Geotextile fill construction and quality control method for railway subgrade subbase

Abstract

A kind of geotextile filling construction and quality control method for railway subgrade bed, including: geotextile performance design, geotextile cutting, shoulder and line are hardened, line excavation, ballast removal, bed surface treatment, lay high suction geotextile, fine sand cushion laying, cyclic excavation, ballast backfill, line recovery, old ballast removal is completed to new ballast backfill, tamping, check line geometry, until meet the requirements.The present application has the advantages of less interference, does not affect driving, low cost, simple construction and the like, the composite subgrade structure formed can significantly improve the strength and toughness of subgrade soil body, can achieve the effects of anti-seepage, isolation, reinforcement, reverse filtration, drainage, protection or heat preservation, etc., has wide applicability to high-speed railway construction in complex geological conditions area.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of filling construction, and particularly relates to a geotextile filling construction and quality control method for a railway subgrade bed. BACKGROUND

[0002] Under the combined action of long-term complex natural stress and train cyclic load, the railway subgrade may have partial area sealing layer waterproof failure. Surface water intrusion into the subgrade is easy to cause frost heaving, upward arching, settlement, mud pumping and other diseases.

[0003] At present, the common remediation engineering technology of the domestic railway maintenance department for the subgrade bed mud pumping and other bed diseases includes excavation and replacement of sand cushion, sealing of bed surface, bed surface reinforcement, bed surface replacement, and bed pile reinforcement.

[0004] The remediation technology of excavation and replacement of sand cushion, i.e. excavation and removal of mud pumping and bed ballast, backfilling of a layer of medium-coarse sand, and backfilling of ballast, has certain effect in the short term, but after several years of operation, rainwater infiltration will cause mud pumping disease to recur again, and it is difficult to eradicate mud pumping disease.

[0005] The remediation technology of sealing of bed surface has simple design, low investment, and good effect, and is suitable for soil or weathered rock surface disease, but is not suitable for subgrade with insufficient strength, and cannot remove the poor soil on the bed surface.

[0006] The bed surface reinforcement remediation technology has lower investment, shorter construction period, and less traffic interference compared with replacement of sand cushion. The technology is similar to replacement and laying of geocell, but the depth of bed remediation is shallower.

[0007] The bed surface replacement remediation technology is complete and has wide application range, and the replacement material can be selected from multiple types, and is currently widely used. However, the construction is difficult, the progress is slow, the traffic interference is more, and some remediation schemes are high-risk.

[0008] The bed pile reinforcement can improve the bearing capacity of the subgrade and reduce the settlement, has wide application range, does not need to raise the line, and has small workload. However, in the section with high underground water level, underground water precipitation measures need to be constructed in advance.

[0009] Preventing water softening of the bed is the fundamental of remediation of mud pumping and other diseases of the subgrade. Laying of geotextile with water blocking and drainage functions can effectively reduce the slurry and upward effect of dynamic load. The conventional geotextile laying technology has slow construction progress, high cost, requires closed line, and affects traffic. SUMMARY

[0010] In order to overcome the problems in the prior art, one of the purposes of the present application is to provide a geotextile filling construction method for railway subgrade bed, in particular, an anti-seepage and anti-cracking high-suction geotextile filling construction method for railway subgrade bed, aiming at the urgent demand for engineering materials under complex geological conditions, the present application proposes a filling construction process of anti-seepage and anti-cracking high-suction geotextile laid on the surface layer or bottom layer of railway subgrade bed, and the formed composite subgrade structure has durability and long-term service performance in harsh environment.

[0011] The present application adopts the following technical solutions:

[0012] The present application provides a geotextile filling construction method for railway subgrade bed, comprising the following steps:

[0013] Step 1, geotextile performance design: the new high-suction geotextile is composed of three materials, the radial direction is flat wire, which plays a reinforcing role; the weft direction is composed of net-shaped wire and special-shaped fiber, the net-shaped wire provides a drainage channel; the special-shaped fiber is composed of a plurality of monofilaments, the cross section of each monofilament is branch-shaped, which generates strong suction and provides micro-channels for water migration;

[0014] Step 2, geotextile cutting: the geotextile laying size is determined in advance according to the site excavation operation surface condition and cutting is performed;

[0015] Step 3, using three-seven lime soil to harden the shoulder and the line;

[0016] Step 4, line excavation: two excavators excavate from the middle position to both ends of the line, the excavation width determines the geotextile cutting size, including: working groove excavation, line interval closed layer breaking, line interval filling layer excavation, line excavation;

[0017] Step 5, ballast removal: the sleeper is pulled out, the excavator excavates the ballast down to the bed surface, the excavated ballast is piled on the shoulder, if there is bad filler, it is excavated down from the subgrade surface, and the sand is backfilled and tamped;

[0018] Step 6, bed surface treatment: initially flatten the bed surface, and then lay a fine sand cushion layer;

[0019] Step 7, laying high-suction geotextile, the geotextile is rolled in advance, the rolled thickness is not more than the height from the bottom of the sleeper to the surface of the shoulder, after the excavator excavates the first section, the rolled geotextile is pushed into the track below and laid in the excavation direction;

[0020] Step 8, fine sand cushion laying, after the geotextile is laid, a layer of fine sand is laid manually on it;

[0021] Step 9, cycle excavation, after the fine sand cushion is laid, the excavator pushes the adjacent sleeper to the top of the excavation area, and uses the bagged graded gravel cushion under the sleeper as support, the excavator continues to excavate forward, and then the process of steps 5-8 is repeated to process the subgrade surface layer, lay the geotextile, and lay the fine sand cushion;

[0022] Step 10, ballast backfilling, line recovery, after the old ballast is removed, the new ballast is backfilled, tamped, and the line geometry is checked until the requirements are met.

[0023] Further, in step 1, the high-suction geotextile can guide the water flow through the capillary, and the capillary forms a matrix suction to discharge the stored water in the adjacent unsaturated soil body;

[0024] The cross section of the high-suction geotextile contains deep grooves with a diameter of 8 μm, which act as capillaries to transport liquid along the longitudinal axis through narrow channels;

[0025] The high-suction geotextile has two forms of pressure difference drainage and evaporation, and the soil body is in a saturated state through pressure difference drainage and in an unsaturated state through evaporation drainage;

[0026] Further, in step 7, for the case of a single excavator, a single-sided paving method is used, and for the case of a double excavator, a double-sided paving method is used.

[0027] Further, in step 7, the paving scheme of the geotextile includes: paving a single layer of high-suction geotextile; paving a double layer of high-suction geotextile; paving a single layer of geotextile and a geomembrane.

[0028] Further, paving a single layer of high-suction geotextile includes: fully paving a single layer of high-suction geotextile, and the geotextile is longitudinally laid to closely cooperate with the excavator to reduce the number of longitudinal overlaps.

[0029] Further, paving a double layer of high-suction geotextile includes: fully paving two layers of high-suction geotextile, the geotextile has a transverse width of 5.2 m, 5 cm of sand is laid between the two layers of geotextile, the geotextile covers 20 cm thick ballast at the ballast corner position, and the geotextile is longitudinally laid to closely cooperate with the excavator to reduce the number of longitudinal overlaps.

[0030] Further, paving a single layer of geotextile and a geomembrane includes: paving a waterproof geomembrane, and paving a single layer of high-suction geotextile on the geomembrane, and the geotextile is longitudinally laid to closely cooperate with the excavator to reduce the number of longitudinal overlaps.

[0031] Further, in step 10, the line recovery includes: working groove and filling layer backfilling, closed layer recovery, and track fine adjustment.

[0032] The application also provides a geotextile filling quality control method for a railway subgrade bed.

[0033] Step 1, control the process of geotextile spreading;

[0034] Step 2, protect the geotextile spreading;

[0035] Step 3, overlap the geotextile;

[0036] Step 4, detect the engineering quality: the engineering quality detection of the subgrade bed filled with high-suction geotextile includes the filling compaction detection and the permeability detection.

[0037] The technical scheme of the present application can realize the following beneficial technical effects:

[0038] The present application provides a construction process of filling high-suction geotextile in railway subgrade bed, which has the advantages of less interference, no influence on train running, low cost, simple construction and the like, and the formed composite subgrade structure can significantly improve the strength and toughness of the subgrade soil body, and can achieve the effects of anti-seepage, isolation, reinforcement, reverse filtration, drainage, protection or heat preservation, and has wide applicability to the high-speed railway construction in complex geological conditions.

[0039] The present application provides a construction quality control system of filling high-suction geotextile in subgrade bed, which ensures the flatness and drainage performance of the geotextile during the filling of the subgrade bed, and provides a basis for the quality acceptance after the completion of construction.

[0040] The geotextile filling construction process provided by the present application is constructed within the window time, and the single line is blocked within the window time, which has less interference, no influence on train running, simple construction and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is the anti-seepage and anti-cracking high-suction geotextile filling construction flowchart of the railway subgrade bed of the present application;

[0042] Figure 2 is the drainage principle of high-suction geotextile;

[0043] Figure 3 is the water migration path of high-suction geotextile

[0044] Figure 4 is the ballast excavation schematic view of the present application;

[0045] Figure 5 is the bed surface treatment view of the present application;

[0046] Figure 6 is the single-side spreading view of geotextile of the present application;

[0047] Figure 7 is the double-side spreading view of geotextile of the present application;

[0048] Figure 8 This is a schematic diagram of the single-layer high-absorption geotextile railway subgrade structure for seepage prevention and crack resistance according to the present invention;

[0049] Figure 9 This is a schematic diagram of the double-layer high-absorption geotextile railway subgrade structure for seepage prevention and crack resistance according to the present invention;

[0050] Figure 10 This is a schematic diagram of the single-layer high-absorption geotextile + geomembrane railway subgrade seepage prevention and crack resistance structure of the present invention;

[0051] Figure 11 This is a schematic diagram of the laying of the high-absorption geotextile fine sand cushion layer of the present invention;

[0052] Figure 12 This is the ballast backfill diagram of the present invention. Detailed Implementation

[0053] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0054] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0055] It should be understood that although the terms "first," "second," "third," etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] This invention provides a construction process for impermeable and crack-resistant high-absorption geotextile filling in railway subgrade. Based on the conventional fine sand replacement method, a new type of high-absorption geotextile is laid during the sand replacement layer, providing both waterproofing and drainage functions, effectively preventing subgrade diseases such as frost heave and mudslides. Specifically, as...Figure 1 As shown, after the track bed is excavated, first, the base surface layer is padded with sand and leveled, then high suction geotextile is laid on the base surface layer, then a layer of fine sand is laid on the high suction geotextile, and finally the ballast is backfilled.

[0057] The performance of the geotextile material shall meet the corresponding functional design requirements. The mechanical properties, hydraulic properties, durability properties and friction coefficient between the geotextile and the soil shall be determined through tests; when the test conditions are not available, the requirements shall be determined in combination with engineering experience or relevant data.

[0058] Specifically, the method comprises the following steps:

[0059] Step 1: Geotextile performance design: the new high-suction geotextile is composed of three materials, the radial direction is a flat wire (PP) with high tensile strength, which plays a reinforcing role; the weft direction is composed of net-shaped wires and special-shaped fibers, the net-shaped wires provide large-pore drainage channels; the special-shaped fibers are composed of hundreds of monofilaments, and the composition is a composite polyester, the cross section of each monofilament is dendritic, the diameter is several tens of microns, the specific surface area is large, can generate strong suction, and can provide micro-channels for the migration of water.

[0060] The high-suction geotextile can guide the water flow through the small capillary tube, the capillary tube forms the matrix suction, which is helpful for draining the stored water in the adjacent unsaturated soil body. The unique cross section of the high-suction geotextile contains deep grooves with a diameter of about 8 μm, which act as capillary tubes, transporting liquid along the longitudinal axis through the narrow channels. These special fibers are made of nylon with hydrophilic and hygroscopic properties, which will absorb water from the surrounding soil and transport water along its longitudinal channel.

[0061] The high-suction geotextile is different from the traditional drainage method, which has both pressure difference drainage and evaporation functions. The soil is drained by pressure difference in the saturated state, and by evaporation in the unsaturated state.

[0062] When the water content is large, the dynamic load generates excess pore pressure, and the water is mainly drained from the net-shaped large pores.

[0063] When the water content decreases, the soil changes from saturated to unsaturated, and the water in the soil is suction. At this time, the large specific surface area of the special-shaped fiber generates strong suction, which can adsorb the water in the unsaturated soil, Figure 2 , Figure 3 As shown, the water in the fiber migrates to both sides through the micropores; the water in the geotextile at both ends is drained by evaporation, causing the water content of the end geotextile to decrease; for porous media, the water content is inversely proportional to the suction, and the decrease in water content at the end of the fiber will cause the suction to increase, thereby adsorbing the water in the middle of the fiber to the two ends; after the water content of the middle fiber decreases, it continues to adsorb the water in the soil base. This continuous cycle realizes the active drainage of water.

[0064] ​Based on the drainage principle and experimental data of the high-absorption geotextile above, the performance design indicators of the high-absorption geotextile used in this invention are determined, as shown in Table 1:

[0065] Table 1 Performance Requirements of High Absorption Geotextiles

[0066]

[0067] Step 2, Geotextile Cutting: When using single-line construction, the ballast is piled up at the construction site, manually cleaned and sieved, and the excavation and replacement work area is small, resulting in tight construction time. To save construction time, the geotextile laying size needs to be determined in advance based on the on-site excavation work area and then cut.

[0068] Step 3: Use a 3:7 mixture of lime and soil to harden the area between the road shoulder and the lane, to a thickness of 10cm;

[0069] Step 4, as follows Figure 4 As shown, the line excavation: two excavators excavate from the middle position to both ends of the line. The excavation width determines the cutting size of the geotextile (for example, if the excavation width is 4m, one excavator can complete 10m long ballast excavation and replacement at one skylight point, then the cutting size of the geotextile is 10m*4m or 20m*4m).

[0070] Specifically, the excavation of the line includes the following steps: excavation of the working trench, removal of the inter-line sealing layer, excavation of the inter-line filling layer, and excavation of the line itself.

[0071] Step 5, Ballast Removal: First, the sleepers are manually removed, and then an excavator is used to remove the ballast down to the surface of the subgrade. The excavated ballast is then piled on the shoulder. If there is unsuitable fill material, it is removed from the surface of the subgrade, backfilled with sand, and compacted. The compacted sand layer should be at least 10cm higher than the original ground level.

[0072] Step 6, Subgrade Surface Treatment: Manually level the subgrade surface, then lay a 5cm thick layer of fine sand for leveling. (Example: ...) Figure 5 As shown.

[0073] Step 7: Lay high-absorption geotextile. The geotextile should be pre-rolled, with the roll thickness not exceeding the height from the bottom of the sleeper to the shoulder surface. After the excavator completes the first section, push the roll of geotextile under the track and spread it out in the excavation direction. Figures 6-7 As shown, for the case of a unidirectional excavator, a single-sided deployment method is used; for the case of two excavators, a double-sided deployment method is used.

[0074] There are three laying schemes for geotextiles: Scheme 1, laying a single layer of high-absorption geotextile; Scheme 2, laying a double layer of high-absorption geotextile; Scheme 3, laying a single layer of geotextile + geomembrane. The laying scheme should be selected according to the drainage conditions and drainage requirements. For poor drainage conditions and high drainage requirements, the double layer of high-absorption geotextile should be selected.

[0075] Scheme 1: Laying single layer of high suction geotextile

[0076] As shown in Figure 8 , the single layer of high suction geotextile is fully laid, with the geotextile having a lateral width of 5.2 m, and the geotextile at the ballast corner covering 20 cm thick ballast to ensure that the geotextile has good evaporation effect. The longitudinal laying of the geotextile should be closely coordinated with the excavator to minimize the number of longitudinal overlaps.

[0077] Scheme 2: Laying double layer of high suction geotextile

[0078] As shown in Figure 9 , the double layer of high suction geotextile is fully laid, with the geotextile having a lateral width of 5.2 m, and 5 cm of sand being laid between the two layers of geotextile, and the geotextile at the ballast corner covering 20 cm thick ballast to ensure that the geotextile has good evaporation effect. The longitudinal laying of the geotextile should be closely coordinated with the excavator to minimize the number of longitudinal overlaps.

[0079] Scheme 3: Laying single layer of geotextile + geomembrane

[0080] As shown in Figure 10 , the waterproof geomembrane is laid, and the single layer of high suction geotextile is laid on the geomembrane, with the geotextile having a width of 5.2 m, and the geotextile at the ballast corner covering 20 cm thick ballast to ensure that the geotextile has good evaporation effect. The longitudinal laying of the geotextile should be closely coordinated with the excavator to minimize the number of longitudinal overlaps.

[0081] The high suction geotextile has strong suction, with vertical suction reaching more than 20 cm, and after uneven settlement occurs, it does not affect the drainage effect.

[0082] Under rainfall conditions, there is a certain height difference at the end of the geotextile, and it is difficult for rainwater to enter in the opposite direction; only in extreme cases, the end of the geotextile is soaked in water and is in a saturated state, and water will migrate inward, but when the rainfall reaches this level, the rainwater has already filled the bed through the ballast. After the weather clears, the water in the subgrade is drained out through the geotextile to both ends.

[0083] The geotextile migrates liquid water, and it is not clear whether it has any effect on gaseous water. Therefore, the humid state only changes the evaporation rate at the end, and does not change the direction of water migration.

[0084] Step 8: Fine sand cushion laying Figure 11 After the geotextile is laid, a layer of fine sand with a thickness of about 50 mm is laid manually on it, as shown in

[0085] Step 9, cycle excavation, after the fine sand cushion is laid, the excavator pushes the adjacent sleeper to the top of the excavation area, and uses the bagged graded gravel cushion under the sleeper as support, the excavator continues to excavate forward, and then repeats the process of steps 5-8 to process the subgrade surface layer, lay the geotextile, and lay the fine sand cushion. As shown in Figures 8-11

[0086] Step 10, ballast backfilling, line recovery. After the old ballast is removed, new ballast is backfilled, tamped, and the line geometry is checked until the requirements are met. As shown in Figure 12

[0087] Specifically, the line recovery includes: working groove and filling layer backfilling, closed layer recovery, track fine adjustment, and the like.

[0088] Specifically, after the backfilling is completed, the geometry of the line is checked until the requirements are met.

[0089] The second aspect of the present application provides a geotextile filling quality control method for a railway subgrade bed, specifically, the method comprises:

[0090] Step 1, control the process of laying the geotextile.

[0091] The geotextile is gradually laid from one end, and if the surface of the subgrade surface layer is uneven or the geotextile is laid at different speeds along the width of the two ends, the geotextile may be twisted during the laying process, causing the width of the exposed geotextile outside to become smaller and smaller, affecting the drainage effect. Therefore, during the laying process of the geotextile, firstly, the flatness of the coarse sand layer of the subgrade surface layer is controlled. Secondly, the flatness of the surface of the geotextile during the laying process is controlled.

[0092] This step controls the flatness by using a total station. First, install the total station at the center of the measurement area and keep it stable. Then adjust the viewing angle so that the line of sight is directly opposite the boundary line of the measurement area. Then, use the level of the total station to measure the reference height, i.e. the elevation of the measurement area. Finally, use the digital theodolite of the total station to measure the coordinates of the measurement area, and use software to process the data to obtain the flatness data of the measurement area. Through the above steps, the flatness of the coarse sand layer of the subgrade surface layer and the surface of the geotextile during the laying process can be measured by using the total station, and the measurement area can be neutralized and leveled.

[0093] Step 2, protect the laying of the geotextile.

[0094] Although the geotextile has certain strength and toughness, it can be punctured when pressed by sharp objects. During construction, workers will use tools such as shovels and iron rods, and care should be taken to avoid damaging the geotextile during laying.

[0095] Step 3, overlap the geotextile. ​​

[0096] The ballast excavation is carried out in sections, and the ballast excavation replacement and the geotextile laying are completed on the same day, the replacement section is in units of 10m (or 20m, two excavators dig towards each other), each section is independent, and each section of the geotextile also exists independently without lap joint. In order to ensure the drainage effect of the geotextile, the method that two excavators dig towards each other can be adopted when replacing, so as to increase the length of the whole section of the geotextile as much as possible, and the influence of the length of each section of the geotextile on the drainage effect in the case of lap joint and no lap joint is analyzed through on-site test.

[0097] Step 4, detecting the engineering quality.

[0098] The engineering quality detection of the subgrade bed filled by the high-suction geotextile includes filling compaction detection and permeability detection. The present application proposes the control standards of the ground coefficient index K 30 and the bed filling permeability coefficient K, and requires that the ground coefficient K 30 of the bed surface layer is above 150MPa / m, the ground coefficient of the bottom layer is above 130MPa / m, and the permeability coefficient K is less than 5*10 -3 cm / s, which provides a basis for quality acceptance after construction.

[0099] The filling compaction detection index is the ground coefficient K 30 of the subgrade surface layer filling and the bottom layer filling, and the core drilling sampling machine is used to drill core sampling on site at a specified frequency, and the static pressure flat plate load test is carried out.

[0100] According to the test results, the load intensity and the sinking amount relationship curve is drawn, the load intensity σs corresponding to the sinking amount reference value (1.25mm) is obtained from the load intensity and the sinking amount relationship curve, and the ground coefficient K 30 is calculated, and the calculation formula is as follows:

[0101] K 30 =σs / 1.25, unit: MPa / m.

[0102] The index of the permeability detection is the permeability coefficient of the bed filling, and the test pit water seepage test is usually used for detection on site.

[0103] When the water seepage test is carried out to the seepage water amount tends to be stable, the permeability coefficient can be accurately calculated according to the following formula.

[0104] K (permeability coefficient) = QL / F (H+Z+L)

[0105] Q----- stable seepage water amount (cubic centimeter / minute);

[0106] F------ the water seepage area of the test pit inner ring (square centimeter);

[0107] Z----- the water thickness in the test pit inner ring (centimeter);

[0108] H-----Capillary pressure (generally equal to half of the height of capillary rise of soil) (cm);

[0109] L-----Infiltration depth of water at the end of the test (determined by excavation after the test) (cm).

[0110] The present application requires that the formed roadbed anti-seepage sealing layer structure has a permeability coefficient less than 5*10 -3 cm / s, which is superior to the test data of the performance of the road surface structure obtained by the conventional process.

[0111] In summary, the present application provides a method for geotextile filling construction and quality control for railway roadbed subgrade, which comprises: geotextile performance design, geotextile cutting, hardening of the shoulder and line, line excavation, ballast removal, subgrade surface treatment, laying of high-suction geotextile, fine sand cushion laying, cyclic excavation, ballast backfilling, line restoration, old ballast removal, new ballast backfilling, tamping, line geometry inspection, and so on until the requirements are met. The present application has the advantages of less disturbance, no influence on train operation, low cost, simple construction, etc. The formed composite roadbed structure can significantly improve the strength and toughness of the roadbed soil body, and can achieve the effects of anti-seepage, isolation, reinforcement, reverse filtration, drainage, protection, or heat preservation, etc. It has wide applicability to the construction of high-speed railways in areas with complex geological conditions.

[0112] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings. In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0113] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing geotextile filling in railway subgrade, characterized in that, Includes the following steps: Step 1, Geotextile performance design: The new high-absorption geotextile is composed of three materials: flat yarns in the radial direction, which serve as reinforcement; mesh yarns and shaped fibers in the weft direction, with the mesh yarns providing drainage channels; and shaped fibers composed of multiple monofilaments, each monofilament having a dendritic cross-section, generating strong suction and providing microchannels for water migration. Step 2, Geotextile cutting: Determine the geotextile laying size in advance based on the on-site excavation conditions and cut it accordingly; Step 3: Harden the area between the road shoulder and the road line using a 3:7 mixture of lime and soil. Step 4, Line Excavation: Two excavators excavate from the middle to both ends of the line. The excavation width determines the cutting size of the geotextile. This includes: excavation of the working trench, removal of the inter-line sealing layer, excavation of the inter-line filling layer, and line excavation. Step 5, Ballast Removal: Remove the sleepers, and use an excavator to remove the ballast down to the surface of the subgrade. The excavated ballast is piled on the shoulder. If there is unsuitable fill material, it is removed from the surface of the subgrade, backfilled with sand and compacted. Step 6, Subgrade surface treatment: Initially level the subgrade surface, then lay a fine sand cushion layer for leveling; Step 7: Lay high-absorption geotextile. The geotextile is rolled into rolls in advance, and the thickness of the rolls does not exceed the height from the bottom of the sleeper to the surface of the shoulder. After the excavator has finished excavating the first section, push the rolls of geotextile under the track and spread them out in the excavation direction. Step 8: Laying a fine sand cushion layer. After the geotextile is laid, a layer of fine sand is manually laid on top of it. Step 9, cyclic excavation: After the fine sand cushion layer is laid, the excavator pushes the adjacent sleepers above the excavation area and uses bagged graded crushed stone as support under the sleepers. The excavator continues to excavate forward and then repeats the process of steps 5-8 to carry out subgrade surface treatment, geotextile laying and fine sand cushion layer laying. Step 10: Ballast backfilling and track restoration. After the old ballast is removed, new ballast is backfilled, tamped, and the track geometry is checked until the requirements are met.

2. The method for geotextile filling construction for railway subgrade according to claim 1, characterized in that, In step 1, the high-absorption geotextile can guide water flow through capillaries, which form matrix suction and drain water stored in adjacent unsaturated soil. The cross-section of the high-absorption geotextile contains deep grooves with a diameter of 8μm. These grooves act as capillaries, transporting liquid along the longitudinal axis through narrow channels. High-absorption geotextiles have two forms of drainage: pressure difference drainage and evaporation. When the soil is saturated, drainage is achieved through pressure difference, and when it is unsaturated, drainage is achieved through evaporation.

3. The geotextile filling construction method for railway subgrade according to claim 1, characterized in that, In step 7, for the case of a unidirectional excavator, a single-sided spreading method is used; for the case of a dual excavator, a double-sided spreading method is used.

4. The method for geotextile filling construction for railway subgrade according to claim 1, characterized in that, In step 7, the geotextile laying scheme includes: laying a single layer of high-absorption geotextile; laying a double layer of high-absorption geotextile; and laying a single layer of geotextile and geomembrane.

5. The geotextile filling construction method for railway subgrade according to claim 4, characterized in that, Laying a single layer of high-absorption geotextile includes: fully laying a single layer of high-absorption geotextile, laying the geotextile longitudinally, closely cooperating with the excavator, and reducing the number of longitudinal overlaps.

6. The geotextile filling construction method for railway subgrade according to claim 4, characterized in that, Laying double-layer high-absorption geotextile includes: laying two layers of high-absorption geotextile with a transverse width of 5.2m, laying 5cm of sand between the two layers of geotextile, covering the ballast corners with 20cm thick ballast, and laying the geotextile longitudinally in close coordination with the excavator to reduce the number of longitudinal overlaps.

7. The geotextile filling construction method for railway subgrade according to claim 4, characterized in that, Laying a single layer of geotextile and geomembrane includes: laying a waterproof geomembrane and then laying a single layer of high-absorption geotextile on top of it. The geotextile is laid longitudinally and closely cooperates with the excavator to reduce the number of longitudinal overlaps.

8. The method for geotextile filling construction for railway subgrade according to claim 1, characterized in that, In step 10, track restoration includes: backfilling of the working groove and filling layer, restoration of the sealing layer, and fine-tuning of the track.

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