CN111364471A - Construction method of excavation roadbed of high-speed railway in karst area - Google Patents

Abstract

The invention discloses a construction method of a high-speed railway excavation roadbed in a karst area, which comprises the following steps: determining the development degree of a karst through physical exploration and drilling; step two, surface cleaning of the original ground, excavation of earth and stone and blasting; step three, slope cleaning and protection; step four, arranging a foreign matter invasion preventing protective net; fifthly, reinforcing the karst foundation; and sixthly, constructing a ballastless track structure on the karst foundation after the karst foundation reinforcement detection is qualified. The method can ensure the construction quality of the excavation roadbed of the high-speed railway in the karst area, ensure the reliability of the construction and operation of the excavation side slope of the roadbed, ensure the stability of the roadbed and the qualification of the settlement of the roadbed after construction, and ensure that the roadbed does not have the defects of collapse, rockfall and the like.

Description

Construction method of excavation roadbed of high-speed railway in karst area

Technical Field

The invention relates to the technical field of high-speed railway roadbed construction, in particular to a construction method of a high-speed railway excavation roadbed in a karst area.

Background

The construction of high-speed railways is the need for rapid economic development and great improvement of railway transportation capacity, and is one of the important signs whether the country is developed or not, developed countries in the world such as Japan, France and Germany have built relatively high-efficiency and beautiful high-speed rail nets in the nineteenth century, and the pulling effect on economic development and urbanization construction along high-speed rails is particularly obvious. The high-speed railway technology is researched from the nineteenth century, large-scale construction and continuous opening are started in 2004, and the operating mileage of the high-speed railway built into a communication car in China is nearly 3.5 kilometres. In the design of high-speed railways, professional detailed design determines the stability and safety of railway operation, and particularly, the requirement of millimeter-scale settlement control in high-speed railway base design is a central importance in high-speed railway design.

The land is vast in China, geological conditions of different regions are different, a large amount of limestone, dolomite and other soluble rocks are distributed in southwest mountainous areas and Guangxi areas, and foundation collapse, dangerous rock invasion and the like are easy to occur in high-speed rail engineering construction in the areas.

The railway is a ballastless track trunk high-speed railway of 350km/h in China, the technical standard is high, the section of engineering passes through a roadbed excavation part, the center excavation part is about 5m, the highest side slope on the right side reaches 20m, the surface of a stratum in the engineering range is covered with fourth system all-new-system slope residual layer powdery clay, the covering layer is thin and is less than 3m, a second-system lower-system sunny new group limestone is covered under the engineering range, the underground water type is fourth system pore diving, bed rock fracture water, the buried depth is 3 m-7.8 m, and the karst is developed in a medium mode. The natural slope on the right side has certain exposed limestone, and the possibility of falling rocks exists.

Disclosure of Invention

The invention aims to provide a construction method of a high-speed railway excavation roadbed in a karst area, which can ensure the construction quality of the excavation roadbed of the high-speed railway in the karst area, ensure the reliability of roadbed excavation side slope construction and operation, ensure the stability of the roadbed and the qualification of roadbed settlement after construction, and ensure that the roadbed does not have the defects of collapse, rockfall and the like.

In order to achieve the purpose, the specific technical scheme of the construction method of the excavation roadbed of the high-speed railway in the karst area is as follows:

a construction method of a high-speed railway excavation roadbed in a karst area comprises the following steps:

determining the development degree of a karst through physical exploration and drilling;

step two, surface cleaning of the original ground, excavation of earth and stone and blasting;

step three, slope cleaning and protection;

step four, arranging a foreign matter invasion preventing protective net;

fifthly, reinforcing the karst foundation;

and sixthly, constructing a ballastless track structure on the karst foundation after the karst foundation reinforcement detection is qualified.

The construction method of the excavation roadbed of the high-speed railway in the karst area has the advantages that:

1) reasonable and reliable foundation treatment and slope protection engineering are adopted, so that the requirement of post-construction settlement control can be met, and the requirement of high-speed railway operation safety can also be met;

2) the comprehensive treatment measures such as karst treatment, rockfall remediation and slope protection can be taken for karst development areas with poor geological conditions, so that the requirements of high-speed rail post-construction settlement, slope stability and later-stage railway operation safety are met;

3) the construction quality of the excavation roadbed of the high-speed railway in the karst area can be ensured, the reliability of construction and operation of the excavation side slope of the roadbed can be ensured, the stability of the roadbed and the qualification of settlement of the roadbed after construction can be ensured, and the beneficial effects that the roadbed does not have the defects of collapse, rockfall and the like can be ensured;

4) the method mainly solves a series of technical problems of determining the development degree of the karst roadbed, clearing the surface of the roadbed base, excavating and blasting earthwork, cleaning and protecting a side slope, setting a foreign matter invasion preventing protective net, treating the karst foundation and the like when the excavation roadbed is constructed in the karst area of the high-speed railway;

5) the construction method can be used for construction of the excavation square section of the karst subgrade of the expressway and the ordinary-speed railway with higher requirements on post-construction settlement, the construction quality of the excavation subgrade in the karst area of the expressway can be ensured, the stability and the attractiveness of the excavation side slope of the subgrade are ensured, the qualification of the post-construction settlement of the subgrade and the risk of foreign matter invasion in the operation process are ensured, and the damage of the subgrade such as karst collapse and the like is avoided.

Drawings

FIG. 1 is a schematic diagram of a construction method of a high-speed railway excavation roadbed in a karst area;

FIG. 2 is a flow chart of the construction method of the excavation roadbed of the high-speed railway in the karst area.

In the figure: 1. a natural ground line; 2. spraying and mixing plant growing protection slope; 3. spraying and seeding grass planting for slope protection; 4. a soil layer; 5. A limestone layer; 6. a foreign matter invasion preventing protective net; 7. a stratigraphic rock boundary; 8. a karst foundation stabilization zone.

Detailed Description

In order to better understand the purpose, structure and function of the present invention, the following will describe in further detail a construction method of an excavation roadbed of a high-speed railway in a karst area with reference to the accompanying drawings.

As shown in fig. 1, the construction method of the excavated roadbed of the high-speed railway in the karst area, which is disclosed by the invention, comprises the following steps:

s1, determining the development degree of the karst through physical exploration, drilling and other means;

s2, surface cleaning of the original ground, excavation of earth and stone and blasting;

s3, slope cleaning and protection;

s4, arranging a foreign matter intrusion prevention protective net;

s5, reinforcing the karst foundation;

and S6, constructing the ballastless track structure on the karst foundation after the karst foundation reinforcement detection is qualified.

Specifically, step one, S1, step one, the karst development degree is determined by means of physical exploration, drilling, etc.

In the field fixed-survey stage of the high-speed railway, the geological conditions of the area where the line passes are explored in detail by comprehensive means such as engineering geological survey, physical survey, drilling, in-situ or indoor test and the like, geophysical prospecting lines and drilling holes are arranged according to the requirements of relevant specifications such as railway engineering geological survey specification, geotechnical engineering survey specification and the like, and the exploration range is comprehensively explored by adopting a mechanical core drilling machine, a total station instrument and an ultrasonic tester in cooperation with indoor test equipment, so that the development degree of the karst of the area where the engineering is located is judged.

The specific process flow is as follows:

(1) engineering geology adjustment and drawing:

according to the landform and geological conditions, engineering setting is closely combined, and a working method of distance observation, near observation, surface-to-point combination and point-surface combination is adopted. And supplementing, modifying and perfecting the data of the initially measured geological survey result, reasonably arranging exploration test work on the basis, and providing geological data required by circuit scheme selection and engineering design. Stratigraphic divisions were divided by 1: 20 ten thousand regional geological maps and reports are taken as the basis, stratum units are generally divided into groups, and soluble rock strata and coal measure strata are divided into sections. Further finding out karst cave, underground river, karst spring and other karst phenomena and artificial cave distribution of coal cave, mine pit and other artificial cave.

(2) Physical exploration:

and carrying out geophysical prospecting on the karst roadbed section for determining the electrical parameters of the stratum, the integrity of the stratum, the weathering degree of the stratum, the underground water-containing condition, the structure, the development degree of the karst, the goaf and the like. And if necessary, carrying out geophysical prospecting on the heavy and unfavorable geologic body. Two geophysical prospecting lines are arranged on the double-track railway, and are generally arranged on a left central line and a right central line; the station yard and the positive lines of the multi-line section are respectively provided with one measuring line, and other station lines are properly increased with measuring lines according to the width. And (4) carrying out geophysical prospecting on the subgrade in the underground river or karst cave region under the condition of ground collapse in the shallow covered karst region by the gravity. The roadbed engineering can adopt a high-density electrical method or a direct current sounding method.

(3) Drilling:

drilling: according to the exploration purpose, an appropriate drilling machine type is selected, a reasonable drilling method is adopted, safe operation is realized, detailed records are recorded, the drilling process and the core condition are analyzed seriously, and the drilling quality is ensured. According to the exploration purpose, an appropriate drilling machine type is selected, a reasonable drilling method is adopted, safe operation is realized, detailed records are recorded, the drilling process and the core condition are analyzed seriously, and the drilling quality is ensured. The drilling work shall meet the regulations of the current geological drilling regulations for railway engineering (TB 10014). When the hydrogeological parameters such as water quantity, flow direction, flow velocity and the like of underground water need to be measured or a water sample needs to be taken, the drill hole needs to carry out water lifting, water pumping and other tests and observation work according to relevant regulations, and if necessary, a water pressing or water injection test is carried out. When the aquifer is more and the water quality and water quantity of each layer change greatly, the measurement and the test are carried out by combining the project with the need of layering and stopping water. The position and the elevation of the exploration point are measured by an instrument, and the longitude and latitude coordinates of the exploration point are recorded on a drilling core identification table (a drilling log and a geological histogram). Under the same geological conditions, not less than six groups of rock and soil samples are collected in each lithological layer.

(4) Sampling:

and (3) performing indoor tests by hierarchically adopting representative rock and soil samples in the drilled hole, wherein the number of exploration points of the soil samples is determined according to the stratum structure, the uniformity of foundation soil and design requirements. The sampling quantity is required to meet the statistical requirements of relevant geotechnical parameters, and the sampling quantity of each major geotechnical layer of each major construction point or each geomorphic geological unit is not less than eight groups. And drilling sampling is strictly carried out according to the requirements of a drilling task book, and the sampling depth and name of the water, soil, gravel and sand sample are accurately recorded. The sample is sealed and properly preserved quickly and is sent in time. The positions and the number are determined according to the engineering type and the design requirement. According to the requirements of drilling task specifications, sampling various lithologies of weak and slightly weathered limestone layers (namely the limestone layer 5) in the sampling hole respectively; sealing the rock sample immediately after the rock sample is taken out to prevent weathering; the diameter of the rock sample is not less than 89 mm.

(5) Indoor test and hydrogeological test:

the in-situ test was performed according to the railroad engineering geology in-situ test protocol (TB 10041-2003). Rock laboratory tests are carried out on relative density, density (natural, dried and natural saturation), water content, saturated water absorption, porosity, compressive strength (natural, natural and dried), softening coefficient and the like. And when the rock strength index is directly measured and cannot meet the requirement, performing a point load test. The clay rocks are subjected to free expansion rate, saturated water absorption and expansive force tests. The stone sampling site is specified by the needs specialty. In order to obtain hydrogeological parameters of each aquifer, know hydraulic connection of each aquifer, evaluate water-rich property of each aquifer and obtain related hydrogeological parameters, hydrogeological tests need to be carried out, and the hydrogeological tests are strictly in accordance with railway engineering hydrogeological survey regulations. The engineering hydrogeological test should select a proper test method according to the water quantity and the water level, and the pumping test is preferably carried out under certain conditions. During hydrogeological test, a representative water sample is adopted for water quality test. Sampling before the test is finished when the water pumping test and the water pumping test are carried out; the water pressing test and the water injection test are to sample after cleaning the drill hole and before the test, and the quality and the quantity of the water pressing test and the water injection test are determined according to the test purpose and the test requirement.

(6) And determining the development degree of the karst.

The generation and development of the karst have certain conditions, wherein the conditions mainly include the solubility and the fracture of the rock and the erosiveness and the circulation conditions of water, the former belongs to the lithology and geological structure problems of the rock, the latter depends on the hydrogeological conditions, geological painting, rock drilling revelation, indoor and hydrographic tests and is comprehensively judged by combining physical exploration results, the karst is classified into four categories of strong development, medium development, weak development and weak development according to the development degree according to the classification section of the karst in the appendix E of railway adverse geological survey regulations, and the development degree of the karst is comprehensively judged according to the form and the connectivity of the karst and the condition of underground water.

And step two S2, surface cleaning of the original ground, excavation of earth and stone and blasting.

Specifically, after the land acquisition and removal of the site is completed, the original ground is subjected to surface cleaning and leveling, construction drainage measures and dangerous rock falling stone cleaning are carried out, machinery is adopted to carry out earthwork excavation on a covering layer, when the earthwork excavation reaches the top surface of a bed rock and cannot be carried out by the machinery, blasting or controlled blasting is adopted for the rocky excavation according to the on-site external environment, and small blasting or mechanical construction is adopted for the positions close to a side slope and a bed so as to avoid overbreak. And carrying out layered excavation and layered protection in the earth and stone excavation process.

The specific construction process flow is as follows:

(1) and (5) after the expropriation and removal of land is finished, constructing to enter the field.

(2) Reexamination of high-voltage lines above ground, oil and gas pipelines below ground, national defense optical cables and the like is carried out:

after land acquisition and removal are finished, construction is carried out, and the high-voltage line above the ground, the oil and gas pipeline below the ground, the national defense optical cable and the like are rechecked: after the construction is completed and the building enters the field after the removal, the high-voltage line above the ground, the water pipe below the ground, the oil pipeline, the national defense optical cable and the like are checked, and the construction can be carried out after the safety of the pipeline and the safety of the construction are ensured. For pipelines which may be affected during construction, attention must be paid to the selection of construction methods and reinforcement protection.

(3) Rechecking surface water and underground water:

rechecking surface water and underground water: and sampling and rechecking the surface water, the underground water and the construction water in the section. The water quality has erosive working points, and anti-erosion treatment is carried out according to the requirements of a working point design drawing. If the rechecking results of the surface water and the underground water are not in accordance with the design, the relevant units should be informed to recheck again in time, and the aggressive water cannot be used as the construction water.

(4) Clear away dangerous rock falling over the moat and in time do the protection:

and for the sections with dangerous rock falling rocks, the sections should be cleaned so as not to cause potential safety hazards to engineering construction. And (3) an overlying soil layer (namely a soil layer 4) is used for timely constructing a retaining and protecting project after the side slope is excavated, and the exposure time is not more than half a month. The limestone cutting under the side slope adopts a small step blasting method within 2m of the design line of the side slope, the construction of an enlarging gun is strictly forbidden, the damage of the side slope and the pile caused by excavation is reduced, the phenomenon of serious over-underexcavation is avoided, and the smoothness and the integrity of the side slope are ensured.

(5) Constructing a drainage cut ditch and a gutter:

all retaining and protecting projects dig the foundation soil and stones, and the drainage projects dig the foundation soil and stones and must be transported to the section of roadbed or the tunnel slag abandoning field for centralized stacking, so as to avoid abandoning along with digging, polluting the environment and endangering the safety of the railway main project. Reasonably organizing and densely arranging construction, and strictly prohibiting random stacking and random discharge of waste water and waste slag generated in the construction according to local environment-friendly requirements so as to achieve civilized construction.

Before construction, removing weeds, silt and planting soil on the ground (on the ground line 1), wherein the removed silt and planting soil are used for greening and reclamation as much as possible; leveling the field and building drainage facilities. Construction in rainy season is avoided as much as possible, and smooth drainage of a construction site is guaranteed. In the construction process, whether the surface and the underground are exposed or not should be checked, and relevant units should be informed to carry out treatment in time.

(6) And excavating layer-by-layer blasting from top to bottom and applying slope protection in time.

And step three S3, slope cleaning and protection.

Adopt the grass irrigation bank protection to soil property cutting side slope, to rock property cutting side slope for guaranteeing the afforestation effect, adopt side slope protection forms such as spray-mixed vegetation or bagged foreign soil, need clear up the side slope before the safeguard measure construction, guarantee that the side slope does not have unstable ground body, side slope protection engineering and soil and rock excavation engineering should excavate the layering protection in layers, implement subordinate earthwork and side slope engineering after guaranteeing higher level's side slope stability again.

Specifically, the construction process flow of the grass-irrigation slope protection (namely the spray-seeding grass-planting slope protection 3) is as follows in sequence: cleaning side slopes → spraying grass seeds from top to bottom → covering non-woven fabrics → maintaining → planting shrubs → supplementing grass seeds → maintaining and shaping.

The construction process flow of the spray-mixed vegetation protection slope 2 is as follows in sequence: cleaning side slopes → constructing slope anchor rods → paving galvanized steel wire meshes → spraying bottom planting base materials → spraying planting base materials containing grass seeds and shrub seeds → covering harmless geotextile → maintaining and forming.

The grass seeds and shrub seeds sprayed on the slope surface should be selected from the varieties suitable for local climate, especially strong cold resistance, mixed grass seeds should be adopted, and the intercropped shrubs should be selected from the low shrubs with developed root systems, flourishing branches and leaves and rapid growth. And (4) carrying out acceptance according to the acceptance standard of the construction quality of the railway roadbed engineering after maintenance and forming.

Step four S4, the foreign matter invasion preventing protective net 6 is arranged.

Existing work point place section is slope cutting, for preventing small-size rockfall and foreign matter invasion high speed railway clearance, guarantees railway operation safety, sets up one row or multirow protection network that prevents the foreign matter invasion at cutting barricade wall top, cutting side slope platform or cutting top etc. and protection network protection energy level is not less than 50 KJ.

The construction process flow sequentially comprises the following steps: construction of a cut retaining wall or a steel column foundation → positioning of the steel column and installation of the steel column → interception of a steel wire rope, installation and debugging of an end lock → paving and hanging of a steel wire net → installation of an interval pressing plate of the interception of the steel wire rope.

When the steel column bases are paid off, the positions of the steel column bases are arranged on the same contour line as much as possible, the foundation is constructed in a manual vertical cutting mode, and construction in dry seasons and sunny days is required.

When the foreign matter invasion protection net is arranged on the side slope platform, the stand column foundation is constructed in advance before the side slope platform foot protector, the band, the catch basin and the platform are closed.

When the width of the protective net arranged on the top of the cutting wall is more than 0.7m, the retaining wall can be used as a foundation, and foundation anchor rods or preformed holes are pre-buried during construction; when the protection network sets up at the wall tops such as the soil nailing wall between the stake, can suitably adjust the stand interval to 5 ~ 7m to make stand basis position and pile position coincide, the base stock should reserve or reserve the hole when the construction anchor stake.

When the mountain is a hard rock layer, the anchor rod can be fixed by direct punching and grouting.

When the protective net is arranged outside the cutting top or the slope toe, the plane position can be adjusted according to the natural terrain. When the natural hillside terrain has large fluctuation, a continuous strip foundation can be arranged if necessary to ensure that the lower part of the protective net is not suspended.

The steel column reinforcing member adopts direct current carbon dioxide gas shielded welding deep-melting welding, and the welding seam is regular and has no splash. The steel strand is prestressed by 5KN according to the requirement, so that the steel strand is tensed and straight.

And step five S5, reinforcing the karst foundation (namely the karst foundation reinforced area 8).

The karst improvement section is generally an easily-collapsed area and an easily-collapsed area, and the karst weak development area is subjected to targeted improvement treatment. Generally, the method adopts the measures of backfill, sealing, crossing of pile plate structures, drilling and grouting and the like, and simultaneously strengthens and perfects the earth surface drainage facility. When drilling and grouting are adopted, the principle of 'probing and grouting combination and dynamic design' is implemented. When the thickness of the covering layer of the karst area of the erosion plain is more than 30m and the thickness of the covering layer of the karst area of the karst slope is more than 20m, the treatment is not generally carried out. The renovation width is that when 5m outside the slope toe of the newly-built railway embankment, the cutting side ditch platform and the slope toe (cut top) have obvious karst to endanger the stability of the slope, the renovation range is properly enlarged.

(1) For the covering type karst, when the thickness of the covering layer of the karst area of the erosion plain is less than 30m and the thickness of the covering layer of the karst area of the karst slope is less than 20m (the thickness of the covering layer does not contain filling soil), the reinforcing treatment is generally required. The treatment measures mainly comprise drilling and grouting, and meanwhile, the surface drainage is enhanced and perfected, and the surface water infiltration condition is reduced. The renovation width is that when 5m outside the slope toe of the newly-built railway embankment, the cutting side ditch platform and the slope toe (cut top) have obvious karst to endanger the stability of the slope, the renovation range is properly enlarged.

(2) For exposed karst or karst cutting, the treatment measures should be determined according to the karst form. When the bottom cave is not provided with enough safe thickness of the top plate, measures such as uncovering and backfilling, pile plate spanning or drilling and grouting filling can be adopted for treatment.

(3) For shallow covering karst with covering soil thickness less than 3m, foundation treatment can be combined, and the covering soil is removed and then the shallow covering karst is treated according to the exposed karst.

(4) A layer of high-strength reinforced composite geotextile is laid on the ballastless track karst cutting base.

And step six S6, constructing the ballastless track structure on the karst foundation after the karst foundation reinforcement detection is qualified.

Specifically, after the karst improvement project construction is completed, the improvement effect is detected according to the requirements of relevant technical specifications such as 'railway roadbed project construction quality acceptance standard' and 'railway project foundation treatment technical specification', and the foundation bed and the ballastless track structure can be constructed on the karst improvement project after the karst improvement project construction is qualified. Before the ballastless track is paved, settlement evaluation analysis must be carried out according to settlement observation results, and the ballastless track can be paved only when the ballastless track paving conditions are met.

The invention has the beneficial effects that: the invention relates to a construction method of a high-speed railway excavation roadbed in a karst area, which mainly solves a series of technical problems of determining the development degree of the karst roadbed, clearing the surface of the roadbed base, excavating and blasting earthwork, cleaning and protecting a side slope, setting a foreign matter invasion preventing protective net, treating the karst foundation and the like when the excavation roadbed is constructed in the karst area by a high-speed railway. The construction method can be used for construction of the karst subgrade excavation square section of the expressway and the ordinary-speed railway with higher requirements on post-construction settlement. The construction method of the excavation subgrade in the karst area of the high-speed railway can ensure the construction quality of the excavation subgrade in the karst area of the high-speed railway, ensure the stability and the attractiveness of the excavation side slope of the subgrade, ensure the qualification of subgrade settlement after construction and the risk of foreign matter invasion in the operation process, and ensure that the subgrade does not generate the defects of karst collapse and the like.

The construction method of the excavation roadbed of the high-speed railway in the karst area can ensure the construction quality of the excavation roadbed of the high-speed railway in the karst area, ensure the construction and operation reliability of the excavation side slope of the roadbed, ensure the stability of the roadbed and the qualification of the settlement of the roadbed after construction, and ensure that the roadbed does not generate collapse, rockfall and other diseases.

The present invention has been further described with reference to specific embodiments, but it should be understood that the detailed description should not be construed as limiting the spirit and scope of the present invention, and various modifications made to the above-described embodiments by those of ordinary skill in the art after reading this specification are within the scope of the present invention.

Claims (6)

1. A construction method of a high-speed railway excavation roadbed in a karst area is characterized by comprising the following steps:

determining the development degree of a karst through physical exploration and drilling;

step two, surface cleaning of the original ground, excavation of earth and stone and blasting;

step three, slope cleaning and protection;

step four, arranging a foreign matter invasion preventing protective net;

fifthly, reinforcing the karst foundation;

and sixthly, constructing a ballastless track structure on the karst foundation after the karst foundation reinforcement detection is qualified.

2. The construction method according to claim 1, wherein in the step one, the process flow for determining the development degree of the karst is as follows in sequence: engineering geological mapping, physical exploration, drilling, sampling, indoor test and hydrogeological test, and determining the development degree of karst.

3. The construction method according to claim 1, wherein in step three, grass irrigation slope protection is adopted for the soil cutting slope, and the process flow sequentially comprises: cleaning the side slope, spraying grass seeds from top to bottom, covering non-woven fabrics, maintaining, planting shrubs, supplementing the grass seeds, maintaining and forming.

4. The construction method according to claim 1, wherein in step three, the rocky cut slope is protected by spraying and planting or bagging foreign soil, and the process flow sequentially comprises: cleaning a side slope, constructing a slope anchor rod, laying a galvanized steel wire mesh, spraying a bottom planting substrate, spraying a planting substrate containing grass seeds and shrub seeds, covering harmless geotextile, and maintaining and forming.

5. The construction method according to claim 1, wherein in the fourth step, the process flow for arranging the foreign matter intrusion prevention protective net sequentially comprises: the method comprises the following steps of constructing a cutting retaining wall or a steel column foundation, positioning the steel column, installing and debugging an intercepting steel wire rope and an end lock, paving and hanging a steel wire net, and installing the intercepting steel wire rope at intervals by using a pressing plate.

6. The construction method according to claim 1, wherein in step five:

for the covering type karst, when the thickness of the covering layer of the karst area of the erosion plain is less than 30m and the thickness of the covering layer of the karst area of the karst slope is less than 20m, reinforcement treatment is carried out: drilling and grouting, and reinforcing and improving surface drainage;

determining treatment measures for the exposed karst or the karst cutting according to the karst form; when the bottom karst cave is under and the safe thickness of the top plate is insufficient, uncovering and backfilling, pile plate crossing or drilling and grouting filling are adopted for processing;

for shallow covering karst with the covering soil thickness less than 3m, combining foundation treatment, and treating according to exposed karst after removing the covering soil;

a layer of high-strength reinforced composite geotextile is laid on the ballastless track karst cutting base.

Images