Construction Of Hydraulic Tunnels Research Articles

Evaluation of the collapsible deformation of surrounding rock of loess hydraulic tunnel considering ground stress variation

BackgroundUneven settlement will occur as a result of the collapsible deformation of the loess strata, and the hydraulic tunnel lining structure will also fail. In this work, laterally confined compression tests were carried out on loess and the double-line method was employed to evaluate the loess collapsibility. The deformation of the surrounding rock of a loess hydraulic tunnel under various ground stresses and its effect on the lining structure was modeled.ResultsThree stages were noted in the collapsible deformation of loess. The critical point between the former two stages corresponds to the pre-consolidation pressure of saturated loess and that between the latter two is taken as the structural yield pressure of unsaturated loess.ConclusionFrom the relationship between the collapsibility coefficient and vertical stress, the deformation of the tunnel under ground seepage primarily originates from two sources, i.e., the collapsible and compressive deformation. The latter source accounts for the deformation of loess adjacent to the lining when the seepage depth is low, while both sources are included when the bottom of the tunnel invert is infiltrated. The collapsible deformation is lower than that of the original stratum due to the stress relaxation during tunnel excavation. The tensile and compressive stresses of tunnel lining increase linearly with the seepage depth, with the maximum appearing at a position of 20 m away from the midline of the collapse and non-collapse domains. The results will provide a theoretical reference to the design and construction of hydraulic tunnels in collapsible loess stratum.

Analysis of Characteristics of Plastic Zone and Mechanical Properties of Anchor Structure in Hydraulic Tunnels with High Ground Temperature

In order to explore the characteristics of plastic zone and the mechanical properties of anchor structure during the construction of hydraulic tunnels with high ground temperature, the high-temperature section of the diversion tunnel of a hydropower station in Xinjiang was studied. Based on the temperature data and the axial force data of the bolt on-site, the Drucker-Prager constitutive model and the finite element method were adopted to simulate and analyze the temperature-stress coupled field and the initial anchoring support during the construction of the high ground temperature tunnels. The results showed that, after the excavation of the tunnel, a crescent-shaped plastic zone first appeared at the hance, then expanded to the spandrel and vault, and finally formed an irregular ring-shaped plastic zone around the tunnel. The higher the initial temperature of surrounding rocks, the larger the plastic deformation and the range of the plastic zone. When the temperature exceeded 80∘∘C, the plastic zone was more likely to expand to the spandrel and vault; and meanwhile, when the bolt was closer to the hance, the neutral point was closer to the cavity wall. As the stress was released, the neutral point moved from close to the cavity wall to away from the cavity wall. Anchoring support can effectively limit the development of plastic zone in surrounding rocks under high ground temperature. After 10 days of anchoring support at 60∘∘C, 80∘∘C, and 100∘∘C, the range of the plastic zone decreased by 9%, 20%, 24%, respectively, and the maximum axial force of a single bolt was 19.4 kN, 20.1 kN, and 23.8 kN, respectively. The higher the temperature, the higher the strength of the bolt.

Means of intensifying construction of hydraulic tunnels

1. Conversion to the mechanized method of driving extended tunnels (L>4 km), which limit the placement of the underground project into service under rather well understood and favorable geologic-engineering circumstances along the route of the tunnel (stable rock and rocky soils easily worked by cutters) that eliminate unforeseen situations, is expedient and economically effective. 2. Solution of organizational problems, and a clear-cut definition of the interaction between suppliers, producer, and customer will contribute largely to radical acceleration of the rate of construction of extended underground structures.

Gas shows during construction of hydraulic tunnels

1. The given examples indicate that when driving tunnels in the Caucasus regions builder as a rule, come across in one form or another gas releases, mainly methane and carbon dioxide. 2. The presence of gas-containing or gas-conducting rocks along routes of tunnels has a considerable effect on construction time and cost and also requires the introduction of special safety measures and often the conversion of the working to a gas regime. 3. When driving tunnels it is necessary to carry out thorough engineering-geological documentation. Upon a change in the mining-geological conditions compared with the design conditions it is necessary to revise the issued forecasts on possible gas shows and accordingly to introduce corrections and methods of tunneling, supporting the workings, and checking the state of the underground atmosphere.

USSR experience in construction of hydraulic tunnels : Mostkov, V M Proc International Tunnel Symposium, Tokyo, 1978, P81–88. Publ Oxford: Pergamon Press, 1979

USSR experience in construction of hydraulic tunnels : Mostkov, V M Proc International Tunnel Symposium, Tokyo, 1978, P81–88. Publ Oxford: Pergamon Press, 1979

Using the artificial ground freezing technique in the construction of hydraulic tunnels : Trupak, NG In Russian. 2F. Gidrotekhn. Stroit. N4, 1973, P45–48.

Using the artificial ground freezing technique in the construction of hydraulic tunnels : Trupak, NG In Russian. 2F. Gidrotekhn. Stroit. N4, 1973, P45–48.

Expanding concrete for the construction of hydraulic tunnels

Expanding concrete for the construction of hydraulic tunnels

A method for formulating a rational technique and construction organization for hydraulic tunnels

1. A scientific formulation of the work-cycle parameters in underground hydraulic construction has great economic significance, especially in connection with the changeover to a new system of planning and economic simulation. 2. For solving this problem a method has been developed and adopted for studying the basic work-cycle processes in the construction of small-size hydraulic tunnels by using various technical measures. Qualitative and quantitative characteristics are established for determining the interrelationship between the various construction factors under definite tunnelling conditions. 3. The principles suggested for formulating the rational technique and construction organization for hydraulic tunnels envisage the consideration of many factors and point to the advisability of developing economic-mathematical models for describing the basic cycle processes with a view to solving them by computer methods. The authors have formulated a work-volume algorithm for solving the cycle processes, according to which engineer-programmers of the Computer Laboratory of the Erevan Polytechnic Institute, with the participation of the authors, developed programs for a “Razdan-2” Computer. 4. The suggested mathematical models (within the investigated range) can be used for optimizing the basic work-cycle parameters for the construction of hydraulic tunnels of 8–20m2 cross-sectional area in medium-hard to hard materials.

Conference on Organizational Improvements for Construction of Hydraulic Tunnels in Armenia

A science-engineering conference on construction improvements of Armenia's hydraulic tunnels took place at the end of 1968 in the City of Erevan'. The conference was called by the Administration Board of the PowerConstruction Section of the Science and Engineering Society of the Power and Electrical Engineering Industry in conjunction with the Armenian Hydro-Power Construction Division of the Ministry of Power and Electrification of the USSR. Approximately 90 experts, representing 22 construction, design, operational and scientific-research organizat ions,part ic ipated in the conference, such as Armenia's Hydro-Power Construction (Armgidroenergostroi'), Armenia Central Power Department (Armglavdnergo), S. Ya. Zhuk Institute of Hydro-Power Design including its Armenia and Tiflls branches, Bureau for Construction of Power Stations (Org4nergostroi'), the Moscow Central Scientific-Research Institute for Excavation Equipment (Tsniipodzemmash). State Institute for Industrial Coal Mining Equipment (Giprouglegormash, City of Karaganda), the [3. E. Vedeneev All-Union Scientific-Research Institute for Hydro-Engineering, Leningrad (VNIIG) as well as the Office of State Construction of the Armenian Soviet Socialist Republic, and the Erevan' Karl Marx Politechnical Institute, and others.