Construction method for high embankment

Abstract

A construction method for a high embankment, which relates to the technical field of foundation construction. The method comprises non-self-weight collapsible silt base treatment, earthwork embankment filling, slope punching and grouting, etc. According to the construction method of the present invention, foundation excavation and foundation construction process parameters and embankment laying process parameters are designed, and steel-plastic geogrids, prefabricated cement panels, and concrete pouring hole structures are used in a coordinated manner, so that the bearing capacity of earthwork high embankments can be greatly increased, the service life can be prolonged, and settlement, deformation, collapse, and landslides can be prevented even after long-term use. By increasing the filling gradient and occupying a small area, construction of high-quality high embankments can be achieved by using earthwork filling, wherein the total height of embankment filling is 30 m or more, the gradient of an embankment slope is 70° to 80°, and the bearing capacity is greater than or equal to 220 kPa.

Description

A construction method for high embankment Technical Field

[0001] The invention belongs to the technical field of foundation construction, and in particular relates to a construction method of a high embankment. Background Art

[0002] A high embankment is an embankment with a roadbed fill slope height of more than 20m. Due to the large height difference between the high embankment and the ground, the large amount of fill, and the large area occupied, in order to ensure the stability of the roadbed and the economical and reasonable cross-section, the embankment and slope need special design treatment, especially for areas with poor soil quality, which require stability reinforcement treatment to ensure long-term load without deformation, settlement, cracking, collapse, or landslide, thereby ensuring the safety of road use.

[0003] Conventional technology for embankment filling uses a fill material with a stiffness comparable to that of the bedrock, typically graded crushed stone and cement. High embankment slopes are constructed in a zigzag or stepped pattern, with a steep top and a gentle bottom. A slope guard is installed in the middle of the slope, and appropriate slope protection and reinforcement measures, such as turf laying and stone masonry, are implemented to prevent water erosion and scouring.

[0004] However, for relatively high embankments, it is inevitable that they will pass through some areas with complex terrain and encounter relatively cracked geological conditions such as collapsible silt, highly saline soil, and collapsible loess. The use of graded crushed stone and cement filling treatment is not enough to achieve the service quality of high embankments, and deformation, settlement, cracking, and collapse still exist. Therefore, achieving the construction of high embankments with high heights and poor terrain and geology to ensure safety, stability, and long service life remains a problem that needs to be solved. In addition, due to the high height of high embankments, a large amount of fill area is required, that is, a relatively gentle slope requires a large area of ​​land. If the slope is steep, the risk of collapse and landslide is very high, making it difficult to ensure the service quality.

[0005] Summary of the Invention

[0006] The existing high embankment construction technology is difficult to meet the safety and stability requirements of high embankments with high heights and poor terrain and geology, and high embankments usually occupy a large area. The present invention provides a high embankment construction method, which is aimed at the earth filling embankment on the non-self-weight collapsible silt base, the foundation excavation and foundation construction process parameters, as well as the embankment paving process parameters. The use of steel-plastic geogrids, cement board prefabricated parts and concrete pouring hole structures can greatly improve the bearing capacity of the earth high embankment, increase the service life, and prevent settlement, deformation, collapse and landslides in long-term use; increase the filling slope, reduce the occupied area, and use earth filling to achieve high-quality high embankment construction. The specific technical solution is as follows:

[0007] A method for constructing a high embankment, the method comprising the following steps:

[0008] S1, non-self-weight collapsible silt base treatment:

[0009] Excavate the collapsible silt within a depth of 1.4m to 1.6m from the surface, then use hydraulic compaction or impact rolling to impact compact the base to eliminate the collapsibility within 1.5m below the base, or make the collapsibility coefficient within 1.5m below the base less than 0.01; then fill a 0.5m to 0.6m lime soil cushion layer or cement soil cushion layer, and after compaction, fill gravel soil to a position 0.8m to 1m below the ground surface, and lay composite geotextile.

[0010] Lime soil is: slaked lime: collapsible silt = (8-10): (90-92); collapsible silt is collapsible silt dug from the ground or silt with a plasticity index greater than 4, with a sieved particle size no larger than 15mm; slaked lime is standard third-grade quicklime that has been slaked for 3-4 days and sieved, with a sieved particle size no larger than 5mm. Cement soil is: 32.5 grade Portland cement: collapsible silt = (4-6): (94-96); collapsible silt is collapsible silt dug from the ground or silt with a plasticity index greater than 4, with a sieved particle size no larger than 15mm. The compaction coefficient of a lime soil or cement soil cushion layer should be no less than 0.97, and the compaction coefficient of gravel soil should be no less than 0.95. The compaction coefficient is the ratio of the actual dry density achieved during rolling of the cushion layer to the maximum dry density obtained through indoor compaction testing.

[0011] S2, earthwork embankment filling:

[0012] Continue to use gravel soil for filling, filling in layers, with each layer compacted no more than 30cm thick and a compaction degree of ≥95%, until the filling is flush with the ground surface. After compaction, continue to fill in layers above the ground surface with each layer compacted no more than 30cm thick and a compaction degree of ≥95% to form an embankment. Slopes are formed on both sides of the embankment; from the ground surface upwards, each 6m to 8m is a level of slope, and 1.5m to 2m wide stepped platforms are set at adjacent level slopes to form stepped slopes;

[0013] Fill the ground in layers above the surface, control the moisture content of the gravel soil within the range of ±2%, and use impact rolling or hydraulic compaction machine to enhance the pressure every 2m to 3m; after pressure replenishment, lay the steel-plastic geogrid and cement board prefabricated parts, and mark the laying position of the cement board prefabricated parts on the slope surface.

[0014] The prefabricated cement board is a prefabricated comb-shaped cement board. The thickness of the comb back of the prefabricated cement board is 6cm to 8cm, and the longitudinal steel bars of the board are embedded in the comb back. The comb teeth of the prefabricated cement board are 8cm to 12cm in length, the comb tooth spacing is 1m to 1.2m, and the comb teeth are inverted trapezoidal. The width of the prefabricated cement board is 0.5m to 0.8m, and the length of the prefabricated cement board is 0.4m to 0.6m from both sides of the embankment slope of the paving surface. The prefabricated cement board is laid horizontally every 2m to 3m along the route.

[0015] Before laying the precast cement slabs, lay and compact a layer of gravel soil on the steel-plastic geogrid. The compacted thickness of the gravel soil should be within 5 cm of the comb tooth length or higher. Then insert and press the precast cement slabs into the gravel soil to lay the precast cement slabs. The two ends of the precast cement slabs should be 0.4m to 0.6m away from both sides of the embankment slope of the paving surface. Mark the laying position of the precast cement slabs on the slope surface.

[0016] Each layer of gravel soil is filled with a vibratory roller of no less than 22t, which is rolled back and forth for 2 to 6 times. The rolling order is from both sides to the middle of the straight section and from the inside to the outside of the curve in the curved section. The rolling is carried out in rows longitudinally with a longitudinal overlap of 1 / 3 of the wheel width. The rolling speed is slow at first and then fast, with a maximum speed of <4km / h. The vibration frequency and amplitude are from weak to strong.

[0017] During the embankment filling process, each stepped slope is trimmed.

[0018] The surface fill width of the embankment is at least 2m smaller than the underground fill width.

[0019] S3, Slope drilling and grouting:

[0020] After the embankment is completely filled, according to the laying position of the cement slab prefabricated parts marked on the slope surface, an inclined hole is drilled from the slope to the end of the cement slab prefabricated parts above the mark, and then the bottom of the hole is manually excavated and trimmed until the end of the cement slab prefabricated parts is exposed, and then concrete is injected into the inclined hole to seal it.

[0021] S4, Slope protection and vegetation:

[0022] According to the conventional slope protection and vegetation methods, slope protection and vegetation are carried out to complete the embankment construction.

[0023] The total height of the embankment is more than 30m, the slope of the embankment is 70°~80°, and the bearing capacity is ≥220kPa.

[0024] Compared with the prior art, the construction method of a high embankment of the present invention has the following beneficial effects:

[0025] 1. The present invention designs a high-bearing-capacity high embankment construction method for non-self-weight collapsible silt base, which can achieve high-quality embankment construction while saving floor space, solves the problem of easy settlement, deformation and collapse of high embankments constructed on non-self-weight collapsible silt base, and can greatly improve the load-bearing capacity of earth filling, ensuring the safety and stability of embankment construction.

[0026] 2. The construction method of the present invention is designed to excavate the collapsible silt within the depth range of 1.4m to 1.6m on the surface, and then use hydraulic compaction or impact rolling to impact compact the base, which can reduce or eliminate the collapsible nature of the base. During subsequent construction and use, the base will not settle significantly, ensuring the stability of the roadbed pad.

[0027] 3. The construction method of the present invention is designed to fill the compacted base with a 0.5m to 0.6m lime soil cushion layer or cement soil cushion layer, and then fill gravel soil to a position 0.8m to 1m below the ground surface after compaction, and lay a composite geotextile. Among them, laying a lime soil cushion layer or a cement soil cushion layer can further consolidate the foundation and ensure the stability of the embankment construction; and can withstand the pressure generated in the subsequent earth filling and compaction without sinking. In addition, it can better block groundwater and prevent water seepage, freezing, landslides or bulging. Among them, laying a composite geotextile is also to prevent water seepage and further ensure that the foundation is not water seepage or freezing deformation.

[0028] Fourth, the construction method of the present invention is designed based on the bearing capacity and self-load of the high embankment. The lime soil is designed as follows: slaked lime: collapsible silt = (8-10): (90-92); slaked lime is standard third-grade quicklime that has been slaked for 3-4 days and sieved, with a sieved particle size of no more than 5mm. The cement soil is designed as follows: 32.5 grade Portland cement: collapsible silt = (4-6): (94-96); collapsible silt is collapsible silt excavated from the ground or silt with a plasticity index greater than 4, with a sieved particle size of no more than 15mm. The compaction coefficient of the lime soil cushion layer or cement soil cushion layer is no less than 0.97, and the compaction coefficient of gravel soil is no less than 0.95. This ensures that the lime soil cushion layer or cement soil cushion layer is suitable for the construction of embankments with high bearing capacities exceeding 30m, and that the foundation will not collapse or deform over long-term use.

[0029] 5. The surface filling width of the embankment designed by the construction method of the present invention is more than 2m smaller than the underground filling width, which can well protect the surface boundary of the embankment, isolate the surrounding original soil, and prevent collapse, water seepage, and deformation.

[0030] 6. The construction method of the present invention is designed to fill in layers, with the compacted thickness of each layer not exceeding 30 cm, and the moisture content of the gravel soil controlled within the range of ±2%. The compaction degree of each layer is ≥95%. Impact rolling or hydraulic rammer is used for enhanced pressure every 2m to 3m, which can ensure the compaction density of each layer of gravel soil, improve bearing capacity and reduce deformation.

[0031] 7. The construction method of the present invention is designed to lay the steel-plastic geogrid and then lay the cement board prefabricated parts. The cement board prefabricated parts are laid horizontally every 2m to 3m along the route. The cement board prefabricated parts are designed to be prefabricated comb-shaped cement boards, and the size parameters and laying distances are designed. The comb-shaped cement boards can greatly improve the bearing capacity of the high earth embankment and increase the shear strength of the soil. The restraining force of the comb teeth part can also prevent the embankment from deformation and landslide; the cement board prefabricated parts are laid on the steel-plastic geogrid. The steel-plastic geogrid can well restrain the cement board prefabricated parts and prevent them from sinking, ensuring that the cement board prefabricated parts maintain good stability during long-term use. Therefore, the construction of high embankments on steep slopes can be realized, with a small footprint and a long service life, and is not prone to deformation, settlement, collapse and landslide.

[0032] 8. The construction method of the present invention is designed so that the two ends of the cement slab precast parts are 0.4m to 0.6m away from both sides of the embankment slope of the paving surface; the laying position of the cement slab precast parts is marked on the slope surface, and an oblique hole is drilled from the slope to the end of the cement slab precast part above the mark, and then the bottom of the hole is manually excavated and trimmed until the end of the cement slab precast part is exposed, and then concrete is injected into the oblique hole to seal it. On the one hand, the concrete pouring hole can permanently mark the laying position of the cement slab precast part; on the other hand, the concrete pouring and sealing of both ends of the cement slab precast part can ensure that the cement slab precast part does not tamper with or deform during long-term use. When the cement slab precast part is subjected to pressure load, the concrete pouring and sealing structure can play a partial restraining role, restraining the middle part of the cement slab precast part from bending downward and deforming; on the other hand, the concrete pouring and sealing structure can show the degree of soil erosion on the slope, which can be used as a reference for measurement and maintenance; in addition, the concrete pouring and sealing structure can also play an auxiliary role in slope protection.

[0033] In summary, the construction method of the present invention designs the foundation excavation and foundation construction process parameters, as well as the embankment paving process parameters. The use of steel-plastic geogrids, cement board prefabricated parts and concrete pouring hole structures can greatly improve the bearing capacity of the earth high embankment and increase its service life. Long-term use can also prevent settlement, deformation, collapse and landslides; the filling slope is increased, less floor space is occupied, and the use of earth filling can also achieve the construction of high-quality high embankments. The total height of the embankment filling is more than 30m, the slope of the embankment side slope is 70°~80°, and the bearing capacity is ≥220kPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a cross-sectional view of a high embankment constructed by a construction method of a high embankment according to an embodiment of the present invention;

[0035] Figure 2 is an enlarged view of point A in Figure 1;

[0036] Figure 3 is an enlarged view of point B in Figure 1;

[0037] Figure 4 is an enlarged view of point C in Figure 1;

[0038] FIG5 is a partial top view of a half-section of a cement board prefabricated member used in a method for constructing a high embankment according to an embodiment of the present invention;

[0039] FIG6 is a bottom view of a portion of a cement board prefabricated member used in a method for constructing a high embankment according to an embodiment of the present invention;

[0040] FIG7 is a top view of a settlement plate used in a construction method for a high embankment according to an embodiment of the present invention;

[0041] FIG8 is a front view of a settlement plate used in a construction method for a high embankment according to an embodiment of the present invention;

[0042] In the figure, 1-composite geotextile, 2-steel-plastic geogrid, 3-comb back, 3.1-rebar, 4-comb teeth, 5-inclined hole; 6.1-steel pipe, 6.2-casing, 6.3-base, 6.4-reinforcement steel plate. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to specific implementation cases, but the present invention is not limited to these embodiments.

[0044] Example

[0045] There are 5 high fill roadbed sections with fill heights ranging from 30.5m to 38.6m. The specific parameters are shown in Table 1 below.

[0046] Table 1 List of high embankments

[0047] The materials for high embankments come from four sources: nearby excavated materials used as fillers, borrow yard materials, purchased materials, or tunnel slag.

[0048] Topography: The region's topography and landforms are complex, with well-developed river valleys, crisscrossing gullies, and sharply dissected terrain. The route corridor crosses many geomorphic units. From north to south, the route area's major geomorphic units are divided into piedmont rush, alluvial plains, intermontane fault basins, erosional high mountain areas, and erosional mid-mountain areas. The terrain is generally high in the middle and low in the north and south.

[0049] Geological conditions: The main strata include Quaternary Holocene alluvial pebbles and boulders (Q4al+pl); Quaternary Upper Pleistocene alluvial-diluvial layers (Q3al+pl); Lower Jurassic Badaowan Formation (J1b) sandstone; Lower Carboniferous Qiergusitao Group (C1qr) tuff, tuffaceous siltstone, and Yamansu Formation (C1y) conglomerate; Upper Devonian Tianger Formation second subgroup (D3tb) limestone, etc.; the surface is mostly non-self-weight collapsible silt.

[0050] Climate: The region along the route features a typical mid-temperate continental climate. Mountain climates exhibit a vertical distribution, with alpine cold zones and year-round snow. The mid-mountain temperate zone offers mild temperatures, abundant sunlight, and significant diurnal temperature differences. See Table 2 for regional meteorological factors.

[0051] Table 2 List of main meteorological elements in the project area

[0052] Hydrological conditions: Surface water: Snow begins to melt in April and May each year. From June to August, rising temperatures cause significant melting of mountain snow and ice, leading to heavier rainfall and increased surface water volumes. Groundwater, primarily composed of bedrock fissure water and tectonic groundwater, has relatively good water-rich conditions, but the degree of enrichment is relatively weak. Recharge is primarily through atmospheric precipitation and melting mountain snow and ice.

[0053] The geology is poor, with collapsible silt sections. There are five high embankment construction sections. The geological conditions are described as follows:

[0054] At the first location, the ground surface is covered with a silt layer with an average thickness of 4.2 meters, a collapsible coefficient of 0.017-0.079, moderate collapsibility, and a collapsible grade of 1.

[0055] At the second location, the ground surface is covered with a silt layer with an average thickness of 4.5 meters, a collapsible coefficient of 0.021-0.079, moderate collapsibility, and a collapsible grade of 1.

[0056] At the third location, the ground surface is covered with a silt layer with an average thickness of 4 meters, a collapsible coefficient of 0.023-0.079, moderate collapsibility, and a collapsible grade of 1.

[0057] Fourthly, the ground surface has an average thickness of 4.3 meters with a silt layer, a collapsible coefficient of 0.018-0.079, and is of medium collapsible nature, with a collapsible grade of 1.

[0058] At the fifth location, the surface average thickness is 3.9 mm, which is a silt layer with a collapsible coefficient of 0.025-0.079, showing moderate collapsibility and a collapsible grade of 1.

[0059] Pre-construction measurement, preparation, and precautions: Re-survey of traverses and leveling points, and supplementary cross-section inspections. To facilitate construction, the section uses total stations and GPS to encrypt traverse points, ensuring line of sight between adjacent traverse points during road construction and high accuracy. Before construction begins on the roadbed test section, re-survey the original ground. Based on the results of the original ground re-survey, the roadbed slope opening line, slope foot line, drainage ditches, intercepting ditches, and land acquisition red lines are verified. The roadbed centerline and side lines are then staked out, and control stakes are set for construction guidance. The main control stakes along the route are fixed, and when the centerline is restored, the centerline of the construction section adjacent to the structure center is closed. During construction, all useful landmarks, especially the original control points, are protected. Regular re-survey of traverse points and leveling points is conducted. There are two borrowing sites along the section, one of which is a local borrowing site and the other is a purchased commodity borrowing site. During the construction and material taking process, the soluble salt test monitoring is strengthened. It is strictly prohibited to use medium and strong saline soil to fill the roadbed. Weak salt is used to fill the part of the roadbed below the roadbed. Salt-containing materials are not allowed to be used for filling within the roadbed.

[0060] Before construction begins, a test section must be constructed to clarify construction parameters such as loose-lay thickness, number of compaction passes, ash dosage, optimal moisture content, maximum dry density, and the optimal mechanical equipment combination. The number of compaction passes for collapsible silt subgrade treatment will be determined by the test section, and site drainage measures must be in place before construction begins.

[0061] (1) The lime soil is sampled layer by layer with a ring knife to determine the dry density of the lime soil. The number of inspection points is: for foundation pits, every 50 to 100 m 2 Randomly inspect one spot, but not less than one. The vertical sampling point should be 2 / 3 of the thickness below the surface of each layer. Random inspections should also be conducted based on the reliability of compaction. For collapsible silt, three points should be selected for every 100 square meters.

[0062] (2) After the ash soil is compacted, the quality standard is identified according to the compaction coefficient, which is the ratio of the dry density actually achieved by the soil during construction to the maximum dry density obtained by the compaction test indoors.

[0063] (3) Inspection of lime soil foundation quality, as shown in Table 3 below:

[0064] Table 3 Lime-soil foundation quality inspection standards

[0065] A method for constructing a high embankment, the method comprising the following steps:

[0066] S1, non-self-weight collapsible silt base treatment:

[0067] Excavate the collapsible silt within the depth of 1.4m to 1.6m from the surface, and then use hydraulic compaction or impact rolling to impact compact the base to eliminate the collapsibility within the range of 1.5m below the base, or make the collapsibility coefficient within the range of 1.5m below the base less than 0.01; then fill a 0.5m to 0.6m lime soil cushion layer or cement soil cushion layer, and after compaction, fill gravel soil to a position 0.8m to 1m below the ground surface, and lay composite geotextile 1, as shown in Figures 1 and 2.

[0068] Lime soil is: slaked lime: collapsible silt = (8-10): (90-92); collapsible silt is collapsible silt dug from the ground or silt with a plasticity index greater than 4, with a sieved particle size no larger than 15mm; slaked lime is standard third-grade quicklime that has been slaked for 3-4 days and sieved, with a sieved particle size no larger than 5mm. Cement soil is: 32.5 grade Portland cement: collapsible silt = (4-6): (94-96); collapsible silt is collapsible silt dug from the ground or silt with a plasticity index greater than 4, with a sieved particle size no larger than 15mm. The compaction coefficient of a lime soil or cement soil cushion layer should be no less than 0.97, and the compaction coefficient of gravel soil should be no less than 0.95. The compaction coefficient is the ratio of the actual dry density achieved during rolling of the cushion layer to the maximum dry density obtained through indoor compaction testing.

[0069] S2, earthwork embankment filling:

[0070] Continue to use gravel soil for filling, filling in layers, with each layer compacted no more than 30cm thick and a compaction degree of ≥95%, until the filling is flush with the ground surface. After compaction, continue to fill above the ground surface in layers with a compaction thickness of no more than 30cm per layer, with a compaction degree of ≥95% per layer, to form an embankment. Slopes will form on both sides of the embankment, and the surface fill width of the embankment will be at least 2m less than the underground fill width. From the ground surface upward, each 6m to 8m is a level of slope, and 1.5m to 2m wide terraces will be set at adjacent slope levels to form a stepped slope.

[0071] Fill the ground in layers above the surface, control the moisture content of the gravel soil within the range of ±2%, and use impact rolling or hydraulic compaction machine to enhance the pressure every 2m to 3m. After the pressure is increased, lay the steel-plastic geogrid 2 and cement board prefabricated parts, as shown in Figures 1 and 3, and mark the laying position of the cement board prefabricated parts on the slope surface.

[0072] The cement board prefabricated part is a prefabricated comb-shaped cement board, as shown in Figures 1, 3, 5 and 6. The thickness of the comb back 3 of the cement board prefabricated part is 6cm to 8cm, and the comb back 3 is pre-embedded with the plate longitudinal steel bars 3.1. The comb teeth 4 of the cement board prefabricated part are 8cm to 12cm in length, the comb teeth 4 are spaced 1m to 1.2m apart, and the comb teeth 4 are in an inverted trapezoidal shape; the width of the cement board prefabricated part is 0.5m to 0.8m, and the length of the cement board prefabricated part is 0.4m to 0.6m from both sides of the embankment slope of the paving surface; the cement board prefabricated part is laid horizontally every 2m to 3m along the route.

[0073] Before laying the cement board prefabricated parts, lay and compact a layer of gravel soil on the steel-plastic geogrid 2. The compacted thickness of the gravel soil should be the length of the comb teeth 4 or within 5 cm of the length of the comb teeth 4. Then insert and press the cement board prefabricated parts into the gravel soil to achieve laying of the cement board prefabricated parts. The two ends of the cement board prefabricated parts should be 0.4m to 0.6m away from both sides of the embankment slope of the paving surface. Mark the laying position of the cement board prefabricated parts on the slope surface.

[0074] Each layer of gravel soil is filled with a vibratory roller of no less than 22t, which is rolled back and forth for 2 to 6 times. The rolling order is from both sides to the middle of the straight section and from the inside to the outside of the curve in the curved section. The rolling is carried out in rows longitudinally with a longitudinal overlap of 1 / 3 of the wheel width. The rolling speed is slow at first and then fast, with a maximum speed of <4km / h. The vibration frequency and amplitude are from weak to strong.

[0075] During the embankment filling process, each stepped slope is trimmed.

[0076] In this example, the five construction sections utilize TGDG90HDPE, TGDG130HDPE, and TGDG200HDPE unidirectional geogrids, which exhibit corrosion resistance, acid and alkali resistance, fatigue resistance, and aging resistance. To enhance the stability of steep embankments (preventing collapse and landslides and improving bearing capacity), mitigate differential deformation between excavation and fill, and prevent differential deformation during staged filling, precast cement slabs are placed above the geogrids.

[0077] The steel-plastic geogrid 2 is fully paved. When laying, the direction with high main strength of the reinforcement is perpendicular to the axis of the embankment. The overlapping length (longitudinal) of each piece is not less than 20cm and is fixed with U-shaped nails or connectors. The spacing is 1.0m, the horizontal overlap length is 30-90cm, and the overlap position is fixed with U-shaped nails. After the steel-plastic geogrid 2 is laid, the next step of filling construction should be carried out in time to avoid the steel-plastic geogrid 2 being directly exposed to sunlight for a long time. The time of direct exposure to sunlight cannot exceed 24 hours, otherwise the laid geogrid should be removed and a new geogrid should be laid. During the construction process, the geogrid cannot be damaged, otherwise it should be laid again.

[0078] S3, Slope drilling and grouting:

[0079] After the embankment is completely filled, according to the laying position of the cement slab prefabricated parts marked on the slope surface, an inclined hole 5 is drilled from the slope to the end of the cement slab prefabricated part above the mark, and then the bottom of the hole is manually excavated and trimmed until the end of the cement slab prefabricated part is exposed, and then concrete is injected into the inclined hole 5 to seal it, as shown in Figures 1 and 4.

[0080] S4, Slope protection and vegetation:

[0081] According to conventional slope protection and vegetation methods, slope protection and vegetation are carried out to complete the embankment construction. In the 5 construction sections of the present embodiment, the embankment slope protection construction is carried out. Before the slope is drilled and grouting, the slope is trimmed, mainly by mechanical brushing. When the slope is brushed mechanically, 20 cm is reserved and the slope is brushed manually. After the slope is drilled, grouted and formed, the slope protection construction is carried out, and the grid prefabricated blocks are laid. An expansion joint with a width of 2 cm is set every 10 m along the slope. The joint is filled with asphalt hemp. In order to ensure that the cast-in-place concrete foot guard is vibrated and compacted, the grid slope protection adopts the method of supporting the formwork above the slope foot guard to cast the concrete and inserting the vibrating rod to vibrate and compact it, so as to ensure that the concrete of the foot guard is solid inside and smooth outside. After the grid slope protection is paved and poured, and the skeleton has a certain strength, the skeleton is prepared for soiling and grass planting.

[0082] Embankment settlement and stability monitoring in this embodiment:

[0083] During the construction of high fill embankments, a network of observation points is established to monitor the roadbed loading speed, horizontal displacement, and vertical displacement to ensure roadbed stability.

[0084] 1. Settlement observation

[0085] (1) Settlement observation piles

[0086] High embankment settlement observation piles utilize a casing and steel pipe settlement plate for observation, as shown in Figures 7 and 8. The settlement plate consists of a steel pipe 6.1, casing 6.2, base 6.3, and reinforcing steel plate 6.4. Steel pipe 6.1 is nestled within casing 6.2, with base 6.3 welded to the bottom of casing 6.2. Base 6.3 is reinforced to casing 6.2 via reinforcing steel plate 6.4. The settlement plate is buried at a depth of no less than 2m into stable ground. Casing 6.2 and steel pipe 6.1 are welded together in sections as the fill rises, extending the casing to 150cm above the ground. Steel pipe 6.1 is exposed 50cm above the top surface of casing 6.2. Excavation is used for burial. After burial, the area surrounding the pile is densely backfilled, the upper portion of the pile is painted a conspicuous color, and a small red flag is placed on the top cover to prevent displacement due to collisions.

[0087] (2) The outer diameter of the observation steel pipe 6.1 is 5 cm, and the wall thickness is 4 mm. The outer diameter and thickness of the casing 6.2 are 10.8 cm, and the wall thickness is 4 mm. The steel plate thickness of the base 6.3 and the reinforcement steel plate 6.4 are 3 mm.

[0088] (3) Settlement observation is carried out after each layer is filled. After the embankment is completed and enters the settlement preloading period, observation is carried out every 14 days. If settlement is found, supplementary filling is carried out in time to always maintain the elevation required by the design.

[0089] 2. Stable monitoring

[0090] (1) Observation points are set at the center of the roadbed, the edge of the two-way shoulder, various slope platforms, and the original surface of the same cross section, and are measured using a total station. The settlement observation pile sections are set at intervals of 50m, and the displacement side pile sections are set every 100m.

[0091] (2) The frequency of horizontal displacement observations should be synchronized with the measurement time and settlement monitoring. During the slope construction period, the displacement of fixed piles should be observed every 15 days, once every 7 days during the rainy season, and once a day in case of heavy rainfall and sudden rainstorms. From the completion of slope construction to the opening of the road for one and a half years, the displacement should be observed once a month, and once a day within one week after heavy rain.

[0092] (3) The horizontal displacement is observed using the single triangle forward intersection method.

[0093] The cross-section of the embankment after filling is shown in Figures 1 to 4. After testing, the earth filling height of the five sections is 30.5m to 38.6m, and the slope of the embankment is 70° to 80°. The results of the bearing capacity test are shown in the following table.

Claims

1. A method for constructing a high embankment, characterized in that: The method comprises the following steps: S1, non-self-weight collapsible silt base treatment: Excavate the collapsible silt within the depth of 1.4m to 1.6m on the ground surface, and then use hydraulic tamping or impact rolling to impact roll the base to eliminate the collapsibility within 1.5m below the base, or make the collapsibility coefficient within 1.5m below the base less than 0.01; then fill a 0.5m to 0.6m lime soil cushion layer or cement soil cushion layer, and after compaction, fill gravel soil to 0.8m to 1m below the ground surface, and lay composite geotextile; S2, earthwork embankment filling: Continue to use gravel soil for filling, filling in layers, with each layer compacted no more than 30cm thick, and each layer compaction degree ≥ 95%, until it is filled flush with the ground surface. After compaction, continue to fill in layers above the ground surface with each layer compacted no more than 30cm thick, and each layer compaction degree ≥ 95%, to form an embankment, and slopes are formed on both sides of the embankment; from the ground surface upward, every 6m to 8m is a first-level slope, and 1.5m to 2m wide step platforms are set at adjacent level slopes to form a stepped slope; Fill in layers above the ground surface, control the moisture content of gravel soil within ±2%, and use impact rolling or hydraulic compaction machine to enhance the compaction every 2m to 3m; after compaction, lay steel-plastic geogrid and cement board prefabricated parts, and mark the laying position of cement board prefabricated parts on the slope surface; Before laying the cement board prefabricated parts, lay and compact a layer of gravel soil on the steel-plastic geogrid, and the compacted thickness of the gravel soil should be within 5 cm of the comb tooth length or higher than the comb tooth length; then insert and press the cement board prefabricated parts into the gravel soil to achieve the laying of the cement board prefabricated parts, with the two ends of the cement board prefabricated parts 0.4m to 0.6m away from both sides of the embankment slope of the laying surface; mark the laying position of the cement board prefabricated parts on the slope surface; The cement board prefabricated part is a prefabricated comb-shaped cement board. The thickness of the comb back of the cement board prefabricated part is 6cm to 8cm. The longitudinal steel bars of the board are embedded in the comb back. The comb teeth of the cement board prefabricated part are 8cm to 12cm long, the comb teeth are 1m to 1.2m apart, and the comb teeth are inverted trapezoidal. The width of the cement board prefabricated part is 0.5m to 0.8m, and the length of the cement board prefabricated part is 0.4m to 0.6m from both sides of the embankment slope of the paving surface. The cement board prefabricated part is laid horizontally every 2m to 3m along the route. S3, Slope drilling and grouting: After the embankment is fully filled, according to the laying position of the cement slab prefabricated parts marked on the slope surface, an inclined hole is drilled from the slope to the end of the cement slab prefabricated parts above the mark, and then the bottom of the hole is manually excavated and trimmed until the end of the cement slab prefabricated parts is exposed, and then concrete is injected into the inclined hole to seal it; The total height of the embankment is more than 30m, the slope of the embankment is 70°~80°, and the bearing capacity is ≥220kPa.

2. A method for constructing a high embankment according to claim 1, characterized in that: In S1, lime soil is slaked lime: collapsible silt = (8-10): (90-92); collapsible silt is collapsible silt dug out from the ground or silt with a plasticity index greater than 4, and the sieved particle diameter is not greater than 15 mm; slaked lime is quicklime of third-grade lime standard that is slaked for 3d-4d and sieved, and the sieved particle diameter is not greater than 5 mm.

3. A method for constructing a high embankment according to claim 1, characterized in that: In S1, cement soil is 32.5 grade silicate cement: collapsible silt = (4-6): (94-96); collapsible silt is collapsible silt dug out from the surface or silt with a plasticity index greater than 4, and the diameter of the sieved particles is not greater than 15 mm.

4. A method for constructing a high embankment according to claim 1, characterized in that: In S1, the compaction coefficient of the lime soil cushion layer or cement soil cushion layer shall not be less than 0.97, and the compaction coefficient of the gravel soil shall not be less than 0.

95. The compaction coefficient is the ratio of the actual dry density achieved by the cushion layer during rolling to the maximum dry density obtained by the compaction test indoors.

5. A method for constructing a high embankment according to claim 1, characterized in that: In S2, each layer of gravel soil is compacted back and forth by a vibratory roller of no less than 22t, and the vibration rolling is carried out 2 to 6 times. The rolling order is from both sides to the middle of the straight section, and from the inside to the outside of the curve in the curved section, and it is carried out in rows longitudinally with a longitudinal overlap of 1 / 3 of the wheel width. The rolling speed is slow at first and then fast, with a maximum speed of <4km / h, and the vibration frequency and amplitude are from weak to strong. The surface filling width of the embankment is more than 2m less than the underground filling width.

6. A method for constructing a high embankment according to claim 1, characterized in that: In S2, during the embankment filling process, each stepped slope is trimmed.

7. A method for constructing a high embankment according to claim 1, characterized in that: The method also includes, S4, Slope protection, vegetation: According to the conventional slope protection and vegetation methods, slope protection and vegetation are carried out to complete the embankment construction.

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