1 Foundation excavation method
The construction of corrugated pipe culvert is generally on natural ground or strictly tamped fill soil. First dig trenches for buried pipes. The width of the trench should be convenient for the ramming and filling of the soil on the side of the pipe, and it should also meet the width of the foundation required by the design. Construction experience shows that it is better to construct a culvert on a road section that is not high in fill and to fill the subgrade first and then excavate trenches to bury the culvert. The foundation or foundation of the metal bellows needs to be uniform, strong and durable.
2 Treatment methods of various soil texture foundations.
2.1 Soft soil foundation
When the culvert pipe is on the soft soil foundation, the soft soil roadbed needs to be treated, and then a layer of high-quality gravel cushion with a thickness greater than 500px is filled on it and compacted tightly.
2.2 For ordinary foundations with low bearing capacity, a certain thickness of foundation shall be provided. However, if the undisturbed soil of the foundation groove of the culvert pipe is strictly compacted (its compaction degree is more than 90% of the heavy compaction density), the bellows can also be directly placed on the foundation.
2.3 High-quality land foundation
Unsifted sand, gravel, gravel soil and sandy soil are ideal foundation materials, but hard materials such as stones above 10em need to be removed.
Metal Corrugated Pipe
2.4 Rock foundation
The metal corrugated pipe cannot be placed directly on the rock or concrete bed. The excessively rigid support will not only reduce the good flexibility of the pipe wall itself, but also reduce the carrying capacity of the culvert. Therefore, part of the soft rock should be dug out of the rock foundation, replaced with a layer of high-quality soil, and carefully tamped. Excavation of soft rock trenches, strong explosives and deep-hole guns can not be used, in order to avoid the excessive outer layer to be loosened.
3 Reserved arch
The metal bellows buried on the general soil foundation often have a certain amount of subsidence after a period of time, and the middle of the pipe is often larger than the two ends. Therefore, the tube body of the metal bellows laid under the embankment should be provided with a reserved arch. Its size should be comprehensively considered according to the factors such as the subsidence of the foundation soil, the vertical slope of the culvert and the height of the fill, which can usually be 0.6% to 1% of the length of the pipe, and should not be greater than 2%, to ensure that no sag appears in the middle of the pipe Or landslide.
1) The backfill on both sides of the culvert should be made of gravel or the same material as the roadbed filler.
2) The backfill on both sides of the culvert should be constructed symmetrically, backfilled in layers, with a thickness of 20em per layer.
3) Both sides of the culvert pipe are mechanically tamped, and the coarse sand below the bottom of the pipe is vibrated by the "watertight method" oscillator.
4) The backfill on both sides of the culvert should be compacted layer by layer using a vibrating compactor, with a density of not less than 95%.
5) When the thickness of the backfill above the culvert exceeds 750px, a static pressure is applied by the roller. After the thickness of the backfill exceeds 1500px, the roller is used to vibrate and the degree of compaction is not less than 95%.
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