“Guizhou’s special landforms determine the status and role of bridges in Guizhou’s economic and social development.†A few days ago, Deng Wenzhong, an academician of the American Academy of Engineering and a foreign academician of the Chinese Academy of Engineering, said that when he inspected the Baling River Bridge, he said that Guizhou has adopted local conditions and built Balings in the mountains. The river bridge, using technological innovation to promote the development of mountain highway bridges across the development. The Balinghe Bridge is a single-span steel-truss reinforced beam suspension bridge with a span of 1088 meters. The bridge is 2,237 meters in length and 370 meters from the bridge surface to the river surface. It is the highest-technical bridge ever built in Guizhou, and a number of construction techniques in the construction of the bridge. And technology has reached the leading level both at home and abroad. It is a microcosm of Guizhou's reliance on technological innovation in the past decade to provide technical support and guarantee for the sound and rapid development of transportation construction.
Located in the eastern part of the Yunnan-Guizhou Plateau, Guizhou has high mountains and valleys, ravines, and 97% of mountains and hills. It is the only province in the country with no plains. The conditions for highway construction are especially difficult. For a long time, the weak transportation infrastructure has constrained the economic and social development in Guizhou.
Under the conditions that the roads are getting harder and harder and the bridges being built and more complicated, the demand for road building in Guizhou Province for the innovation of mountain bridge construction technology is particularly urgent. In 2004, Guizhou Province built the first cable-stayed bridge, the Hongfeng Lake Bridge, and opened a new starting point for the special structural bridge in the province. Since then, Guizhou has built Balinghe Bridge, Malinghe Bridge and other special structural bridges. Nowadays, a new technology bridge has been built and a large span bridge has been erected proudly. There are thousands of “plateau rainbows†shaped by traffic builders.
Guizhou's bridge construction continues to break through and innovate in its span and structural form. In the cable-stayed bridge, the Bipan-Dujiang Expressway Beipan River Bridge under construction uses the main span 720m steel truss girder cable-stayed bridge, which is the largest span of the world's existing bridges. In terms of suspension bridges, the proposed Qingshuihe Bridge on the Guiyang-Pan'an Expressway will have a main span of 1,130 meters and will break through the main span of the existing suspension bridge in Guizhou. Continuous rigid arch bridges and arch bridges are more large-span bridge-type structures used in Guizhou. The Beipanjiang Bridge, which is under construction from Liupanshui to Panxian Expressway, is a 270-meter fast-span continuous rigid-framed bridge. The Bijie-Weining Highway Hezhang Bridge under construction is a continuous rigid-framed bridge with a pier height of 195 meters.
Luo Qiang, deputy director of the Guizhou Provincial Department of Transportation, said that Guizhou has made great progress in bridge construction technology, such as the use of deck cranes in the erection of steel truss girders; the use of rotary construction technology in the construction of arch bridges, development of climbing steel Hanging basket construction technology; in the construction of high piers, step-by-step sliding mode technology and comprehensive monitoring technology are adopted. In the use of materials, machine-made sand high-strength concrete has been widely used, large volume pouring of machine-made sand concrete, high-lift pumping technology has made breakthroughs, and development of special mechanisms such as self-compacting, anti-disturbing and anti-dispersion sand concrete has expanded the use of machine-made sand. The range of applications for local materials represented.
At present, Guizhou is trying to open up a large-scale highway to the outside, and the traffic infrastructure that is dominated by highways is changing with each passing day. The province is currently constructing 3,142 kilometers of expressways, and nearly 1,000 kilometers are currently carrying out preliminary work. It is expected that by 2015, the mileage of highways throughout the province will reach more than 5,100 kilometers and the county-to-county highway will be realized.
When reaming stainless steel, the problems that are often encountered are: grooves are easy to be drawn on the surface of the hole, the roughness is poor, the aperture is out of tolerance, it is bell mouth, and the reamer is easy to wear. Different types of stainless steel have different machinability, and the problems in reaming are also different. For example, when reaming austenitic stainless steel such as 1Cr18Ni9Ti and stainless steel resistant to concentrated nitric acid, the main problem is reamer wear; while for 2Cr13, etc. When reaming martensitic stainless steel, the main problem is that it is not easy to ensure the roughness and dimensional accuracy of the reaming hole. To avoid these problems, the following should be noted:
1. Reasonable selection of reamer and reaming amount is the key to ensure the smooth progress of reaming.
2. Improve the quality of the pre-processing process and prevent the occurrence of grooves, ellipses, polygons, tapers or bell mouths, waist drum shapes, axis line bending, deflection and other phenomena in the pre-processing holes.
3. Keep the hardness of the workpiece material moderate, especially for 2Cr13 martensitic stainless steel, the hardness after quenching and tempering treatment is preferably below HRC28.
4. To install the reamer and the workpiece correctly, the reamer must be installed correctly, and the axis of the reamer should be consistent with the axis of the pre-machined hole of the workpiece to ensure uniform cutting of each cutter tooth.
5. Selecting a suitable cutting fluid can solve the chip adhesion problem of stainless steel and make it smooth chip removal, thereby reducing the surface roughness of the hole and improving the durability of the tool. Generally, it is advisable to use vulcanized oil. Adding 10% to 20% CCl4 to vulcanized oil or adding 20% to 30% CCl4 to lard will have a significant effect on reducing surface roughness. Since CCl4 is harmful to the human body, it is advisable to use a mixture of 85% to 90% vulcanized oil and 10% to 15% kerosene. When the diameter of the reamer is large, internal cooling can be used.
6. Carefully pay attention to the reaming process and strictly check the runout of the cutter teeth, which is the key to obtain uniform reaming. During the reaming process, pay attention to the shape of the chips. Due to the small reaming allowance, the chips are in the form of foil rolls or very short spiral coils. If the chips are of different sizes, some are in the form of fine powder, and some are in the form of small blocks, it means that the reaming is uneven. If the chip is in the shape of a strip of spring, it means that the reaming allowance is too large. If the chip is needle-like or fragment-like, it means that the reamer has been blunted. To prevent chips from clogging, you should be diligent in observing whether there are sticky chips on the cutter teeth to avoid excessive hole diameter. When reaming a hole with a carbide reamer, hole shrinkage will occur. In order to prevent the hole from being roughened when the tool is retracted, the situation can be improved by increasing the lead angle.
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