Geotechnical engineering is a branch of civil engineering, and it is a science that uses engineering geology, soil mechanics and rock mechanics to solve engineering technical problems related to geotechnical engineering in various projects. According to the division of engineering construction stages, the work content can be divided into: geotechnical engineering investigation, geotechnical engineering design, geotechnical engineering management, geotechnical engineering monitoring and geotechnical engineering detection.
Classification and pressure of tunnel surrounding rock, basic methods and special construction methods of tunnel construction (full-face boring machine method, shield method and immersed tube method), shallow-buried tunnel construction, tunnel construction in special rocks and bad sections, auxiliary operation of construction, NATM, construction organization and highway tunnel.
In today's world, human beings are developing underground, ocean and universe. Underground development can be summarized into three aspects: underground resources development, underground energy development and underground space development. The utilization of underground space is also progressing from the utilization of "line" to the utilization of "space" with large cross section and long distance.
In 1980s, ITA put forward the slogan of "vigorously developing underground space and opening a new era of human caves". In line with the trend of the times, many countries regard underground development as a national policy. For example, Japan put forward the idea of underground development and tenfold expansion of territory. In a sense, the utilization history of underground space echoes the history of human civilization and can be divided into four periods:
channel tunnel,le tunnel sous la manche
The first era was from the appearance of human beings to ancient times in 3000 BC. Human primitive caves and natural caves have become places where human beings can avoid cold and heat, wind and rain, and wild animals.
The ancient period from 3000 BC to the 5th century. The pyramids of Egypt and the Babylonian diversion tunnel are both architectural models of this era. The tombs and underground granaries in Qin and Han dynasties in China have reached a considerable technical level and scale.
The third era is the medieval era from the 5th century to14th century. The emergence of ore mining technology in the world has promoted the development of underground engineering.
The fourth era, modern times and modernity, started from15th century. During the industrial revolution in Europe and America, Nobel invented explosives, which became a powerful weapon to develop underground space. During the Meiji era in Japan, tunnel and railway technology began to be introduced and developed.
The development and utilization of underground space in China began in the 1960s. 1965 Beijing builds underground railway. The first phase of the project is from Beijing Railway Station to Apple Orchard, with a total length of 24. 17km, and is constructed in cut and cover. The second phase of the project is a ring road, built under the wall of the old city, 16. 1km, with open excavation and underground burial. Fuxingmen subway station and turn-back line are located in the area with dense buildings and underground pipelines, and the shallow buried and underground excavation method is adopted for construction. In 1960s, Shanghai built the underwater highway tunnel of Dapu Road. In 1970s, a large number of civil air defense projects were built in China, and a considerable part of them have been developed and transformed into underground streets, underground shopping malls, underground factories and warehouses. In 1980s, the underwater highway tunnel of Yan 'an East Road was built in Shanghai, with a total length of 226 1m, which was constructed by a super-large grid hydraulic mechanical shield tunneling machine with a diameter of1.3m. 1984 was started, and 1989 was completed and opened to traffic in May. At that time, the third long tunnel constructed by shield method in the world was built. During the same period, Shanghai also built more than 20 cable tunnels and other municipal public tunnels, with a total length of more than 30 kilometers. From 1985 to 1987, the first phase of the diversion tunnel in the upper reaches of Huangpu River was completed in Shanghai, with a daily diversion flow of 2.3 million tons, which has remarkable social benefits. After the underground garage of People's Square is completed, the plane size is 176× 146m, and the depth is11m.. During this period, Guangzhou Metro and Nanjing Metro entered the stage of design and construction preparation, and Ningbo started the construction of underwater highway tunnels. Since 1990s, the construction of underground transportation and municipal facilities has been accelerated. Shanghai Metro 1 Line and Metro Line 2 were opened one after another. The network system of underground space development and utilization in China has begun to be built, and most underground projects are built in shallow layers within-30m from the surface. It can be predicted that with the development of economy, China's underground engineering will enter a period of vigorous development.
Modern underground engineering has developed rapidly, and various typical projects are famous all over the world. Hundreds of cities around the world have built underground railways. Dayaoshan Railway Tunnel in China, with a total length of 65,438+04,295 m, was completed in 6 years. The Japanese Han Qing Tunnel, 53,850 meters long, lasted for half a century from planning to completion; The British-French cross-harbour tunnel is 50 kilometers long and the seabed is 37 kilometers long. It took 7 years to build. The total length of the Japan-Korea tunnel is 250km, and the sectional construction scheme is adopted. The inclined shaft is surveyed at the end of 1986. Well-known highway tunnels, such as the connecting method through Alps, the Mont Blanc tunnel between Italy and Italy, and the Guan Yue tunnel connecting Gunma and Niigata, are all over 10 km. Various types of underground power stations have developed rapidly, among which the number of underground hydropower generation has exceeded 400 in the world, and the power generation has reached more than 4.5 billion watts. The construction of underground power station is a very huge underground project. The Rogo Hydropower Station in the former Soviet Union has 565,438+million cubic meters of earthwork, 654,38+0.6 million cubic meters of concrete, and 294 tunnels and chambers with a total length of 62km. A large number of underground storage rooms have been built all over the world, and their construction technology is constantly innovating. At present, the development and utilization of urban underground space has become an important content of urban construction. Some industrialized countries have gradually integrated underground commercial streets, underground parking lots, underground railways and underground pipelines into a multifunctional underground complex.
Tunnel is a passage or space built underground, but its aperture is too small, which belongs to the so-called pipeline category. At the tunnel conference in 1970, OECD defined a tunnel as a chamber with a cross-sectional area greater than 2, which was built underground for a certain purpose, according to the specified shape and size, by any method.
The construction of the Xitieshan watershed tunnel on the Qinghai-Tibet Railway and the use of underground space have become a way of making a living for mankind since primitive times. With the development of modern civilization, it has become a subject of civil engineering, and many tunnels are built by using modern engineering technology.
Modern tunnel technology has made great progress, so it can be carried out more accurately, quickly and economically. It can not only drill through rocks or hard strata as before, but also promote the method of building tunnels in soft strata and underwater. These technologies are developed to meet the needs of social development for a large number of diversified tunnels.
At present, tunnels are not only used for railway, highway traffic, hydropower, irrigation and other hydraulic tunnels, but also for the passage of large pipelines such as sewers and power transmission lines. In addition, the concept of tunnel, which used to be understood as underground passage, is extended to the utilization of underground space, including underground power generation substations, underground parking lots, large underground stations, underground streets and other buildings suitable for tunnel engineering technology.
In addition to the above purposes, tunnels can be divided into rock tunnels and earth-sand tunnels according to the excavation objects, and can be divided into highway tunnels, urban tunnels and underwater tunnels according to different construction sites. In addition, shield method or immersed tube method, which used to be considered as special construction methods, has become popular today, so these methods can also be included and classified in detail according to construction methods and means.
With the development of social economy, there is an increasing demand for tunnels all over the world. For railways and highways, in order to expand long-distance high-speed traffic, more mountain tunnels need to be built. In addition, in recent years, in order to accommodate underground high-speed railways and highways, large-capacity sewers and multi-storey urban facilities using underground space, a large number of multi-purpose tunnels need to be built. According to the survey of the above-mentioned OECD Tunnel Conference, it can be predicted that the future demand will be twice that of the same period in the past, especially in transportation facilities and public utilities, and the increase will be more significant in the utilization of underground space for various special purposes in cities.
Tunnel engineering should dig out the required space underground and build a lining structure that can withstand external pressure for a long time. During the project, the pressure generated by the gravity of surrounding rock, soil and sand should not only prevent possible collapse, but also avoid the adverse effects caused by groundwater gushing. Therefore, in order to adapt to a variety of conditions, tunnel technology is also complex and multifaceted, and with the development of technology, the scope is expanding day by day.
Tunnel technology is closely related to geology and hydrology, geotechnical mechanics, applied mechanics and material mechanics. It is applied to various engineering disciplines such as measurement, construction machinery, blasting, lighting, ventilation and communication. And it is related to a wide range of fields because of the effective use of chemicals such as metal, cement, concrete and pressure injection chemicals. Therefore, the basic theory and practical application of tunnel technology not only involve civil engineering and other related disciplines, but also involve the scope of other engineering and science, from which the development prospect of tunnel engineering can be predicted.
The tunnel technology of Badaling Highway Tunnel in Beijing, corresponding to each stage of the tunnel construction process, can be roughly divided into:
Survey and planning technology (investigation, prediction and measurement related to geology and hydrology, etc.). );
Design technology (rock mechanics, soil mechanics, structural mechanics, materials, etc. );
Construction technology (refers to excavation, transportation, supporting lining construction, foundation improvement, special construction methods adopted to improve construction conditions, safety and hygiene, etc.). );
Technical application (lighting, ventilation, maintenance and management, disaster prevention, etc.). ).
The oldest tunnel is the pedestrian tunnel connecting the palace and the temple in Babylon, which was built between 2 160-2 180 BC. The tunnel is about 1km in length and 3.6m×4.5m in section. During the construction period, the water flow of the Euphrates River was diverted and built in cut and cover. This tunnel is a brick building. 1895- 1906 railway tunnel across the Alps 19.23km long. At present, the longest automobile tunnel in the world is the St. Gotha tunnel in central Switzerland, with a total length of 16.3km. Nitroglycerin explosive was used for the first time when the tunnel was dug.
The earliest traffic tunnel in China is the Shimen Tunnel in Hanzhong County, Shaanxi Province, which was built in 66 AD.
Shallow-buried tunnels are generally constructed by cut and cover, while deep-buried tunnels are mostly constructed by underground excavation. In ancient times, the slowest way to dig with primitive tools was to drive 30 thousand slaves to dig, and the footage per week was only 75 mm. It was not until the19th century that drilling and blasting operations were adopted in tunnel construction. After a century of innovation, it has developed into today's large-scale mechanical operation.
Highway tunnel line
The plane alignment of highway tunnel is the same as that of ordinary highway, and it is designed according to the requirements of highway specification. Generally, the plane alignment of tunnels adopts straight lines and avoidance curves. If a curve must be set, a curve with a larger radius should be used as far as possible, and the sight distance should be guaranteed. The longitudinal slope of highway tunnel is determined by tunnel ventilation, drainage, construction and other factors, and gentle slope is suitable. The longitudinal slope of the tunnel should usually be not less than 0.3% and not more than 3%. If the tunnel is excavated from two opposite openings, a herringbone slope can be adopted for the convenience of construction drainage. When passing in one direction, setting a downward single slope is beneficial to ventilation.
The space surrounded by the inner contour of tunnel lining is called tunnel clearance. Tunnel clearance includes building clearance, ventilation and other required road cross-sectional areas. Building clearance refers to the clearance that no building such as tunnel lining can invade. The building clearance of highway tunnel includes the width of driveway, shoulder, side strip and sidewalk, and the clear height of driveway and sidewalk. Cross-section clearance of highway tunnel includes not only building clearance, but also the space needed to pass through auxiliary equipment such as pipeline, lighting, disaster prevention, monitoring and operation management, as well as the allowance and construction allowable error.
The shape of tunnel clearance section is the inner contour shape of lining. The determined shape should make the lining stress reasonable and the surrounding rock stable. The lining shape can be arc arch and straight wall. The circular section is beneficial to pressure bearing and shield construction. Shallow-buried and deep-buried highway tunnels mostly adopt rectangular or nearly elliptical sections. The main cross-sectional shapes of highway tunnels are shown in the following figure.