Construction method for retreat-type grouting protection of important underground pipelines in cities

Abstract

The application discloses a construction method for retreat-type grouting protection of important underground pipelines in cities, which comprises the following steps: step one, excavating a foundation pit and a sewage main pipe laying groove, and installing the sewage main pipe in the groove; step two, rechecking the buried depth of the sewage main pipe before dewatering, and the water level outside the pit should not be lower than the pipe center line elevation of the sewage main pipe; step three, using the retreat-type grouting method to pour and support soil blocks on the side of the sewage main pipe close to the foundation pit; step four, reinforcing a row of the support soil blocks at an interval of 1.5 m along the pipe direction of the sewage main pipe; and step five, using integral pouring to form the support soil blocks within a range of 30 m from the side of the sewage main pipe close to an earth removal ramp. Through retreat-type grouting reinforcement, the application can maximally reduce the disturbance of soil bodies and simultaneously achieve the effect of reinforcement and protection.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, specifically to a construction method for retreat grouting protection of important underground pipelines in cities. Background Technology

[0002] Underground pipelines are a crucial component of urban infrastructure. They encompass several major categories, including water supply, drainage, gas, telecommunications, electricity, and industrial pipelines. Like the "nerves" and "blood vessels" of the human body, they tirelessly transmit information and energy, forming the material foundation for a city's survival and development. With urban development, available land for construction is becoming increasingly scarce, and construction sites are increasingly located close to critical municipal pipelines. During construction projects, deep foundation pit excavation causes the greatest disturbance to the surrounding soil. Therefore, developing protection plans and implementing protective measures for important pipelines before this stage is of paramount importance. How to effectively protect pipelines with minimal disturbance remains a topic worthy of further research. Summary of the Invention

[0003] The purpose of this invention is to provide a construction method for retreat grouting protection of important underground pipelines in cities. This method overcomes the problem that traditional grouting reinforcement causes great disturbance to the soil and is prone to damage to sewage trunk lines during the reinforcement process. During the grouting process, the grouting pressure is strictly controlled to minimize soil disturbance and achieve a good pipeline protection effect.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A construction method for retreat grouting protection of important urban underground pipelines includes the following steps:

[0006] Step 1: Excavate the foundation pit and the trench for laying the sewage trunk line, and install the sewage trunk line in the trench.

[0007] Step 2: Before dewatering, verify the burial depth of the sewage trunk line. The water level outside the pit must not be lower than the centerline elevation of the sewage trunk line.

[0008] Step 3: On the side of the sewage trunk line closest to the foundation pit, cast supporting soil blocks using a backward grouting method;

[0009] Step 4: The supporting soil blocks are reinforced at 1.5m intervals along the direction of the sewage trunk pipeline;

[0010] Step 5: The supporting soil blocks within 30m of the side of the sewage trunk line near the excavation ramp are integrally cast.

[0011] As a further aspect of the present invention: the upper end of the supporting soil block is flush with the upper end of the sewage trunk line, and the depth of the supporting soil block is 20m.

[0012] As a further aspect of the present invention: the specific steps for casting the supporting soil blocks using the backward grouting method are as follows:

[0013] The grouting hole is positioned, and the grouting pipe is inserted by vibration after positioning. After the grouting pipe is inserted, grouting is performed by single / double liquid injection. As the grouting height increases, the grouting pipe is lifted upward until the grouting height set for the supporting soil block is reached.

[0014] As a further aspect of the present invention: the grouting holes are symmetrically distributed 500mm on both sides of the sewage trunk line, and the grouting holes are distributed at intervals of 1.5m along the length of the sewage trunk line.

[0015] As a further aspect of the present invention: the positional deviation of the grouting hole shall not exceed 6 cm, the verticality deviation shall be less than 1%, and when the grouting hole has a design angle, the inclination deviation shall not exceed 5°.

[0016] As a further aspect of the present invention: the grouting pressure of the backward grouting method is 0.2MPa to 0.5MPa, and the grouting flow rate is 10 to 20L / min.

[0017] As a further aspect of the present invention: the retreating grouting method uses cement grout for grouting, wherein the volume ratio of cement grout to water glass is 4:1; the water-cement ratio in the cement grout is 0.8:1; the water glass Baume degree is 35°Bé; and the grout setting time is controlled within the range of 60s to 180s.

[0018] As a further aspect of the present invention: the grouting pipe is a 1-inch galvanized pipe of 1-5m or a steel pipe with a diameter greater than 30mm.

[0019] The beneficial effects of this invention are:

[0020] (1) By reinforcing with backward grouting, the soil disturbance is minimized, while the reinforcement and protection effect is achieved.

[0021] (2) Breaking through the traditional grouting reinforcement method, which causes great disturbance to the soil and is prone to damage to sewage trunk lines during the reinforcement process, the grouting pressure is strictly controlled during the grouting process to minimize soil disturbance and achieve a good pipeline protection effect. Attached Figure Description

[0022] The present invention will now be further described with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic diagram of the structure supporting the soil according to the present invention.

[0024] In the diagram: 1. Site floor; 2. Sewage trunk line; 3. Supporting soil; 4. Protective frame. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1 As shown, this invention provides a construction method for retreat grouting protection of important underground pipelines in cities, comprising the following steps:

[0027] Step 1: Excavate the foundation pit and lay the trench for sewage trunk line 2, and install sewage trunk line 2 in the trench.

[0028] Step 2: Before dewatering, check the burial depth of sewage trunk line 2. The water level outside the pit must not be lower than the centerline elevation of sewage trunk line 2.

[0029] Step 3: On the side of the sewage trunk line 2 closest to the foundation pit, cast supporting soil blocks 3 using the backward grouting method;

[0030] Step 4: Reinforce the supporting soil blocks 3 at 1.5m intervals along the direction of the sewage trunk line 2;

[0031] Step 5: The supporting soil blocks 3 within 30m of the side of the sewage trunk line 2 near the excavation ramp are integrally cast.

[0032] A protective frame 4 is installed on the ground 1 above the sewage trunk 2 at the entrance. The protective frame 4 is made of channel steel and steel bars welded into a steel frame, and steel plates are laid on top to protect the sewage trunk 2.

[0033] The upper end of the supporting soil block 3 is flush with the upper end of the sewage trunk 2, and the depth of the supporting soil block 3 is 20m.

[0034] The specific steps for casting the supporting soil block 3 using the retreating grouting method are as follows:

[0035] The grouting hole is positioned, and the grouting pipe is inserted by vibration after positioning. After the grouting pipe is inserted, grouting is performed by single / double liquid injection. As the grouting height increases, the grouting pipe is lifted upward until the grouting height set by the supporting soil block 3 is reached.

[0036] Retreating grouting is a technique used to reinforce weak foundations, control ground settlement, prevent seepage and plug leaks in foundation pits, and correct building tilt. Through grouting pipes, pressure forces grout into the soil in a squeezed, penetrating, and fracturing manner, thereby increasing the soil's strength and elastic modulus.

[0037] Before inserting the pipe, prepare the grouting pipe. Generally, use 1-inch galvanized pipe of 1-5m or steel pipe with a diameter greater than 30mm. The grouting pipe must be checked in advance to see if there are any foreign objects blocking the pipe, whether the threads are intact, whether the plug at the bottom of the grouting pipe is flexible, and whether the rubber on the perforated pipe is tight.

[0038] Grouting holes are symmetrically distributed 500mm on both sides of sewage main pipe 2, and the grouting holes are distributed at intervals of 1.5m along the length of sewage main pipe 2.

[0039] The positional deviation of the grouting hole shall not exceed 6cm, the verticality deviation shall be less than 1%, and when the grouting hole has a design angle, the inclination deviation shall not exceed 5°.

[0040] The grouting pressure should be determined through field tests. In sandy silt, the grouting pressure is 0.2 MPa to 0.5 MPa.

[0041] Minimum grouting pressure calculation:

[0042]

[0043] In the formula: P min —Minimum grouting pressure, MPa;

[0044] h—Depth from the ground to the grouting section, in meters;

[0045] γ — Natural unit weight of grouting foundation, kN / m 3 ;

[0046] σ t —The tensile strength of the soil can be taken as 0.005MPa-0.040MPa.

[0047] Calculation of grouting volume per hole:

[0048] Q = C1V

[0049] Where: Q—grouting volume, m 3 .

[0050] C1—Empirical coefficient, which can be taken as 0.1 to 0.3; it should be determined according to the reinforcement requirements of the soil, and a larger value should be taken when higher reinforcement strength is required;

[0051] V—Soil mention, m 3 .

[0052] Grouting flow rate: generally 10-20 L / min, which can be adjusted according to the formation and grouting pressure.

[0053] The retreating grouting method uses cement grout for grouting, wherein the volume ratio of cement grout to water glass is 4:1; the water-cement ratio in the cement grout is 0.8:1; the water glass Baume degree is 35°Bé; and the grout setting time is controlled within the range of 60s to 180s.

[0054]

[0055] Cement slurry is expressed as water-cement ratio (W / C), and water glass concentration is expressed as Baume degree °Bé.

[0056] The grouting process and effective range should be determined according to the different requirements of the project, and must fully meet the purposes of seepage prevention and plugging, improving soil strength and modulus, filling voids, and underpinning. The soil cover at the grouting point should be greater than 2m.

[0057] The design of the grout and its mix ratio must take into account the purpose of grouting, geological conditions, the pore size of the foundation soil, and the state of groundwater, and select the optimal mix ratio within the range that meets the required purpose.

[0058] For grouting treatment of soft soil, a suspension with cement as the main component can be selected as the grouting material.

[0059] The grouting fluid used to improve the strength of the supporting soil block 3 can be a suspension with cement as the main component.

[0060] The initial setting time must be determined based on the soil conditions and the purpose of grouting. In sandy soil grouting, the initial setting time of the grout is generally 5 to 20 minutes, while in cohesive soil splitting grouting, the initial setting time is generally 1 to 2 hours.

[0061] The grouting volume depends on factors such as the properties of the foundation soil and the permeability of the grout. During large-scale grouting operations, it is advisable to conduct test grouting at the construction site to determine the grouting volume; generally, the grout injection rate in cohesive soils is 15%–20%.

[0062] Grouting pressure mainly depends on the consistency of the grout material, the grouting depth, and the properties of the soil layer. Generally, it is 0.2 to 0.5 MPa for sandy soil and 0.2 to 0.3 MPa for cohesive soil.

[0063] The arrangement of grouting holes should be such that the supporting soil blocks 3 are connected as a whole in both plane and depth.

[0064] The grouting sequence must be tailored to the soil conditions, site environment, and grouting purpose. Generally, a staggered, skip-row, skip-hole method is used to prevent cross-contamination of grout and improve the strength and confinement of the grout within the grouting holes. In special cases with groundwater flow, the migration effect under the flow should be considered, and grouting should begin from the end with the higher water head.

[0065] Grouting should be performed from the outer perimeter first, then from the inner perimeter. If there are boundary constraints outside the grouting area, a method of grouting from the inner side to the outer side can also be used.

[0066] When using cement grout for grouting, ordinary Portland cement with a grade of not less than PO42.5 should be used, and the water-cement ratio of the cement grout should be 3:1 to 0.6:1.

[0067] To improve slurry performance, the following admixtures can be added during slurry mixing: a. To improve slurry diffusion capacity, surfactants (or water-reducing agents) can be used, generally at a dosage of 0.3% to 0.5% of the cement weight. b. To improve slurry uniformity and stability, and prevent segregation and sedimentation of solid particles, bentonite can be added, but its dosage should not exceed 5% of the cement weight.

[0068] When mixing the slurry, the materials should be added accurately according to the formula requirements, and attention should be paid to the order of addition. Generally, the order of addition of materials to the slurry is water → cement → admixture.

[0069] The cement slurry is strictly filtered, and the filter mesh density is not less than 40 mesh.

[0070] The water used for mixing should be potable tap water, river water, well water, or other clean water. Acidic water with a pH value less than 4 and industrial wastewater should not be used.

[0071] During the grouting process, the grouting flow rate is generally 7-10 L / min. For filling-type grouting, the flow rate can be appropriately increased, but should not exceed 20 L / min.

[0072] To ensure uniform grouting in the grouting section, the grouting pipe should be pulled up according to the designed grouting volume per meter during grouting. The pulling height should be 330mm when grout exits through the end of the grouting pipe and 500mm when grout exits through the 50cm long perforated pipe.

[0073] Grouting construction should follow the principle of sequential densification. When grouting multiple rows of holes, the order should follow the principle of grouting the outer rows first and then the middle rows; for curtains composed of multiple rows of holes, it is advisable to grout the upstream rows first and then the downstream rows; for grouting holes on the same row, an intermittent skipping method or three-sequence grouting should be used.

[0074] Holes of the same sequence can be constructed simultaneously, while holes of different sequences should be constructed in the prescribed order.

[0075] When reinforcing the foundation of an existing building, a large-interval, skip-step construction sequence should be adopted.

[0076] The selection of mechanical equipment during construction in this invention:

[0077] The machinery used in grouting projects mainly includes pipe insertion machinery, grouting machinery, mixing machinery, lifting equipment, and some pipes and display instruments.

[0078] The cannulation machinery can be selected according to the geological conditions, and rotary machinery is often used for drilling and cannulation.

[0079] Grouting machinery: mainly grouting pumps. Based on the characteristics of grouting, grouting pumps with adjustable pressure and flow rate and low piston wear should be selected; generally, the Xy200 hydraulic grouting pump is chosen.

[0080] External circulation mixers are commonly used for mixing, but horizontal blade mixers can also be used. The mixing time is controlled to achieve uniform mixing of the slurry.

[0081] Pipe lifting equipment commonly uses guide pipe lifters, manual hoists, or leverage principles to lift pipes.

[0082] Other tools include instruments (pressure gauges, flow meters), plugs, grouting galvanized pipes, and wire-wound hoses.

[0083] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A construction method for retreat grouting protection of important urban underground pipelines, characterized in that, Includes the following steps: Step 1: Excavate the foundation pit and sewage trunk line (2) Lay the trench and install the sewage trunk line (2) in the trench; Step 2: Before the rain, check the burial depth of the sewage trunk (2). The water level outside the pit shall not be lower than the center line elevation of the sewage trunk (2). Step 3: On the side of the sewage trunk line (2) near the foundation pit, cast supporting soil blocks (3) using the backward grouting method; The specific steps for casting the supporting soil block (3) using the retreating grouting method are as follows: Position the grouting hole, and after positioning, insert the grouting pipe by vibration. After the grouting pipe is inserted, perform single / double liquid grouting. As the grouting height increases, lift the grouting pipe upward until the grouting height set by the supporting soil block (3) is reached. The grouting pressure of the retreating grouting method is 0.2MPa to 0.5MPa, and the grouting flow rate is 10 to 20L / min; The retreating grouting method uses cement grout for grouting, wherein the volume ratio of cement grout to water glass is 4:1; the water-cement ratio in the cement grout is 0.8:1; the water glass Baume degree is 35°Bé; and the grout setting time is controlled within the range of 60s to 180s. Step 4: The supporting soil blocks (3) are reinforced at intervals of 1.5m along the direction of the sewage trunk pipe (2); Step 5: The supporting soil blocks (3) within 30m of the side of the sewage trunk line (2) near the excavation slope are integrally cast.

2. The construction method for retreat grouting protection of important urban underground pipelines according to claim 1, characterized in that, The upper end of the supporting soil block (3) is flush with the upper end of the sewage trunk pipe (2), and the depth of the supporting soil block (3) is 20m.

3. The construction method for retreat grouting protection of important urban underground pipelines according to claim 1, characterized in that, The grouting holes are symmetrically distributed 500 mm on both sides of the sewage main pipe (2), and the grouting holes are distributed at intervals of 1.5 m along the length of the sewage main pipe (2).

4. The construction method for retreat grouting protection of important urban underground pipelines according to claim 3, characterized in that, The positional deviation of the grouting hole shall not exceed 6 cm, the verticality deviation shall be less than 1%, and when the grouting hole has a design angle, the inclination deviation shall not exceed 5°.

5. The construction method for retreat grouting protection of important urban underground pipelines according to claim 1, characterized in that, The grouting pipe is a 1-inch galvanized pipe of 1-5m or a steel pipe with a diameter greater than 30mm.

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