阅读说明：本技术 桩基托换施工中的基坑回填方法 (Foundation pit backfill method in pile foundation underpinning construction ) 是由 闵健 杨志刚 周浩 刘兰其 蒋艳 胡光华 于 2020-10-30 设计创作，主要内容包括：本发明公开了一种桩基托换施工中的基坑回填方法,该基坑回填方法在基坑内完成桩基托换结构的施工后,将基坑底的松散杂质清理干净,再将土方回填摊铺到基坑底部形成一层厚度为200mm～250mm的回填土层,然后将该层回填土层夯实形成一层夯实层,最后按照该方法再依次施工一层以上夯实层,直至将基坑填满。采用该基坑回填方法可提高回填密实度,对桩基托换结构影响小,可提高施工安全性、提高桩基托换结构的稳定性、提高桩基托换施工质量。(The invention discloses a foundation pit backfilling method in pile foundation underpinning construction, which is characterized in that after the construction of a pile foundation underpinning structure is completed in a foundation pit, loose impurities at the bottom of the foundation pit are cleaned, earthwork is backfilled and spread to the bottom of the foundation pit to form a backfill soil layer with the thickness of 200-250 mm, the backfill soil layer is tamped to form a tamping layer, and at least one tamping layer is sequentially constructed according to the method until the foundation pit is filled. By adopting the foundation pit backfilling method, the backfilling compactness can be improved, the influence on the pile foundation underpinning structure is small, the construction safety can be improved, the stability of the pile foundation underpinning structure can be improved, and the pile foundation underpinning construction quality can be improved.)

1. A foundation pit backfilling method in pile foundation underpinning construction is characterized by comprising the following steps:

(A) after the construction of the pile foundation underpinning structure is completed in the foundation pit, cleaning loose impurities at the bottom of the foundation pit;

(B) backfilling and paving earthwork to the bottom of the foundation pit to form a backfill soil layer with the thickness of 200-250 mm, and then tamping the backfill soil layer to form a tamped layer;

(C) and (C) constructing more than one layer of rammed layer in sequence according to the method in the step (B) until the foundation pit is filled.

2. The method of claim 1, wherein during the tamping of each backfill layer, the backfill layers are tamped around the pile foundation underpinning structure to form an annular tamped layer, such that an annular gap is left between the annular tamped layer and the pile foundation underpinning structure, and the backfill layers in the annular gap are tamped in a symmetrical manner.

3. The method for backfilling a foundation pit according to claim 2, wherein the step of symmetrically compacting the backfill soil layer of the annular gap is carried out by dividing the annular gap into a plurality of pairs of compacting zones symmetrically distributed with respect to the pile foundation underpinning structure, and compacting the backfill soil layer of the plurality of pairs of compacting zones pair by pair.

4. The foundation pit backfilling method according to claim 3, wherein the tamping is performed three or more times when the backfill soil layer of each pair of tamping zones is tamped, and the backfill soil layer of one tamping zone is tamped first and then the backfill soil layer of the other tamping zone is tamped each time.

5. The method of claim 4, wherein the backfill layer in each lateral ramming zone is progressively compacted from a location remote from the pile underpinning structure in a direction toward the pile underpinning structure during the tamping of the backfill layer.

6. The method as claimed in claim 1, wherein during backfilling and paving each backfill soil layer, an annular soil layer is formed by backfilling and paving from the pile foundation underpinning structure toward the sidewall of the foundation pit, an annular space is left between the annular soil layer and the pile foundation underpinning structure, and then earthwork is backfilled and paved toward the annular space in a symmetrical manner.

7. The method for backfilling a foundation pit according to claim 6, wherein the symmetrically backfilling of earthwork to the annular space is carried out by dividing the annular gap into a plurality of pairs of backfilled paving areas symmetrically distributed relative to the pile foundation underpinning structure, and backfilling the earthwork to the plurality of pairs of backfilled paving areas.

8. The method of claim 6, wherein the annular gap is divided into two pairs of backfill paving zones, all of which are the same length in the axial direction around the annular gap.

9. The method of claim 1, wherein the loose impurities comprise loose soil, mortar and stones.

Technical Field

The invention relates to the technical field of civil engineering construction, in particular to a foundation pit backfilling method in pile foundation underpinning construction.

Background

With the vigorous development of urban construction, urban ground traffic is increasingly busy, and in order to relieve ground traffic pressure, the construction of convenient and rapid underground railways becomes a choice of a plurality of urban traffics. Because underground excavation construction underground railways have small influence on ground traffic, and the underground excavation method becomes the main construction method of urban underground railway construction along with the maturity of the underground excavation construction method, but inevitably can cross ground buildings, the pile foundation underpinning technology is needed to underpin the pile foundation of the ground buildings deeply into the tunnel, and the upper structure load born by the part of the pile foundation is transferred to the pile foundation outside the influence range of tunnel construction through the newly constructed underpinning structure.

After the pile foundation underpinning construction is completed, the excavated foundation pit needs to be backfilled, and the existing method for backfilling the foundation pit is to backfill earthwork into the foundation pit around the pile foundation underpinning structure, tamp the backfilled earthwork by adopting the step-by-step motion of a tamping device around the pile foundation underpinning structure, and then continuously backfill the earthwork around the pile foundation underpinning structure and tamp the backfilled earthwork so as to backfill the foundation pit. This kind of mode of asymmetric formula backfill and tamping for backfill and tamp the earthwork process and backfill accomplish the back earthwork relatively poor to pile foundation underpin structure lateral force equilibrium nature that produces all around, cause negative effects to the structural performance of pile foundation underpin structure, also can influence backfill accomplish the bearing performance and the stability of back pile foundation underpin structure, lead to the pile foundation underpin construction the quality relatively poor.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide the foundation pit backfilling method in pile foundation underpinning construction, which has good backfilling compactness and small influence on a pile foundation underpinning structure, and can improve construction safety, stability and construction quality.

In order to solve the technical problems, the invention adopts the following technical scheme:

a foundation pit backfilling method in pile foundation underpinning construction comprises the following steps:

(A) after the construction of the pile foundation underpinning structure is completed in the foundation pit, cleaning loose impurities at the bottom of the foundation pit;

(B) backfilling and paving earthwork to the bottom of the foundation pit to form a backfill soil layer with the thickness of 200-250 mm, and then tamping the backfill soil layer to form a tamped layer;

(C) and (C) constructing more than one layer of rammed layer in sequence according to the method in the step (B) until the foundation pit is filled.

Preferably, in the process of tamping each backfill layer, the backfill layer is tamped around the pile foundation underpinning structure to form an annular tamped layer, so that an annular gap is reserved between the annular tamped layer and the pile foundation underpinning structure, and then the backfill layer with the annular gap is tamped in a symmetrical mode.

Preferably, in the foundation pit backfilling method, the backfill soil layers in the annular gap are compacted in a symmetrical mode by dividing the annular gap into a plurality of pairs of compacting areas which are symmetrically distributed relative to the pile foundation underpinning structure, and compacting the backfill soil layers in the plurality of pairs of compacting areas one by one.

Preferably, when the backfill soil layer of each pair of tamping areas is tamped, the tamping passes are more than three times, and the backfill soil layer of one tamping area is tamped in each time, and then the backfill soil layer of the other tamping area is tamped.

Preferably, in the process of tamping the backfill soil layer in each side tamping area, the backfill soil layer is gradually tamped from the position far away from the pile foundation underpinning structure to the direction of the pile foundation underpinning structure.

Preferably, in the process of backfilling and paving each backfill soil layer, the pile foundation underpinning structure is backfilled and paved towards the side wall direction of the foundation pit to form an annular soil layer, an annular space is reserved between the annular soil layer and the pile foundation underpinning structure, and then the circular space is backfilled and paved with earthwork in a symmetrical mode.

Preferably, the backfilling and paving earthwork to the annular space by adopting a symmetrical mode is to divide the annular gap into a plurality of pairs of backfilling and paving areas which are symmetrically distributed relative to the pile foundation underpinning structure, and the backfilling and paving earthwork is backfilled to the plurality of pairs of backfilling and paving areas one by one.

In the above foundation pit backfilling method, preferably, the annular gap is divided into two pairs of backfilled paving areas, and the lengths of all the backfilled paving areas in the axial direction around the annular gap are the same.

In the above foundation pit backfilling method, preferably, the loose impurities include loose soil, mortar and stones.

Compared with the prior art, the invention has the advantages that:

the foundation pit backfilling method in the pile foundation underpinning construction of the invention adopts a mode of backfilling the foundation pit layer by layer and layer by layer in multiple layers, when each layer is backfilled, a backfill soil layer with the thickness of 200 mm-250 mm is paved firstly, and is tamped, so that the backfilling compactness is high, the quality is good, and compared with the traditional one-time backfilling and tamping method, the backfilling is divided into multiple layers, the lateral pressure of the paved and tamped earthwork on the pile foundation underpinning structure is smaller in the backfilling process of each layer, the lateral acting force on the pile foundation underpinning structure is not easy to cause negative influence on the pile foundation underpinning structure in the backfilling process, the lateral acting forces of the multiple layers of independently paved and tamped earthwork on the pile foundation underpinning structure can be partially offset mutually after the foundation pit is backfilled, and then improve the homogeneity of the lateral force that the pile foundation underpins the structure and receive, improve the bearing capacity and the stability of pile foundation underpins the structure, guarantee pile foundation underpins construction quality.

Drawings

Fig. 1 is a flowchart of a foundation pit backfilling method in pile underpinning construction.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

As shown in fig. 1, the method for backfilling a foundation pit in pile foundation underpinning construction of the embodiment includes the following steps:

(A) after the construction of the pile foundation underpinning structure is completed in the foundation pit, cleaning loose impurities at the bottom of the foundation pit, wherein the pile foundation underpinning structure is a connector of an underpinning pile, an underpinning beam and an underpinned pile foundation;

(B) backfilling and paving earthwork to the bottom of the foundation pit to form a backfill soil layer with the thickness of 200-250 mm, and then tamping the backfill soil layer to form a tamped layer;

(C) and (C) constructing more than one ramming layer in sequence according to the method in the step (B) until the foundation pit is filled.

The foundation pit backfilling method in the underpinning construction of the pile foundation adopts a mode of backfilling the foundation pit in layers layer by layer and layer by layer, when each layer is backfilled, a backfill soil layer with the thickness of 200 mm-250 mm is paved firstly, and is tamped, so that the backfilling compactness is high, the quality is good, and compared with the traditional one-time backfilling and tamping method, the backfilling is divided into multiple layers, the lateral pressure of the paved and tamped earthwork on the pile foundation underpinning structure is smaller in the backfilling process of each layer, the lateral acting force on the pile foundation underpinning structure is not easy to cause negative influence on the pile foundation underpinning structure in the backfilling process, the lateral acting forces of the multiple layers of independently paved and tamped earthwork on the pile foundation underpinning structure can be partially offset mutually after the foundation pit is backfilled, and then improve the homogeneity of the lateral force that the pile foundation underpins the structure and receive, improve the bearing capacity and the stability of pile foundation underpins the structure, guarantee pile foundation underpins construction quality.

In this embodiment, in the process of tamping each backfill soil layer, the backfill soil layer is tamped around the pile foundation underpinning structure to form an annular tamped layer, so that an annular gap is left between the annular tamped layer and the pile foundation underpinning structure, and then the backfill soil layer in the annular gap is tamped in a symmetrical manner. Leave an annular clearance between annular layer of ramming and the pile foundation underpinning structure, not contacted with the pile foundation underpinning structure by the earthwork when ramming annular layer of ramming, can not form the side direction effort to the pile foundation underpinning structure, construction that can be quick to can improve the efficiency of construction greatly. Furthermore, the backfill soil layer of the annular gap is tamped in a symmetrical mode, the stress of the pile foundation underpinning structure is even, the influence on the pile foundation underpinning structure is small, and the improvement of the pile foundation underpinning construction quality is facilitated.

Preferably, the backfill soil layer tamping the annular gap in a symmetrical mode is to divide the annular gap into a plurality of pairs of tamping areas which are symmetrically distributed relative to the pile foundation underpinning structure, and tamp the backfill soil layers of the plurality of pairs of tamping areas one by one.

In the embodiment, when the backfill soil layer of each pair of tamping areas is tamped, the tamping pass is more than three times, the backfill soil layer of one side of the tamping area is tamped each time, and the backfill soil layer of the other side of the tamping area is tamped, so that the tamping is performed for multiple times, the compactness of the backfill soil can be improved, and the problem that the lateral stress of the pile foundation replacement structure is too large in the tamping process can be avoided.

In this embodiment, carry out the tamping in-process to the backfill soil layer in each side tamping zone, progressively tamp to the direction of pile foundation underpinning structure from the position of keeping away from pile foundation underpinning structure, make the lateral force that pile foundation underpinning structure receives increase gradually, do benefit to the reduction and do benefit to the influence to pile foundation underpinning structure.

In this embodiment, in the process of backfilling and paving each backfill soil layer, an annular soil layer is formed by backfilling and paving from the pile foundation underpinning structure to the side wall direction of the foundation pit, an annular space is left between the annular soil layer and the pile foundation underpinning structure, and then earthwork is backfilled and paved to the annular space in a symmetrical mode. Have certain space between when backfilling annular soil layer and the pile foundation underpinning structure, be difficult for causing the interference, and fill out that the machinery is difficult for touchhing the pile foundation underpinning structure, make the completion construction that annular soil layer can be quick, provide the efficiency of construction. Furthermore, the earthwork is backfilled and paved in the annular space in a symmetrical mode, so that the influence of the earthwork on the pile foundation underpinning structure is small, the stress of the pile foundation underpinning structure is uniform, and the improvement of the pile foundation underpinning construction quality is facilitated.

Preferably, the step of backfilling and paving earthwork to the annular space in a symmetrical mode is to divide the annular gap into a plurality of pairs of backfilling and paving areas which are symmetrically distributed relative to the pile foundation underpinning structure, and the earthwork is backfilled and paved on the plurality of pairs of backfilling and paving areas.

In this embodiment, the annular gap is divided into two pairs of backfill paving areas, and the lengths of all the backfill paving areas are the same in the axial direction around the annular gap, so that the stress of the pile foundation underpinning structure is uniform and better.

In the embodiment, the loose impurities comprise loose soil, mortar and stones, and the impurities are removed, so that the backfill soil can be better combined with the interior of the foundation pit, and the compactness is improved.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. Modifications and variations that may occur to those skilled in the art without departing from the spirit and scope of the invention are to be considered as within the scope of the invention.