The rockfill subgrade of high grade highway construction site process analysis and applied
(highway bridge construction in changsha city, hunan province, a limited liability company, 410007)
Pick to: the paper first analyzes the rockfill graded control and paving stone material craft, and combined with the engineering practice of high grade highway subgrade construction technology of the rockfill analysis for building the rural highway lay a good foundation technology.
Key words: the rockfill subgrade; The construction technology; Application research
For a long time, because mountain building roads level is low, the highway departments to fill in the stone roadbed construction technology research is less. With the development of economy, high grade highway construction from the center of the coastal area has the mountains extended city authors, is going to build a large stone roadbed fill. Domestic to fill in the stone roadbed later start, building technology has not mature. Combining with the project examples, the rockfill subgrade of high grade highway construction process are analyzed, and the building of the mountainous area highway lay a good foundation technology.
1 fill in the stone graded control
In the excavation rock packing, through the test select the best blasting parameters, make critical pile of packing with particle size of roadbed filling materials requirements. In the packing shipment, pour materials, spreading process, pay attention to the packing degree even collocation, prevent packing segregation.
(1) the non-uniform coefficient
For the Lord of the rock embankment fill packing, the non-uniform coefficient should be 10 ~ 40; Used for basement, road bed, structures and backfilling slope, non-uniform coefficient is appropriate for more than 10 above; The curvature coefficients rock packing should be in 1 ~ 3 range.
(2) water stone fill subgrade construction of packing gradation requirements
Soaking in the rocky fill subgrade construction can use stone code build by laying bricks or stones or level filling ingredients. The stone code build by laying bricks or stones, and the slope of the same requirements; The level when filling ingredients, its biggest particle size should not be more than 20 cm, less than 5 mm particles ratio not less than 30%, less than 0.074 mm particles proportion of no more than 10%. When necessary shall set up the filter layer to prevent fine material loss.
(3) the filter layer aggregates graded requirements
The filter layer aggregates 20% through the amount particle size of 10 ~ 40 mm, and protected by 20% the amount of packing of the ratio of the particle size for 2 ~ 4.
(4) transition layer aggregates graded requirements
In the external fill subgrade construction filling fine-grained soils, if aggregates of the R15 / F85 > 5, should set transition layer, the transition layer should meet M15 / framework > 5, M15 / F85 < 5. Which R for aggregates, M for transition layer aggregates, F for fine aggregates, digital said the passing rate of the corresponding size.
(5) maximum diameter of packing materials control
Maximum diameter of packing materials in engineering consideration is mainly from filling the uniformity of the body and compaction effect into consideration, packing more than fill maximum diameter can't two-thirds of the layer thickness. At the same time in the construction process should avoid super size between ports of stone, the stone in the bottom of the layer should fill, bedding face down in a steady state.
(6) aggregates and fine aggregates ratio
For the Lord of the rock embankment fill in below 20 mm packing of fine aggregates the proportion of less than 10%, general should be 10% ~ 40%; More than 200 mm in the proportion of the giant granular materials shall not be higher than 40%; 0.074 mm particles of the ratio should be greater than 10%.
2 paving stone material craft
2.1 paving method
To fill in the stone roadbed, it generally paving method has three. A method is back to pave the material, the surface of the compaction in already, back unloading, dense material to form a number of, again with bulldozers leveling. This method of materials is it difficult to grasp the point, so bad control layer thickness, generally don't use. 2 it is the progressive paving method, the shop is material is shipped materials in the new car fill material gradually the loose forward unloading, bulldozers and at any time leveling, this is fill in the stone is widespread in the construction method of application. Three is to pave the material mix method, has on the level of compaction method with back first unloading, form scattered material pile of, again in its gradual method with paving material unloading, bulldozers level off, to reach the required layer thickness. This method is also quite common. The progressive paving method commonly used in road width is not big, filling sections short sections.
2.2 the progressive paving method and hybrid method to pave the material technology is more
Paving push in the process of material, big rocks in the role of the bulldozer, are more likely to get more kinetic energy, so in the process of promoting commonly, in the external force and the force of gravity, large stone will roll to fill in the lower part of the layer, feed is high, the more obvious this phenomenon, this is our hope, because to fill in the layer in the process of rolling and paving pore of interstitial, ensure the best lock the transmission of embedded pressure, so the progressive paving method to pave the material than mix method is more likely to make big rocks in the bottom layer fill, and blending of paving material will appear more spread local big rocks on the top of the phenomenon in. The two process will appear in paving stone on the bottom end of the phenomenon, and the stone is mainly about 30 cm stone, this part of the stone can be used as a code build by laying bricks or stones slope stone, pushed to the side can.
2.3 paving thickness and packing size control
The highway subgrade construction technology standard "(JTJ 033-95) requirements, in the absence of 12 tons of heavy duty vibratory roller, work quality of the above 2.5 rammer or 25 tons of tyre roller (ram) real-time, highway roadbed fill the biggest stone thick layer of no more than 50 cm, packing more than a thick layer of maximum diameter can't the 2/3. When have more than 12 t heavy roller, fill in the thickness of the layer should be relaxed to less than 100 cm.
Three engineering example analysis
3.1 project profile
Guangxi Co. (water as) to nanning highway (hereinafter referred to as the road)) is a main highway chongqing to zhanjiang is an important part of highway. This section is a 235.53 km, along the complicated topography and geology condition, especially the karst geological problems, the test section k202 + 260 for k202 ~ + 320 period of stone-filled roads, the embankment, embankment height in 2.5 ~ 3.5 m between, the largest number of times stamping 30 times. The test process in 10 times before, stamping, 15 times, 20 times, 25 times and 30 times the height measurement. In the experiment, the point every five meters by 10 meters or a section, each section 8 points in the midline symmetric distribution.
3.2 rolling machine
The filling roadbed using stratified rolling YCT25 impact type roller to enhance type fill pressure, main performance parameters: the impact energy 2 5 KJ, impact round the work quality 1500 Kg, the speed of work 8 to 15 Km/h, impact frequency 60 ~ 110 / min, impact round shape, structure for the trilateral CAM structure, impact round 900 mm width, compaction width 3 m, shape dimension (long x width × high) 10176 mm x 3000 mm x 3685 mm.
3.3 k202 + 260 ~ 320 testing stamping data analysis
Table 1 different impact compaction times several sedimentation value table
Figure 1 stamping reinforcing the relative settlement after
Data analysis shows that on both sides of the subgrade error between big than absolute value, we think this is mainly stamping before on the edge of the roadbed compaction degree no middle good, the surface is loose, data error absolute value is relatively large some.
3.4 k193 + 360-420 period of test data analysis
Choose) GK193 road in 360-420 to + for impact compaction effect do the compaction test. The ChangLin roller (18, became the most weight T power 50 T), the first time static pressure, the second third time weak vibration, after three times the strong vibration, total rolling seven times. The measurement points, some flour for 20 X20cm2, take its 5 points for the average of the points, seven times before the CYZ25 impact roller type stamping 20 times, measurement and the conventional rolling observation point.
Figure 2 stamping effect schemes
Because the surface stone to some mobile dislocation abnormal data, part of the point settlement appear a negative value. The type CYZ25 impact roller press after 20 times the average settlement 39.0 mm, roadbed settlement is an average 6.95% increase. After the examination, the roadbed compaction quality requirements.
3.5 the result analysis
(1) every compaction 5 layers and road surface should be constructed by impact type vibratory roller vibration compaction, stamping speed should be held in 12 km/h, stamping influence depth about 150 cm range. Limestone rock subgrade of general impact compaction times for 15 times or so that is to meet requirements.
(2) the surface in the roadbed compaction effect of impact can be eased, so when using the roller of subgrade for strong, still should use the ground machine leveling, use all round roller compaction, in order to ensure that the surface quality.
(3) settlement can intuitivey reflect the roadbed compaction quality, but due to the impact of roller CAM type for roller, settlement will be part of the first movement, so that some of the testing point elevation higher after impact instead; Only after a first laid, sedimentation value to a representative every 5 m for a suggestion sections, each section or so arranged on each side at least four check points.
(4) impact type roller excitation force is big, to installations unsafe, near slope of stamping work, want to have enough safety distance.
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