Brother: I will give you a complete set of railway equipment, including roadbed, bridges and tunnels. I hope it can be helpful to you. 3.1.4.2 Subgrade filling construction technology and methods Subgrade filling refers to the filling of the embankment body, which is the part from the bottom of the embankment bed to above the ground. For this part of the embankment, Group A and B fill or improved soil shall be selected in accordance with the provisions of the "Road Regulations", and the compaction standards shall be implemented to meet the design standards. Before roadbed filling construction, surface treatment and foundation reinforcement must be carried out. In the soil base section, foundation stress condition analysis is carried out before filling the roadbed. The roadbed will be filled and constructed according to the "three-stage, four-section, eight-process" method. Before filling, conduct a filling and compaction test to determine the various process parameters that meet the compaction requirements, and then promote it to large-area construction. 3.1.4.2.1 Subgrade filling construction process The detailed roadbed filling construction process flow is shown in Figure 3.1.4-6. Unqualified, qualified, filling the next layer Preparation stage Construction stage Renovation and acceptance stage
Figure 3.1.4-6 Subgrade filling construction process flow chart 3.1.4.2.2 Filling subgrade construction method ⑴ Construction preparation ① Measure and set out, restore the center line and release the side lines; carry out geological surveys and soil quality tests; carry out roadbed waterproofing and drainage measures; organize personnel and machinery to come on site; determine the construction sequence and earthwork allocation plan. ② Before starting construction, on-site verification and supplementary investigation must be conducted on the location of various existing obstacles and facilities within the subgrade range as shown in the drawings or provided by the supervision engineer, and the site clearance status, and the results must be notified to the supervision engineer for verification. After reviewing the design and laying out the roadbed, the site will be cleaned according to the actual ground conditions and soil conditions on site and in accordance with the construction specifications and design requirements. Site cleanup will be carried out in phases and batches according to the needs of the filling construction. In principle, the site will be cleared comprehensively and abandoned in sections. Site cleaning includes removing tree roots, turf and other plant roots within the subgrade range, and clearing and digging out 30cm thick planting soil and non-suitable soil within the subgrade filling base until the foundation soil meets the requirements. Soil that does not meet the requirements for roadbed fill shall be excavated and transported to a designated spoil site. ③Construction of the test section Before the embankment filling construction, select a section (length not less than 200m) with representative geological conditions and cross-sectional form as the test section. According to the actual situation of this contract section, the filling test construction will be carried out for the filling. The on-site compaction test is carried out until the filler can be effectively used to achieve the specified compaction degree. Records should be kept during the test to record the type of compaction equipment, combination method, number of rolling passes and rolling speed, process, and materials of each layer. The thickness of the loose paving, the moisture content of the material, etc., find out the regular curves between the machine model, layer thickness, number of compaction passes and the design specified indicators, and find out the relationship between the K30 value and the compaction coefficient Kh, porosity n, EvⅡ relation. Through the construction of the test section, reasonable compaction process parameters and process flow were determined. After the test results are approved by the supervision engineer, they will be used as the basis for the use of this type of filler during construction. During construction, the thickness of loose filling shall not exceed 90% of the value determined by testing. ⑵ Construction method ① Embankment filling shall be carried out in layers across the full width of the cross section and in longitudinal segments. In order to ensure the compaction of the roadbed, the loose paving thickness must be controlled to 90% of the filling thickness of the subgrade in the test section, and the thickness of each loose paving layer should not be greater than 30cm, and the thickness of each layer after compaction should be approximately 25cm. During construction, a ruler pole is erected at the shoulder to control the paving thickness. Each layer of filling is placed in place at one time according to the thickness of the loose paving. The unloading spacing is calculated based on the volume of the carriage and the thickness of the loose paving. A dedicated person will direct the unloading. If the ground has a slope, fill in layers starting from the lower part. High-fill embankments should be started with priority and completed as early as possible to allow sufficient settlement time, but the filling rate must be strictly controlled. When a high-fill embankment is supported by a retaining wall, the backfilling of the wall shall be carried out after the strength of the wall mortar or concrete reaches more than 75% of the design strength or meets the design regulations. ② The subgrade filler must meet the design requirements. When filling the same operation area with different fillers, the various fillers must be filled in layers. The same filler should be used for the full width of each horizontal layer and must not be mixed to avoid uneven settlement on the left and right sides of the subgrade. all. If different fillers are used for filling, the number of different filler layers should be reduced as much as possible, and the thickness of each filler should not be less than 50cm. Each filling layer must meet the design requirements for smoothness and road arch to ensure that water does not accumulate on the roadbed filling surface in rainy days. The road crowns are set up when the first layer is filled with full cross-section, and the second layer is filled with uniform thickness from the beginning. ③ In order to ensure that the slope compaction is consistent with the entire section of the embankment, both sides of the slope should be overfilled by 0.4 to 0.5m. The slope should be brushed manually with an excavator before the roadbed protection construction.
After each layer of roadbed is filled and compacted, the edge line is measured and lime is sprinkled to control the filling of the upper layer and ensure the slope of the side slope of the roadbed. ④ Paving and leveling: While unloading soil, use a grader to level the filling section. Pay attention to setting road crowns on each layer as required. After the bulldozer completes the bulldozing of a section, a grader is used for leveling. The grader travels longitudinally from both sides and gradually scrapes toward the center of the roadbed. At the same time, manual labor is used to fill the pits to ensure compaction quality. ⑤ Sprinkle water or dry in the sun: When filling the embankment, check the moisture content of the filler at any time. For fine-grained soil and clayey sand soil, the moisture content of the filler before rolling shall not exceed ±2% of the optimal moisture content obtained during the filling test of the test section. When the moisture content is low, add water stuffing material to the soil field to ensure that the moisture content of the filler reaches the optimal moisture content. When the moisture content exceeds the specified value, use a plow or a rotary plow to plow the embankment fill, and appropriately reduce the thickness of the fill layer to reduce the moisture content of the fill so that the moisture content of the fill is always controlled within the allowable moisture content range for construction. within to ensure the best compaction effect. Under necessary conditions, quicklime can be used to improve the soil to reduce the moisture content, thereby speeding up the filling process. ⑥Rolling and compaction: According to the layered construction drawings and different filling conditions, select the appropriate rolling machinery. A heavy-duty vibratory roller is used for filling and compaction operations, and the excitation force of the roller is 30 to 60t. The rolling sequence is from both sides to the middle. The curved section is first inside and then outside. The transverse joints overlap by more than 0.5m or about one-third of the wheel width. The two adjacent sections at the front and back overlap by more than 1m. According to the filler type, filling thickness and compactness standards, the number of compaction passes is controlled based on the data obtained in the test section. Static pressing is performed 2 times first, followed by vibration pressing. The number of vibrating compaction passes under normal circumstances is: 6 to 8 times for the surface layer of the road bed, 5 to 6 times for the bottom layer of the road bed, and 4 to 5 times for the main road bed. For compaction near the slope, first use a bulldozer to initially compact the road shoulder until the road shoulder does not slide, and then use a road roller to compact it. The outer rim of the roller should be kept about 30cm away from the edge of the overfilled roadbed to ensure the safety of the roller. Use small tamping machines to compact areas that are not suitable for rolling by road rollers. ⑦ Before sampling or testing, test personnel must ensure whether the filler meets the requirements, whether the rolling section is compacted evenly, and whether the thickness of the filling layer exceeds the specified thickness. The quality inspection of roadbed filling and compaction is carried out along with the layered inspection of layered filling and rolling compaction construction. On the basis that the filling quality, filling thickness, vertical and horizontal smoothness of the filling surface, etc. meet the prescribed standards, the sand filling method and K30 load plate are used to determine the compaction coefficient and foundation coefficient of fine-grained soil, coarse-grained soil and gravel The K30 load plate and nuclear density meter are used to detect the foundation coefficient and porosity of the similar soil. After reaching the specifications and design standards, the next layer of filling will be carried out. ⑧ Subgrade renovation: After the embankment is filled according to the design elevation, it will be repaired and measured. Restore the center line, set up piles every 20m, measure the horizontal elevation, calculate the trimming height, place road shoulder piles, build road arches, and roll them over with a flat roller to make the roadbed surface smooth and free of floating soil, and the transverse drainage slope meets the requirements. For fine-grained soil slopes, according to the road shoulder edge piles, use manual brushing to remove the overfill part according to the design slope rate, and carry out repairs and compaction. After the trimming, the slope has obvious ridges at the turning points, straight lines, and rounded changes. The slope surface is smooth and has no unevenness, and the compaction density is qualified. The renovation includes the drainage cross slope, flatness, side slope and other renovation contents of the subgrade surface. The subgrade renovation is carried out in strict accordance with the designed structural dimensions and meets the technical standards. The side slope is trimmed to release the roadbed edge piles. According to the requirements of the design specifications, the overfilled portion is removed by artificial hanging lines on the widened part, and the turning points are trimmed. After trimming, the edge lines at the turning points are obvious, the straight lines are straight, and the curves are smooth. 3.1.4.2.3 Construction method of stone filling embankment. When the stone content in the embankment filler is equal to or greater than 70%, the construction shall be carried out as a stone filling embankment. When filling the embankment with stone, the filling test section shall be constructed first, and the compaction degree shall be determined on site. The test is confirmed and submitted to the supervision engineer for inspection and approval. The dumping method shall not be used in construction to prevent the separation of soil and rock, and the filling shall be carried out in layers. When filling in layers, the thickness of loose paving should be 400mm or determined through testing. Ensure that the earth and rock are fully mixed in the filler, and the filler must be well graded. If the filler does not meet the requirements, use manual or mechanical mixing. The rock fill embankment stones meet the strength and dimensions required by the code. In order to ensure that the slope compaction is consistent with the entire section of the embankment, construction must be carried out strictly according to the position and slope of the slope. After each layer of roadbed is filled and compacted, the edge line is measured and released to control the filling of the upper layer and ensure the slope of the side slope.
Paving and leveling: The stone filling section is leveled with a bulldozer while unloading the stone. After the bulldozer completes the leveling of a section, it is leveled and arranged manually. The large side of the stone is facing down, placed stably, and small stones are used to level the stone. Block leveling. Rolling and compaction: According to the layered construction and different filling conditions, appropriate rolling machinery is selected, and impact rollers are used for filling and compaction operations. The rolling sequence is from both sides to the middle. The curved section is first inside and then outside. The transverse joints overlap by more than 0.5m or about one-third of the wheel width. The two adjacent sections at the front and back overlap by more than 1m. The renovation includes subgrade surface drainage cross slope, flatness, side slope and other renovation contents. The subgrade renovation is carried out in strict accordance with the designed structural dimensions and meets the technical standards. The roadbed renovation of stone-filled embankments mainly uses road rollers combined with manual renovation. 3.1.4.3 Cutting excavation construction technology and methods After the cutting is excavated, the earth and stone shall be prepared according to the allocation plan. For short and shallow cuttings on relatively gentle sections, full-section excavation without layering is adopted; when the center height of the cutting is greater than 5m, layered layer-by-layer excavation along the slope or longitudinal step excavation is adopted. Before excavation of the road cutting, first check the geological data, and at the same time, prepare the anti-drainage facilities on the top of the cutting. The temporary drainage facilities should be combined with the permanent drainage facilities and connected with the original drainage system. In order to ensure that rainwater does not wash away the slope during the excavation of the cutting, 50cm should be reserved on each side to be completed in one go when the excavation reaches the design elevation or platform position. Brush the slope to ensure the slope slope and smoothness, and do slope protection work for special parts. Take timely measures to divert surface water and groundwater that affect slope stability, and set drainage slopes on the surface of road cuttings to facilitate drainage. Before excavation of cuttings, check the dangerous rocks, cracks and other unstable conditions on the slope top and surface, and take measures to deal with them properly according to the situation to ensure construction safety. Cutting excavation is carried out from top to bottom to prevent bottom excavation. ⑴After the soil cuttings are excavated to the design elevation, the strata within the thickness of the subgrade bed shall be inspected and tested using methods such as engineering geological mapping, in-situ testing, electrical geophysical prospecting, and drilling and sampling if necessary. According to The test results show that for sections that cannot meet the dynamic stability requirements of the foundation bed, replacement filling or foundation reinforcement construction will be carried out according to the design according to the line grade. ⑵ Hard rock cuttings are excavated by loose blasting. According to the lithology, occurrence and excavation height of the rocks in the cutting excavation area, the blasting design is carried out in detail and the charge amount is strictly controlled. After blasting, the slope and the cutting top mountain are stable, the foundation bed and slope are smooth and unbroken, and the edges are Use concrete or mortar rubble to make up for uneven slopes. The blasting construction uses a down-the-hole drilling rig to drill holes and carry out loose blasting. During the blasting construction, it is segmented longitudinally, layered vertically, and constructed layer by layer. After the crushing and grading particle size meets the requirements of Group A and Group B fillers, it is excavated and loaded with loaders and excavators, and then transported to the filling area by dump trucks for utilization. Smooth blasting excavation of slopes. When digging to the design elevation of the surface of the cutting bed, shallow hole blasting or hole bottom buffer charging will be used, and the amount of chemicals used will be controlled for smooth blasting. After the road cutting bed construction is excavated to the bottom of the cutting, the rocks are identified and checked, and then the lines are measured and laid out according to the designed section, and the excavation is corrected. For non-soluble rock sections, the surface layer of the foundation bed and below will not be replaced, and only C15 concrete will be used to level the uneven areas; for soluble rock sections, an over-excavation of 0.2m will be carried out according to the design requirements, and C20 concrete will be replaced, and C15 chip concrete will be used to inlay the concave and convex areas. pits, karsts, karsts, karsts, etc., and take measures to remediate the karst areas below the foundation bed that are not filled. ⑶ The construction of expansive soil cuttings should be avoided as much as possible in the rainy season. When construction is required in the rainy season, the slopes with supporting and protective structures should be constructed in time, and the construction should be carried out along with the excavation, and the slopes should be closed in time. When excavation and masonry cannot be followed closely, a protective layer of no less than 0.5m thick shall be reserved for the slope, and the slope shall be brushed in place once for masonry construction in the future. The expansion soil cutting bed replacement and filling will be carried out immediately following the excavation. If there are difficulties in connecting the previous and subsequent processes, a 0.5m thick protective layer will be temporarily left and the excavation will be carried out during the replacement and filling. The excavation surface of the expansive soil cutting construction should always maintain a drainage slope of no less than 4% to prevent water accumulation. For clay soil with greater viscosity and high water content, it should be properly dried before excavation. ⑷ Before construction of deep cutting and high slopes (excavated slope height is greater than 30m), review in detail the engineering geological data and cutting slopes of the deep cutting and high slope sections determined in the design documents, and collect and understand soil and rock boundaries, engineering grades, and rock formation weathering Thickness and degree of fragmentation, and rock formation engineering characteristics. Equip an appropriate number of mechanical equipment and labor according to the detailed understanding of the engineering geology, the size of the project and the construction period. The construction of deep road cuts and high slopes shall be strictly in accordance with the design slope.
If the actual geology of the slope does not match the geological data of the designed survey, especially if the geology is looser than the design, suggestions for changing the design should be put forward in a timely manner and implemented after approval. For steep slopes with soft rocks such as sandstone and mudstone, shale and other deep cuttings and high side slopes, the slope foot shall be reinforced with cutting retaining walls between piles, anchor piles, pile plate walls, anchor cable plates and other supports according to the ground cross slope conditions. A first-level anchor rod (cable) is installed every 10m on the top of the pile (wall) to provide spray-mixed vegetation slope protection within the frame beam, and a 2 to 4m wide platform is left. The drainage facilities on the platform must be connected to the drainage system. For complete weakly weathered hard rock slopes, graded smooth blasting embedding is used, and the upper weathered slope is treated by leaving a platform behind and setting up a herringbone water-cutting skeleton slope protection; for high slopes with gentle terrain and deep road cuttings, low slope toes are used Retaining wall (soft rock section), retaining wall (more broken hard rock section), graded grading and excavation of the slope above the top of the wall, the slope surface uses a herringbone water-cutting frame (or anchor frame beam) internal spraying Mixed planting, spray-seeded grass planting and shrub slope protection. The construction of single-slope deep cutting and high slope adopts multi-layer transverse full-width excavation method. The construction of high side slopes with deep cuts and double slopes adopts the layered longitudinal excavation method and the channel longitudinal excavation method. If the longitudinal length of the cutting is large and the thickness and height of the soil wall on one side of the slope are not large, the segmented longitudinal excavation method can be used. Construction machinery can use excavators in conjunction with dump trucks or bulldozers and loaders in conjunction with dump trucks. Excavation of deep cuttings and high slopes must be carried out in stages from top to bottom to prevent bottom excavation. 3.1.4.4 Subgrade bed construction technology and methods The bottom layer of the bed is mechanized construction using Group A and B fillers or improved soil. Before construction, conduct compaction process tests based on the machinery used and the fillers planned to be used. The filling construction will be carried out according to the "three-stage, four-section, eight-process" method. The first layer was filled using the setback method. The foundation bed shall be filled and compacted horizontally in layers according to the full width of the cross section. The surface layer of the foundation bed shall be filled in layers up to the design elevation and graded gravel shall be used. The gravel is transported from the sand and gravel field to the graded gravel mixing station along the line. After being mixed with the best grade through on-site testing, it is transported to the construction site for layering, paving with paver and rolling with heavy-duty rollers. The surface layer of the foundation bed is mechanized according to the "four sections and six processes". Before filling construction, according to the original filler mix ratio determined by indoor testing, select representative sections to conduct filling and compaction construction process tests to determine the compaction construction process parameters.