High underground water level pipeline anti-sedimentation backfilling method based on gravel seepage path optimization

Abstract

The invention relates to the field of drainage pipe network construction, and particularly discloses a high underground water level pipeline anti-sedimentation backfilling method based on gravel seepage path optimization, which comprises the following steps: S1, constructing suspended Larsen steel sheet pile waterproof curtains on the two sides of a groove to block underground water seepage on the two sides of the groove; s2, arranging carding wells on the two sides of the groove in a plum blossom shape, and adopting a down-the-hole hammer hole forming process to ensure that the permeability coefficient of the wells meets the precipitation requirement; s3, a water collecting pit is excavated in the downstream end of the groove; through the triple synergistic effect of the suspension type Larsen steel sheet piles, the combing well and the water collecting pit, the pipeline construction safety under the high underground water level condition is remarkably improved; lateral underground water permeation is effectively blocked through the suspension type Larsen steel sheet piles, the water level of the combing dry well is rapidly lowered through the down-the-hole hammer hole forming technology, the water collecting pit thoroughly solves the problem of water accumulation in the groove, the underground water level is stably controlled to be 20 cm below the groove bottom through cooperation of the suspension type Larsen steel sheet piles, the down-the-hole hammer hole forming technology and the water collecting pit, and ideal conditions are created for dry groove operation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sewer network construction, and particularly relates to a high groundwater level pipe anti-settlement backfilling method based on gravel seepage path optimization. BACKGROUND

[0002] In the construction of sewer network in high groundwater level areas, groundwater control is a key technical problem. The traditional construction method mainly adopts the mode of well point dewatering combined with steel sheet pile support, wherein the steel sheet pile is mostly arranged in a closed manner to form a complete water stop curtain, and the well point dewatering system commonly uses a slurry wall to form a hole. This method can still meet the requirements under ordinary geological conditions, but has obvious limitations in special geological environments such as pebble strata.

[0003] The pebble strata have the characteristics of large permeability coefficient and loose structure, and the traditional slurry wall hole forming process will cause a large amount of slurry to seep into the strata, which not only reduces the permeability of the strata and affects the dewatering effect, but also may cause environmental pollution. At the same time, due to the unevenness of the pebble layer, the conventional steel sheet pile is difficult to achieve complete closure, resulting in poor water stopping effect. In addition, the existing backfilling process mostly uses ordinary sand and stone materials, which are easy to produce uneven settlement under the action of long-term seepage, affecting the stability of the pipe system.

[0004] The main defects of the prior art are that effective dewatering and reliable support cannot be simultaneously achieved in high permeability pebble strata, especially in the working condition that the steel sheet pile cannot be completely closed, the conventional method is difficult to reduce the groundwater level to the required depth, which seriously affects the construction quality and progress. This technical bottleneck needs to be broken through to meet the increasing demand for urban underground pipe network construction. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a high groundwater level pipe anti-settlement backfilling method based on gravel seepage path optimization, to solve the technical problems that effective dewatering, reliable support and long-term anti-settlement cannot be simultaneously achieved in high permeability pebble strata in the prior art, especially the problem of groundwater control in the working condition that the steel sheet pile cannot be completely closed.

[0006] The high groundwater level pipe anti-settlement backfilling method based on gravel seepage path optimization comprises the following steps:

[0007] S1. A suspended Larsen steel sheet pile water curtain is constructed on both sides of the trench to block the seepage of groundwater on both sides of the trench;

[0008] S2. Dry wells are arranged in a plum blossom type on both sides of the trench, and a down-the-hole hammer hole forming process is used to ensure that the permeability coefficient of the well meets the dewatering requirements;

[0009] S3. A water collecting pit is excavated at the downstream end of the trench, and the groundwater seeping into the pit is discharged by a sewage pump;

[0010] S4, installing the pipeline directly on the gravel layer, or replacing the unqualified material with graded gravel to the bottom elevation of the trench after excavation on the non-gravel layer;

[0011] S5, after the pipeline installation is completed, graded gravel is backfilled on both sides below the top of the pipeline to optimize the seepage path of underground water and improve the backfill density.

[0012] Preferably, in step S1, the installation of the suspended Larsen steel sheet pile is carried out by separate driving, inserted by a vibration hammer, to ensure the verticality and tightness of the steel sheet pile.

[0013] Preferably, in step S2, the down-the-hole hammer drilling process specifically includes the following steps:

[0014] S2.1, using a high-pressure pneumatic down-the-hole hammer drill equipped with a down-the-hole hammer bit of a specific size;

[0015] S2.2, driving the piston in the down-the-hole hammer to make high-frequency reciprocating motion by high-pressure air to transfer impact work to the drill bit;

[0016] S2.3, the drill bit implements impact crushing on the gravel layer under the action of impact work to form volume crushing;

[0017] S2.4, the crushed rock debris is blown away from the bottom of the hole and discharged outside the hole by high-pressure air;

[0018] S2.5, maintaining continuous drilling to a design well depth of 15m to ensure that the verticality error of the formed hole is less than 1%.

[0019] Preferably, the diameter of the down-the-hole hammer bit is determined according to the design diameter of the comb well, and the hardness of the drill bit is not less than HRC60.

[0020] Preferably, in step S2, the well depth of the comb well is 15m, and the water pump flow rate in the well is 50m 3 / hour.

[0021] Preferably, in step S3, the size of the water collection pit is 3.0m long, 3.0m wide, and 1.5m deep, which is used to collect underground water that cannot be blocked in the trench and discharge it through a sewage pump.

[0022] Preferably, in step S5, the particle size of the graded gravel is 5-40mm, and the clay content is not more than 3%.

[0023] Preferably, in step S5, the layer thickness of the backfilled graded gravel is not more than 30cm, and each layer is tamped 3-5 times by a vibrating tamper.

[0024] Preferably, the method reduces the underground water level to 20cm below the bottom of the trench through the combined drainage reduction structure to meet the dry trench operation conditions.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The triple synergy of the suspended Larsen steel sheet pile, the comb well and the water collecting pit significantly improves the safety of pipeline construction under high groundwater level; the suspended Larsen steel sheet pile effectively blocks the lateral groundwater seepage, the comb well quickly reduces the water level by using the down-the-hole hammer hole forming process, and the water collecting pit completely solves the problem of water accumulation in the trench, so that the groundwater level is stably controlled below 20cm below the trench bottom, creating ideal conditions for dry trench operation.

[0027] By strictly controlling the particle size and silt content of the graded gravel, and combining with the layered backfilling and vibration compaction process, the pipeline foundation bearing capacity and seepage performance are double guaranteed, the problem of groundwater level rising due to poor seepage is effectively avoided, and the pipeline settlement is prevented from the root. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The backfilling method flowchart of the present application;

[0029] Figure 2 The down-the-hole hammer hole forming process flowchart of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] As shown in Figure 1 :

[0032] Embodiment one: the present application provides a high groundwater level pipeline anti-settlement backfilling method based on graded gravel seepage path optimization, comprising the following steps:

[0033] S1, a suspended Larsen steel sheet pile waterproof curtain is constructed on both sides of the trench to block the groundwater seepage on both sides of the trench;

[0034] S2, comb wells are arranged in a plum blossom type on both sides of the trench, and a down-the-hole hammer hole forming process is used to ensure that the permeability coefficient of the well meets the dewatering requirements;

[0035] S3, a water collecting pit is excavated at the downstream end of the trench, and the groundwater seeped into the pit is discharged by a sewage pump;

[0036] S4, the pipeline is directly installed in the pebble stratum, or the unqualified material is removed and replaced with graded gravel to the trench bottom elevation in the non-pebble stratum;

[0037] S5, after pipeline installation, the two sides of the pipe top are backfilled with graded gravel, the groundwater seepage path is optimized, and the backfill density is improved.

[0038] As can be seen from the above, the method forms a combined dewatering and drainage structure by using the suspended Larsen steel sheet pile, the dry well, and the water collecting pit, effectively solving the construction problem under the condition of high groundwater level;

[0039] Among them, the suspended Larsen steel sheet pile is used as a waterproof curtain to block lateral seepage, the dry well uses a down-the-hole hammer hole forming process to ensure the dewatering effect, and the water collecting pit is responsible for collecting and removing residual groundwater in the trench;

[0040] The method takes advantage of the characteristics of the pebble stratum, directly using the pebble layer as the foundation during pipeline installation, or improving the soft foundation by replacing graded gravel; during backfilling, layered rammed graded gravel is used, which not only ensures the backfill density, but also optimizes the groundwater seepage path, effectively preventing pipeline settlement;

[0041] Through the combined application of the above technical measures, the groundwater level is successfully lowered to 20 cm below the trench bottom, meeting the dry trench operation requirements. This method not only has high construction efficiency, but also significantly reduces engineering cost, providing a reliable technical solution for pipeline construction under similar geological conditions.

[0042] Embodiment two: This embodiment is basically the same as the previous embodiment, except that in step S1, the suspended Larsen steel sheet pile is installed using a separate driving method, which ensures the verticality and tightness of the steel sheet pile through vibration hammer insertion.

[0043] Specifically, as shown in Figure 2

[0044] The down-the-hole hammer hole forming process in step S2 includes the following steps:

[0045] S2.1, a high-pressure pneumatic down-the-hole hammer drill is used, equipped with a down-the-hole hammer drill bit of a specific size;

[0046] S2.2, the piston in the down-the-hole hammer is driven by high-pressure air to make high-frequency reciprocating motion, transferring impact work to the drill bit;

[0047] S2.3, the drill bit impacts and breaks the pebble layer under the action of impact work, forming volume breaking;

[0048] S2.4, the broken rock debris is blown away from the bottom of the hole by high-pressure air and discharged outside the hole;

[0049] S2.5, keep continuous drilling to a design depth of 15 m, ensure that the verticality error of the hole is less than 1%.

[0050] ​From the above, the suspended Larsen steel sheet pile is constructed by separate driving method, the insertion process is accurately controlled by vibration hammer, the verticality deviation of the steel sheet pile is ensured to be less than 1%, and the lock catch is tightly engaged, which significantly improves the sealing performance of the waterproof curtain. This method is particularly suitable for supporting construction in complex geological conditions such as pebble stratum.

[0051] In the comb well construction link, a high-pressure pneumatic down-the-hole hammer drill is used with a specially designed drill bit. The high-frequency impact is generated by driving the piston with high-pressure air, which enables the drill bit to implement volume crushing on the pebble layer. This process can maintain the verticality of the 15m deep hole, and at the same time, the rock debris is quickly discharged through the air flow, avoiding the adverse effects of traditional mud wall protection on the permeability of the pebble layer.

[0052] Through the above process optimization, the embodiment further improves the construction precision and efficiency under the premise of ensuring the dewatering effect. In particular, the application of the down-the-hole hammer hole forming process solves the technical problem of difficult hole forming in the pebble stratum, and provides a replicable technical solution for similar projects.

[0053] Embodiment three: the embodiment is basically the same as the previous embodiment, the difference is that the diameter of the down-the-hole hammer drill bit is determined according to the design aperture of the comb well, and the hardness of the drill bit is not less than HRC60.

[0054] Specifically, in step S2, the well depth of the comb well is 15m, and the water pump flow rate in the well is 50m 3 / hour.

[0055] Specifically, in step S3, the size of the water collection pit is 3.0m long, 3.0m wide, and 1.5m deep, which is used to collect underground water that cannot be blocked in the trench and discharge through the sewage pump.

[0056] Specifically, in step S5, the particle size of the graded gravel is 5-40mm, and the clay content is not more than 3%.

[0057] Specifically, in step S5, the layer thickness of the backfill graded gravel is not more than 30cm, and each layer is tamped 3-5 times by vibration rammer.

[0058] Specifically, the method reduces the underground water level to 20cm below the bottom of the groove by using the combined dewatering and drainage structure, which meets the dry groove operation conditions.

[0059] From the above, the down-the-hole hammer drill bit adopts high hardness material above HRC60, and its diameter strictly matches the design aperture of the comb well. Combined with a 50m 3 / hour high-flow water pump, the stable operation of the dewatering system is ensured. The water collection pit is designed with a standard size of 3.0m x 3.0m x 1.5m, which significantly improves the underground water collection efficiency by optimizing the geometric parameters;

[0060] In backfill process, the particle size of graded broken stone is controlled in the range of 5-40mm, the clay content is ≤3%, and the compaction process with 30cm layer thickness and 3-5 times of vibration ramming is adopted.

[0061] Through the synergistic effect of the combined drainage reduction structure, the underground water level is successfully reduced to 20cm below the tank bottom, and the dry tank construction requirement is completely met.

[0062] The embodiments of the present application are given for example and description, although the embodiments of the present application have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary, and cannot be understood as the limitation of the present application, the changes, modifications, replacements and modifications of the above-mentioned embodiments by the ordinary skilled in the art within the scope of the present application should be included in the protection scope of the present application.

Claims

1. A method for preventing settlement and backfilling pipelines at high groundwater levels based on optimized gravel seepage path, characterized in that, Includes the following steps: S1. Install suspended Larssen sheet pile waterproof curtains on both sides of the trench to block groundwater seepage on both sides of the trench. S2. Arrange the combing wells in a quincunx pattern on both sides of the trench, and use down-the-hole hammer drilling technology to ensure that the permeability coefficient of the wells meets the precipitation requirements. S3. Excavate a water collection pit at the downstream end of the trench and use a sewage pump to openly discharge the groundwater that seeps into the pit. S4. Install pipes directly in gravel strata, or replace graded crushed stone with non-pebble strata after removing substandard materials to the bottom elevation of the trench. S5. After the pipeline is installed, backfill graded crushed stone on both sides below the top of the pipe to optimize the groundwater seepage path and improve the backfill density.

2. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 1, characterized in that, In step S1, the suspended Larssen sheet piles are installed using a single driving method, which involves driving the piles with a vibratory hammer to ensure verticality and tightness of the interlocking.

3. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 1, characterized in that, The down-the-hole hammer drilling process in step S2 specifically includes the following steps: S2.

1. High-pressure pneumatic down-the-hole hammer drill is used, equipped with a down-the-hole hammer drill bit of a specific size; S2.

2. High-pressure air drives the piston inside the down-the-hole hammer to perform high-frequency reciprocating motion, transmitting the impact energy to the drill bit. S2.3 The drill bit impacts and breaks up the pebble layer under the action of impact energy, resulting in volumetric fracturing; S2.4 The broken rock fragments are blown away from the bottom of the borehole by high-pressure air and discharged outside the borehole; S2.

5. Continue drilling to the designed well depth of 15m, ensuring that the verticality error of the borehole is less than 1%.

4. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 3, characterized in that, The diameter of the down-the-hole hammer drill bit is determined according to the designed borehole diameter of the comb well, and the hardness of the drill bit is not less than HRC60.

5. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 1, characterized in that, In step S2, the depth of the combing well is 15m, and the flow rate of the water pump inside the well is 50m³ / h. 3 / Hour.

6. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 1, characterized in that, In step S3, the water collection pit is 3.0m long, 3.0m wide, and 1.5m deep, and is used to collect groundwater that cannot be isolated in the trench and discharge it through a sewage pump.

7. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 1, characterized in that, In step S5, the particle size of the graded crushed stone is 5-40 mm, and the mud content does not exceed 3%.

8. The method for preventing settlement and backfilling of pipelines at high groundwater levels based on optimized seepage path of crushed stone as described in claim 1, characterized in that, In step S5, the thickness of each layer of backfill graded crushed stone shall not exceed 30cm, and each layer shall be compacted 3-5 times with a vibratory tamper.

9. The high groundwater level pipeline anti-settlement backfilling method based on crushed stone seepage path optimization as described in claim 1, characterized in that, The method uses a combined dewatering structure to lower the groundwater level to 20cm below the bottom of the trench, thus meeting the conditions for dry trench operation.

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