China is a country with a vast territory ,a country with mountains that occupy more than two thirds of the territory,with plateaus rising and falling,rivers spreading in length and breadth,and with complicated geology.A great number of tunnels including long and extra long ones are required to build to develop the railway construction,consequently the task of railway tunnel construction is rather formidable and complicated.

　Tunneling technology is a comprehensive one which includes many specialties and also a technology of crisscross character.More than a century,the development of railway tunneling technology in China can be in general divided into three stages:

　1) Before the founding of the People's Republic of China(1988~1949).

　This was a stage during which the technique was backward,characterized by the manpower excavation,hand working and with simple equipment.There were not a fixed professional technical team and perfect specifications for design and construction .There were few machines and equipment,the working process being simple,workers working with high intensity and low efficiency.There were only three tunnels longer than 3km among the accomplished.

　2) Form the fifties to the seventies.

　This was a period during which railway developed quickly,tunnel construction process transformed from handicraft to small and medium mechanized .This was a stage during which the technology of tunnel design and construction developed considerably.

　Since the fifties the Ministry of Railway paid special attention to the organization of the professional troops for tunnel construction,worked out step by step the specifications for surveying and design as well as for construction of railway tunnels and the standard of tunnel structure clearance,and compiled a serious of standard design drawings of tunnel structures.Formulated the regulations for plane control surveying,putting forward the formulae of the errors of piercing was initially set up .Acesss adits,parallel adits,inclined shafts and shafts were adlpted in construction,the eepest shaft was 136m in depth.Belgium method with top and bottom headings was mainly adopted for excavation .Gallery ventilatioin was used in construction by means of parallel adits.Since 1957 mucking was carried out by using shovel loaders,battery locomotives and track haulage,Waterproofing was conducted by gtouting cement mortar..Restricted by the technical conditions and the time of construction ,in the fifties there were only two tunnels longer than 3km constructed: Duanjialing tunnel(twin tunnels )on north Tongpu line and Liangfengya tunnel on Chuanqian line.

　From the sixties to the seventies ,both the means of surveying and design and the method of construction organization were improved through practice and researches,more machinery and equipment were used in construction .Beginning from the construction of southwest railways with Cheng-Kun line as the representative ,a series of equipment were bought for surveying and design as well as for construction .Remote sensing and engineering geophysical exploration techniques were applied step by step.Route design and site investigation were carried out according to the requirements jof tunnel construction.To control plane surveying applied closed traverse and triangulation with one base line,Upward excavation from bottom drift was the most popular metho

　Adopted in construction with part of the works performed by full-face excavation .Smooth blasting was tentatively applied.Experience was gtadully accumulated in the respect of karst,rock burst,collapse, water outburst and gas outburst treatment.Railway construction technology promoted quickly with long mountain railway tunnels increased obviously .In the sixties there were 20 tunnels longer than 3km constructed and in the seventies there were 33 tunnels longer than 3km constructed,and in each period there were 5 tunnels longer than 5km constructed.

　Since the fifties the Ministry of Railway paid special attention to the organization of the professional troops for tunnel construction,worked out step by step the specifications for surveying and design as well as for construction of railway tunnels and the standard of tunnel structure clearance,and compiled a serious of standard design drawings of tunnel structures.Formulated the regulations for plane control surveying,putting forward the formulae of the errors of piercing was initially set up .Acesss adits,parallel adits,inclined shafts and shafts were adlpted in construction,the eepest shaft was 136m in depth.Belgium method with top and bottom headings was mainly adopted for excavation .Gallery ventilatioin was used in construction by means of parallel adits.Since 1957 mucking was carried out by using shovel loaders,battery locomotives and track haulage,Waterproofing was conducted by gtouting cement mortar..Restricted by the technical conditions and the time of construction ,in the fifties there were only two tunnels longer than 3km constructed: Duanjialing tunnel(twin tunnels )on north Tongpu line and Liangfengya tunnel on Chuanqian line.

　From the sixties to the seventies ,both the means of surveying and design and the method of construction organization were improved through practice and researches,more machinery and equipment were used in construction .Beginning from the construction of southwest railways with Cheng-Kun line as the representative ,a series of equipment were bought for surveying and design as well as for construction .Remote sensing and engineering geophysical exploration techniques were applied step by step.Route design and site investigation were carried out according to the requirements jof tunnel construction.To control plane surveying applied closed traverse and triangulation with one base line,Upward excavation from bottom drift was the most popular metho

　Adopted in construction with part of the works performed by full-face excavation .Smooth blasting was tentatively applied.Experience was gtadully accumulated in the respect of karst,rock burst,collapse, water outburst and gas outburst treatment.Railway construction technology promoted quickly with long mountain railway tunnels increased obviously .In the sixties there were 20 tunnels longer than 3km constructed and in the seventies there were 33 tunnels longer than 3km constructed,and in each period there were 5 tunnels longer than 5km constructed.

　3) Since the eighties

　Railways greatly developed with big amount of long tunnels constructed Tunneling technique developed from the traditional mining method to a series of new techniques with relevant equipment under the guidance of the principles of NATM.This was a stage for China to catch up the world's advanced level of
technique .Utilizing long tunnels can lower the height for crossing the mountain ridges thereupon to avoid the application of a group of short tunnels,improve the condition of the railway line,eliminate hazards and guarantee the safe operation.A large amount of advanced.

　Techniques and equipment were introduced from abroad to suit for the requirements of the projects of extra long tunnels and enabled the fast progress in railway tunneling technology. In the eighties, with the of Dayaoshan tunnel on Heng-Guang double track railway line as a representative, difficult problems were solved for the design and construction of extra long double track tunnels, and also for the proper equipment allocation with necessary accessories. Success of the full face construction of a large section tunnel under the guidance of the principles of NATM was a new breakthrough in the history of tunneling in China, indicating that the technology and equipment for a double track tunnel construction ranked among the world's most advanced. In the eighties there were 10 long tunnels longer than 3km constructed, eight of them were double tracked, two of them were longer than 8km.Dayaoshan tunnel (14.29km) on Heng-Guang dou-ble track line is the first extra long tunnel over 10km with an overburden of about 910m,and the longest double track tunnel ever constructed in China.

　In the nineties, in the process of strengthening the construction of big passages in the west rail-way net, it was shown from engineering practice that two single track tunnels were superior to one double track tunnel in the respect of capital investment, hazard protection and operation. As a result, single track long tunnels increased continuously. In accordance with the backward techniques adopted for single track railway tunnels ,in the nineties the Ministry of Railways set up a key project to study the complex techniques and equipment for the rapid excavation of long single track railway tunnels under the guidance of the fully mechanized construction of long double track tunnels. Results of the study were applied to the project of Mihualing tunnel, bringing forth the best record in the country with 769m completed tunnel in two directions in one month and a maximum monthly progress of 515.9m completed tunnel in one direction. Later on tunnel boring ma-chine (TBM) was adopted in the excavation of Qinling line I tunnel, indicating that the tunneling technology of our country in the construction of single track long railway tunnels also ranked among the world's most advanced. At the same time, obvious results were obtained in the application of advanced techniques to long tunnels, these were: geophysical exploration, advance geo-logic prediction, global position system (GPS), etc. In consequence, railway tunneling technique stepped upward a new step. In the nineties there were 79 tunnels longer than 3km completed, 67 among them were single track tunnels, with two extra long tunnels longer than 10km.Qinling line I tunnel (18.46km long with a maximum overburden 1600m) on Xi-Kan line is the longest single track tunnel, Changliangshan tunnel (12.78km) on Su-Huang line is the second longest double track tunnel in our country. The successful completion of railway long tunnels indicated the new level of the railway tunnel construction in our country, reflecting the progress in modern tunneling technology.

　Distribution of railway tunnels in China is as follows: in the southwest and northwest, about 70%;in the north and northeast, about 25%;in the east and middle south,about5%.Railways (longer than 200km) with high density of tunnels are: XiKang line, the percentage of total tunnel length to total line length being 45.9%,the first among all railways; Xiangyu line,33.4%,the second; Chng-Kun line,31.5%,the thinrd. The percentages for lines Hon-Yue, Feng-Sha, Jing-Yuan, Nan-Kun, Zhi-Liu are more than 20%.