土木工程毕业论文外文翻译盾构外文原文+中文翻译.docx

1、土木工程毕业论文外文翻译盾构外文原文+中文翻译 毕业设计（论文）外文文献翻译院 系：土木工程与建筑系年级专业： 姓 名： 学 号： 附 件：盾构SHIELDS指导老师评语： 指导教师签名：年 月 日SHIELDS【Abstract】A tunnel shield is a structural system, used during the face excavation process. The paper mainly discusses the form and the structure of the shield. Propulsion for the shield is provi

2、ded by a series of hydraulic jacks installed in the tail of the shield and the shield is widespread used in the underground environment where can not be in long time stable. The main enemy of the shield is ground pressure. Non-uniform ground pressure caused by the steering may act on the skin tends

3、to force the shield off line and grade. And working decks inside the shield enable the miners to excavate the face, drill and load holes. 【Keywords】shield hydraulic jacks ground pressure steering working decksA tunnel shield is a structural system, normally constructed of steel, used during the face

4、 excavation process. The shield has an outside configuration which matches the tunnel. The shield provides protection for the men and equipment and also furnished initial ground support until structural supports can be installed within the tail section of the shield. The shield also provides a react

5、ion base for the breast-board system used to control face movement. The shield may have either an open or closed bottom. In a closed-bottom shield, the shield structure and skin provide 360-degree ground contact and the weight of the shield rests upon the invert section of the shield skin. The open

6、shield has no bottom section and requires some additional provision is a pair of side drifts driven in advance of shield excavation. Rails or skid tracks are installed within these side drifts to provide bearing support for the shield.Shield length generally varies from1/2 to 3/4 of the tunnel diame

7、ter. The front of the shield is generally hooded to so that the top of the shield protrudes forward further than the invert portion which provides additional protection for the men working at the face and also ease pressure on the breast-boards. The steel skin of the shield may vary from 1.3 to 10 c

8、m in thickness, depending on the expected ground pressures. The type of steel used in the shield is the subject of many arguments within the tunneling fraternity. Some prefer mild steel in the A36 category because of its ductility and case of welding in the underground environment where precision wo

9、rk is difficult. Others prefer a high-strength steel such as T-1 because of its higher strength/weight ratio. Shield weight may range from 5 to 500 tons. Most of the heaviest shields are found in the former Sovier Union because of their preference for cast-iron in both structural and skin elements.P

10、ropulsion for the shield is provided by a series of hydraulic jacks installed in the tail of the shield that thrust against the last steel set that has been installed. The total required thrust will vary with skin area and ground pressure. Several shields have been constructed with total thrust capa

11、bilities in excess of 10000 tons. Hydraulic systems are usually self-contained, air-motor powered, and mounted on the shield. Working pressures in the hydraulic system may range from 20-70 Mpa. To resist the thrust of the shield jacks, a horizontal structure member (collar brace) must be installed o

12、pposite each jack location and between the flanges of the steel set. In addition, some structural provision must be made for transferring this thrust load into the tunnel walls. Without this provision the thrust will extend through the collar braces to the tunnel portal.An Englishman, Marc Brunel, i

13、s credited with inventing the shield. Brunel supposedly got his idea by studying the action of the Teredo navalis, a highly destructive woodworm, when he was working at the Chatham dock yard. In 1818 Brunel obtained an English patent for his rectangular shield which was subsequently uses to construc

14、t the first tunnel under the River Thames in London. In 1869 the first circular shield was devised by Barlow and Great Head in London and is referred to as the Great Head-type shield. Later that same year, Beach in New York City produced similar shield. The first use of the circular shield came duri

15、ng 1869 when Barlow and Great Head employed their device in the construction of the 2.1 in diameter Tower Subway under the River Thames. Despite the name of the tunnel, it was used only for pedestrian traffic. Beach also put his circular shield to work in 1869 to construct a demonstration project fo

16、r a proposed New York City subway system. The project consisted of a 2.4 m diameter tunnel, 90 m long, used to experiment with a subway car propelled by air pressure.Here are some tunnels which were built by shield principle.Soft-ground tunneling Some tunnels are driven wholly or mostly through soft

17、 material. In very soft ground, little or no blasting is necessary because the material is easily excavated.At first, forepoling was the only method for building tunnels through very soft ground. Forepoles are heavy planks about 1.5 m long and sharpened to a point. They were inserted over the top ho

18、rizontal bar of the bracing at the face of the tunnel. The forepoles were driven into the ground of the face with an outward inclination. After all the roof poles were driven for about half of their length, a timber was laid across their exposed ends to counter any strain on the outer ends. The fore

19、poles thus provided an extension of the tunnel support, and the face was extended under them. When the ends of the forepoles were reached, new timbering support was added, and the forepoles were driven into the ground for the next advance of the tunneling. The use of compressed air simplified workin

20、g in soft ground. An airlock was built, though which men and equipment passed, and sufficient air pressure was maintained at the tunnel face to hold the ground firm during excavation until timbering or other support was erected.Another development was the use of hydraulically powered shields behind

21、which cast-iron or steel plates were placed on the circumference of the tunnels. These plates provided sufficient support for the tunnel while the work proceeded, as well as full working space for men in the tunnel.Under water tunneling The most difficult tunneling is that undertaken at considerable

22、 depths below a river or other body of water. In such cases, water seeps through porous material or crevices, subjecting the work in progress to the pressure of the water above the tunneling path. When the tunnel is driven through stiff clay, the flow of water may be small enough to be removed by pu

23、mping. In more porous ground, compressed air must be used to exclude water. The amount of air pressure that is needed increases as the depth of the tunnel increases below the surface.A circular shield has proved to be most efficient in resisting the pressure of soft ground, so most shield-driven tun

24、nels are circular. The shield once consisted of steel plates and angle supports, with a heavily braced diaphragm across its face. The diaphragm had a number of openings with doors so that workers could excavate material in front of the shield. In a further development, the shield was shoved forward

25、into the silty material of a riverbed, thereby squeezing displaced material through the doors and into the tunnel, from which the muck was removed. The cylindrical shell of the shield may extend several feet in front of the diaphragm to provide a cutting edge. A rear section, called the tail, extend

26、s for several feet behind the body of the shield to protect workers. In large shields, an erector arm is used in the rear side of the shield to place the metal support segments along the circumference of the tunnel.The pressure against the forward motion of a shield may exceed 48.8 Mpa. Hydraulic ja

27、cks are used to overcome this pressure and advance the shield, producing a pressure of about 245 Mpa on the outside surface of the shield.Shields can be steered by varying the thrust of the jacks from left side to right side or from top to bottom, thus varying the tunnel direction left or right or u

28、p or down. The jacks shove against the tunnel lining for each forward shove. The cycle of operation is forward shove, line, muck, and then another forward shove. The shield used about 1955 on the third tube of the Lincoln Tunnel in New York City was 5.5 m long and 9.6 m in diameter. It was moved abo

29、ut 81.2 cm per shove, permitting the fabrication of a 81.2 cm support ring behind it.Cast-iron segments commonly are used in working behind such a shield. They are erected and bolted together in a short time to provide strength and water tightness. In the third tube of the Lincoln Tunnel each segmen

30、t is 2 m long, 81.2 cm wide, and 35.5 cm thick, and weighs about 1.5 tons. These sections form a ring of 14 segments that are linked together by bolts. The bolts were tightened by hand and then by machine. Immediately after they were in place, the sections were sealed at the joints to ensure permane

31、nt water tightness.Shields are most commonly used in ground condition where adequate stand-up time does not exist. The advantage of the shield in this type of ground, in addition to the protection afforded men and equipment , is the time available to install steel ribs, liner plates, or precast conc

32、rete segments under the tail segment of the shield before ground pressure and movement become adverse factors.One of the principle problems associated with shield use is steering. Non-uniform ground pressure acting on the skin tends to force the shield off line and grade. This problem is particularl

33、y acute with closed bottom shield that do not ride on rails or skid tracks. Steering is accomplished by varying the hydraulic pressure in individual thrust jacks. If the shied is trying to dive, additional pressure on the invert jacks will resist this tendency. It is not unusual to find shield wandering sev