Construction method for preventing settlement of buried drainage pipeline in soft foundation

Abstract

The invention discloses a construction method for preventing settlement of an underground drainage pipeline in a soft foundation. The construction method comprises the steps of trench excavation, replacement filling treatment on the bottom of the pipeline after excavation, pipeline route planning and measurement, settlement transition section construction, pipeline installation and trench backfilling. According to the novel construction method for preventing the underground drainage pipeline from settling in the soft foundation, the problem of uneven settlement of the underground drainage pipeline in the existing soft foundation is solved, the settlement difference of the foundations at adjacent parts is reduced, the deformation difference along the pipeline is reduced, the problem of tension fracture of the pipeline due to differential settlement is avoided, the welding seam strength of the pipeline can be enhanced, and the service life of the pipeline is prolonged. The inner plastic-coated layer at the welding seam is prevented from being damaged, the construction procedures are few, and the construction of the buried drainage pipeline in the soft foundation is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of drainage pipeline construction in soft foundation, and in particular to a construction method for preventing subsidence of buried drainage pipelines in soft foundation. Background Art

[0002] Structures in soft soil areas often use pile foundations, with almost no settlement. However, because the foundation soil layer of the buried drainage pipes connected to the structures is mainly soft soil and silt soil, the foundation bearing capacity of soft soil and silt soil is below 12kpa. Therefore, buried drainage steel pipes often have the following problems due to low foundation bearing capacity:

[0003] 1) The pipeline settles unevenly, which causes the connection weld to be damaged during installation;

[0004] 2) When the pipeline is installed and welded, the joint structure is set unreasonably, resulting in the destruction of the inner plastic coating layer at the weld;

[0005] 3) At the connection between the pipeline and the structure, since the structure has a brick foundation with very little settlement, while the pipeline settles greatly in the soft foundation, there is a large settlement difference, which causes damage to the nearby welds, leading to problems such as pipeline cracking and leakage. Summary of the invention

[0006] In view of the technical problems existing in the existing pipeline and flange welding construction process, the technical problem to be solved by the present invention is to provide a new installation method for buried drainage pipes in soft foundations, which solves the problems existing in traditional construction methods, reduces the foundation settlement difference of adjacent parts, reduces the deformation difference along the pipeline, avoids the problem of pipeline cracking due to differential settlement, strengthens the strength of the pipeline weld, avoids the damage of the inner plastic coating layer at the weld, and provides a construction method that is convenient for construction.

[0007] In order to solve the problems of the prior art, the present invention provides a construction method for preventing the settlement of an underground drainage pipe in a soft foundation, and the construction method includes the following construction process:

[0008] Step 1) Trench excavation: Use steel plate column support and excavate in sections;

[0009] Step 2) After excavation, the bottom of the pipeline is replaced: the silt at the bottom of the pre-buried pipeline is filled with rubble sand layers and crushed stone layers in layers and compacted to reserve the pipeline position;

[0010] Step 3) Pipeline route planning and measurement: After the pipeline comes out of the structure, an upward inclination angle is set. This section of the pipeline is installed upwardly with the height difference of the inclined section being half of the total settlement of the soft foundation;

[0011] Step 4) Construction of the settlement transition section: several cement-soil mixing piles are set along the pipeline installation axis in the inclined section;

[0012] Step 5) Pipeline installation: Two welders weld the pipeline in a symmetrical welding sequence;

[0013] Step 6) Trench backfill: After the pipeline is in place, backfill the medium and coarse sand layers on both sides of the lower half of the pipeline, and backfill the stone chips layer on the upper half and top of the pipeline. Backfill the two sides of the pipeline symmetrically in layers.

[0014] Furthermore, in step 4), a stainless steel braided metal hose is provided at the place where the pipeline is connected to the outside of the structure for flexible connection to eliminate the influence of uneven settlement of the pipeline so as to adapt to the large settlement difference between the structure and the soft foundation. A stainless steel braided metal hose is provided at the outside of the cement soil mixing pile for flexible connection to adapt to the settlement difference of different foundations.

[0015] Furthermore, in step 4), a cement soil mixing pile is set every 5 m along the pipeline installation axis, and the lengths of the set cement soil mixing piles are different.

[0016] Furthermore, in step 5), before the symmetrical welding of the pipeline segments, the segmented pipelines are prefabricated in a processing plant, an inner lining plate is installed on the inner side of the pipeline installation interface, and a stainless steel electrode is used to fully weld between the inner side of the pipeline installation interface and the inner lining plate. After the welding of the pipeline and the inner lining plate is completed, the pipeline anti-corrosion work is carried out.

[0017] Further, step 5) pipeline installation includes:

[0018] Step 51) After the pipeline welding is completed, mark the installation position control line of the channel steel with the center of the pipeline weld as the center;

[0019] Step 52) first install the lower semicircular channel steel on the surface of the lower half of the pipeline, and then install the upper semicircular channel steel on the surface of the upper half of the pipeline.

[0020] Further, in step 52), first use a feeler gauge to check the fit between the upper semicircular channel steel and the lower semicircular channel steel and the pipe surface. When the gap exceeds 1 mm, set a horse plate at the place where the gap is larger, first weld the horse plate to the pipe surface and fix it, then use an inclined iron to knock and squeeze the lower semicircular channel steel or the upper semicircular channel steel, so that the inner arc surface of the lower semicircular channel steel or the upper semicircular channel steel fits tightly with the pipe surface to achieve a seamless state, and then spot weld the channel steel to the pipe surface.

[0021] Further, in step 52), when the gap between the upper semicircular channel steel and the lower semicircular channel steel and the pipe surface is less than 1 mm, the upper semicircular channel steel and the lower semicircular channel steel are welded first, and then the weld between the upper semicircular channel steel and the pipe surface and the weld between the lower semicircular channel steel and the pipe surface are welded.

[0022] Compared with the prior art, the solution of the present invention has at least the following beneficial effects:

[0023] The construction method of the present invention includes trench excavation, replacement and filling treatment of the bottom of the pipeline after excavation, pipeline route planning and measurement, settlement transition section construction, pipeline installation, and trench backfilling. The present invention provides a new construction method for preventing settlement of buried drainage pipelines in soft foundations, solves the problem of uneven settlement of existing buried drainage pipelines in soft foundations, reduces the settlement difference of foundations at adjacent parts, reduces the deformation difference along the pipeline, avoids the problem of pipeline cracking due to differential settlement, and can also strengthen the strength of pipeline welds to avoid damage to the inner plastic coating layer at the welds. The construction process is small, which is convenient for the construction of buried drainage pipelines in soft foundations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0025] Figure 1 It is a structural diagram of the welding of auxiliary pipelines and flanges by the multi-group construction method of the present invention;

[0026] Figure 2 It is a schematic diagram of the change of the elevation of the pipeline in the transition section of the present invention;

[0027] Figure 3 It is a schematic elevation view of the installation of the settling transition section pipeline of the present invention;

[0028] Figure 4 It is a cross-sectional schematic diagram of the foundation treatment of the present invention;

[0029] Figure 5 It is a schematic elevation view of the channel steel reinforced pipeline of the present invention;

[0030] Figure 6 It is a schematic cross-sectional elevation view of the channel steel reinforced pipeline of the present invention;

[0031] Figure 7 It is a partial enlarged schematic diagram of the channel steel reinforced pipeline of the present invention;

[0032] Figure 8 It is a partial enlarged schematic diagram of the installation of the horse plate and the pipeline of the present invention;

[0033] Fig. 9 It is a partially enlarged schematic diagram of the horse plate and the inclined iron adjustment channel steel of the present invention.

[0034] In the figure: pipeline 1, inner lining plate 11, upper semicircular channel steel 12, lower semicircular channel steel 13, horse plate 14, inclined iron 15, settlement transition section 2, cement soil mixing pile 3, stainless steel braided metal hose 4, rough stone sand layer 5, crushed stone layer 6, medium and coarse sand layer 7, stone chip layer 8. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] like Figure 1-4 As shown, the present invention provides a construction method for preventing the settlement of an underground drainage pipe 1 in a soft foundation, and the construction method includes the following construction process:

[0037] Step 1) Trench excavation: Use steel plate column support and excavate in sections;

[0038] Step 2) After excavation, the bottom of the pipeline 1 is replaced and filled: the rubble sand layer 5 and the crushed stone layer 6 are layered and compacted at the silt at the bottom of the pre-buried pipeline 1, and the position of the pipeline 1 is reserved. The present invention replaces the soft soil and silt soil at the bottom of the original pipeline 1 with the rubble sand layer 5 and the crushed stone layer 6, which can improve the bearing capacity of the foundation and make the foundation bearing capacity exceed 100Kpa. The thickness of the rubble sand layer 5 and the crushed stone layer 6 is 70cm, and the thickness of the crushed stone layer 6 is 20cm;

[0039] Step 3) Pipeline route planning and measurement: After the pipeline 1 comes out of the structure, an upward inclination angle is set. This section of the pipeline 1 is installed upwardly and the height difference of the inclined section is half of the total settlement of the soft foundation, that is, 50% of the final deformation of the soft foundation. The reason for setting the settlement transition section 2 is mainly to reduce the deformation difference of different foundations. The present invention first performs route planning and measurement, comprehensively considers the impact of the pipeline layout area on other pipelines and facilities, and formulates a reasonable route and elevation based on the position of the casing and drain outlet of the structure. After the pipeline 1 comes out of the structure, it is installed upwardly and inclined for a distance of no less than 10m. The height difference of the inclined section is 50% of the final deformation of the foundation, and the height difference of the inclined section is 220;

[0040] Step 4) Construction of the settlement transition section 2: several cement soil mixing piles 3 are arranged along the installation axis of the pipeline 1 in the inclined section;

[0041] Step 5) Installation of pipeline 1: Two welders weld pipeline 1 in a symmetrical welding sequence in sections;

[0042] Step 6) Trench backfilling: After the pipeline 1 is in place, the medium and coarse sand layers 7 are backfilled on both sides of the lower half of the pipeline 1, and the stone chip layer 8 is backfilled on the upper half of the pipeline 1 and the top of the pipeline 1. The two sides of the pipeline 1 are backfilled symmetrically in layers, and the thickness of the backfill on the top of the pipe is not less than 700mm.

[0043] When the present invention is implemented specifically, in step 4), a stainless steel braided metal hose 4 is provided at the place where the pipeline 1 is connected to the outside of the structure for flexible connection to eliminate the influence of uneven settlement of the pipeline so as to adapt to the large settlement difference between the structure and the soft foundation. A stainless steel braided metal hose 4 is provided at the outside of the cement soil mixing pile 3 for flexible connection to adapt to the settlement difference of different foundations.

[0044] In step 4), a cement soil mixing pile 3 is set every 5m along the installation axis of the pipeline 1. The lengths of the cement soil mixing piles 3 are different. The present invention sets a plurality of cement soil mixing piles 3 of different lengths to coordinate the settlement difference. In specific implementation, the cement soil mixing piles 3 set by the present invention have a pile diameter of 1200, and the pile lengths of the cement soil mixing piles 3 are 9m, 7m, and 5m, respectively. Among them, the pile length of the cement soil mixing pile 3 close to the structure is 9m, and the pile length of the cement soil mixing pile 3 away from the working well of the structure is 5m.

[0045] like Figure 5-9 As shown, in step 5), before the pipeline 1 is symmetrically welded in sections, the sectioned pipeline 1 is prefabricated in a processing plant, an inner lining plate 11 is installed on the inner side of the installation interface of the pipeline 1, and a stainless steel electrode is used to fully weld the inner side of the installation interface of the pipeline 1 and the inner lining plate 11. After the pipeline 1 and the inner lining plate 11 are welded, the pipeline 1 is anti-corrosion. In specific implementation, the inner lining plate 11 of the present invention uses a 6mm thick stainless steel inner lining plate 11, and the width of the inner lining plate 11 is 190-200mm. The width of the stainless steel is greater than the width of the channel steel by 220mm.

[0046] When the present invention is specifically implemented, the step 5) of installing the pipeline 1 includes:

[0047] Step 51) After the welding of pipeline 1 is completed, the installation position control line of the channel steel is marked with the center of the weld of pipeline 1 as the center;

[0048] Step 52) first install the lower semicircular channel steel 13 on the lower half surface of the pipeline 1, and then install the upper semicircular channel steel 12 on the upper half surface of the pipeline 1.

[0049] When it is specifically implemented, in step 52), first use a feeler gauge to check the fit between the upper semicircular channel steel 12 and the lower semicircular channel steel 13 and the surface of the pipeline 1. When the gap exceeds 1 mm, set a horse plate 14 at the place where the gap is larger, first weld the horse plate 14 to the surface of the pipeline 1, and then use an inclined iron 15 to knock and squeeze the lower semicircular channel steel 13 or the upper semicircular channel steel 12, so that the inner arc surface of the lower semicircular channel steel 13 or the upper semicircular channel steel 12 is closely fitted to the surface of the pipeline 1 to achieve a seamless state, and the channel steel is spot welded and fixed to the surface of the pipeline 1; when the gap between the upper semicircular channel steel 12 and the lower semicircular channel steel 13 and the surface of the pipeline 1 is less than 1 mm, first weld the upper semicircular channel steel 12 and the lower semicircular channel steel 13, and then weld the weld between the upper semicircular channel steel 12 and the surface of the pipeline 1 and the weld between the lower semicircular channel steel 13 and the surface of the pipeline 1. The present invention adopts upper semicircular channel steel 12 and lower semicircular channel steel 13 to strengthen the weld of pipeline 1 installation connection, the width of the upper semicircular channel steel 12 and the lower semicircular channel steel 13 is not less than 140mm, and the upper semicircular channel steel 12 and the lower semicircular channel steel 13 are formed by bending the channel steel, which is convenient for installation of the upper semicircular channel steel 12 and the lower semicircular channel steel 13. The horse plate 14 is welded on the surface of the pipeline 1, so that the bending curvature of the upper semicircular channel steel 12 and the deviated position of the pipeline 1 that is inconsistent can be closely fitted. The pipeline 1 reinforcement construction process of the present invention can improve the weld strength of the pipeline 1 installation and avoid damage to the plastic coating of the inner lining of the pipeline 1.

[0050] In specific implementation, the upper semicircular channel steel 12 and the lower semicircular channel steel 13 of the present invention are channel steel 16a with a size of 160×63×6.5mm. The channel steel is bent into a semicircular arc in a processing plant, the inner arc diameter is ф820, and the diameter deviation is less than 3mm.

[0051] The specific construction process of the construction method of the present invention applied to a certain project to pump water from a working well with a depth of 100m and a diameter of 50m to a nearby river is as follows:

[0052] The buried pipeline 1 is a ф820×15 steel pipe. The pipeline 1 is installed on the alluvial plain, which is mainly soft soil and silt soil. The pipeline 1 is connected by welding. The inner coating thickness of the pipeline 1 is 450um, and the outer coating thickness is 500um.

[0053] Step 1) Use steel plate column support and excavate in sections;

[0054] Step 2) After excavation, the foundation is replaced with 70 cm of rubble stone, and a 20 cm gravel layer 6 and a 20 cm medium-coarse sand layer are added. The interface position of the pipe 1 is reserved;

[0055] Step 3) First, conduct route planning and measurement, comprehensively consider the impact of the pipeline layout area on other pipelines and facilities; formulate a reasonable route and elevation based on the location of the casing and drain outlet of the working well. After the pipeline 1 comes out of the structure, it is installed 10m upward at an angle, and the height difference of the inclined section is 220;

[0056] Divide the pipeline 1 into sections, determine the specifications and quantity of pipelines 1, and give priority to pipelines 1 with a maximum length of 12m;

[0057] The segmented pipeline 1 is prefabricated in a processing plant. A 6mm thick inner lining plate 11 is arranged on the inner side of the installation interface of the pipeline 1. The width of the inner lining plate 11 is 190mm. The inner lining plate 11 and the inner side of the pipeline 1 are fully welded with a stainless steel welding rod.

[0058] Select channel steel 16a, the size of which is 160×63×6.5mm. The channel steel is bent into upper semicircular channel steel 12 and lower semicircular channel steel 13 in a processing plant. The inner arc diameter is ф820mm, and the diameter deviation is less than 3mm.

[0059] Step 4) Three cement soil mixing piles 3 are set up close to the pipeline foundation of the working well, with a pile diameter of 1200. The first pile is set on the pipeline no more than 5m away from the edge of the working well wall, and one pile is set every 5m. The pile lengths are 9m, 7m, and 5m respectively;

[0060] Step 5) using two welders to weld the pipeline 1 in a segmented symmetrical welding sequence to reduce welding deformation;

[0061] After the welding of pipeline 1 is completed, mark the installation position control lines of upper semicircular channel steel 12 and lower semicircular channel steel 13 with the center of the weld as the center, install the lower semicircular channel steel 13 first, and then install the upper semicircular channel steel 12, use a feeler gauge to check the fit between the lower semicircular channel steel 13 and the surface of pipeline 1 and the fit between the lower semicircular channel steel 13 and the surface of pipeline 1. When the gap exceeds 1mm, set a horse plate 14 at the place where the gap is larger, first weld the horse plate 14 to the surface of pipeline 1, and then use the inclined iron 15 to knock and squeeze the channel steel, so that the inner arc surface of the channel steel fits tightly with the surface of pipeline 1 without gaps, and fix the channel steel on the surface of pipeline 1 by spot welding. When the gap between the channel steel and the surface of pipeline 1 at all positions is 1mm, first weld the upper and lower semicircular channel steels 13, and finally weld the weld between the channel steel and the surface of pipeline 1;

[0062] A stainless steel braided metal hose 4 is provided as a soft connection on the outside of the working well of the pipeline 1 to eliminate the influence of uneven settlement of the pipeline;

[0063] Step 6) After the pipeline 1 is in place, the lower half of the pipeline 1 is backfilled with medium-coarse sand on both sides, and the upper half and the top are backfilled with stone chips. The backfill thickness of the top of the pipe is not less than 700mm.

[0064] Compared with the prior art, the technical solution disclosed in the above embodiment has the following beneficial effects:

[0065] In the above embodiment, after the construction method of the present invention leads the pipeline 1 out of the structure, a settlement transition section 2 is set, and the pipeline 1 is installed inclined upward. The height difference of the inclined section is 50% of the final deformation of the foundation. A plurality of cement-soil mixing piles 3 of different lengths are provided to coordinate the settlement difference. The present invention arranges stainless steel braided metal hoses 4 on both sides of the settlement transition section 2 for soft connection to coordinate the settlement difference between the pipeline 1 and the different foundations on both sides, thereby reducing the deformation difference along the pipeline 1, avoiding problems such as cracking of the pipeline 1 due to differential settlement, and facilitating the pre-buried construction of the pipeline 1.

[0066] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A construction method for preventing subsidence of buried drainage pipes in soft foundation, characterized by: The construction method includes the following construction process: Step 1) Trench excavation: Use steel plate column support and excavate in sections; Step 2) After excavation, the bottom of the pipeline is replaced: the silt at the bottom of the pre-buried pipeline is filled with rubble sand layers and crushed stone layers in layers and compacted to reserve the pipeline position; Step 3) Pipeline route planning and measurement: After the pipeline comes out of the structure, an upward inclination angle is set. This section of the pipeline is installed upwardly with the height difference of the inclined section being half of the total settlement of the soft foundation; Step 4) Construction of the settlement transition section: several cement-soil mixing piles are set along the pipeline installation axis in the inclined section; Step 5) Pipeline installation: Two welders weld the pipeline in a symmetrical welding sequence; Step 6) Trench backfill: After the pipeline is in place, backfill the medium and coarse sand layers on both sides of the lower half of the pipeline, and backfill the stone chips layer on the upper half and top of the pipeline. Backfill the two sides of the pipeline symmetrically in layers.

2. The construction method for preventing subsidence of buried drainage pipes in soft foundation according to claim 1 is characterized by: In step 4), a stainless steel braided metal hose is set at the place where the pipeline is connected to the outside of the structure for flexible connection to eliminate the influence of uneven settlement of the pipeline so as to adapt to the large settlement difference between the structure and the soft foundation. A stainless steel braided metal hose is set at the outside of the cement soil mixing pile for flexible connection to adapt to the settlement difference of different foundations.

3. The construction method for preventing subsidence of buried drainage pipes in soft foundation according to claim 1 is characterized by: In step 4), a cement soil mixing pile is set every 5 m along the pipeline installation axis, and the lengths of the set cement soil mixing piles are different.

4. The construction method for preventing subsidence of buried drainage pipes in soft foundation according to claim 1 is characterized by: In step 5), before the symmetrical welding of the pipeline segments, the segmented pipelines are prefabricated in a processing plant, an inner lining plate is installed on the inner side of the pipeline installation interface, and a stainless steel electrode is used to fully weld between the inner side of the pipeline installation interface and the inner lining plate. After the welding of the pipeline and the inner lining plate is completed, the pipeline anti-corrosion work is carried out.

5. The construction method for preventing subsidence of buried drainage pipes in soft foundation according to claim 1 is characterized by: Step 5) Pipeline installation includes: Step 51) After the pipeline welding is completed, mark the installation position control line of the channel steel with the center of the pipeline weld as the center; Step 52) first install the lower semicircular channel steel on the surface of the lower half of the pipeline, and then install the upper semicircular channel steel on the surface of the upper half of the pipeline.

6. The construction method for preventing the underground drainage pipe from settling in a soft foundation according to claim 5 is characterized by: In step 52), first use a feeler gauge to check the fit between the upper semicircular channel steel and the lower semicircular channel steel and the pipe surface. When the gap exceeds 1 mm, set a horse plate at the place where the gap is larger, first weld the horse plate to the pipe surface, and then use an inclined iron to knock and squeeze the lower semicircular channel steel or the upper semicircular channel steel so that the inner arc surface of the lower semicircular channel steel or the upper semicircular channel steel fits tightly with the pipe surface to achieve a seamless state, and then spot weld the channel steel to the pipe surface.

7. The construction method for preventing subsidence of buried drainage pipes in soft foundation according to claim 6 is characterized by: In step 52), when the gap between the upper semicircular channel steel and the lower semicircular channel steel and the pipeline surface is less than 1 mm, the upper semicircular channel steel and the lower semicircular channel steel are welded first, and then the weld between the upper semicircular channel steel and the pipeline surface and the weld between the lower semicircular channel steel and the pipeline surface are welded.

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