Drainage construction method for underground railway

Abstract

The invention relates to the technical field of building construction, and discloses an underground railway drainage construction method which comprises the following steps: carrying out detailed geological survey and underground water level measurement on a construction area to obtain accurate data for designing parameters of a drainage ditch; according to the design scheme, drainage ditches are dug around the construction area, and the bottoms of the drainage ditches are flattened; according to the design gradient and position requirements, a drainage pipeline is buried; a water collecting well is excavated in a low-lying place, the inner wall of the water collecting well is reinforced after excavation is completed, then a water level monitoring device and a submersible pump are installed, and related electrical circuits and drainage pipelines are connected; after the whole drainage system is installed, comprehensive inspection and debugging are carried out. All links of the drainage system can be more scientific and reasonable, the conditions of construction delay, reworking, interruption and the like caused by unreasonable design, non-standard construction, improper equipment installation, fault hidden dangers and the like are reduced, the drainage efficiency is improved, and the problem that the underground railway drainage construction efficiency is poor is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building construction, in particular to a subway drainage construction method. BACKGROUND

[0002] With the acceleration of urbanization, as a core component of urban transportation, the construction scale of subway continues to expand. In the construction process of subway, the design and construction quality of drainage system is crucial, which is directly related to the overall quality of the project, the construction period and the operation and maintenance cost in the later period, and even has a profound impact on the normal operation of the city and the safety of residents' life.

[0003] The traditional subway drainage construction technology is complicated and slow when facing complex geological conditions. In soft soil layer, due to the instability of soil, a large amount of time is often spent on foundation reinforcement treatment before laying drainage pipeline, which not only increases the construction process, but also causes the construction progress to be greatly delayed. In rock stratum, when excavating drainage ditch and collecting well, blasting or mechanical crushing operation is needed, which is difficult and low in efficiency, so that underground water cannot be discharged in time, affecting the whole construction progress. In some narrow construction area, large construction equipment is difficult to use, which further reduces the construction efficiency, causing the construction period of subway drainage to be prolonged, affecting the overall progress of the project. SUMMARY

[0004] In view of the shortcomings of the prior art, the present application provides a subway drainage construction method, which solves the problem of poor efficiency of subway drainage construction.

[0005] To achieve the above purpose, the present application realizes a subway drainage construction method by the following technical scheme, comprising the following steps: S1, detailed geological survey and underground water level measurement are carried out on the construction area to obtain accurate data for designing the parameters of drainage ditch, drainage pipeline and collecting well; S2, according to the design scheme, excavate drainage ditch around the construction area, strictly control the depth and slope during the excavation process, and make the bottom of the drainage ditch flat; S3, according to the design slope and position requirements, bury the drainage pipeline, and use special sealing rubber ring for sealing treatment at the pipeline connection part; S4, excavate collecting well at low-lying place, reinforce the inner wall of the collecting well after excavation, and then install water level monitoring device and submersible pump, and connect the related electrical circuit and drainage pipeline; S5, after the whole drainage system is installed, carry out comprehensive inspection and debugging.

[0006] Preferably, the geological survey is arranged with a survey point every 20m, and when there is a fault or a different stratum interface, the survey point spacing should be encrypted to 10-15m.

[0007] Preferably, the drain pipe is made of high-strength PVC material, the wall thickness deviation is not more than ±0.3mm, the tensile strength is not less than 40MPa, and the ring stiffness is not less than 8kN / ㎡.

[0008] Preferably, during the excavation of the drainage ditch, the depth and slope of the drainage ditch are measured every 2m, and the level gauge and slope gauge are used for measurement, so that the depth error is controlled within ±50mm, and the slope error is controlled within ±0.1%.

[0009] Preferably, the flatness deviation of the bottom of the drainage ditch is ±20mm, and the gap between each measurement point and the ruler should be controlled within 20mm.

[0010] Preferably, the buried drainage pipe is laid on a sand cushion foundation, and the sand compaction method is used to detect the compaction degree, and the compaction degree should be not less than 95%, and one detection is performed every 10m.

[0011] Preferably, the sealing treatment adopts a special rubber ring for the pipeline, and the test pressure is usually 1.5 times the working pressure of the pipeline, which should be above 0.6MPa, the pressure holding time is not less than 30 minutes, and the pressure drop should be within 0.05MPa to be qualified.

[0012] Preferably, the reinforcement treatment adopts HPB300 grade steel bars, and the end should be bent at 180°, and the cold drawing rate of the HPB300 grade steel bar should be within 4%.

[0013] Preferably, the installation position deviation of the submersible pump is within ±10mm, and the elevation deviation is within ±5mm.

[0014] Preferably, when simulating the condition of low underground water level, the water level of the drainage ditch is controlled at 0.2-0.3m from the ditch bottom, so that the water pump can be normally started when the water level reaches the starting set value, and after 5-10 minutes of operation, the water level of the collection well should be obviously decreased by not less than 0.1m.

[0015] The application provides an underground railway drainage construction method and a use method thereof. 1、The underground railway drainage construction method can be more scientific and reasonable through each link of the drainage system, construction delay, rework, interruption and the like caused by unreasonable design, non-standard construction, improper equipment installation and fault hidden dangers are reduced, drainage efficiency is improved, stable and reliable operation of the drainage system under different working conditions is ensured, and the overall underground railway drainage construction efficiency is improved, and the problem of poor underground railway drainage construction efficiency is solved.

[0016] 2. The exploration point layout method in this invention enables precise understanding of the geological conditions of the construction area. In conventional geological areas, exploration points arranged every 20m can obtain sufficient data at a reasonable cost, constructing a basic framework of the geological conditions of the entire construction area. This allows designers to preliminarily determine the approximate parameters of drainage ditches, drainage pipes, and collection wells, solving the problem of inaccurate and incomplete geological information.

[0017] 3. This invention utilizes high-strength PVC drainage pipes to achieve reliable and efficient drainage. Under normal use, the pipes can stably withstand external soil pressure. Based on relevant simulation tests and practical engineering experience, when the burial depth reaches a certain depth and the surrounding soil density is taken as conventionally, the pipes, with a ring stiffness of not less than 8kN / ㎡, can effectively resist soil pressure, ensuring that the pipe diameter deformation rate is controlled within 5%, guaranteeing the cross-sectional area for drainage, maintaining normal drainage flow rate, and improving the overall drainage efficiency of the drainage system. This solves the problem of maintaining stable drainage performance even under complex geological conditions and extreme weather.

[0018] 4. This invention achieves high sealing performance at pipe connections by using specialized pipe-specific rubber rings for sealing and strictly adhering to the aforementioned pressure test requirements. In actual operation, when the pipe is subjected to normal groundwater pressure, the rubber rings reliably prevent water leakage through the joints, keeping the leakage rate at pipe joints extremely low and effectively ensuring the drainage efficiency of the drainage system. This solves the problem of high maintenance costs caused by poor pipe sealing. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the construction steps of a subway drainage method proposed in this invention. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0021] Please see the appendix Figure 1 This invention provides a method for constructing drainage systems in underground railways, comprising the following steps: S1. Conduct detailed geological surveys and groundwater level measurements in the construction area to obtain accurate data for designing parameters for drainage ditches, drainage pipes, and collection wells; S2, according to the design, a drainage ditch is excavated around the construction area, and the depth and slope are strictly controlled during the excavation process to make the bottom of the drainage ditch flat; S3, according to the design slope and position requirements, the drainage pipe is buried, and a special sealing rubber ring is used for sealing treatment at the pipe connection part; S4, a water collecting well is dug at the low-lying place, the inner wall of the water collecting well is reinforced after the excavation is completed, then the water level monitoring device and the submersible pump are installed, and the related electrical lines and drainage pipes are connected; S5, after the whole drainage system is installed, comprehensive inspection and debugging are carried out.

[0022] Specifically, the geological survey and underground water level measurement of the construction area are carried out by professional equipment at a specific interval to provide a basis for subsequent design; then the drainage ditch is precisely excavated according to the design, and its parameters are controlled; the drainage pipe that meets the high standard is selected and buried after the foundation, connection and sealing detection are completed; the water collecting well is standardizedly dug at the low-lying place, the inner wall is reinforced, the water level monitoring device and the submersible pump are precisely installed, and the related lines are connected; finally, the whole drainage system is comprehensively inspected and debugged, the performance is tested under different water level conditions.

[0023] Through each link of the drainage system, the construction delay, rework, interruption and other situations caused by unreasonable design, non-standard construction, improper equipment installation and hidden troubles can be more scientific and reasonable, the drainage efficiency is improved, the stable and reliable operation of the drainage system under different working conditions is ensured, the overall underground railway drainage construction efficiency is improved, and the problem of poor underground railway drainage construction efficiency is solved.

[0024] Geological survey is arranged every 20m, and for geological faults and different stratum junctions, the survey point spacing should be encrypted to 10-15m.

[0025] Specifically, the geological survey work is based on the basic principles of geotechnical engineering, that is, different geological structures and stratum characteristics will affect the groundwater flow direction, water level change and soil stability, etc. A survey point is arranged every 20 m, which is a comprehensive consideration of the general change rule of geological conditions and construction cost benefit. In the conventional geological area, the parameters such as soil characteristics and groundwater level are relatively stable within a certain range, and the interval of 20 m can comprehensively and economically obtain the geological information of the area, providing basic data for subsequent design. Through drilling, geophysical prospecting and other means, the geological data of each survey point is obtained, such as the stratification of soil layer, the physical and mechanical properties of rock and soil, the depth of groundwater level, etc., and then the overall geological conditions of the construction area are inferred. When there are faults and different stratum junctions in the geological conditions, the geological conditions of these areas change dramatically and are complex. At the fault, there may be rock crushing, abnormal groundwater activity, etc. At the junction of different strata, there may be large differences in rock and soil properties, changes in groundwater seepage path, etc. The survey point interval is encrypted to 10-15 m, which can more densely collect the geological information of these special areas and capture the sharp changes of geological parameters within a short distance, so as to more accurately depict the geological characteristics of the area.

[0026] Through the above survey point arrangement mode, the geological conditions of the construction area can be accurately mastered. In the conventional geological area, the survey points arranged every 20 m can obtain sufficient data at a reasonable cost to build a basic framework of the geological conditions of the entire construction area, so that the designer can preliminarily determine the approximate parameters of the drainage ditch, drainage pipeline and catch basin. According to the depth of groundwater level and the permeability coefficient of soil layer obtained by survey, the pipe diameter and slope of the drainage pipeline can be preliminarily determined, solving the problem of inaccurate and incomplete geological information.

[0027] The drainage pipe is made of high-strength PVC material, the wall thickness deviation is not more than ±0.3 mm, the tensile strength should be not less than 40 MPa, and the ring stiffness should be not less than 8 kN / ㎡.

[0028] Specifically, in the underground railway drainage construction, the drainage pipe needs to bear various external forces, including the pressure from the surrounding soil, the static water pressure of groundwater and the additional pressure possibly transmitted by the ground load, etc. The high-strength PVC material itself has good chemical stability, corrosion resistance and certain flexibility, which enables it to be used in complex underground environment for a long time.

[0029] The strict control of the wall thickness deviation is not more than ±0.3 mm, because whether the wall thickness is uniform or not directly relates to the overall structural strength of the pipe. Uniform wall thickness can ensure that the pipe bears external pressure uniformly, avoiding the weak point of deformation or rupture caused by local thin wall thickness.

[0030] The tensile strength of no less than 40 MPa is based on the tensile stress that the pipe may face in the underground environment. For example, when uneven settlement occurs in the underground, the soil is displaced, or the pipe is stretched due to temperature changes, the pipe will be subjected to axial tensile force, and sufficient tensile strength can ensure that the pipe will not be pulled apart when subjected to such stress, maintaining its structural integrity.

[0031] The ring stiffness of no less than 8 kN / m2 is set for the ability of the pipe to resist external radial pressure. After being buried in the underground, the soil will exert radial pressure on the pipe from all directions, and the ring stiffness reaching this standard can make the pipe maintain a stable circular cross-section, prevent it from being flattened or deformed due to excessive external pressure, and ensure smooth flow in the pipe and normal drainage function.

[0032] The high-strength PVC material drainage pipe with the above parameter requirements can achieve reliable and efficient drainage function. In normal use, the pipe can stably withstand external soil pressure. According to relevant simulation tests and actual engineering experience, when the burial depth reaches a certain depth (such as the common underground railway drainage pipe burial depth of 2-5 m), and the surrounding soil gravity is normally valued (about 18-20 kN / m3), the pipe with ring stiffness of no less than 8 kN / m2 can effectively resist soil pressure, ensure that the pipe diameter deformation rate is controlled within 5%, ensure the water cross-sectional area of the drainage, maintain normal drainage flow rate (generally can be maintained at 0.6-1.2 m / s), improve the overall drainage efficiency of the drainage system, and solve the problem that the pipe can still maintain stable drainage effect even in complex geological conditions and extreme weather.

[0033] During the excavation of the drainage ditch, the depth and slope of the drainage ditch are measured every 2 m using a level and a slope gauge to ensure that the depth error is controlled within ±50 mm and the slope error is controlled within ±0.1%.

[0034] Specifically, during the excavation of the drainage ditch, the level and slope gauge are used for measurement based on the principles of geometric measurement and the relationship between water flow and slope in hydraulics. The level establishes a horizontal sight reference to measure the elevation difference of different positions relative to the reference to determine the depth values of each point in the drainage ditch. The slope gauge can directly measure the slope value corresponding to the angle between the slope surface formed by the ditch bottom and the wall and the horizontal plane. Every 2 m, a measurement point is set, which is based on the consideration of the possible changes in the geological conditions in the length direction of the drainage ditch and the construction precision control requirements.

[0035] In actual operation, first, according to the elevation and slope requirements of the starting point, end point and intermediate key control points of the drainage ditch given by the design, a stable leveling base point is set at the construction site as the reference for the leveling measurement. The construction personnel use the level to measure the actual elevation of the ditch bottom at each 2m interval measurement point in turn, and the depth difference is obtained by comparing with the design elevation; at the same time, the slope ruler is placed on the ditch bottom and wall, and the actual slope angle is measured, which is converted into slope value and compared with the design slope. In this way, during the excavation process, the deviation between the construction condition and the design requirement can be grasped in real time, and the construction operation can be adjusted in time.

[0036] If the starting point elevation of a certain section of the drainage ditch is 100m, the slope is 0.2%, and the length is 50m, according to the requirement of measuring every 2m, the design elevation at 4m from the starting point should be 100+4x0.2%=100.008m. After measuring the actual elevation of this point using the level, the depth error can be calculated. By placing the slope ruler on the ditch bottom, if the slope corresponding to the design slope angle should be 0.2%, comparing the actual slope converted from the measured angle with it, the slope error can be known.

[0037] By measuring the depth and slope every 2m, the precise forming of the drainage ditch in the longitudinal direction can be realized, and the depth error is strictly controlled within ±50mm, and the slope error is controlled within ±0.1%. When the slope error is within ±0.1%, the water flow speed can be maintained within a reasonable range (such as 0.5-1m / s or so, depending on factors such as the size of the drainage ditch cross section), avoiding the problems of excessive slope leading to intensified scouring of the ditch wall by water flow, or slow water flow and sediment accumulation caused by too small slope, effectively improving the drainage efficiency. Compared with the drainage ditch without such strict slope control, the drainage speed can be improved by about 30%-40%, solving the problem of poor drainage effect caused by poor control of drainage ditch depth and slope.

[0038] The flatness deviation of the drainage ditch bottom is ±20mm, and the gap between each measurement point and the ruler should be controlled within 20mm.

[0039] Specifically, the control of the flatness of the drainage ditch bottom is based on the principle of flatness measurement and the requirement of water flow uniformity in hydraulics. The ruler is a kind of intuitive measurement tool, which has a high-precision flat reference. When the ruler is placed at different measurement points on the bottom of the drainage ditch, the gap between the ruler and the ditch bottom can be observed to judge the height difference of the point relative to the flat reference of the ruler, so as to measure the flatness of the bottom.

[0040] During construction, excavators were first used for preliminary excavation of the drainage ditch. Since excavator operation could not achieve the required level of flatness in one go, manual labor was used for fine leveling after the initial excavation. Workers used straightedges, placing them at regular intervals (e.g., every 1-2 meters longitudinally and every 0.5-1 meters laterally) along the longitudinal and transverse directions of the drainage ditch. The gap between the straightedge and the bottom of the ditch was measured using feeler gauges and other tools. If the gap exceeded the specified 20mm, shovels and other tools were used to adjust the higher or lower sections to ensure they were as close to the straightedge as possible, guaranteeing that the gap between each measuring point and the straightedge was controlled within 20mm. This achieved the requirement of controlling the flatness deviation of the drainage ditch bottom within ±20mm.

[0041] By controlling the flatness deviation of the bottom of the drainage ditch to ±20mm and the gap between each measuring point and the straightedge to within 20mm, uniform and smooth water flow can be achieved within the ditch. Under such flatness conditions, the water flow will not experience turbulence, eddies, or other unstable flow states due to local bumps or depressions at the bottom, reducing water flow resistance and allowing groundwater to flow towards the collection well at a more stable velocity (generally maintained at around 0.4-0.8m / s, depending on factors such as the slope and cross-sectional dimensions of the ditch). This solves the problems of poor water flow and water accumulation caused by uneven bottoms.

[0042] For laying drainage pipes, a sand cushion foundation should be used. The compaction degree should be tested using the sand filling method. The compaction degree should not be less than 95%, and a test should be conducted every 10m.

[0043] Specifically, the use of a sand cushion foundation and the sand filling method to test compaction during the installation of drainage pipes is based on the principles of soil mechanics and structural engineering. The sand cushion foundation provides uniform and stable support for the drainage pipes, distributing the pressure from the overlying soil and ground loads. Sand, as a granular material, has certain particle size distribution characteristics. Under appropriate compaction, the particles interlock and fill each other, forming a relatively stable structure that can effectively withstand external forces.

[0044] When laying the sand cushion layer, first determine its thickness (generally ranging from 100-200mm) and width (usually extending 100-150mm beyond each side of the pipe) according to design requirements. Evenly spread sand that meets the particle size requirements (e.g., commonly used medium sand, with a particle size between 0.25-0.5mm) and mud content standards (generally not exceeding 3%) at the bottom of the pipe trench. Then, use small compaction equipment (such as a plate vibrator) to compact the sand cushion layer in layers, controlling the thickness of each layer to approximately 150-200mm. The number of compaction passes is determined based on on-site testing, generally no less than 3-5 passes.

[0045] The principle of sand replacement method for detecting compaction degree is that, using standard sand with known density, the density of sand cushion in the test pit is calculated according to the mass of standard sand poured into the test pit and the volume of the test pit, and then the compaction degree is calculated. In specific operation, at the position to be detected (according to the regulation of detecting every 10 m), a test pit with a diameter slightly larger than the sand pouring cylinder is first dug out using a tool, and the depth reaches the bottom surface of the sand cushion. The sand pouring cylinder is placed above the test pit, and the standard sand in the cylinder falls freely to fill the test pit. The mass of the sand reduced in the cylinder and the size of the test pit (the diameter and depth are measured by a ruler to calculate the volume) are measured, and the compaction degree value of the point is obtained according to the corresponding calculation formula (compaction degree = measured dry density of sand cushion ÷ maximum dry density of sand cushion × 100%, wherein the measured dry density of sand cushion is calculated from the mass of standard sand poured and the volume of the test pit, and the maximum dry density is determined in advance by standard methods such as indoor compaction test), to determine whether it meets the requirement of not less than 95%.

[0046] By laying sand cushion foundation and strictly controlling the compaction degree detection according to the requirements, a stable support foundation can be provided for the drainage pipeline. When the compaction degree reaches not less than 95%, the bearing capacity of the sand cushion is effectively guaranteed, and under the common underground railway drainage pipeline burial depth (generally about 2-5 m) and the upper soil density (about 18-20 kN / m³ according to the conventional value), the settlement of the pipeline foundation can be controlled within a small range (for example, the annual average settlement is not more than 5 mm), avoiding the damage of pipeline deformation, rupture and other damages caused by uneven settlement of the foundation, ensuring that the pipeline can maintain normal drainage function for a long time, maintaining the shape and size stability of the pipeline water section, ensuring the smoothness of drainage, and stabilizing the water flow velocity in a reasonable range (such as about 0.6-1.2 m / s). The problems of pipeline damage and leakage caused by unstable pipeline foundation are solved.

[0047] The sealing treatment adopts a special rubber ring for pipeline. During the pressure test, the test pressure is usually 1.5 times of the working pressure of the pipeline, which should be above 0.6 MPa, and the pressure holding time should be not less than 30 minutes, and the pressure drop should be within 0.05 MPa to be qualified.

[0048] Specifically, the special rubber ring for pipeline is usually made of rubber material with good elasticity and aging resistance. Its working principle is that when the rubber ring is sleeved on the spigot end of the pipeline and inserted into the bell to complete the connection, the rubber ring will be extruded at the pipeline joint and deformed by relying on its own elasticity, thereby tightly filling the gap between the pipeline joints and forming an effective sealing barrier to prevent underground water and other fluids from leaking from the joint.

[0049] The pressure test is to inject water into the connected pipeline system and apply a certain pressure to simulate the internal pressure of the pipeline in actual operation, so as to test the sealing effect of the rubber ring and the sealing of the entire pipeline system. The test pressure is set to 1.5 times the working pressure of the pipeline and not less than 0.6 MPa. This is because the internal pressure may fluctuate due to various factors such as instantaneous water flow impact, water hammer effect, etc. during actual operation. Appropriately increasing the test pressure can fully test the sealing capacity of the rubber ring under the pressure exceeding the normal working pressure, ensuring stable sealing in long-term use.

[0050] The pressure stabilization time is not less than 30 minutes, which is based on the characteristics of fluid pressure transmission and stabilization in the pipeline. After applying the test pressure, sufficient time is needed to allow the pressure in the pipeline to be evenly distributed and stabilized, so that the rubber ring can be accurately judged whether it can continuously maintain sealing, and false judgment can be avoided due to unstable pressure.

[0051] The pressure drop should be within 0.05 MPa as the basis for judging whether it is qualified. It is to measure the sealing performance by comparing the pressure change in the pipeline before and after stabilization. If the pressure drop is within 0.05 MPa within the specified stabilization time, it means that the rubber ring is sealed well and there is no obvious leakage point in the pipeline system. If the pressure drop exceeds this range, it means that there is leakage, which causes water to leak out of the pipeline, thereby reducing the pressure.

[0052] By using the special rubber ring for pipeline sealing and strictly implementing the above pressure test requirements, high sealing performance of the pipeline connection part can be achieved. In actual operation, when the pipeline bears the normal underground water pressure (generally about 0.1-0.5 MPa according to different burial depths), the rubber ring can reliably block the water flow from leaking through the interface, and the leakage rate at the pipeline interface can be controlled at a very low level (such as not more than 0.3-0.5 m³ per 24 hours per kilometer of pipeline), effectively ensuring the drainage efficiency of the drainage system and ensuring that the underground water can be smoothly transported from one end of the pipeline to the other end, avoiding water resource waste and adverse effects on the surrounding soil (such as avoiding excessive water content in the surrounding soil, which may cause soil settlement). The problem of high maintenance cost caused by poor pipeline sealing is solved.

[0053] Reinforcement treatment, HPB300 grade steel bar, end should be made 180° hook, the cold drawing rate of HPB300 grade steel bar should be within 4%.

[0054] Specifically, the HPB300 grade steel belongs to hot-rolled smooth round steel, which has good ductility and certain yield strength, can deform reasonably when bearing tension and pressure, and can work together with concrete to bear the external force of the structure. When the water collecting well is subjected to lateral pressure from the surrounding soil, the buoyancy of groundwater, and the vertical load of the upper soil, etc., the steel will share part of the tension and pressure to maintain the stability of the water collecting well structure. The principle of bending the end of the steel by 180° is to effectively increase the anchoring length and anchoring force between the steel and the concrete. The cold drawing rate of the HPB300 grade steel is controlled within 4%, because cold drawing is a method of cold processing of steel, which can appropriately increase the yield strength of the steel by stretching the steel. However, if the cold drawing rate is too high, the plasticity and toughness of the steel will be significantly reduced, the brittleness will be increased, and the steel will be prone to brittle fracture under stress during subsequent use, affecting the safety of the structure.

[0055] By using the above reinforcement treatment method, the structural strength of the water collecting well can be effectively improved. When the water collecting well bears normal external load (for example, when the water collecting well is buried at a depth of 5-10 m, the specific gravity of the surrounding soil is about 18-20 kN / m³ according to the conventional value, the lateral soil pressure coefficient is about 0.5, and the groundwater buoyancy is calculated according to the actual water level), the steel and the concrete work together to control the deformation of the well wall within a small range (such as the horizontal displacement of the well wall is not more than 10-20 mm), to ensure the stability of the shape and size of the water collecting well, prevent the well wall from cracking, collapsing and other damage due to excessive deformation of the structure, and ensure that the water collecting well can collect and discharge groundwater stably for a long time. The problem of insufficient structural strength of the water collecting well caused by improper selection of steel is solved.

[0056] The installation position deviation of the submersible pump is within ±10 mm, and the elevation deviation is within ±5 mm.

[0057] Specifically, when the submersible pump is working, the impeller needs to be in a specific water level range to ensure efficient water suction and discharge through the centrifugal force generated by the rotation of the impeller, realizing stable water pumping function. If the installation position deviates from the designed ideal position, the water flow state around the impeller and the suction port will be affected, which may cause uneven water flow into the impeller, resulting in vortex, turbulence and other phenomena that are not conducive to water pumping, thereby reducing the water pumping efficiency of the water pump. If the elevation deviation is too large, such as installation is too high, the water suction lift may exceed the normal working range of the water pump, causing insufficient water suction or water suction; installation is too low, which may cause the water pump to be in a deep submerged state for a long time, increasing the load of the motor and affecting the service life of the water pump, and even may cause motor water ingress and other faults.

[0058] By controlling the installation position deviation of the submersible pump within ±10mm and the elevation deviation within ±5mm, efficient and stable operation of the submersible pump can be achieved. In normal operation, the water pump impeller can uniformly and smoothly suck in water flow, avoiding the situation of insufficient water suction or water flow disorder caused by installation deviation, so that the water pumping efficiency of the water pump can reach 90%-95% of the design efficiency (depending on the performance of the water pump itself and the actual working condition). For example, a submersible pump with a design flow rate of 100m³ / h can stably maintain a water pumping flow rate of about 90-95m³ / h under the condition of meeting the installation precision requirement, effectively ensuring the timely discharge of groundwater in the collection well and maintaining the normal drainage function of the underground railway drainage system. The problem of low water pumping efficiency caused by insufficient installation precision is solved.

[0059] When simulating the condition of low underground water level, the water level of the drainage ditch is controlled at 0.2-0.3m from the ditch bottom, so that the water pump can be normally started when the water level reaches the starting set value, and the water level in the collection well should decrease significantly after 5-10 minutes of operation, with a decrease amplitude of not less than 0.1m.

[0060] Specifically, the submersible pump is usually provided with a starting set value, which is determined according to the performance of the water pump and the normal operation requirement of the drainage system, and is generally related to the water level height. When the water level of the drainage ditch reaches the corresponding starting set value, it means that the water pressure generated by the water level can provide enough power for the water pump to overcome the starting resistance, so that the motor can operate normally to drive the impeller to rotate and realize the water pumping function. When simulating the condition of low underground water level, the water level of the drainage ditch is controlled at 0.2-0.3m from the ditch bottom, which is considered in the relatively low water level state. The water pump still needs to be reliably started to test the starting performance of the water pump under different working conditions. For example, the starting water level set value of different types of submersible pumps may be different, and some may be set at about 0.25m from the ditch bottom. At this time, the static water pressure generated by the water level acts on the water suction port of the water pump, so that the impeller can start to rotate and enter the normal water pumping state.

[0061] There is a close hydraulic connection between the parts of the drainage system. After collecting the surrounding groundwater, the drainage ditch guides the water to the collection well through gravity, and the water level change in the collection well reflects the drainage efficiency of the entire drainage system. The submersible pump pumps water from the collection well. When the water pump is normally started and operated, the water level in the collection well should show a downward trend within a certain time, which is based on the principle of water balance. When the water amount entering the collection well (mainly from the water collected by the drainage ditch) is less than the water amount pumped out by the water pump, the water level will decrease.

[0062] During the debugging process, the water level change is monitored in real time by a water level monitoring device (such as a liquid level sensor) installed in the water collecting well, and the height value of the water level is accurately measured. The water pump is set to run for 5-10 minutes, because within this time range, the change trend of the water level in the water collecting well and whether the decline amplitude meets the requirements can be observed more intuitively and reasonably. If the time is too short, the drainage effect cannot be accurately judged; if the time is too long, it may be disturbed by other factors (such as continuous groundwater infiltration), affecting the accurate evaluation of the drainage capacity of the water pump. For example, at 5 minutes, the water level monitoring device starts recording the initial water level, and as the water pump continues to pump water, the water level is recorded again at 10 minutes. By comparing the two water level values, the water level decline amplitude is calculated to determine whether the drainage system is working properly.

[0063] By simulating the condition of low underground water level for debugging, the starting reliability of the submersible pump under less favorable water level conditions can be effectively verified. When the water level in the drainage ditch is controlled within the corresponding range as required, the water pump can start normally, indicating that the starting performance of the water pump is good, and its adaptability to different water levels meets the design expectation, avoiding the situation that the water pump cannot start due to slight reduction of the water level in actual operation, ensuring that the drainage system has the basic conditions for starting drainage under various underground water level conditions, and solving the problems of water pump working condition adaptability and poor drainage.

[0064] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for constructing drainage systems in underground railways, characterized in that, Includes the following steps: S1. Conduct detailed geological surveys and groundwater level measurements in the construction area to obtain accurate data for designing parameters for drainage ditches, drainage pipes, and collection wells; S2. According to the design plan, excavate drainage ditches around the construction area. During the excavation process, strictly control the depth and slope to ensure that the bottom of the drainage ditches is flat. S3. Lay drainage pipes according to the design slope and location requirements, and use special sealing rings to seal the pipe connections. S4. Excavate a water collection well in a low-lying area. After excavation, reinforce the inner wall of the water collection well, then install a water level monitoring device and a submersible pump, and connect the relevant electrical lines and drainage pipes. S5. After the entire drainage system is installed, conduct a comprehensive inspection and commissioning.

2. The method for constructing drainage systems for underground railways according to claim 1, characterized in that, The geological survey is conducted with a survey point every 20m. When there are faults or boundaries between different strata, the spacing between survey points should be increased to 10-15m.

3. The method for constructing drainage systems for underground railways according to claim 1, characterized in that, The drainage pipe is made of high-strength PVC material, with a wall thickness deviation of no more than ±0.3mm, a tensile strength of no less than 40MPa, and a ring stiffness of no less than 8kN / ㎡.

4. The method for constructing drainage systems for underground railways according to claim 1, characterized in that, During the excavation of the drainage ditch, the depth and slope of the drainage ditch are measured every 2m using a level and a slope gauge to ensure that the depth error is controlled within ±50mm and the slope error is controlled within ±0.1%.

5. The method for constructing drainage systems for underground railways according to claim 1, characterized in that, The flatness deviation of the bottom of the drainage ditch is ±20mm, and the gap between each measuring point and the straightedge should be controlled within 20mm.

6. The method for constructing drainage systems for underground railways according to claim 1, characterized in that, The buried drainage pipes are laid on a sand cushion foundation. The compaction degree is tested using the sand filling method. The compaction degree should not be less than 95%, and a test is conducted every 10m.

7. The method for constructing drainage systems for underground railways according to claim 1, characterized in that, The sealing treatment uses a special rubber ring for pipelines. During the pressure test, the test pressure is usually 1.5 times the working pressure of the pipeline, which should be above 0.6MPa. The pressure stabilization time should not be less than 30 minutes, and the pressure drop should be within 0.05MPa to be considered qualified.

8. A method for constructing drainage systems for underground railways according to claim 1, characterized in that, The reinforcement treatment uses HPB300 grade steel bars, and the ends should be bent into 180° hooks. The cold drawing rate of HPB300 grade steel bars should be within 4%.

9. A method for constructing drainage systems for underground railways according to claim 1, characterized in that, The submersible pump's installation position deviation is within ±10mm, and its elevation deviation is within ±5mm.

10. A method for constructing drainage systems for underground railways according to claim 1, characterized in that, The water level parameters are adjusted to simulate a low groundwater level. The water level in the drainage ditch is controlled at 0.2-0.3m from the bottom of the ditch so that the water pump can start normally when the water level reaches the start-up setting value. After running for 5-10 minutes, the water level in the collection well should drop significantly, with a drop of no less than 0.1m.

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