Roadbed heightening structure based on active service pipe group and construction method and design method thereof

Abstract

The invention discloses a roadbed heightening structure based on an active-service pipe group and a construction method and a design method thereof, and the roadbed heightening structure based on the active-service pipe group comprises compaction grouting holes, strip-shaped piers, pipe ditch filling materials, a settlement structure, roadbed filling soil and a newly-built pavement; compression grouting holes are formed between the adjacent pipelines and used for conducting grouting on a soft soil layer below the active service pipe group, and a pile-soil composite foundation is formed. A strip-shaped pier is arranged between any two adjacent pipelines; the pipe ditch filler is filled between the adjacent strip-shaped piers and the pipeline and above the pipeline; the settlement structure is laid above the pipe ditch filler, and the settlement structure has a certain compression modulus; the subgrade filling soil is filled above the settlement structure and the strip-shaped piers; and the newly-built pavement is paved above the roadbed filling soil. According to the technical scheme, the problems of fill roadbed soft soil foundation treatment and active-service pipe group protection in an active-service pipe group area are solved.

Description

Technical Field

[0001] The invention relates to the technical field of urban riverside road construction engineering, and in particular to a roadbed heightening structure based on an existing pipe group. Background Art

[0002] The construction of urban riverside roads is an important part of the development of urban transportation infrastructure. In the local sections of riverside roads near the rainwater pumping station, there will be existing drainage pipe groups in service. The relationship between the existing pipe group and the proposed riverside road is either vertical, parallel, or oblique, and the top elevation of the existing pipe group is basically the same as the existing ground elevation. The existing pipe group undertakes the important drainage function of the pump station, ensuring the normal operation of the city and the safety of life and property of residents, and generally cannot be relocated. Due to flood control requirements, urban riverside roads generally require 3-5m high fill roadbeds, and the foundations are often distributed with soft soil layers such as silt soil. The existing pipe group that cannot be relocated restricts the soft foundation treatment of the riverside road, and the impact of the cover soil and fill load of the riverside road on the existing pipe group cannot be ignored.

[0003] In view of this situation, in current actual projects, due to the influence of the pipe group, the soft soil foundation at the bottom of the pipe group is generally not effectively treated. Only the planned riverside road on the top of the pipe is backfilled with foam lightweight soil, but the construction quality control of foam lightweight soil is difficult, the construction cost is high, and the durability is greatly affected by the environment. Some projects also set rigid piles on both sides of the pipeline and cover plates on the top of the pipeline to protect the pipeline, but for large-diameter pipe groups parallel to the riverside road, a large area of ​​reinforced concrete cover plates is required, which is expensive, and uneven settlement is prone to occur in the pipe group and non-pipe group areas. Summary of the invention

[0004] The main purpose of the present invention is to propose a roadbed heightening structure based on an existing pipe group, aiming to solve the problems of soft soil foundation treatment of fill roadbed in the area of ​​the existing pipe group and protection of the existing pipe group.

[0005] To achieve the above-mentioned purpose, the present invention proposes a roadbed heightening structure based on an existing pipe group, comprising:

[0006] A plurality of compaction grouting holes, wherein the compaction grouting holes are arranged between any two adjacent pipes, the top of the compaction grouting holes are located between the bottom and the top of the active pipe group, and the compaction grouting holes are used to grout the soft soil layer below the active pipe group to form a pile-soil composite foundation;

[0007] A plurality of strip piers are arranged on the pile-soil composite foundation, and the strip piers are arranged between any two adjacent pipelines, and the tops of the strip piers are higher than the active pipe group;

[0008] Pipe trench filling material is filled between the adjacent strip piers and the pipes, and above the pipes, and the top of the pipe trench filling material is not higher than the top of the strip pier;

[0009] A settlement structure is laid above the trench filling material, and the settlement structure has a certain compression modulus;

[0010] The roadbed fill is filled above the settlement structure and the strip pier, and the settlement structure is compressed by the weight load to cause settlement, and the settlement structure and the top surface of the strip pier are differentially settled, so that a soil arch effect is generated inside the roadbed fill; and

[0011] A new road surface is constructed on top of the roadbed fill.

[0012] Optionally, the roadbed heightening structure based on the existing pipe group also includes a bidirectional geogrid, which is laid between the settlement structure and the roadbed fill, and the nominal tensile strength of the bidirectional geogrid is ≥80kN / m, and the elongation at the nominal tensile strength is ≤3%.

[0013] Optionally, the settlement structure is paved with EPS blocks.

[0014] Optionally, the trench filling material is medium-coarse sand.

[0015] Optionally, the strip pier has a width of 0.8-1.2 m, a height of 1.0-1.5 m, a net spacing of 0.15-0.3 m from the pipeline, and a spacing of 0.15-0.3 m from the adjacent pipeline.

[0016] Optionally, when the distance between adjacent pipelines is less than 1.5 m, an enlarged pier cap is provided on the top of the strip pier to form a T-shaped structure.

[0017] Optionally, the compaction grouting hole is a PVC sleeve valve pipe, and the radius R is 37.55 mm, the grouting liquid uses 42.5 grade ordinary Portland cement, and the water-cement ratio is 1.0.

[0018] Optionally, two rows of compaction grouting holes parallel to the axial direction of the pipeline are included between every two adjacent pipelines, and the two rows of compaction grouting holes are staggered and distributed with each other.

[0019] The present invention also proposes a construction method for a roadbed heightening structure based on an existing pipe group, which is used to form the above-mentioned roadbed heightening structure based on an existing pipe group, and comprises the following steps:

[0020] S1. Use compaction grouting to reinforce the soft soil layer between each adjacent pipeline to form a pile-soil composite foundation;

[0021] S2. Cast a strip pier on top of the pile-soil composite foundation, exceeding the height of the pipeline;

[0022] S3. Fill the trench filler between the adjacent strip piers and the pipeline, and make the trench filler submerge the top of the pipeline, and make the compaction coefficient ≥ 0.95;

[0023] S4. Paving EPS blocks above the trench filler and above the strip pier to form a settlement structure;

[0024] S5. Laying geogrids above the settlement structure and above the strip piers;

[0025] S6. Paving the roadbed fill on top of the geogrid, the settlement structure is compressed under the weight load of the roadbed fill, so that the roadbed fill produces a soil arch effect

[0026] S7. Performing road surface construction on top of the roadbed fill to form the newly built road surface.

[0027] The present invention also proposes a design method for a roadbed heightening structure based on an existing pipe group, which is used to form the above-mentioned roadbed heightening structure based on an existing pipe group, and includes the following steps:

[0028] P1. Measure and determine the parameters of the existing pipeline group: number of pipelines, pipeline diameter D, distance between adjacent pipelines, distance between adjacent pipeline centers L, height of pipeline center from the existing ground hz, height of the proposed road elevation from the existing ground H;

[0029] P2. Design of compaction grouting reinforcement for soft soil foundation. In order to effectively support the strip piers, fully reinforce the soft soil foundation between the pipelines, and appropriately overlap the compaction grouting reinforcement influence area, the horizontal spacing Lx, the vertical spacing Ly, and the grouting depth h of the compaction grouting holes staggered between the pipelines are designed based on economic considerations. zj You can confirm by pressing the formula

[0030]

[0031] P3. Assuming that the thickness of the settlement structure hc is 0.3m, we can get h d =D / 2+w+h c , h=H+h z -h d .

[0032] P4. Take h e =S, in order to avoid uneven settlement of the top surface of the proposed road, it is obviously necessary to require h e <h is used as a constraint condition. According to the soil arching effect theory, the following calculation formula can be derived:

[0033] Strip pier area replacement rate

[0034] Friction coefficient of roadbed fill

[0035] Active earth pressure coefficient of roadbed fill

[0036] Earth pressure acting on the top surface of the strip pier

[0037] Earth pressure acting on the top surface of the settlement structure

[0038] The stress ratio of the top surface of the strip pier and the settlement structure is n=p d / p c

[0039] Fill load sharing ratio of strip pier

[0040] Differential settlement Δs between the top surface of the strip pier and the settlement structure

[0041]

[0042] P5. Calculate the settlement of the soft soil layer in the foundation according to the layered summation method. Generally speaking, the compression modulus can be increased by about 40% to 60% after compaction grouting reinforcement. Therefore, when calculating the settlement of the soft soil layer in the foundation under the center of the strip pier, the compression modulus is calculated based on the increased value.

[0043] Additional pressure at the bottom of strip pier p fd =p d +γ d h d -γ s h z

[0044] Additional pressure at the bottom of the pipe p fg =p c +γ c h c +γ 砂 w

[0045] Settlement of soft soil layer under the center of strip pier

[0046] Settlement of soft soil layer under the center of pipeline

[0047] Where Esi is the compression modulus of the i-th layer of foundation soil, and the compression modulus E after compaction grouting is used to calculate the settlement of the soft soil layer under the center of the strip pier. s ′ i Calculate; i is the i-th layer, z i-1 is the distance between the bottom surface of the i-1th layer of soil and the surface acting on the additional pressure; α iis the average additional stress coefficient from the additional pressure action surface to the bottom surface of the i-th soil layer, i-1 is the average additional stress coefficient from the additional pressure action surface to the bottom surface of the i-1th soil layer, which can be adopted according to Appendix K of the current "Code for Design of Building Foundations" for strip foundations.

[0048] P6. Ignore the deformation of the concrete strip pier and the pipe itself, when S / 2≤h s When tanθ (θ is the foundation pressure diffusion angle after compaction grouting treatment, which can be 20-30°), the additional stress at the bottom of the strip pier can be considered to be evenly distributed in the deep bearing layer of the foundation, and the uneven settlement of the strip pier and the center of the pipeline in the deep bearing layer of the foundation can also be ignored. Therefore, the compression amount s of the settlement structure set on the top of the pipeline c =Δs+s d -s g .

[0049] P7. According to the elastic deformation theory, Calculate the thickness of the settlement structure h c , and change this step h c The calculated value is the same as that in step S3 c The assumed values ​​are compared and judged. If the difference is within 10%, the calculation is terminated. Otherwise, E is appropriately adjusted within the appropriate range (1.0~10.0MPa). c If the difference still exceeds 10%, then the current step h c Substitute the calculated value into step P3 and iterate again until h c The calculation is terminated when the difference is within 10%, thereby completing the design calculation.

[0050] The technical solution of the present invention arranges a plurality of compaction grouting holes between adjacent pipelines, so that grouting can be performed on adjacent pipelines and the soft soil layer below the pipelines through the compaction grouting holes to form a pile-soil composite foundation with high strength, and then a strip pier is cast with concrete above the pile-soil composite foundation between each two adjacent pipelines, and at the same time, the top surface of the strip pier exceeds a certain height of the pipeline. After the strip pier is consolidated, a trench filling material is filled between the adjacent strip piers and the pipeline, and the pipeline is semi-surrounded by the trench filling material, which not only ensures the wrapping support effect on the pipeline, but also avoids the formation of rigid constraints, and then a settlement structure is paved above the trench filling material until it is flush with the top surface of the strip pier, and then a roadbed fill is paved above the settlement structure and the strip pier. The purpose of the settlement structure is to regulate the amount of compression of the settlement structure under the action of the upper roadbed fill and superimpose it with the foundation settlement under the center of the pipeline. Compared with the foundation settlement under the strip pier, the settlement structure and the top surface of the strip pier produce differential settlement, which causes a soil arch effect inside the roadbed fill. Under the action of the soil arch effect, part of the fill load above the pipeline is transferred to the strip pier and then to the deep foundation, thereby reducing the fill pressure acting on the pipeline. After the construction is completed, the stress on the top of the existing pipe group is relatively small, avoiding the stress concentration of the existing pipe group and being damaged. In addition, compared with the use of foam lightweight soil for backfilling or the installation of a large area of ​​reinforced concrete cover, the structure of this scheme is more convenient for on-site construction, and can save engineering investment and avoid uneven settlement. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0052] Figure 1 It is a structural schematic diagram of an embodiment of a roadbed heightening structure based on an existing pipe group according to the present invention;

[0053] Figure 2 for Figure 1 Schematic diagram of the layout of medium-pressure grouting holes;

[0054] Figure 3 for Figure 1 The force analysis diagram of the roadbed heightening structure based on the existing pipe group;

[0055] Figure 4 It is a flow chart of the construction method of the roadbed heightening structure based on the existing pipe group of the present invention;

[0056] Figure 5The present invention is a flow chart of the design method of the roadbed heightening structure based on the existing pipe group.

[0057] Explanation of the reference numerals: 10, compaction grouting hole; 11, grouting influence area; 20, strip pier; 30, trench filling material; 40, settlement structure; 50, pipeline;

[0058] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0059] 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.

[0060] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0061] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0062] The present invention proposes a roadbed heightening structure based on an existing pipe group, which is used for the existing pipe group. The existing pipe group includes a plurality of pipes arranged in parallel.

[0063] In the embodiment of the present invention, Figures 1 to 3As shown, the roadbed heightening structure based on the existing pipe group includes a plurality of compaction grouting holes 10, a plurality of strip piers 20, a pipe trench filling material 30, a settlement structure 40, a roadbed fill and a newly built road surface; a compaction grouting hole 10 is arranged between any two adjacent pipes 50, and the top of the compaction grouting hole 10 is located between the bottom and the top of the existing pipe group. The compaction grouting hole 10 is used to grout the soft soil layer under the existing pipe group to form a pile-soil composite foundation; a plurality of strip piers 20 are arranged on the pile-soil composite foundation, and a strip pier 20 is arranged between any two adjacent pipes 50, and the top of the strip pier 20 is higher than Existing pipe groups; the trench filling material 30 is filled between the adjacent strip piers 20 and the pipes 50, as well as above the pipes 50, and the top of the pipe 50 filling material is not higher than the top of the strip pier 20; the settlement structure 40 is laid above the trench filling material 30, and the settlement structure 40 has a certain compression modulus; the roadbed fill is filled above the settlement structure 40 and the strip pier 20, and the settlement structure 40 is compressed by the weight load to produce settlement, and the settlement structure 40 and the top surface of the strip pier 20 produce differential settlement, so that a soil arch effect is generated inside the roadbed fill; the new road surface is paved above the roadbed fill.

[0064] Specifically, in this embodiment, the roadbed heightening structure based on the existing pipe group proposed in this scheme is used for the fill roadbed section of the urban riverside road covering the existing pipe group area. The existing pipe group is generally composed of three to four parallel arranged ductile iron pipes 50. The diameter D of the pipe 50 is generally between 0.6m and 1.4m, and the center distance L of each adjacent pipe 50 is generally between 1.5m and 3m.

[0065] After a plurality of compaction grouting holes 10 are arranged between every two adjacent pipes 50 , grouting can be performed into the soft soil layer between the adjacent pipes 50 through the compaction grouting holes 10 to reinforce the soft soil layer, and a pile-soil composite foundation is formed after the slurry is solidified.

[0066] Then, a strip pier 20 can be formed by pouring plain concrete on top of the pile-soil composite foundation. After the strip pier 20 is solidified, the trench filling material 30 is filled between the adjacent strip piers 20 until the trench filling material 30 covers the pipeline 50 to a certain height, surrounding the upper part of the pipeline 50. Then, the settlement structure 40 is paved on the trench filling material 30 until it is flush with the top surface of the strip pier 20. Then, the roadbed fill is filled on top of the strip pier 20 and the settlement structure 40. The purpose of setting the settlement structure 40 is to regulate the compression amount sc of the settlement structure 40 under the action of the upper roadbed fill and superimpose it with the foundation settlement amount sg below the center of the pipeline 50. Compared with the foundation settlement amount sd below the strip pier 20, the settlement structure 40 and the top surface of the strip pier 20 produce a differential settlement Δs=s c +s g -s d, this differential settlement Δs causes a soil arching effect inside the roadbed fill. (The soil arching effect refers to the stress redistribution phenomenon in the roadbed fill caused by the differential settlement Δs between the top surface of the strip pier 20 and the top surface of the settlement structure 30. Under the action of the soil arching effect, part of the fill load above the pipeline 50 is transferred to the strip pier 20 and then to the deep foundation, thereby reducing the fill pressure acting on the pipeline 50.)

[0067] As the height from the top surface of the strip pier 20 increases, the differential settlement between the strip pier 20 and the upper fill of the settlement structure 30 gradually decreases until it disappears. The plane differential settlement disappears at the soil arch height he (measured from the top surface of the strip pier 20), also known as the equal settlement surface. There is no uneven settlement in the roadbed fill above the equal settlement surface.

[0068] The technical solution of the present invention arranges a plurality of compaction grouting holes 10 between adjacent pipes 50, so that grouting can be performed on the adjacent pipes 50 and the soft soil layer below the pipes 50 through the compaction grouting holes 10 to form a pile-soil composite foundation with higher strength. Since it is impossible to use high-pressure rotary jet piles, cement-soil mixing piles and other construction measures to treat the soft foundation in the existing pipe group area of ​​Binjiang Road, the soft foundation is reinforced by compaction grouting in this way, which is simple to construct, can improve the bearing capacity of the soft soil foundation, and reduce the settlement of the roadbed after construction.

[0069] Then, a strip pier 20 is cast with concrete above the pile-soil composite foundation between each two adjacent pipelines 50, and at the same time, the top surface of the strip pier 20 is made to exceed a certain height of the pipeline 50. After the strip pier 20 is solidified, the trench filling material 30 is filled between the adjacent strip piers 20 and the pipeline 50, and the pipeline 50 is semi-surrounded by the trench filling material 30, which not only ensures the wrapping support effect on the pipeline 50, but also avoids the formation of rigid constraints. Then, a settlement structure 40 is paved above the trench filling material 30 until it is flush with the top surface of the strip pier 20, and then the roadbed fill is paved above the settlement structure 40 and the strip pier 20. The purpose of the settlement structure 40 is to regulate the amount of compression of the settlement structure 40 under the action of the upper roadbed fill and to superimpose it with the foundation settlement below the center of the pipeline 50. Compared with the foundation settlement below the strip pier 20, the settlement structure 40 and the top surface of the strip pier 20 produce differential settlement, which causes a soil arch effect inside the roadbed fill. Under the action of the soil arch effect, part of the fill load above the pipeline 50 is transferred to the strip pier 20 and then to the deep foundation, thereby reducing the fill pressure acting on the pipeline 50. After the construction is completed, the stress on the top of the existing pipe group is relatively small, which avoids the stress concentration of the existing pipe group and its damage. In addition, compared with the use of foam lightweight soil for backfilling or the setting of a large area of ​​reinforced concrete cover, the structure of this solution is more convenient for on-site construction, and can save engineering investment and avoid uneven settlement.

[0070] In some embodiments, the roadbed heightening structure based on the existing pipe group further includes a bidirectional geogrid, which is laid between the settlement structure 40 and the roadbed fill, and the nominal tensile strength of the bidirectional geogrid is ≥80kN / m, and the elongation under the nominal tensile strength is ≤3%. Specifically, the high tensile strength of the geogrid can transfer the roadbed fill load to the strip pier 20, limit the displacement of the soil in the horizontal and vertical directions, and at the same time utilize the lifting effect to increase the height of the soil arch, reduce the load above the pipeline 50, and avoid road cracking.

[0071] In some embodiments, the thickness hc of the settlement structure 30 is generally 0.3-0.5m, and it is paved with EPS blocks. The compression modulus Ec of the EPS blocks is generally 1.0-10.0MPa, and the gravity γc is generally 9.0-11.0kN / m3. Specifically, in this embodiment, the thickness hc of the settlement structure 30 is set to 0.3m, the width S is set to 1.8m, Ec is 1.5MPa, and the gravity γc is 10.0kN / m3. The settlement structure 30 and the top surface of the strip pier 20 produce a differential settlement Δs=s c +s g -s d . The EPS block has a low compression modulus, and as a settlement structure 30, it can bring about a better settlement difference. In addition, the EPS block is light in weight, which can greatly reduce the load acting on the existing pipe group and the lower foundation, and help reduce the total settlement of the foundation, thereby reducing the risk of damage to the pipeline 50 due to excessive settlement. In addition, EPS blocks usually have regular shapes and sizes, which are easy to carry and lay at the construction site, can improve construction efficiency, and shorten the construction period. Moreover, EPS blocks can be connected by splicing and other methods, which can better adapt to different roadbed shapes and size requirements. In addition, in other embodiments, foam lightweight soil is used as the settlement structure 40.

[0072] In some embodiments, the trench filler 30 is medium-coarse sand. Specifically, the compaction coefficient of the medium-coarse sand is not less than 0.95. The medium-coarse sand has a higher porosity and is much more permeable than fine sand or clay. It can quickly drain the water in the trench and avoid corrosion or softening of the foundation caused by long-term immersion of the pipeline 50. Moreover, the medium-coarse sand has a loose particle structure and a low compression modulus. It forms a flexible cushion between the strip pier 20 and the pipeline 50, allowing a certain deformation to avoid rigid constraints on the pipeline 50. Furthermore, the high friction characteristics of the medium-coarse sand can transfer part of the load above the pipeline 50 to the strip piers 20 on both sides through friction, thereby enhancing the load transfer efficiency of the soil arch effect. In addition, in other embodiments, foam lightweight soil can also be used instead of the medium-coarse sand.

[0073] In some embodiments, the strip pier 20 is rectangular, and a settlement joint is arranged every 10 to 20 meters along the direction of the pipeline 50. The width dimension d of the strip pier 20 is generally 0.8-1.2m, the height dimension hd is 1.0-1.5m, and the net spacing w between the strip pier 20 and the adjacent pipeline 50 is 0.15-0.3m. In this embodiment, the height hd is set to 1.2m, the width d is set to 0.8m, and the net spacing w with the pipeline 50 is set to 0.2m. Specifically, the width dimension of the strip pier 20 effectively disperses the upper roadbed fill load while meeting the compressive strength of the plain concrete strip pier 20 itself, avoiding the fracture of the strip pier 20 or local shear failure of the foundation caused by stress concentration; the height dimension of the strip pier 20 can ensure that a sufficient differential settlement Δs (about 5-15mm) is formed between the top surface of the strip pier 20 and the settlement structure 40, triggering a significant soil arch effect, so that the load transfer efficiency above the pipeline 50 is increased by 30%-50%. By setting a gap between the strip pier 20 and the adjacent pipeline 50, a "rigid-flexible transition zone" can be formed between the strip pier 20 and the pipeline 50, which can avoid stress concentration in the pipeline 50 caused by rigid contact and transfer about 20%-30% of the load above the pipeline 50 to the strip pier 20 through friction, thereby enhancing the soil arch effect.

[0074] In some embodiments, when the distance between adjacent pipes 50 is less than 1.5m, an enlarged pier cap is set on the top of the strip pier 20 to form a T-shaped structure. Specifically, by increasing the bearing area at the top of the strip pier 20, the load originally concentrated in the narrow area can be diffused to both sides, thereby reducing the pressure per unit area. At the same time, the flange part of the T-shaped structure can form a local stiffness coordination area with the pier cap of the adjacent strip pier 20, effectively suppressing the differential settlement mutation caused by the close distance between the pipes 50, and ensuring the continuity of the soil arch effect. Furthermore, in addition, this can also enhance the integrity of the roadbed fill through the bite effect of the flange and the trench filling material 30, make the load transfer path more uniform, and avoid local stress concentration damage caused by the dense pipes 50.

[0075] In some embodiments, the compaction grouting hole 10 is a PVC sleeve valve pipe, and has a radius of 37.55 mm and a depth of 4.5 m. The grouting liquid uses 42.5-grade ordinary Portland cement, and the water-cement ratio is 1.0. Specifically, the PVC sleeve valve pipe can achieve directional and quantitative grouting in the soft soil layer through a segmented open-loop design, and the slurry diffusion radius is controlled at 0.8-1.2 m, which can avoid overpressure damage to the existing pipeline 50. The 42.5-grade cement slurry has a high compressive strength after consolidation, and the pile-soil composite foundation pile formed with the original soil has a good bearing capacity.

[0076] In some embodiments, two rows of compaction grouting holes 10 parallel to the axial direction of the pipes 50 are provided between each two adjacent pipes 50, and the two rows of compaction grouting holes 10 are staggered. Specifically, compared with only a single row of compaction grouting holes, the diffusion range of the slurry during grouting is larger, and the range of the pile-soil composite foundation formed is larger, which can better support the strip pier 20 and eliminate the potential stress weak area under the strip pier 20.

[0077] A construction method for a roadbed heightening structure based on an existing pipe group is used to form the roadbed heightening structure based on an existing pipe group in the above embodiment, such as Figure 4 As shown, the following steps are included:

[0078] S1. Use compaction grouting to reinforce the soft soil layer between each adjacent pipeline 50 to form a pile-soil composite foundation;

[0079] S2. On the basis of the pile-soil composite foundation, the strip pier 20 is cast between each adjacent pipe 50 and exceeds the height of the pipe 50;

[0080] S3. Fill the trench filler 30 between the adjacent strip piers 20 and the pipe 50, and make the trench filler 30 submerge the top of the pipe 50, and make the compaction coefficient ≥ 0.95;

[0081] S4. EPS blocks are laid above the trench filler 30 and above the strip pier 20 to form a settlement structure 40;

[0082] S5. Paving geogrids above the settlement structure 40 and above the strip pier 20;

[0083] S6. The roadbed fill is laid on top of the geogrid. Under the weight load of the roadbed fill, the settlement structure 40 is compressed, and the roadbed fill produces a soil arch effect.

[0084] S7. Carry out pavement construction on top of the roadbed fill to form a new pavement.

[0085] Specifically, since it is impossible to use high-pressure jet grouting piles, cement-soil mixing piles and other construction measures to treat the soft foundation in the area of ​​the existing pipe group of Binjiang Road, the soft foundation is reinforced by compaction grouting, which is simple to construct, can improve the bearing capacity of the soft soil foundation, and reduce the settlement of the roadbed after construction. Moreover, after the strength pile-soil composite foundation is formed, the strip pier 20 can be subsequently cast to stabilize the foundation and provide stable support for the consolidated strip pier 20. The strip pier 20 can form a stable rigid support and transfer the upper load to the depth of the pile-soil composite foundation. The pipe trench filling material 30 is made of medium-coarse sand. After the medium-coarse sand filled between the pipe trenches is compacted, part of the upper load can also be transferred to the strip pier 20 through friction between the particles. The purpose of the settlement structure 40 is to regulate the compression of the settlement structure 40 under the action of the upper roadbed fill and superimpose it with the foundation settlement below the center of the pipeline 50. Compared with the foundation settlement below the strip pier 20, the settlement structure 40 and the top surface of the strip pier 20 produce differential settlement, which causes a soil arch effect inside the roadbed fill. Under the action of the soil arch effect, part of the fill load above the pipeline 50 is transferred to the strip pier 20 and then transferred to the deep foundation, thereby reducing the fill pressure acting on the pipeline 50. After the roadbed fill and geogrid are paved in turn, the high tensile strength of the geogrid can transfer the roadbed fill load toward the strip pier 20, limit the displacement of the soil in the horizontal and vertical directions, and at the same time utilize the lifting effect to increase the height of the soil arch, reduce the load above the pipeline 50, and avoid cracking of the newly constructed road surface in the subsequent construction. The construction scheme proposed in this scheme is used to construct the existing pipe group, solve the technical problem of raising the roadbed above the existing pipe group, and achieve the engineering goals of safety, economy and efficiency.

[0086] A design method for a roadbed heightening structure based on an existing pipe group is used for the roadbed heightening structure based on an existing pipe group in the above embodiment, such as Figure 5 As shown, the following steps are included:

[0087] P1. According to the proposed road design and on-site measurements of the existing pipeline group, H = 4.4m, L = 2.6m,

[0088] D=1.4m、h z = 0.8m, take w = 0.2m, then we know S = D + 2w = 1.4 + 2*0.2 = 1.8m,

[0089] d=L-S=2.6-1.8=0.8m; According to the selected filler source, the roadbed fill γ=19kN / m 3 , E = 10MPa; According to the survey data, the weight of the soft soil layer under the pipe group is γ s =18kN / m 3 , compression modulus E s =5MPa, thickness hs =3.5m (In this example, the calculation is simplified as a uniform soft soil layer, and the compression modulus increases by 50% after compaction grouting reinforcement).

[0090] P2. Design of compaction grouting reinforcement for soft soil foundation. In order to effectively support the strip piers 20, fully reinforce the soft soil foundation between the pipes 50, and appropriately overlap the impact areas of compaction grouting reinforcement, the lateral spacing Lx, longitudinal spacing Ly, and grouting depth hzj of the compaction grouting holes 10 staggered between the pipes 50 should be determined according to the following formula based on economic considerations.

[0091]

[0092] P3. Assume the settlement structure for 30h c The thickness is 0.3m, so h d =D / 2+w+h c =1.4 / 2+0.2+0.3=1.2m, h=H+h z -h d =4.4+0.8-1.2=4.0m.

[0093] P4. Take h e =S=1.8m<h=4.0m, according to the soil arch effect theory, the following contents can be calculated according to the formula derived by the present invention:

[0094] Strip pier 20 area replacement rate

[0095] Friction coefficient of roadbed fill

[0096] Active earth pressure coefficient of roadbed fill

[0097] Earth pressure acting on the top surface of strip pier 20

[0098]

[0099] Earth pressure acting on the top surface of the settlement structure 30

[0100]

[0101] The top surface stress ratio of the strip pier 20 and the settlement structure 30

[0102] Fill load sharing ratio of strip pier 20

[0103] Differential settlement of the top surface of the strip pier 20 and the settlement structure 30

[0104] P5. Calculate the settlement of the soft soil layer in the foundation according to the layered summation method. Generally speaking, the compression modulus can be increased by about 40% to 60% after compaction grouting reinforcement. In this example, the settlement of the soft soil layer in the foundation under the center of the strip pier 20 is calculated based on a 50% increase in the compression modulus. When calculating the settlement of the soft soil layer in the foundation under the center of the strip pier 20, the average additional stress coefficient αi=4*0.0962=0.3848 can be obtained by checking Appendix K of the current "Code for Design of Building Foundations" and interpolating according to the strip foundation of zi=hs=3.5m, zi-1=0.d=0.8m; when calculating the settlement of the soft soil layer in the foundation under the center of the pipeline 50, according to z i =h s -D / 2=3.5-1.4 / 2=2.8mz i-1 = 0.S = 1.8m strip foundation, check Appendix K of the current "Code for Design of Building Foundations" and interpolate to get the average additional stress coefficient α i =4*0.1706=0.6824.

[0105] Additional pressure p at the bottom of strip pier 20 fd =p d +γ d h d -γ s h z =151.91+25*1.2-18*

[0106] 0.8 = 167.51 kPa

[0107] Additional pressure p at the bottom of pipeline 50 fg =p c +γ c h c +γ 砂 w=42.26+10*0.3+18*

[0108] 0.2=48.86kPa

[0109] Settlement of soft soil layer under the center of strip pier 20

[0110]

[0111] Settlement of soft soil layer under the center of pipeline 20

[0112]

[0113] P6. Ignoring the deformation of the concrete strip pier 20 and the pipe 50 itself, when S / 2=0.9m≤h sWhen tanθ=3.5*tan20°=1.27m (θ is the foundation pressure diffusion angle after compaction grouting treatment, which is 20°), the additional stress at the bottom of the strip pier 20 can be considered to be evenly distributed in the deep bearing layer of the foundation, and the uneven settlement of the strip pier 20 and the center of the pipeline 50 in the deep bearing layer of the foundation can also be ignored. Therefore, the compression amount s of the settlement structure 30 set on the top of the pipeline 50 is c =Δs+s d -s g =1.58+30.08-18.67=12.99mm.

[0114] P7. According to the elastic deformation theory, Right now Calculate the settlement structure 30 thickness h c =0.44m, and step S3 h c Assuming a value of 0.3m for comparison and judgment, the error exceeds 10%; adjust E appropriately c The value is adjusted from 1.5MPa to 1.1MPa. Calculate the settlement structure 30 thickness h c =0.32m, and step S3 h c The calculation is ended assuming that the error of the value 0.3m is within 10%; thus completing the design calculation of the above example.

[0115] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A roadbed heightening structure based on an existing pipe group, which is used for an existing pipe group, wherein the existing pipe group includes a plurality of parallel arranged pipes, and is characterized in that: include: A plurality of compaction grouting holes, wherein the compaction grouting holes are arranged between any two adjacent pipes, the top of the compaction grouting holes are located between the bottom and the top of the active pipe group, and the compaction grouting holes are used to grout the soft soil layer below the active pipe group to form a pile-soil composite foundation; A plurality of strip piers are arranged on the pile-soil composite foundation, and the strip piers are arranged between any two adjacent pipelines, and the tops of the strip piers are higher than the active pipe group; Pipe trench filling material is filled between the adjacent strip piers and the pipes, and above the pipes, and the top of the pipe trench filling material is not higher than the top of the strip pier; A settlement structure is laid above the trench filling material, and the settlement structure has a certain compression modulus; The roadbed fill is filled above the settlement structure and the strip pier, and the settlement structure is compressed by the weight load to cause settlement, and the settlement structure and the top surface of the strip pier are differentially settled, so that a soil arch effect is generated inside the roadbed fill; as well as A new road surface is constructed on top of the roadbed fill.

2. The roadbed heightening structure based on the active pipe group according to claim 1 is characterized in that: The roadbed heightening structure based on the existing pipe group also includes a bidirectional geogrid, which is laid between the settlement structure and the roadbed fill. The bidirectional geogrid has a nominal tensile strength of ≥80kN / m and an elongation at the nominal tensile strength of ≤3%.

3. The roadbed heightening structure based on the active pipe group according to claim 1 is characterized in that: The settlement structure is paved with EPS blocks.

4. The roadbed heightening structure based on the active pipe group according to claim 1 is characterized in that: The pipe trench filling material is medium-coarse sand.

5. The roadbed heightening structure based on the active pipe group according to claim 1 is characterized in that: The strip pier has a width of 0.8-1.2m, a height of 1.0-1.5m, a net spacing of 0.15-0.3m from the pipeline, and a spacing of 0.15-0.3m from the strip pier and the adjacent pipeline.

6. The roadbed heightening structure based on the active pipe group according to claim 5 is characterized in that: When the distance between adjacent pipelines is less than 1.5 m, an enlarged pier cap is arranged on the top of the strip pier to form a T-shaped structure.

7. The roadbed heightening structure based on the active pipe group according to claim 5 is characterized in that: The compaction grouting hole is a PVC sleeve valve pipe, and the radius R is 37.55 mm. The grouting liquid uses 42.5 grade ordinary Portland cement, and the water-cement ratio is 1.

0.

8. The roadbed heightening structure based on the active pipe group according to claim 7 is characterized in that: Two rows of compaction grouting holes parallel to the axial direction of the pipelines are provided between each two adjacent pipelines, and the compaction grouting holes in these two rows are staggered and distributed with each other.

9. A construction method for a roadbed heightening structure based on an existing pipe group, used to form a roadbed heightening structure based on an existing pipe group as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Use compaction grouting to reinforce the soft soil layer between each adjacent pipeline to form a pile-soil composite foundation; S2. On the basis of the pile-soil composite foundation, a strip pier is cast between each adjacent pipe and exceeds the height of the pipe; S3. Fill the trench filler between the adjacent strip piers and the pipeline, and make the trench filler submerge the top of the pipeline, and make the compaction coefficient ≥ 0.95; S4. Paving EPS blocks above the trench filler and above the strip pier to form a settlement structure; S5. Laying geogrids above the settlement structure and above the strip piers; S6. Paving the roadbed fill on the top of the geogrid, the settlement structure is compressed under the weight load of the roadbed fill, and the roadbed fill produces a soil arch effect S7. Performing road surface construction on top of the roadbed fill to form a new road surface.

10. A design method for a roadbed heightening structure based on an existing pipe group, used to form a roadbed heightening structure based on an existing pipe group as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: P1. Measure and determine the parameters of the existing pipeline group: number of pipelines, pipeline diameter D, distance between adjacent pipelines, distance between adjacent pipeline centers L, height of pipeline center from the existing ground hz, height of the proposed road elevation from the existing ground H; P2. Design of compaction grouting reinforcement for soft soil foundation. In order to effectively support the strip piers, fully reinforce the soft soil foundation between the pipelines, and appropriately overlap the compaction grouting reinforcement influence area, the horizontal spacing Lx, the vertical spacing Ly, and the grouting depth h of the compaction grouting holes staggered between the pipelines are designed based on economic considerations. zj You can confirm by pressing the formula P3. Assuming that the thickness of the settlement structure hc is 0.3m, we can get h d =D / 2+w+h c , h=H+h z -h d . P4. Take h e =S, in order to avoid uneven settlement of the top surface of the proposed road, it is obviously necessary to require h e <h is used as a constraint condition. According to the soil arching effect theory, the following calculation formula can be derived: Strip pier area replacement rate Friction coefficient of roadbed fill Active earth pressure coefficient of roadbed fill Earth pressure acting on the top surface of the strip pier Earth pressure acting on the top surface of the settlement structure The stress ratio of the top surface of the strip pier and the settlement structure is n=p d / p c Fill load sharing ratio of strip pier Differential settlement of strip pier and top surface of settlement structure P5. Calculate the settlement of the soft soil layer in the foundation according to the layered summation method. Generally speaking, the compression modulus can be increased by about 40% to 60% after compaction grouting reinforcement. Therefore, when calculating the settlement of the soft soil layer in the foundation under the center of the strip pier, the compression modulus is calculated based on the increased value. Additional pressure at the bottom of strip pier p fd =p d +γ d h d -γ s h z Additional pressure at the bottom of the pipe p fg =p c +γ c h c +γ 砂 w Settlement of soft soil layer under the center of strip pier Settlement of soft soil layer under the center of pipeline Where Esi is the compression modulus of the i-th layer of foundation soil, and the compression modulus E after compaction grouting is used to calculate the settlement of the soft soil layer under the center of the strip pier. s ′ i Calculate; i is the i-th layer, z i-1 is the distance between the bottom surface of the i-1th layer of soil and the surface acting on the additional pressure; α i is the average additional stress coefficient from the additional pressure action surface to the bottom surface of the i-th soil layer, i-1 is the average additional stress coefficient from the additional pressure action surface to the bottom surface of the i-1th soil layer, which can be adopted according to Appendix K of the current "Code for Design of Building Foundations" for strip foundations. P6. Ignore the deformation of the concrete strip pier and the pipe itself, when S / 2≤h s When tanθ (θ is the foundation pressure diffusion angle after compaction grouting treatment, which can be 20-30°), the additional stress at the bottom of the strip pier can be considered to be evenly distributed in the deep bearing layer of the foundation, and the uneven settlement of the strip pier and the center of the pipeline in the deep bearing layer of the foundation can also be ignored. Therefore, the compression amount s of the settlement structure set on the top of the pipeline c =Δs+s d -s g . P7. According to the elastic deformation theory, Calculate the thickness of the settlement structure h c , and change this step h c The calculated value is the same as that in step S3 c The assumed values ​​are compared and judged. If the difference is within 10%, the calculation is terminated. Otherwise, E is appropriately adjusted within the appropriate range (1.0~10.0MPa). c If the difference still exceeds 10%, then the current step h c Substitute the calculated value into step P3 and iterate again until h c The calculation is terminated when the difference is within 10%, thereby completing the design calculation.

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