Reinforcing system for stiff piles in passive area in foundation pit and construction method of reinforcing system

Abstract

The invention relates to a passive area stiff pile reinforcing system in a foundation pit and a construction method of the passive area stiff pile reinforcing system. The passive area stiff pile reinforcing system comprises pit edge fender posts (1), an enclosing purlin system (2), a passive area inclined strut system (3), a vertical supporting system (4), a horizontal supporting system (5) and a reinforcing body (6). The pit side fender posts (1) are connected into a whole through the enclosing purlin system (2) and connected with the horizontal supporting system (5), one end of the passive area inclined strut system (3) is connected with or abuts against the pit side fender posts (1), the other end of the passive area inclined strut system (3) is connected with the horizontal supporting system (5), the vertical supporting system (4) is connected with the horizontal supporting system (5), and the reinforcing body (6) is arranged in the end area, making contact with the pit side fender posts (1), of the passive area inclined strut system (3). Compared with the prior art, the method has the advantages of being good in foundation pit deformation control effect, remarkable in foundation pit safety improvement, environmentally friendly and the like.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, and in particular to a passive zone stiffening pile reinforcement system for foundation pits and its construction method. Background Technology

[0002] In current foundation pit retaining systems, the common approach is to install retaining piles along the edge of the pit combined with horizontal or vertical bracing inside the pit. This approach has the following problems:

[0003] First, the support system inside the foundation pit is always constructed after the earthwork excavation reaches the support elevation, i.e., "excavate first, then support". The area with the greatest deformation is always located near the excavation surface of the foundation pit, resulting in the foundation pit deformation increasing with the increase of excavation depth.

[0004] Secondly, in order to control the deformation of the pit bottom, the common practice is to set up mixing piles, high-pressure jet grouting piles, and other methods to reinforce the pit in the passive zone. However, on the one hand, since the construction of the reinforced body is an underground project, the construction dispersion is large and the quality is difficult to guarantee. On the other hand, although the reinforced body has a certain strength, its stiffness is much lower than that of the retaining piles. Therefore, the effect of controlling the deformation of the retaining piles by setting up passive zone reinforcement is not ideal.

[0005] In addition, because the support arrangement needs to create conditions for basement construction, the last support generally needs to meet the construction space requirement of about 3m from the bottom of the basement floor. This results in the bottom of the pit, where the retaining piles are most unfavorable to the pit, having no rigid support before the completion of the floor construction. To meet the strength and stability requirements of the retaining piles in this condition, the retaining piles need to be inserted a long length below the excavation surface of the pit, resulting in high cost of retaining structures for pit projects, especially deep pit projects. Summary of the Invention

[0006] The purpose of this invention is to provide a passive zone stiffening pile reinforcement system and its construction method for foundation pits, which has a good effect on foundation pit deformation control.

[0007] The objective of this invention can be achieved through the following technical solution: a passive zone stiffening pile reinforcement system for foundation pits, comprising pit edge retaining piles, a waler system, a passive zone inclined bracing system, a vertical support system, a horizontal support system, and a reinforcement body;

[0008] The waler system connects the pit edge retaining piles into a whole and connects to the horizontal support system. One end of the passive zone diagonal bracing system is connected to or tightened to the pit edge retaining piles, and the other end is connected to the horizontal support system. The vertical support system is connected to the horizontal support system. The solidification body is set in the end area where the passive zone diagonal bracing system contacts the pit edge retaining piles.

[0009] Preferably, the passive zone inclined bracing system has an ungrouted bag at the pile end. After grouting, the ungrouted bag becomes a grouted bag, and the grouted bag and the reinforced body form a rigid composite.

[0010] More preferably, the grouting uses cement grout with a strength not lower than P.O42.5 or other curing agents with a strength not lower than this.

[0011] In this invention, before construction, ungrouted bags are set at the pile ends of the passive zone inclined bracing system. After construction, grout is injected into the ungrouted bags to form grout bags with a certain strength after volume expansion, which together with the reinforced body constitute a rigid composite.

[0012] Preferably, the solidified material is formed by mixing a curing agent with soil.

[0013] Preferably, the solidified body extends upwards to the ground.

[0014] Preferably, the passive zone bracing system is inclined, with one end connected to or tightened to the side of the pit retaining piles near the pit, and the other end rigidly connected to the horizontal support system.

[0015] Preferably, multiple retaining piles are arranged vertically parallel and spaced apart along the edge of the pit, and the waler system is arranged on the top of the retaining piles and / or on the side close to the pit.

[0016] More preferably, the cross-sectional dimensions and spacing of the retaining piles at the pit edge must meet the strength and deformation requirements when the pit is excavated to the bottom, and the vertical insertion depth into the soil must meet the stability requirements of the pit when it is excavated to the bottom.

[0017] More preferably, the waler system is installed at the top of the retaining piles at the pit edge and on the side near the pit, and both the waler system at the top of the retaining piles at the pit edge and on the side near the pit are connected to a horizontal support system.

[0018] Preferably, the retaining piles along the pit edge are steel structures or reinforced concrete structures.

[0019] Preferably, the waler system is a steel structure or a reinforced concrete structure.

[0020] Preferably, the horizontal support system is a steel structure and / or a reinforced concrete structure.

[0021] Preferably, the horizontal support system has one or more channels along the depth direction.

[0022] Preferably, the passive zone diagonal bracing system has one or more channels along the depth direction.

[0023] Preferably, the horizontal support system and the passive zone diagonal bracing system are provided in two layers along the depth direction.

[0024] A construction method for the above-mentioned passive zone stiffening pile reinforcement system in the foundation pit includes the following steps:

[0025] Step 1: Simultaneous construction of the construction pit retaining piles, vertical support system, passive zone inclined bracing system and reinforcement body, with the un-grouted bags fixed to the pile ends of the passive zone inclined bracing system. At this time, the earthwork excavation surface is located on the ground.

[0026] Step 2: After grouting the un-grouted bags, grouting bags are formed. The construction waler system, horizontal support system, and the junctions of the horizontal support system, vertical support system, and passive zone diagonal bracing system are all rigidly connected. At this time, the earthwork excavation surface is located at the bottom of the first support.

[0027] Step 3: Excavate the foundation pit to the bottom of the second support. The waler system and horizontal support system are constructed. The junctions of the horizontal support system, vertical support system and passive zone diagonal bracing system are all rigidly connected. At this time, the excavation surface is located at the bottom of the second support.

[0028] Step 4: After the second support is formed, excavate the earth to the bottom of the pit, and simultaneously cut and recover the first passive zone diagonal bracing system. At this time, the earth excavation surface is located at the bottom of the pit.

[0029] Step 5: After the earthwork excavation is completed, construct the basement floor slab. The basement floor slab should be tightly or reliably connected to the retaining piles at the edge of the pit. The basement floor slab should also be reliably connected to the boundary area of ​​the passive zone bracing system and waterproof joints should be installed.

[0030] Step 6: After the basement floor slab is formed, cut off and reclaim the passive zone bracing system above the basement floor slab.

[0031] Preferably, the first-stage pit retaining piles, vertical support system, passive zone inclined bracing system, and reinforced body are located below ground level.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The passive zone stiffening pile reinforcement system in the foundation pit of this invention sets the rigid support below the excavation surface, realizing the concept of "support first and then excavate", and has a good deformation control effect;

[0034] 2. The passive zone stiffening pile reinforcement system in the foundation pit of this invention combines rigid support with passive zone reinforcement to form a stiffening composite, which makes construction quality easy to control and reinforcement effect easy to guarantee;

[0035] 3. The passive zone stiffening pile reinforcement system in the foundation pit of this invention will add a passive zone inclined support system within the horizontal and vertical support system, and transfer the support force to the constructed horizontal and vertical support system. The force transmission path is clear, reliable and safe.

[0036] 4. The passive zone stiffening pile reinforcement system in the foundation pit of the present invention can set the support point of the retaining piles at the bottom of the basement floor, without having to consider the construction operation space problem. It can greatly improve the cross-sectional stability of the original retaining system and shorten the length of the retaining piles under the same safety conditions, thus saving project costs.

[0037] 5. The passive zone stiffening pile reinforcement system in the foundation pit of this invention can be gradually removed after the basement floor slab construction is completed, without affecting the basement construction. Some of it can be recycled and reused, making it green and environmentally friendly. Attached Figure Description

[0038] Figure 1 This is a side view of a passive zone stiffening pile reinforcement system for foundation pits according to the present invention.

[0039] Figure 2 This is a top view of a passive zone stiffening pile reinforcement system for foundation pits according to the present invention;

[0040] Figure 3 This is a cross-sectional view of the construction conditions of a passive zone stiffening pile reinforcement system in a foundation pit according to the present invention—the first step;

[0041] Figure 4 This is a cross-sectional view of the construction conditions of a passive zone stiffening pile reinforcement system in a foundation pit according to the present invention—the second step;

[0042] Figure 5 This is a cross-sectional view of the construction conditions of a passive zone stiffening pile reinforcement system in a foundation pit according to the present invention—step three;

[0043] Figure 6 This is a cross-sectional view of the construction conditions of a passive zone stiffening pile reinforcement system in a foundation pit according to the present invention—step four;

[0044] Figure 7 This is a cross-sectional view of the construction conditions of a passive zone stiffening pile reinforcement system in a foundation pit according to the present invention—step five;

[0045] Figure 8 This is a cross-sectional view of the construction conditions of a passive zone stiffening pile reinforcement system in a foundation pit according to the present invention—step six;

[0046] In the diagram: 1-Pit retaining pile, 2-Wallet system, 3-Passive zone bracing system, 31-Ungrouted bag, 32-Grouted bag, 4-Vertical support system, 5-Horizontal support system, 6-Rigid composite structure, 7-Basement floor slab, 8-Waterproofing node, 9-Excavation face. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] Example 1

[0049] A passive zone reinforcement system for foundation pits includes pit retaining piles 1, waler system 2, passive zone inclined bracing system 3, vertical support system 4, horizontal support system 5, and reinforcement body 6.

[0050] The waler system 2 is installed on top of the retaining piles 1 at the pit edge and / or on one side near the pit, connecting the retaining piles 1 into a whole. The waler system 2 is connected to the horizontal support system 5. One end of the passive zone diagonal bracing system 3 is connected to or tightened against the retaining piles 1 at the pit edge, and the other end is rigidly connected to the horizontal support system 5. The vertical support system 4 is rigidly connected to the horizontal support system 5. The reinforcement body 6 is installed at the end area where the passive zone diagonal bracing system 3 contacts the retaining piles 1 at the pit edge. The end area where the passive zone diagonal bracing system 3 contacts the retaining piles 1 at the pit edge also has an ungrouted bag 31. After grouting, the ungrouted bag 31 can become a grouted bag 32 and form a rigid composite with the reinforcement body 6.

[0051] Example 2

[0052] A passive zone stiffening pile reinforcement system for foundation pits, such as Figures 1-2 As shown, it includes pit-side retaining piles 1, retaining pile top or inner waler system 2, passive zone diagonal bracing system 3, vertical support system 4, horizontal support system 5, and reinforcement body 6.

[0053] One end of the passive zone inclined bracing system 3 is connected to or tightened with the pit edge retaining pile 1, and the pile end is surrounded by reinforced bodies 6. The other end is rigidly connected to the horizontal support system 5. The vertical support system 4 is rigidly connected to the horizontal support system 5 at the intersection of the systems.

[0054] The function of the retaining piles 1 is to prevent soil and groundwater from entering the pit. Their material can be steel or reinforced concrete. The function of the waler system 2 (top or inner side of the retaining piles) is to connect the retaining piles 1 into a whole and effectively connect with the horizontal support system 5 to share the load. Its material can also be steel or reinforced concrete. The passive zone bracing system 3 has its pile ends located below the excavation surface of the pit. The pile ends contact the retaining piles 1 below the excavation surface, limiting the deformation of the retaining piles 1 below the excavation surface during excavation. It is generally installed at an angle, with one end tightly against the retaining piles 1 and the other end rigidly connected to the horizontal support system 5. The area where it intersects with the horizontal support system 5 also needs a rigid connection. Its material can be steel or reinforced concrete. Multiple passive zone bracing systems 3 can be installed along the depth direction, and can also be installed at regular intervals along the edge of the pit. The vertical support system 4 provides vertical bearing capacity, ensuring the vertical stress requirements and stability of the horizontal support system 5 and the passive zone diagonal bracing system 3. Its materials can be steel, reinforced concrete, or a combination of both. The horizontal support system 5 provides horizontal bearing capacity, working in conjunction with the pit retaining piles 1, the vertical support system 4, and the passive zone diagonal bracing system 3. The members of the horizontal support system 5, rigidly connected to the passive zone diagonal bracing system 3, must simultaneously meet the horizontal force transmission requirements of the passive zone diagonal bracing system 3 and the vertical force transmission requirements to the adjacent vertical support system 4. Its materials can be steel, reinforced concrete, or a combination of both. It can consist of one member or multiple members along the depth direction. The grouting bags 32 attached to the pile ends of the passive zone inclined support system 3, along with the surrounding mixing piles and jet grouting piles, form a rigid composite structure 6 composed of a solidified body 6 with a certain rigidity and strength, formed by mixing cement, GS soil hardener, and other curing agents with the soil. This structure works in conjunction with the passive zone inclined support system 3 to share the load, increasing the contact area with the pit-side retaining piles 1 and enhancing the resistance of the passive zone. The grouting bags 32 increase the contact area between the pile ends of the passive zone inclined support system 3 and the pit-side retaining piles 1. The ungrouted bags 31 are tightly attached to the passive zone inclined support system 3 and fixed to the pile ends of the passive zone inclined support system 3 before construction, and are constructed simultaneously with it. After the passive zone inclined support system 3 is constructed to the designated position, cement grout or other curing agents with a certain rigidity and strength are injected to form the grouting bags 32 with increased volume. The grouting material is cement grout with a strength not lower than PO 42.5 or other types of curing agent materials with a strength not lower than that of cement grout.

[0055] In this embodiment, as Figures 3-8 As shown, the construction process of a passive zone stiffening pile reinforcement system in a foundation pit includes:

[0056] Step 1: Simultaneous construction of the construction pit retaining pile 1, vertical support system 4, passive zone inclined bracing system 3 and reinforcement body 6, and the ungrouted bag 31 fixed to the pile end of passive zone inclined bracing system 3. At this time, the earthwork excavation surface 9 in the pit is located on the ground.

[0057] Step 2: After grouting, grouting bags 32 are formed. The construction waler system 2, horizontal support system 5, and the junction of the horizontal support system 5, the vertical support system 4, and the passive zone inclined support system 3 are all rigidly connected. At this time, the earthwork excavation surface 9 is located at the bottom of the first support.

[0058] Step 3: Excavate the foundation pit to the bottom of the second support, construct the waler system 2 and the horizontal support system 5. The horizontal support system 5, the vertical support system 4 and the passive zone inclined bracing system 3 are all rigidly connected at their junctions. At this time, the excavation surface 9 is located at the bottom of the second support.

[0059] Step 4: After the second support is formed, excavate the earth to the bottom of the pit, and simultaneously cut and recover the first passive zone inclined support system 3. At this time, the earth excavation surface 9 is located at the bottom of the pit.

[0060] Step 5: After the earthwork excavation is completed, construct the basement floor slab 7. The basement floor slab 7 is tightly attached to or reliably connected to the pit edge retaining piles 1. The basement floor slab 7 is reliably connected to the boundary area of ​​the passive zone inclined bracing system 3 and waterproof nodes 8 are set.

[0061] Step 6: After the basement floor slab 7 is formed, cut off and reclaim the passive zone diagonal bracing system 3 above the basement floor slab 7.

[0062] Comparative analysis with existing support systems:

[0063] Currently, the support system mainly embodies the strength control concept of retaining piles, but its ability in deformation control is limited, especially for deep and large foundation pit projects, where the deformation control effect is not ideal. The main reasons are as follows: 1) The support system is constructed after excavation, and the deformation has fully developed after excavation, which is not conducive to deformation control; 2) Construction space needs to be reserved under the support, resulting in a certain distance between the support and the bottom of the foundation pit. The force balance of the retaining piles below the bottom of the foundation pit depends on the soil reaction force. Since the reaction force that a unit of soil can provide is limited, when the soil quality is poor, a longer insertion depth and a deeper passive zone are required; 3) Measures to improve soil resistance by setting soil mixing piles, jet grouting piles, etc. at the bottom of the pit are usually difficult to achieve the ideal deformation control effect due to the difficulty in ensuring construction quality and the limited width of the reinforced body. This invention overcomes the shortcomings of traditional retaining structure support systems by setting diagonal bracing in the passive zone of the pit and establishing near-rigid support points below the excavation surface. Firstly, the support can be pre-installed below the excavation surface, changing the "excavate first, then brace" approach to "brace first, then excavate," controlling the deformation of the retaining piles from the source and transferring the support force to the horizontal and vertical support systems with a clear and reliable force transmission path. Secondly, the passive zone diagonal support system is only arranged at the edge of the pit, having no impact on large-area basement construction. There is no need to consider reserving construction space under the support, and the support points can be placed below the bottom slab, facilitating construction and significantly improving the safety of the retaining structure. Finally, the passive zone diagonal support system connects the pit edge reinforcement body with the diagonal bracing system to form a rigid reinforcement body, ensuring the quality and effectiveness of the reinforcement. This invention has advantages such as good pit deformation control, significant improvement in pit safety, and environmental friendliness.

[0064] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A passive zone stiffening pile reinforcement system for foundation pits, characterized in that, The pit edge support pile (1), the purlin system (2), the passive area inclined support system (3), the vertical support system (4), the horizontal support system (5) and the reinforcement (6) are connected as a whole by the purlin system (2) and connected with the horizontal support system (5), one end of the passive area inclined support system (3) is connected or tightly connected with the pit edge support pile (1), and the other end is connected with the horizontal support system (5), the vertical support system (4) is connected with the horizontal support system (5), and the reinforcement (6) is arranged in the end region of the passive area inclined support system (3) contacting with the pit edge support pile (1). The pit edge support pile (1), the purlin system (2), the passive area inclined support system (3), the vertical support system (4), the horizontal support system (5) and the reinforcement (6) are connected as a whole by the purlin system (2) and connected with the horizontal support system (5), one end of the passive area inclined support system (3) is connected or tightly connected with the pit edge support pile (1), and the other end is connected with the horizontal support system (5), the vertical support system (4) is connected with the horizontal support system (5), and the reinforcement (6) is arranged in the end region of the passive area inclined support system (3) contacting with the pit edge support pile (1).

2. The passive zone stiffness pile reinforcement system in a foundation pit according to claim 1, characterized in that, The ungrouting bag (31) is arranged at the end of the passive area inclined support system (3), and the ungrouting bag (31) becomes the grouting bag (32) after grouting, and the grouting bag (32) and the reinforcement (6) form a stiff composite.

3. The passive zone system of claim 2, wherein, The grouting uses cement slurry with strength not less than P.O42.5 or other solidifying agent with strength not less than P.O42.

5.

4. The passive zone system of claim 1, wherein, The reinforcement (6) is formed by mixing the solidifying agent and the soil.

5. The passive zone system of claim 1, wherein, The passive area inclined support system (3) is arranged obliquely, one end of which is connected or tightly connected with the pit edge support pile (1) near the side of the foundation pit, and the other end is rigidly connected with the horizontal support system (5).

6. The passive zone system of claim 1, wherein, A plurality of pit edge support piles (1) are vertically and parallelly arranged at the pit edge, and the purlin system (2) is arranged at the top of the pit edge support pile (1) and / or near the side of the foundation pit.

7. The passive zone system of claim 6, wherein, The purlin system (2) is arranged at the top of the pit edge support pile (1) and near the side of the foundation pit, and the purlin system (2) is connected with the horizontal support system (5) at the top of the pit edge support pile (1) and near the side of the foundation pit.

8. The passive zone system of claim 1, wherein, The pit edge support pile (1) is a steel structure or a reinforced concrete structure, and the purlin system (2) is a steel structure or a reinforced concrete structure.

9. The passive zone system of claim 1, wherein, The horizontal support system (5) is a steel structure and / or a reinforced concrete structure and is provided with one or more rows in the depth direction. The passive area inclined support system (3) is provided with one or more rows in the depth direction.

10. A construction method of the stiff pile reinforcement system in the passive zone of the foundation pit according to any one of claims 1-9, characterized in that, The method comprises the following steps: In the first step, the pit edge support pile (1), the vertical support system (4), the passive area inclined support system (3) and the reinforcement (6) are constructed, the ungrouting bag (31) is fixed to the end of the passive area inclined support system (3) and is simultaneously constructed, and the soil excavation surface (9) is located on the ground; In the second step, the ungrouting bag (31) is grouted to form the grouting bag (32), the purlin system (2) and the horizontal support system (5) are constructed, the horizontal support system (5) is rigidly connected with the vertical support system (4) and the passive area inclined support system (3) at the junction, and the soil excavation surface (9) is located on the first support bottom; In the third step, the foundation pit soil is excavated to the second support bottom, the purlin system (2) and the horizontal support system (5) are constructed, the horizontal support system (5) is rigidly connected with the vertical support system (4) and the passive area inclined support system (3) at the junction, and the soil excavation surface (9) is located on the second support bottom; In the fourth step, after the second support is formed, the soil is excavated to the pit bottom, the first passive area inclined support system (3) is simultaneously cut off and recycled, and the soil excavation surface (9) is located on the pit bottom; Step 5: After the completion of the earthwork, the basement floor (7) is constructed, which is closely attached to or reliably connected with the pit edge support pile (1), and the basement floor (7) is reliably connected with the passive area diagonal bracing system (3) at the junction area and a waterproof joint (8) is arranged; Step 6: After the basement floor (7) is formed, the passive area diagonal bracing system (3) above the basement floor (7) is cut off and recycled.

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