Flow state solidified soil backfill light flexible pipe ditch structure and construction method thereof

Abstract

The invention discloses a flow-state solidified soil backfill light flexible pipe ditch structure and a construction method thereof. The construction method comprises the steps that a pipe bottom foundation layer is arranged at the bottom of a pipe ditch and filled with early-strength type flow-state solidified soil poured gravel; the light flexible pipe is placed on the pipe bottom foundation layer, the number of pouring layers is determined based on pipeline anti-floating treatment, and early-strength type flow state solidified soil is sequentially and gradually backfilled and poured on the outer side of the periphery of the pipe layer by layer according to the preset layered pouring thickness to form a stable layer at least wrapping a part of the light flexible pipe; and a backfill layer which is formed by backfilling and pouring light high-rigidity flow-state solidified soil for one time and covers the pipe ditch is arranged above the stable layer and the light flexible pipe. The flow-state solidified soil is adopted, the early strength of layered backfilling is high, the curing time is short, the construction period can be shortened, continuous backfilling can be guaranteed, the construction time is greatly shortened, the anti-floating backfilling layer number and the pouring thickness are given, clear guidance is provided for construction, and efficient backfilling operation and structural stability are guaranteed.

Description

Technical Field

[0001] The invention belongs to the field of soil mechanics and engineering technology, and particularly relates to a fluidized solidified soil backfilled lightweight flexible pipe trench structure and a construction method thereof. Background Art

[0002] Traditional trench backfill uses original soil or sand and gravel materials, which are difficult to compact and it is difficult to achieve the ideal compaction degree, and the pipeline is easily damaged or even ruptured; the moisture content of the backfill soil is difficult to control, the detection technology is limited, and it is difficult to achieve uniform density in the treatment of special parts, which can easily lead to unstable pipeline structure, ground subsidence and erosion; reliance on natural resources leads to waste and destruction, abandoned soil is not reasonably utilized, and transportation causes pollution; during construction, personnel face the risk of trench collapse and mechanical injury, which hinders construction and increases management difficulty.

[0003] Backfilling trenches with fluidized solidified soil has many advantages. Its good fluidity can fully fill every corner of complex trenches. After solidification, it has high compaction and stability, which can ensure the safe operation of pipelines. The moisture content and quality can be accurately controlled, and factory production can be used to ensure project quality. In terms of environmental protection, it can utilize abandoned soil and reduce pollution from resource extraction and transportation. During construction, there is no need for personnel to enter the trench for compaction, which reduces the risk of trench collapse and mechanical injury and improves construction safety.

[0004] Chinese patent document CN114215074A, published (announced) on January 29, 2022, discloses a patent for a method for backfilling a pipe trench. The invention belongs to the technical field of backfilling, and is a method for backfilling a pipe trench.

[0005] Chinese patent document CN118561568A discloses a patent for pipeline backfilling of a self-compacting fluidized solidified soil and its backfilling process, which includes using a pump truck or a chute to transport the mixture to the trench and pour it in sections and layers, making test pieces and simultaneously curing and testing the compressive strength, and when the self-compacting fluidized solidified soil is located below 1 / 2 of the pipe diameter, the layered pouring height is determined according to the pipeline burial depth, pipe diameter, and pipe material to prevent the pipeline from floating up. After exceeding 1 / 2 of the pipe diameter, the pouring height of each layer is not greater than 2m, and the pouring height difference of adjacent areas should not be greater than 100cm, and the upper layer is poured after the lower layer reaches the design strength. However, the requirements for backfill thickness layers are unclear, the anti-floating operation process is not detailed and there is no precise construction guidance, the self-compacting fluidized solidified soil has a long curing period, which is not conducive to the construction of the next process and prolongs the construction period, and the later settlement and deformation and potential impact on the pipeline are not fully considered, and it is not clear whether repeated construction, repair and adjustment are required after settlement and deformation, which brings many uncertainties and potential risks to the long-term stability and subsequent operation and maintenance of the project.

[0006] Chinese patent document CN116608323A discloses a construction method for backfilling pipelines with fluidized solidified soil and steel sheet piles, which can solve the disadvantage that the compaction degree of traditional rolling construction is difficult to meet the requirements, further expand the application scenarios of backfilling trenches with fluidized solidified soil, and meet the engineering requirements of pipeline engineering anti-floating and filling the gaps after steel sheet piles are pulled out. The patent describes the relevant procedures for backfilling trenches with fluidized solidified soil, but does not involve anti-floating measures for pipeline layered backfilling and requirements for fluidized solidified soil.

[0007] Chinese patent document CN220671432U discloses a test device for simulating the interaction model of flexible buried pipe-fluidized solidified soil, and proposes a test device and method for the interaction model of flexible buried pipe-fluidized solidified soil with strong simulation and good applicability, which can restore the actual working conditions on site as much as possible and meet the needs of model test research of different original soil, pipe type, fluidized soil and trench width, which has very important scientific significance and engineering application value for the application and promotion of fluidized solidified soil. This patent simulates the process of backfilling the pipe trench with fluidized solidified soil, but does not involve the requirements for actual engineering guidance. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a fluidized solidified soil backfilled lightweight flexible pipe trench structure and a construction method thereof.

[0009] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0010] In a first aspect, the present invention provides a fluidized solidified soil backfilled lightweight flexible pipe trench structure, comprising a pipe bottom foundation layer, a lightweight flexible pipe, a stabilizing layer and a backfill layer, which are backfilled and cast in layers from the bottom to the top of the trench bottom;

[0011] The pipe bottom foundation layer is arranged at the bottom of the trench and is filled with gravel cast by early-strength fluidized solidifying soil; the lightweight flexible pipe is placed on the pipe bottom foundation layer, and the number of casting layers is determined based on the anti-floating treatment of the pipeline, and the early-strength fluidized solidifying soil is backfilled and cast in layers on the outside of the pipe with a preset layered casting thickness to form a stable layer that at least wraps a part of the lightweight flexible pipe; and a backfill layer of lightweight high-rigidity fluidized solidifying soil is arranged above the stable layer and the lightweight flexible pipe to form a backfill layer covering the trench.

[0012] Furthermore, the early strength fluidized solidified soil is prepared by using 60%-70% of raw soil, 3% of early strength agent, 15%-25% of composite solidifying agent, and 10%-20% of water according to a preset ratio;

[0013] The wet density ρ flow of the early-strength fluidized solidified soil is in the range of 1400-1600 kg / m3, the 12-hour foundation bearing capacity of the early-strength fluidized solidified soil is above 70 kPa, the fluidity needs to be between 180±20 mm, and the water seepage rate does not exceed 5%.

[0014] Furthermore, the lightweight high-rigidity fluidized solidified soil is prepared according to a preset ratio by using 55%-65% of common raw soil, 10%-14% of composite solidifying agent, 8%-12% of lightweight material, 1%-3% of admixture and 12%-16% of water;

[0015] The wet density of the lightweight high-rigidity fluidized solidified soil is in the range of 1200-1600 kg / m 3 The slump is maintained at 150-250mm, the water seepage rate is controlled within 5%, preferably not more than 3%, the 7-day unconfined compressive strength meets 0.5-2MPa, and the 28-day unconfined compressive strength meets 1-5MPa.

[0016] Furthermore, based on the anti-floating treatment of the pipeline and the preset layered casting thickness, the number of casting layers of the stable layer and the backfill height of each layer are pre-calculated and determined according to the pipeline and fluidized solidified soil combined with the trench design requirements, water injection anti-floating treatment is adopted in the pipe and / or the flexible pipe is not subjected to anti-floating treatment.

[0017] Furthermore, if the pipe is filled with water for anti-floating treatment, the thickness of the first layer of the stabilizing layer is expressed by the formula:

[0018]

[0019] Where H1 represents the thickness of the first layer of casting, ρ 流 represents the wet density of early strength fluidized solidified soil; ρ 管 represents the density of lightweight flexible pipe; R represents the outer radius of the pipe; d represents the thickness of the pipe; ρ w Expressed as the density of water; k w It indicates the safety factor against buoyancy;

[0020] The pouring thickness of the nth layer of the stable layer is expressed by the recursive formula:

[0021]

[0022] In the formula, H n , H n-1 Indicates the pouring thickness of the nth and n-1th layers; F 粘 It indicates the force between the fluidized solidified soil and the pipeline after consolidation, and its value ranges from 0.4 to 1 MPa.

[0023] Furthermore, if the flexible pipe is not filled with water for anti-floating treatment, the thickness of the first layer of the stabilizing layer is expressed by the formula:

[0024]

[0025] Where H1 represents the thickness of the first layer of casting, ρ 流 represents the wet density of early strength fluidized solidified soil; ρ 管 represents the density of lightweight flexible pipe; R represents the outer radius of the pipe; d represents the thickness of the pipe; k w It indicates the safety factor against buoyancy;

[0026] The pouring thickness of the nth layer of the stable layer is expressed by the recursive formula:

[0027]

[0028] In the formula, H n , H n-1 Indicates the pouring thickness of the nth and n-1th layers; F 粘 It indicates the force between the fluidized solidified soil and the pipeline after consolidation, and its value ranges from 0.4 to 1 MPa.

[0029] Furthermore, the thickness of the pipe bottom foundation layer is 100-150 mm; the lightweight high-rigidity fluidized solidified soil of the backfill layer is backfilled by one-time pumping or chute backfilling.

[0030] In a second aspect, the present invention provides a construction method for backfilling a lightweight flexible pipe trench structure with fluidized solidified soil as described in the first aspect, comprising the following steps:

[0031] Step S1: laying a 100-150 mm thick gravel layer at the bottom of the trench, pouring early strength fluidized solidified soil on the gravel layer for reinforcement, and forming a pipe bottom foundation layer as a pipe support;

[0032] Step S2: accurately positioning and securely placing the lightweight flexible pipe on the completed pipe bottom foundation layer;

[0033] Step S3: using early-strength fluidized solidified soil to gradually backfill the stable layer in layers, and the backfill height of each layer is pre-calculated and determined by using water injection in the pipe for anti-floating treatment and / or flexible pipe without anti-floating treatment according to the pipeline and fluidized solidified soil combined with the trench construction design requirements to determine the number of pouring layers of the stable layer and the backfill height of each layer;

[0034] Step S4: according to the determined backfill pouring height of each layer, early-strength fluidized solidified soil is used to gradually pour in layers and blocks around the outer side of the lightweight flexible pipe, at least a portion of the lightweight flexible pipe is poured and filled, and the pouring operation is symmetrically backfilled in layers on both sides of the flexible pipe;

[0035] Step S5: After the early strength fluidized solidified soil is solidified, pour the next layer. During pouring, attention should be paid to fluidity and pouring speed. The pouring height difference should not be greater than 1m to reduce the pressure on the pipeline and ensure that the pipeline does not move.

[0036] Step S6: After the stable layer is backfilled and stabilized, lightweight high-rigidity fluidized solidified soil is pumped once to the backfill layer or chute for backfilling, and the fluidized solidified soil is cured after the backfilling is completed.

[0037] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the structure of the light flexible pipe trench backfilled with fluidized solidified soil provided by the present invention and its construction method adopt the pipe bottom foundation layer, light flexible pipe, stabilization layer and backfill layer which are backfilled and cast in layers from the bottom of the trench to the top; the anti-floating treatment is carried out by injecting water into the pipe and / or the flexible pipe is not subjected to the anti-floating treatment to pre-calculate the number of casting layers of the stabilization layer and the backfill height of each layer, and the specific casting thickness of the anti-floating backfill is given, which provides clear guidance for the construction and ensures the high efficiency and structural stability of the backfill operation. The high early strength and short curing time are conducive to speeding up the construction period, can ensure the continuous backfilling and greatly reduce the construction time; the light high-rigidity fluidized solidified soil will not bring too much additional pressure to the foundation, thereby reducing the risk of foundation settlement; the light high-rigidity fluidized solidified soil is relatively less in amount due to its light weight, and the total volume of backfill can be reduced while meeting the same engineering performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of a lightweight flexible pipe trench structure backfilled with fluidized solidified soil provided according to an embodiment of the present invention.

[0039] Figure 2 The present invention is a flow chart of a construction method for backfilling a lightweight flexible pipe trench structure with fluidized solidified soil according to an embodiment of the present invention.

[0040] In the figure:

[0041] 1. Pipe bottom foundation layer; 2. Lightweight flexible pipe: 3. Stabilization layer; 4. Backfill layer. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0043] Example

[0044] like Figure 1 As shown, an embodiment of the present invention provides a fluidized solidified soil backfilled lightweight flexible pipe trench structure, comprising a pipe bottom foundation layer, a lightweight flexible pipe, a stabilizing layer and a backfill layer, which are backfilled and cast in layers from the bottom of the trench from bottom to top;

[0045] The pipe bottom foundation layer is arranged at the bottom of the trench and is filled with gravel cast by early-strength fluidized solidifying soil; the lightweight flexible pipe is placed on the pipe bottom foundation layer, and the number of casting layers is determined based on the anti-floating treatment of the pipeline, and the early-strength fluidized solidifying soil is backfilled and cast in layers on the outside of the pipe with a preset layered casting thickness to form a stable layer that at least wraps a part of the lightweight flexible pipe; and a backfill layer of lightweight high-rigidity fluidized solidifying soil is arranged above the stable layer and the lightweight flexible pipe to form a backfill layer covering the trench.

[0046] In this embodiment, the early-strength fluidized solidifying soil is prepared according to a preset ratio of 60%-70% raw soil, 3% early strength agent, 15%-25% composite solidifying agent, and 10%-20% water.

[0047] The wet density ρ flow of the early-strength fluidized solidified soil is in the range of 1400-1600 kg / m3, the 12-hour foundation bearing capacity of the early-strength fluidized solidified soil is above 70 kPa, the fluidity needs to be between 180±20 mm, and the water seepage rate does not exceed 5%.

[0048] In this embodiment, the lightweight high-rigidity fluidized solidified soil is prepared according to a preset ratio of 55%-65% of common raw soil, 10%-14% of composite solidifying agent, 8%-12% of lightweight material, 1%-3% of admixture and 12%-16% of water;

[0049] The wet density of the lightweight high-rigidity fluidized solidified soil is in the range of 1200-1600 kg / m 3 The slump is maintained at 150-250mm, the water seepage rate is controlled within 5%, preferably not more than 3%, the 7-day unconfined compressive strength meets 0.5-2MPa, and the 28-day unconfined compressive strength meets 1-5MPa.

[0050] In this embodiment, the thickness of the pipe bottom foundation layer is 100-150 mm; the lightweight high-rigidity fluidized solidified soil of the backfill layer is backfilled by one-time pumping or chute backfilling.

[0051] In this embodiment, based on the anti-floating treatment of the pipeline and the preset layered casting thickness, according to the pipeline and fluidized solidified soil combined with the trench design requirements, water injection anti-floating treatment is adopted in the pipe and / or the flexible pipe is not subjected to anti-floating treatment, and the casting layers of the stable layer and the backfill height of each layer are pre-calculated and determined.

[0052] (1) If the pipe is filled with water for anti-floating treatment, the thickness of the first layer of the stabilizing layer is expressed by the formula:

[0053]

[0054] Where H1 represents the thickness of the first layer of casting, ρ 流 represents the wet density of early strength fluidized solidified soil; ρ 管represents the density of lightweight flexible pipe; R represents the outer radius of the pipe; d represents the thickness of the pipe; ρ w Expressed as the density of water; k w It indicates the safety factor against buoyancy;

[0055] The pouring thickness of the nth layer of the stable layer is expressed by the recursive formula:

[0056]

[0057] In the formula, H n , H n-1 Indicates the pouring thickness of the nth and n-1th layers; F 粘 It indicates the force between the fluidized solidified soil and the pipeline after consolidation, and its value ranges from 0.4 to 1 MPa.

[0058] (2) If the flexible pipe is not filled with water for anti-floating treatment, the thickness of the first layer of the stabilizing layer is expressed by the formula:

[0059]

[0060] Where H1 represents the thickness of the first layer of casting, ρ 流 represents the wet density of early strength fluidized solidified soil; ρ 管 represents the density of lightweight flexible pipe; R represents the outer radius of the pipe; d represents the thickness of the pipe; k w It indicates the safety factor against buoyancy;

[0061] The pouring thickness of the nth layer of the stable layer is expressed by the recursive formula:

[0062]

[0063] In the formula, H n , H n-1 Indicates the pouring thickness of the nth and n-1th layers; F 粘 It indicates the force between the fluidized solidified soil and the pipeline after consolidation, and its value ranges from 0.4 to 1 MPa.

[0064] In a second aspect, the present invention provides a construction method for backfilling a lightweight flexible pipe trench structure with fluidized solidified soil as described in the first aspect, comprising the following steps:

[0065] Step S1: laying a 100-150 mm thick gravel layer at the bottom of the trench, pouring early strength fluidized solidified soil on the gravel layer for reinforcement, and forming a pipe bottom foundation layer as a pipe support;

[0066] Step S2: accurately positioning and securely placing the lightweight flexible pipe on the completed pipe bottom foundation layer;

[0067] Step S3: using early-strength fluidized solidified soil to gradually backfill the stable layer in layers, and the backfill height of each layer is pre-calculated and determined by using water injection in the pipe for anti-floating treatment and / or flexible pipe without anti-floating treatment according to the pipeline and fluidized solidified soil combined with the trench construction design requirements to determine the number of pouring layers of the stable layer and the backfill height of each layer;

[0068] Step S4: according to the determined backfill pouring height of each layer, early-strength fluidized solidified soil is used to gradually pour in layers and blocks around the outer side of the lightweight flexible pipe, at least a portion of the lightweight flexible pipe is poured and filled, and the pouring operation is symmetrically backfilled in layers on both sides of the flexible pipe;

[0069] Step S5: After the early strength fluidized solidified soil is solidified, pour the next layer. During pouring, attention should be paid to fluidity and pouring speed. The pouring height difference should not be greater than 1m to reduce the pressure on the pipeline and ensure that the pipeline does not move.

[0070] Step S6: After the stable layer is backfilled and stabilized, lightweight high-rigidity fluidized solidified soil is pumped once to the backfill layer or chute for backfilling, and the fluidized solidified soil is cured after the backfilling is completed.

[0071] Step S7: After each layer is poured, watering or film covering should be used for curing, and the curing time of the completed surface should be no less than 7 days. During the curing period, the fluidized solidified soil should be kept moist to avoid strength reduction or cracks due to rapid water loss.

[0072] Next, the construction and principle of the fluidized solidified soil backfill lightweight flexible pipe trench structure of the present invention are described in combination with the use and operation of the specific embodiment.

[0073] Example 1

[0074] The bottom of the trench is 1.2m and the depth is 2 meters. The outer diameter of the PVC drainage pipe is 800mm, the length is Lmm, the wall thickness is 11.7mm, the density is 1400kg / m3, the early strength flow-cured soil wet density is 1600kg / m3, and the pipeline is filled with water to prevent floating.

[0075] (1) The bottom of the trench has a 150 mm thick gravel base, and early strength fluidized solidified soil is poured to fill the pores for reinforcement.

[0076] (2) Backfill the stable layer and substitute the value into the formula:

[0077]

[0078] Combining the formula to calculate, we get: H1≈390mm.

[0079] After the pipe's own weight, water injection weight and fluidized solidified soil are consolidated, the bonding strength reaches the anti-floating requirement. Therefore, the stabilizing layer of the structural engineering in this embodiment only needs to be cast in one layer, so the stabilizing layer is 390 mm thick.

[0080] The early-strength fluidized solidified soil is backfilled to a thickness of 390 mm.

[0081] (3) Backfill layer: Lightweight high-rigidity fluidized solidified soil backfill with a thickness of 1460 mm.

[0082] Example 2

[0083] The bottom of the trench is 1m and the depth is 1.8 meters. The outer diameter of the PVC drainage pipe is 600mm, the length is Lmm, the wall thickness is 12mm, the density is 1400kg / m3, the early strength flow-cured soil wet density is 1600kg / m3, when the pipeline is not filled with water.

[0084] (1) The bottom of the trench has a 150 mm thick gravel base, and early strength fluidized solidified soil is poured to fill the pores for reinforcement.

[0085] (2) Backfill the stable layer and substitute the value into the formula:

[0086]

[0087] Combined with the formula, we calculated that: H1≈75mm, and the first layer of backfill early-strength fluidized solidified soil is 75mm thick.

[0088] Subsequent backfill layer thickness, substitute the value into the formula:

[0089]

[0090] Combined with the formula to calculate:

[0091] H2≈150mm, the second layer of backfill is 150mm thick with early strength fluidized solidified soil;

[0092] H3≈300mm, the third layer is backfilled with early-strength fluidized solidified soil 300mm thick, and the bonding strength of the pipe’s deadweight and fluidized solidified soil after consolidation reaches the anti-floating requirements.

[0093] Therefore, the stabilizing layer of the trench structure in this embodiment needs to be cast in three layers.

[0094] (3) Backfill layer: Lightweight high-rigidity fluidized solidified soil backfill with a thickness of 1125 mm.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fluidized solidified soil backfill lightweight flexible pipe trench structure, characterized in that: It includes a pipe bottom foundation layer, a lightweight flexible pipe, a stabilizing layer and a backfill layer which are backfilled and poured in layers from the bottom of the trench to the top; The pipe bottom foundation layer is arranged at the bottom of the trench and is filled with gravel cast by early-strength fluidized solidifying soil; the lightweight flexible pipe is placed on the pipe bottom foundation layer, and the number of casting layers is determined based on the anti-floating treatment of the pipeline, and the early-strength fluidized solidifying soil is backfilled and cast in layers on the outside of the pipe with a preset layered casting thickness to form a stable layer that at least wraps a part of the lightweight flexible pipe; and a backfill layer of lightweight high-rigidity fluidized solidifying soil is arranged above the stable layer and the lightweight flexible pipe to form a backfill layer covering the trench.

2. The fluidized solidified soil backfill lightweight flexible pipe trench structure according to claim 1 is characterized in that: The early strength fluidized solidified soil is prepared by using 60% - 70% of raw soil, 3% of early strength agent, 15% - 25% of composite solidifying agent, and 10% - 20% of water according to a preset ratio; The wet density ρ flow of the early-strength fluidized solidified soil is in the range of 1400-1600 kg / m3, the 12-hour foundation bearing capacity of the early-strength fluidized solidified soil is above 70 kPa, the fluidity needs to be between 180 ± 20 mm, and the water seepage rate does not exceed 5%.

3. The fluidized solidified soil backfill lightweight flexible pipe trench structure according to claim 2 is characterized in that: The lightweight high-rigidity fluidized solidified soil is prepared according to a preset ratio of 55% - 65% of common raw soil, 10% - 14% of composite solidifying agent, 8% - 12% of lightweight material, 1% - 3% of admixture and 12% - 16% of water; The wet density of the lightweight high-rigidity fluidized solidified soil is in the range of 1200-1600kg / m³, the slump is maintained at 150-250mm, the water seepage rate is controlled within 5%, preferably not more than 3%, the 7-day unconfined compressive strength meets 0.5-2MPa, and the 28-day unconfined compressive strength meets 1-5MPa.

4. The fluidized solidified soil backfill lightweight flexible pipe trench structure according to claim 3 is characterized in that: Based on the anti-floating treatment of the pipeline, the number of pouring layers is determined to preset the layered pouring thickness. According to the design requirements of the pipeline and the fluidized solidified soil combined with the trench, water injection anti-floating treatment is adopted in the pipe and / or the flexible pipe is not subjected to anti-floating treatment. The number of pouring layers of the stable layer and the backfill height of each layer are pre-calculated and determined.

5. The fluidized solidified soil backfill lightweight flexible pipe trench structure according to claim 4 is characterized in that: If the pipe is filled with water for anti-floating treatment, the thickness of the first layer of the stabilizing layer is expressed by the formula: ； Where H1 represents the thickness of the first layer of pouring, It indicates the wet density of early strength fluidized solidified soil; Indicates the density of lightweight flexible pipe; R indicates the outer radius of the pipe; d indicates the thickness of the pipe; Expressed as the density of water; It indicates the safety factor against buoyancy; The pouring thickness of the nth layer of the stable layer is expressed by the recursive formula: ； In the formula, H n , H n-1 Indicates the pouring thickness of the nth and n-1th layers; It indicates the force between the fluidized solidified soil and the pipeline after consolidation, and its value ranges from 0.4 to 1 MPa.

6. The fluidized solidified soil backfill lightweight flexible pipe trench structure according to claim 5 is characterized in that: If the flexible pipe is not filled with water for anti-floating treatment, the thickness of the first layer of the stabilizing layer is expressed by the formula: ； Where H1 represents the thickness of the first layer of pouring, It indicates the wet density of early strength fluidized solidified soil; Indicates the density of lightweight flexible pipe; R indicates the outer radius of the pipe; d indicates the thickness of the pipe; It indicates the safety factor against buoyancy; The pouring thickness of the nth layer of the stable layer is expressed by the recursive formula: ； In the formula, H n , H n-1 Indicates the pouring thickness of the nth and n-1th layers; It indicates the force between the fluidized solidified soil and the pipeline after consolidation, and its value ranges from 0.4 to 1MPa.

7. The fluidized solidified soil backfill lightweight flexible pipe trench structure according to any one of claims 1 to 6, characterized in that: The thickness of the pipe bottom foundation layer is 100-150mm; the lightweight high-rigidity fluidized solidified soil of the backfill layer is backfilled by one-time pumping or chute backfilling.

8. A construction method for backfilling a lightweight flexible pipe trench structure with fluidized solidified soil as claimed in any one of claims 1 to 7, characterized in that: The steps include: Step S1: laying a 100-150 mm thick gravel layer at the bottom of the trench, pouring early strength fluidized solidified soil on the gravel layer for reinforcement, and forming a pipe bottom foundation layer as a pipe support; Step S2: accurately positioning and firmly fixing the lightweight flexible pipe on the completed pipe bottom foundation layer; Step S3: using early-strength fluidized solidified soil to gradually backfill the stable layer in layers, and the backfill height of each layer is pre-calculated and determined by using water injection in the pipe for anti-floating treatment and / or flexible pipe without anti-floating treatment according to the pipeline and fluidized solidified soil combined with the trench construction design requirements to determine the number of pouring layers of the stable layer and the backfill height of each layer; Step S4: according to the determined backfill pouring height of each layer, early-strength fluidized solidified soil is used to gradually pour in layers and blocks around the outer side of the lightweight flexible pipe, at least a portion of the lightweight flexible pipe is poured and filled, and the pouring operation is symmetrically backfilled in layers on both sides of the flexible pipe; Step S5: After the early strength fluidized solidified soil is solidified, pour the next layer. During pouring, attention should be paid to fluidity and pouring speed. The pouring height difference should not be greater than 1m to reduce the pressure on the pipeline and ensure that the pipeline does not move. Step S6: After the stable layer is backfilled and stabilized, lightweight high-rigidity fluidized solidified soil is pumped once to the backfill layer or chute for backfilling, and the fluidized solidified soil is cured after the backfilling is completed.

Images