优秀英国毕业dissertation节选——英国建筑专业《有关地下建筑结构的浅论》
优秀英国毕业dissertation节选——英国建筑专业《有关地下建筑结构的浅论》
Underground structure
Construction of rock or soil in the construction. It is a modern city of high-speed product development, the city will again ease the contradictions of the role to improve the living environment, but also opened up new human life. Rational development and utilization of human natural and artificial excavation of the underground space, not only help to ease the development of modern urban contradictions, to improve the living environment, but also to open up a new human life. Because of the large-scale development of underground construction, underground architecture is taking shape, its research includes the history of development of underground construction and development of underground space development and utilization of underground space in urban planning, various types of underground construction planning and design, as well as underground construction and related environmental, physiological, psychological and technical issues.
Underground construction has a good protective performance, better thermal stability and confined, as well as an integrated economic, social and environmental benefits. Underground construction in a certain thickness of rock or soil, you can avoid or reduce nuclear weapons, conventional weapons, chemical and biological weapons of destruction, while at the same time more effectively to resist earthquakes, hurricanes and other natural disasters. Underground construction in and around the confined environment of relatively stable existence of the temperature field, temperature, or for creating ultra-clean manufacturing environment and at low temperatures or under high-temperature storage of materials, pollution prevention, especially for energy conservation as well. In the city planned the construction of underground construction, urban land use for savings, lower building density, to improve urban transportation, the expansion of green space, reduce urban pollution and improve the quality of urban life, etc., can play an important role. Underground construction also has shortcomings, such as construction costs are high, the construction complicated.
A Brief History of the development of underground ancient times, humans have been anti-years use of natural caves, and shelter to escape the beast. Zhoukoudian in China found that more than 50 million years ago, Peking Man lived in caves in the natural. According to Yangshao Culture and Longshan Culture found in archaeological sites, to prove that since 7000 ~ 5000 years ago, began living dug caves, from the simple bag-shaped to round or square semi-crypt, above the roof of a simple. Later, the beginning of the construction of housing on the ground, cave gradually ceased to be the main mode of living human beings. However, the ancient tombs on the ground in accordance with the construction method in underground construction. Some grain is also built in the ground, such as the Sui Dynasty in Luoyang warehouse containing Kerry. Northwest China, North China Loess Plateau region, as a result of excavation loess and climate-friendly dry cave tradition continues to this day. Estimated that there are still more than 35 million population live in the cave.#p#分页标题#e#
After the industrial revolution, as a result of mining and the development of transport, mines, roadways, highways, tunnels, railway tunnels have been built. London, England in 1863 into a city of the world's first underground railway. During World War II, the protection of underground construction in the superiority of attention, some veterans of the important military installations and arms factories, warehouses, etc., built in the ground, and the construction of the air-raid shelter for the residents. Since the late 50s, as a result of economic development and scientific and technological progress, the rapid increase in urban population, the increasingly serious environmental pollution, energy crisis and the existence of the danger of war and other factors, underground construction in Japan, the United States, Sweden, the Federal Republic of Germany , France, Switzerland, Norway, Canada, China, the Soviet Union and many other countries, with high speed and large-scale development. Due to geographical, social development, economic development and strategic direction of the differences in thinking, the development of underground construction and the starting point to solve the different conflicts. At present, the world has more than 80 cities in the construction of an underground railway, as well as many cities are under construction. China, the Soviet Union, Switzerland, Sweden, Finland and other countries from the combat readiness requirements of the construction of a large number of underground civil air defense projects, some in peacetime for the use of various types of public buildings. Japan, the Federal Republic of Germany and France, land of smaller, highly concentrated in big cities, city highlights various contradictions, so the construction of the ground floor of a large number of high-speed transportation network and the Mass Transit Street, the underground commercial center. The United States from the mid-70s to the ground floor of the building as energy-saving measures, the development of a semi-underground soil building, with the exception of the need to stay out of the plane, Chaoyang, housing all the other parts of the soil with a certain thickness of buried or covered combined with the use of solar energy to obtain more than 50% of energy-saving effect. Lack of national energy use of a large number of underground storage of energy as a strategic reserve, such as Sweden, Finland and other countries blocked the construction of the groundwater oil (or gas) are a large-scale database, a single storage capacity has more than one million cubic meters. Sweden, Norway, Italy and other countries rich in water resources, many built in the ground station to increase the water gap. Canada's cold climate, so in large cities, the development of underground commercial center of the city of Montreal has a few underground commercial center even as a construction area of 810,000 square meters, forming an underground city. In addition, industrialized countries also paid attention to the protection of underground construction to play the traditional style of the city to improve the urban environment, urban space, etc. to expand the positive role played by. For example, the city of Nagoya, Japan in conjunction with urban roads alteration, in the ground layout of the commercial street and parking lot, stay out of the ground in addition to the necessary pedestrians, carriageway, in the central part of the park into a large-scale city center. Other factors, such as Tokyo, Osaka and other places are also provided with the underground business street. Another example is the University of the United States a number of historical buildings and structures in order to preserve the unity of style and ease tension in the land, the construction of a number of underground construction, such as library, gymnasium, teaching Museum (Figure 2), achieving good results. These facts reflect the tiefbau increasingly wide range of applications.#p#分页标题#e#
Underground construction of the type of underground construction can be classified according to the functions of military, civil, air works, industry, transport and communications, storage and other buildings, and underground utilities. For example: in the construction of military fortifications can be used for shooting, observation of construction, shelter construction, etc.), in civil construction, including residential buildings, public buildings, a variety of civil air defense engineering, industrial construction, transportation and communication construction, warehouse construction, as well as the types of underground utilities, such as underground water plant, solid or liquid waste treatment plant, pipeline and other corridors. Several features of both large-scale underground construction known as the underground complex. Tiefbau classified according to construction method, there are two types of open excavation and mining. Open excavation completely backfilled after construction, the above did not build any buildings, known as single-built underground construction; above to build other buildings, known as the attached underground construction. Open excavation backfill the latter part of the construction, soil or bulldozers, and as bulldozers building construction or soil. Underground mining construction, usually in the deeper layers of rock or digging into the required space for more than a certain thickness at the top of the natural cover. In addition, China also has a habit of classification methods, into the underground tunnel type, tunnel-type (usually mining), opening ceremony (equivalent to a single open excavation built) and the basement air (that is attached open excavation) . Road tunnel and the main difference is that the relationship between inside and outside the ground elevation, internal than external, as the tunnel, which is lower than the outside as the authentic.
Underground construction of the design requirements for the underground architectural design requirements: ① choose engineering geological and hydrogeological conditions of a good place. Underground construction of the planning and design, must be complete and accurate information based on Geological Survey, full use of the favorable geological conditions, to avoid unfavorable factors. Arrangement in the soil in the ground floor of buildings, should be chosen with a certain capacity, and relatively uniform thick soil layer, avoiding the backfill layer, layer of mud, sand and other streaming sites; in the rock should be chosen homogeneous lithology, structure simple, thick stone rock hard to avoid the fault fracture zone, seismic zone and instability, such as the slope. In the plain areas, should pay attention to changes in groundwater level and its direct impact on the burial depth of underground construction, construction measures and construction methods; in the mountains, rock fissures should be based on the volume of water and gushing location, organization of the underground drainage system construction and attention to surface water flow and the excretion of mountain torrents. ② to ensure the necessary protection. Although the underground construction itself with varying degrees of protection against all kinds of weapons, but the air defense of the military construction and engineering, but also the protection levels in accordance with the provisions of the various effects of different weapons, to conduct a comprehensive protection of the design, layout of the various protection facilities, building structures and protection facilities, as well as a variety of holes, I have the appropriate protection, we should focus on building entrances and exits to ensure the security of the site. ③ the creation of an appropriate internal environment. Underground space in the internal environment, including air temperature, humidity, cleanliness, noise intensity, the illumination lights, interior colors and so on. Appropriate depends mainly on improving the quality of air in the ventilation design to ensure; sound insulation and sound absorption of the appropriate use of measures to control the noise level allowed. Building to deal with such as a complete portfolio of interior space and changes in the unity of the material texture and contrast the rich interior colors and harmonization, have helped to create a good internal environment, the elimination of the underground environment on people's poor physical and psychological effects. ④ for structural design and construction to create favorable conditions. Underground construction of the main features of the structural design is a big load, so in the architectural design, from layout, column network options to determine the areas of story should be for the structural design of the economy, create conditions reasonable. The construction of underground construction is rather complicated, the design should be to simplify the construction and shorten the duration and the use of advanced construction technology to create favorable conditions and minimize the ground during the construction period of the normal activities such as transportation and so on.#p#分页标题#e#
As the underground construction of the building structure is different from the specificity of the upper part, involving the design, construction technology, environment and soil mechanics, such as technical progress in a series of problems in engineering applications engineers often encounter the following problems:
(1) of the underground structures of conventional reinforced concrete structures are mainly ordinary reinforced concrete structural system used in the existence of large-scale underground structure of the high cost, even cross-section structure, and the impact of depth of underground structures, construction progressing at a slow pace, as well as the shortcomings of a waste of construction materials, should the new system, the introduction of construction materials and structural design of underground structures to meet the modern requirements of the development of underground space, with limited resources for better results.
(2) as the cause of urban rail transit development, urban towel existing and new buildings and subway lines crisscrossing the upper part of structure is at the top of the subway tunnel, the conventional reinforced concrete structure of care for the larger cross-section of the underground architectural space also have a greater impact. Workers should be the actual situation in innovative technology, choose a reasonable form of structural transformation of the construction and related measures to ensure that the subway project and the safety of the upper structure and to minimize the impact of the underground space.
(3) as an urban development strategy of three-dimensional one, high-rise buildings will continue to challenge the next new height, and construction will continue to increase in the floor, vertical wall structure is not posit the lower part of the greater cross-section, located in Building the lower part of the basement of the building material the use of space caused by an enormous impact; another - aspects of underground construction is the future direction of space, large-span, the vertical component will be an inevitable increase in cross-section. Therefore, the vertical cross-section configuration to optimize materials and even to improve the underground construction of the space is designed to be taken into account.
(4) as a result of large-scale development of underground space and underground construction and use of the water requirements of more demanding, long, extra-wide development of the underground construction joints or less, regardless of the trend is sub-slit, regardless of current underground construction joints maximum length of over 800m, long and spacious underground construction specification requirements higher than the conventional approach has solved the structure of super-long concrete shrinkage, temperature, deformation and so on, the ground floor of building large-scale crack the case more and more. On the other hand, in order to prevent occurrence of cracks to increase the floor, roof and side wall of the reinforcement, so that the sharp increase in the basement of steel, it is therefore necessary to seal a device able to reduce power consumption Ultra - contraction of a long side wall and bottom of the internal force and deformation temperature, effectively improve the problem of cracking of underground construction. #p#分页标题#e#
(5) as a result of underground construction in the fire reached the bottom of the lift requirements for the high-level and ultra-high-rise building, fire pit at the end of the lift is often deeper than 2m, the largest reach 3m. Conventional reinforced concrete pile cap by inch: the requirements of anti-punching greater thickness, and then caused by the lift at the end of the partial concave pits and the requirement of the cap to meet the bending, shear, anti-punching conditions, go on local concave The site needs to be integrated with the cap around the basically the same thickness, such as the 3.0m-thick cap, in the partial concave 3.0, the caps into a partial thickness of 6m, the amount of concrete and reinforced caused a significant increase, while the base pit at the bottom of the second excavation deeper than 5m, the safety of the Foundation have been affected.
Modern underground structure calculation and analysis of three major aspects: 1) the overall structure of underground construction, including both ground-level structures with basement soil - guitar and pure combination of overall analysis of the soil underground construction - combined with the overall analysis of colorectal; 2 ) underground construction structure steel - concrete composite structure components of the calculation of portfolio analysis; 3) against the practice of underground structure calculation and analysis of the simulation. No matter how kind of an underground structure, the system solve the overall analysis, component analysis and dug up the ground floor of the structure of the three aspects of the problem of the real simulation of underground structures of the structural optimization of a certain significance. Calculation methods and design come to the Conclusion, it can be used as the structural design of underground structures of reference.
Most of the use of underground reinforced concrete structures or steel reinforced concrete structure, the current design specifications related to the probability theory are based on limit state design method, the reliability of indicators to measure the reliability of structural components using the design of sub-expressions coefficient design. Limit state can be divided into the carrying capacity limit state and serviceability limit state, for the carrying capacity limit state should be met:
Cracks in the ground floor of building structures to deal with prevention and treatment.
Analysis:
(1) Design factors: emphasis on the general design of underground construction works vertical wall panels of the reinforced structure and intensity, the level of neglect of horizontal reinforcement cracking strength. Cross-section of the wall structure due to the particle stress is non-uniform shrinkage stress and thermal stress of concrete efforts to achieve the ultimate tensile strength, caused by the plastic deformation and fracture;
(2) improper selection of materials, such as contraction of cement, and stone size distribution of the poor, with a large quantity of mud; the diameter of fine sand; doped admixtures, such as poor quality. As a result of commodity high-strength grade concrete, cement, and water consumption, and hydration heat caused by high temperature, when the environmental temperature significantly decreased the role of the temperature difference, the new casting of the linear expansion coefficient of concrete! c = 10 × 10-6 / ℃, when the contraction in the cooling caused by tensile stress increases. Concrete wall surface area larger than the shrinkage stress generated internally binding, the formation of shrinkage, shrinkage, temperature difference between the integrated stress, ultimate tensile strength greater than concrete and cracks; #p#分页标题#e#
(3) The regulations: First, the summer heat without cooling measures construction: concrete mixture into the mold temperature is higher than 35 ℃, when the temperature dropped at night when the temperature both inside and outside the large and prone to fracture; Second, in winter there is no low-temperature thermal insulation during the construction of measures , that is, when the goods after the concrete into the mold, cement hydration heat and the environment significantly increased the temperature at 0 ℃ about, then the outer panel of contraction at low temperatures, resulting in cracks. Third, improper pouring methods, such as pumping to take concrete pouring is not hierarchical, but pouring from one part of the maximum, and then the mobile shop and then pouring a section of pipe; Concrete is a mixture of vertical joints, and pouring speed, vibration trace and uneven, resulting in the concrete wall is not homogeneous, the particle stress is not evenly, resulting in stress cracks Department. Fourth, non-standard installation of reinforced, such as uneven spacing, horizontal transfer has not been reinforced and joint relaxation banding, or the protection of strict control, resulting in a collision so that when pouring concrete reinforced skew, stress is not absorbed, prone to cracks. Especially the "underground engineering specification waterproof" GB50108-2001 of underground water surface reinforced concrete structure to protect the layer thickness is not less than 50 mm since the implementation of the mandatory requirements, long cracks in the basement of the issue of concrete structures have become more prominent.
Treatment and prevention measures:
(1) underground construction of the vertical cracks in the wall: the contraction is mainly concrete, shrinkage, shrinkage, etc. generated under stress cracks generally do not affect the carrying capacity that can be used to deal with chemical grouting method. The purpose of dealing with the gap closed to prevent leakage of water, so that cracks in bonding to restore the original function of the wall and to prevent damage to steel because of cracks and corrosion of passive film role;
(2) in the ground outside the building (that is, water surface), a comprehensive inspection of the quality of irrigation joints until cured slurry to eliminate the wall of the swelling on the skin surface, to paste the cracks Department of Polymer waterproofing membrane, a width of about 250 mm. Cracks formed along the first grinding, clean, brush the grass-roots level to deal with agents, chosen with the membrane of qualified matching binder will be a solid material paste;
(3) do a good job back to the outskirts of underground construction fill, is the underground construction of the first line of defense against water;
(4) the proposed design of the underground construction of the wall panels should be allocated by the hydration of cement can withstand the heat caused by the thermal stress, shrinkage stress, the level of crack control reinforcement, diameter of not less than Ф12, spaced not more than 150mm, joints should be the use of welding, and Cold Drawn Straightening, keep straight after installation, spacing and location of protective layer should be accurate. The addition of reinforced concrete beam and dark columns, enhancing the role of the wall cracking strength, super-long construction of "pouring after sewing" or mixed in concrete ways to UEA expansive agent is effective in reducing measures undertaken Crack. 60d of the late use of concrete strength, can reduce the amount of cement concrete; #p#分页标题#e#
(5) the quality control of raw materials, timely grasp the construction environment, in strict accordance with the construction norms of construction;
(6) the use of thin-layer approach for irrigation, to ensure that the uniform density of concrete, to take the conservation of heat storage method, in order to reduce the temperature difference between inside and outside elements, and strictly control the cooling rate of 1.5 ℃ / d, for the concrete conditions of the creation of stress relaxation, is to prevent shrinkage cracks in concrete structures, one of the main measures;
(7) Construction of the summer heat must be cooled to control the concrete into the mold temperature shall not exceed 28 ℃; the construction site should be shade measures to reduce the construction of temperature;
Winter construction with antifreeze to warm the specific measures, such as the concrete into the mold temperature above 5 ℃, the thermal component to do the work too fast to prevent thermal cracks resulting from shrinkage.
Underground construction of the development trend of increasing: ① type and scale. In recent years, some new, emerging types of underground construction. For example, with the growth of use of nuclear energy, nuclear waste handling and storage become a serious problem; in the deep strata (a few hundred meters to 1000 meters) in the construction of an underground nuclear waste repository is to solve this problem a better way to be a wide range of importance. In another example, the primary purpose of energy saving in the underground construction has developed rapidly; At the same time, underground storage of heat, cold energy, mechanical energy (water, compressed air) and other aspects of the ongoing feasibility study and test. Again, in order to improve the urban environment, the ground floor of a large-scale sewage treatment plants have been built in a small number of developed countries, the construction of urban waste disposal in the ground plant also being investigated. ② design and construction and continuously improved. The type of new construction is often higher technical requirements, so that a new process development and improvement of construction technology. For example, in order to build a database of underground nuclear waste, it is necessary to solve the deep excavation of the post-rock pressure and rock strata in the role of nuclear waste under the stress of high temperature change; order to speed up the construction schedule is necessary to design and manufacture of large-scale mining machinery; in order to reduce project cost, it is necessary to adopt the new structure, high efficiency equipment and high-strength materials. ③ multidisciplinary research. The rapid development of underground construction, so that more and more people in different ways of living in the underground environment, and therefore meet the basic requirements based on the use of underground construction continuously higher quality requirements. From medicine, physiology, psychology and other disciplines, different perspectives, many ways to improve the underground environment of the ways and measures, including some of the more complex issue. For example, the underground environment and its impact on the dose of radioactive elements has been started to conduct research. ④ from individuals to groups, from single to comprehensive development. Urban construction, to a certain stage of development, individual and scattered underground construction can not meet the various needs of urban life, is bound to gradually integrated to the groups and direction. For example, the Mass Transit Railway underground line to increase the formation of high-speed transportation network, the transfer line at different points on the formation of a relatively easy to change stations, car parks and shops, such as the underground complex, which may be expanded to become the underground mall or commercial center . Also, in order to make full use of urban underground space should be to change the city's own utility system and the status of direct-buried pipeline to make it to the layout and use of multi-function integrated pipeline corridor direction. To this end, calls for unity under the guidance of the overall urban planning, the development of urban underground space development and utilization of comprehensive planning, and the same on the ground to unify urban development planning.#p#分页标题#e#
