-stability reinforcing member on the outside of the rear inclined brace or enclosure pile, the self-stability reinforcing member effectively utilizes the self-weight of the soil above the support structure when it has a tendency to rotate, prevents the deflection of the support structure, and has an anti-overturning effect, thereby reinforcing and strengthening the self-stability effect.

[0006] To achieve the above object, the technical scheme of the present application is to design a self-stabilizing supporting structure for deep foundation pit, which is composed of at least one row of retaining piles, a pressure top plate fixedly arranged on the top of the retaining piles, and a diagonal brace fixedly connected with the retaining piles and / or the pressure top plate; the diagonal brace is composed of a front diagonal brace and a rear diagonal brace, and a plurality of self-stabilizing reinforcing members are fixedly arranged on the rear diagonal brace or the retaining piles away from the center of the foundation pit. In consideration of the fact that the amount of soil in the foundation pit is less and less in the later stage of excavation, and the amount of soil supporting the supporting structure is also less and less, the supporting structure has a tendency to deflect inwardly and has an inward torque, and the self-stabilizing effect is reinforced and strengthened by arranging the self-stabilizing reinforcing members on the rear diagonal brace or the retaining piles away from the center of the foundation pit.

[0007] A further technical scheme is that the self-stabilizing reinforcing member is an auxiliary diagonal brace fixedly connected to the surface of the rear diagonal brace away from the center of the foundation pit, the size of the auxiliary diagonal brace is smaller than that of the rear diagonal brace, and the auxiliary diagonal brace and the rear diagonal brace form an included angle of 90-120°. The auxiliary diagonal brace and the rear diagonal brace are arranged obliquely, so that the triangular space formed by the auxiliary diagonal brace and the rear diagonal brace is filled with soil, effectively reducing the inward torque of the supporting structure, and avoiding the deflection of the entire supporting structure when the amount of soil in the foundation pit gradually decreases with the deepening of excavation.

[0008] Another technical scheme is that the self-stabilizing reinforcing member is an auxiliary diagonal brace fixedly connected to the surface of the retaining pile away from the center of the foundation pit, the size of the auxiliary diagonal brace is smaller than that of the retaining pile, and the auxiliary diagonal brace and the retaining pile form an included angle of 45-60°. In combination with the previous technical scheme, the self-stabilizing reinforcing member includes the auxiliary diagonal brace fixedly connected to the surface of the retaining pile away from the center of the foundation pit and the auxiliary diagonal brace fixedly connected to the surface of the rear diagonal brace away from the center of the foundation pit, so as to enhance the self-stabilizing effect of the entire supporting structure. The triangular space formed by the auxiliary diagonal brace and the retaining pile is filled with soil, effectively reducing the inward torque of the supporting structure.

[0009] A further technical scheme is that the front diagonal brace and the rear diagonal brace are both single-row grouting steel pipes.

[0010] The pressure top plate is a 20cm-thick reinforced concrete pressure top plate, and the steel bars in the pressure top plate are HPB300-grade steel bars and HRB400-grade steel bars.

[0011] The retaining piles are cast-in-place piles with a pile diameter of 80cm and a spacing of 200cm.

[0012] A further technical scheme is that the retaining piles are provided in two rows, the top of the diagonal brace is fixedly connected with the pressure top plate, and the middle of the diagonal brace is fixedly connected with the retaining piles.

[0013] Further technical solutions are that the lengths of the double-row fender piles are different, the length of the fender pile close to the center of the foundation pit is greater than the length of the fender pile far from the center of the foundation pit, the bottom of the double-row fender pile is fixedly connected with a self-stabilizing reinforcing inclined support, the top end of the self-stabilizing reinforcing inclined support is fixedly connected to the bottom of the fender pile far from the center of the foundation pit, and the bottom end of the self-stabilizing reinforcing inclined support is fixedly connected to the bottom of the fender pile close to the center of the foundation pit. The double-row fender piles are different in length, and the self-stabilizing reinforcing inclined support is arranged again, so that a space for accommodating the silt layer is provided, the silt layer can be accumulated, the effect of compacting the silt layer is achieved, and the self-stabilizing effect of the self-stabilizing supporting structure is enhanced. The self-stabilizing effect is further enhanced by storing more soil outside the double-row fender piles, and the problem that the supporting structure rotates inward with the bottom end as a fulcrum is effectively avoided as the deep foundation pit is excavated deeper.

[0014] The advantages and beneficial effects of the present application are that the auxiliary inclined support and the rear inclined support are inclinedly arranged, so that the triangular space formed by the auxiliary inclined support and the rear inclined support is filled with soil, the torque of the supporting structure inwardly is effectively reduced, and the deflection of the entire supporting structure is avoided due to the existence of the soil above the auxiliary inclined support when the amount of soil in the foundation pit gradually decreases with the deepening of excavation.

[0015] The triangular space formed by the auxiliary inclined support and the fender pile is filled with soil, and the torque of the supporting structure inwardly is effectively reduced.

[0016] The double-row fender piles are different in length, and the self-stabilizing reinforcing inclined support is arranged again, so that a space for accommodating the silt layer is provided, the silt layer can be accumulated, the effect of compacting the silt layer is achieved, and the self-stabilizing effect of the self-stabilizing supporting structure is enhanced. The self-stabilizing effect is further enhanced by storing more soil outside the double-row fender piles, and the problem that the supporting structure rotates inward with the bottom end as a fulcrum is effectively avoided as the deep foundation pit is excavated deeper, and the anti-overturning effect is good. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of a first embodiment of a self-stabilizing supporting structure for a deep foundation pit of the present application;

[0018] Figure 2 is Figure 1 is a three-dimensional schematic diagram of the double-row fender piles in the embodiment;

[0019] Figure 3 is a schematic diagram of a second embodiment of the present application;

[0020] Figure 4 is a schematic diagram of a third embodiment of the present application;

[0021] Figure 5 is Figure 4 is a partial enlarged schematic diagram of the self-stabilizing reinforcing inclined support and the components near the self-stabilizing reinforcing inclined support;

[0022] Figure 6 is a schematic diagram of embodiment four of the present application;

[0023] Figure 7 is Figure 6 is a partial enlarged schematic diagram of the self-stabilizing reinforcing diagonal brace and the components near it in the middle of the present application.

[0024] In the figure: 1, support pile; 2, top plate; 3, front diagonal brace; 4, rear diagonal brace; 5, auxiliary diagonal brace; 6, self-stabilizing reinforcing diagonal brace; 7, buffer cross pile; 8, diagonal plate; 9, rubber column. DETAILED DESCRIPTION

[0025] The specific embodiments of the present application are further described below in conjunction with the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application. Example one

[0026] As Figure 1 , Figure 2 shown, the present application is a self-stabilizing supporting structure for deep foundation pit, which is composed of two rows of support piles 1, a top plate 2 fixedly arranged on the top of the support piles 1, and diagonal braces. The diagonal braces are fixedly connected with the support piles 1 and / or the top plate 2. The diagonal braces are composed of front diagonal braces 3 and rear diagonal braces 4. A plurality of self-stabilizing reinforcing members are fixedly arranged on the rear diagonal braces 4 or the support piles 1 away from the center of the foundation pit. The top of the diagonal braces is fixedly connected with the top plate 2, and the middle of the diagonal braces is fixedly connected with the support piles 1. The front diagonal braces 3 and the rear diagonal braces 4 are both single-row grouting steel pipes. The top plate 2 is a 20 cm thick reinforced concrete top plate 2. The steel bars in the top plate 2 are made of HPB300 grade steel bars and HRB400 grade steel bars. The support piles 1 are cast-in-place piles with a pile diameter of 80 cm and a spacing of 200 cm. The self-stabilizing reinforcing members are auxiliary diagonal braces 5 fixedly connected to the surface of the rear diagonal braces 4 away from the center of the foundation pit. The size of the auxiliary diagonal braces 5 is smaller than that of the rear diagonal braces 4, and the auxiliary diagonal braces 5 form an included angle of 90-120° with the rear diagonal braces 4. The self-stabilizing reinforcing members are auxiliary diagonal braces 5 fixedly connected to the surface of the support piles 1 away from the center of the foundation pit. The size of the auxiliary diagonal braces 5 is smaller than that of the support piles 1, and the auxiliary diagonal braces 5 form an included angle of 45-60° with the support piles 1. Example two

[0027] The difference from example one is that, as Figure 3 shown, the lengths of the two rows of support piles 1 are different. The length of the support pile 1 near the center of the foundation pit is greater than that of the support pile 1 away from the center of the foundation pit. The bottom of the two rows of support piles 1 is fixedly connected with a self-stabilizing reinforcing diagonal brace 6. The top end of the self-stabilizing reinforcing diagonal brace 6 is fixedly connected to the bottom of the support pile 1 away from the center of the foundation pit, and the bottom end of the self-stabilizing reinforcing diagonal brace 6 is fixedly connected to the bottom of the support pile 1 near the center of the foundation pit.

[0028] The working principle is as follows:

[0029] The double-row fender pile 1 has inconsistent length, and the oblique grouting steel pipe / self-stabilizing reinforcing oblique support 6 is arranged to provide a space for accommodating silt soil, to accumulate and compact the silt soil, to store more soil outside the double-row fender pile 1 to strengthen the self-stabilizing effect, and to effectively prevent the supporting structure from rotating (i.e. overturning) towards the foundation pit with the bottom end as the fulcrum as the deep foundation pit is excavated.

[0030] During the construction of the supporting structure, the double-row fender pile 1 is as close as possible to the side wall of the foundation pit, so that the self-stabilizing reinforcing oblique support 6 at the bottom of the supporting structure can accommodate and compact the silt soil as much as possible, thereby enhancing the self-stabilizing effect. Example Three

[0031] Different from the example one, as shown in Figure 4 , Figure 5 , the silt soil accumulation inclined plate 8 is fixedly connected to the self-stabilizing reinforcing oblique support 6, the inclined plate 8 forms an angle (a right obtuse angle) with the horizontal line, and the self-stabilizing reinforcing oblique support 6 is further provided with a plurality of buffer cross piles 7 located above the inclined plate 8, and the buffer cross piles 7 are fixedly connected to the self-stabilizing reinforcing oblique support 6 through the rubber columns 9.

[0032] The working principle is as follows:

[0033] On the basis of the inconsistent length of the double-row fender pile 1 and the oblique grouting steel pipe (i.e. the self-stabilizing reinforcing oblique support 6), the buffer cross piles 7 and the silt soil accumulation inclined plate 8 are arranged. The arrangement of the buffer cross piles 7 alleviates the pressure of the horizontal displacement of the foundation pit soil on the supporting structure, and the arrangement of the inclined plate 8 is conducive to the accumulation of silt soil, which can not only maintain the compacting effect after displacement (by utilizing the horizontal displacement of the foundation pit soil) but also ensure the stability of the supporting structure. The rubber columns 9 are used as intermediate connecting pieces between the buffer cross piles 7 and the self-stabilizing reinforcing oblique support 6 to absorb a certain degree of horizontal displacement force and reduce the horizontal displacement trend of the entire supporting structure. Example Four

[0034] Different from the example three, as shown in Figure 6 , Figure 7 , even for the middle silt soil layer, a similar inclined chute is arranged, i.e. the double-row fender pile 1 has inconsistent length, the fender pile 1 away from the center of the foundation pit is composed of an upper segment and a lower segment, a spacing is arranged between the upper segment and the lower segment, the spacing is the difference between the length of any fender pile 1 in the front row and the length of any fender pile 1 in the rear row (the lengths of the fender piles 1 in the same row are consistent), the upper segment and the lower segment are fixedly connected through two self-stabilizing reinforcing oblique supports 6 with connected ends, the other ends of the two self-stabilizing reinforcing oblique supports 6 are fixedly connected to the upper segment and the lower segment respectively, the silt soil accumulation inclined plate 8 is fixedly connected to the self-stabilizing reinforcing oblique support 6 located at the lower side, and the buffer cross piles 7 are fixedly connected to the two self-stabilizing reinforcing oblique supports 6 through the rubber columns 9.

[0035] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the technical principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A self-stabilizing support structure for deep foundation pits, characterized in that, It consists of at least one row of retaining piles, a capping plate fixedly installed on top of the retaining piles, and diagonal bracing. The diagonal bracing is fixedly connected to the retaining piles and / or the capping plate. The diagonal bracing consists of a front diagonal bracing and a rear diagonal bracing. Several self-stabilizing reinforcing members are fixedly installed on the rear diagonal bracing or the retaining piles away from the center of the pit. The two rows of retaining piles have different lengths, with the retaining piles closer to the center of the pit being longer than those farther away. The bottom of the two rows of retaining piles is fixedly connected to self-stabilizing reinforcing diagonal bracing. The top of the self-stabilizing reinforcing diagonal bracing is fixedly connected to the bottom of the retaining piles away from the center of the pit, and the bottom of the self-stabilizing reinforcing diagonal bracing is fixedly connected to the bottom of the retaining piles closer to the center of the pit. A silty soil accumulation inclined plate is fixedly connected to the self-stabilizing reinforcing diagonal bracing. The inclined plate forms a positive obtuse angle with the horizontal line. Several buffer horizontal piles located above the inclined plate are also installed on the self-stabilizing reinforcing diagonal bracing. The buffer horizontal piles are fixedly connected to the self-stabilizing reinforcing diagonal bracing through rubber columns.

2. The deep foundation pit self-stabilizing support structure according to claim 1, characterized in that, The self-stabilizing reinforcement is an auxiliary brace fixedly connected to the surface of the rear brace away from the center of the pit. The size of the auxiliary brace is smaller than that of the rear brace, and the auxiliary brace forms an angle of 90 to 120° with the rear brace.

3. The self-stabilizing support structure for deep foundation pits according to claim 1, characterized in that, The self-stabilizing reinforcement is an auxiliary diagonal brace fixedly connected to the surface of the retaining pile away from the center of the pit. The size of the auxiliary diagonal brace is smaller than that of the retaining pile, and the auxiliary diagonal brace forms an angle of 45 to 60 degrees with the retaining pile.

4. The deep foundation pit self-stabilizing support structure according to claim 2 or 3, characterized in that, Both the front and rear diagonal braces are single-row grouting steel pipes; The capping plate is a 20cm thick reinforced concrete capping plate, and the steel bars inside the capping plate are HPB300 grade steel bars and HRB400 grade steel bars; The retaining piles are cast-in-place piles with a diameter of 80cm and a spacing of 200cm.

5. The deep foundation pit self-stabilizing support structure according to claim 4, characterized in that, The retaining piles are arranged in two rows. The top of the diagonal brace is fixedly connected to the capping plate, and the middle part of the diagonal brace is fixedly connected to the retaining piles.

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