(Pdf) an analytical method for groundwater inflow into a drained circular tunnel gas x extra strength vs ultra strength


The impoundment of the Rudbar dam raised underground water level. On the right bank, the elevation of the water table is monitored in exploratory boreholes. The water table has remained below the level of the reservoir. The lower level of the water table is due to underground tunnels and galleries that behave as drains. Special analytic developments have been carried out to analyze the behavior of the water table during impoundment. The peculiarity of the model is that it considers a draining tunnel in an open aquifer gas finder with a free water table. Two new equations are obtained: one for inflow of water and the other for the water table drawdown. These equations are used to assess the water table elevation in the exploratory boreholes, calculate the hydraulic conductivity of the rock mass from the measured seepage in the conveyance tunnel, and determine the efficiency of the sealing from the measured back pressure on the extrados of the drainage gallery. The comparison of the calculated hydraulic conductivity with the available information from measurements with packer tests and DFN predictions will reveal the importance of scale effects and uncertainties.

An analytical method has been proposed to estimate the leakage from a water-filling tunnel between two reservoirs, based on Darcy’s law and the position of the water table, for a phreatic aquifer. The variable water-fill level in the tunnel and an arbitrary intersection angle between the tunnel and horizontal plane were considered. The reliability of this method was validated by numerical analysis and the measured leakage during two water-filling tests in the Heimifeng Pumped Storage Power Station in China. The calculated leakage can represent both the measured value and numerical result due to the small differences between them. Also gas tax, the effect of some parameters on the leakage was analysed. Results indicated that leakage increased with decreasing intersection angle, the increase of hydraulic conductivity of the reinforced concrete lining, and the increase of water-fill level in the tunnel. Other parameters exerted little effect on the leakage. Furthermore, the total leakage was estimated under the simultaneous running of two tunnels. When one tunnel was running, the other tunnel was emptying. The calculated leakage was 4.48–8.85 L/s for both tunnels running, which was about 0.5 L/s less than that with one tunnel running and other tunnel emptying. This revealed that the running tunnel had little effect on the leakage from the other (emptying) tunnel.

The external water pressure is the key factor for lining structural safety in construction, operation and maintenance condition. The traditional method electricity generation capacity for external water pressure estimation is with empirical formula. However, the effects of geology, boundary, excavation and lining construction aren’t adequately taken into account; and the solution results have risks and uncertainties. This paper reviews the general methods for external water pressure estimation, such as discount coefficient method, theoretically analytical method and numerical analysis method. The numerical results compared with the analytical results under different permeability environment and lining support forms illustrate the viability of the numerical analysis method. The numerical model scope is discussed to reduce the calculation error. The evolution process of seepage field is captured along with the tunnel excavation and lining supporting. The results show gas mask art that the external water pressure on lining increases with the increase of permeability of surrounding rock and the lining thickness. The distance from the tunnel center to the boundary should not be less than 30 times tunnel diameter. Considering the transient effect, the tunnel seepage field tends to be stable within 10 days after the excavation; the water pressure distribution tends to be stable within 20 days after the lining supporting.

In this paper, a new practical technical approach for the evaluation of hydraulic conductivity and tunnel water inflow in complex fractured rock masses is presented. This study was performed in order to evaluate water flow into tunnels planned along the new highway project from Firenze Nord gate to Barberino di Mugello (Tuscany). The results are based on detailed and comprehensive geostructural characterization of rock masses, by means of field surveys, geological and hydrogeological studies.Starting from discontinuities properties surveyed in the field, the permeability K tensor was calculated using the Kiraly equation, integrated with the introduction of the effective hydraulic opening of fissures (e). Principal directions of tensor K were calculated for each geostructural survey station using an automated software script especially developed for this purpose.Available K data from Lugeon tests were also collected and analyzed with results that do not fully represent the electricity video ks1 rock mass due to its structural (hydraulic) variability.In order to evaluate water flow into tunnels planned for excavation under the water table (for a total number of eight), a finite elements seepage analysis was performed on 38 representative geological sections transverse to tunnel paths (α-planes). Each section referred to the nearest and geologically most compatible geostructural station.Principal directions of K tensors were projected on the α-planes by means of trigonometric transformations.Unitary water inflows were then evaluated for long-term steady-state, as well as for initial state immediately after tunnel excavation. Inflow values calculated gas exchange in the lungs occurs in the for each unitary section were extended to geologically homogeneous lengths of the tunnel, according to the variability of the water head above excavation, and then summed up for the whole length of each tunnel. Inflow values obtained with FE seepage analysis were also compared to other inflow evaluation methods.

The evolution equation of a drained aquifer during the consolidation process when time is transformed into the Laplace variable is the modified Helmholtz equation. The governing equation of the steady state of a heterogeneous aquifer which hydraulic conductivity when plotted against depth in a semi-log graph has a constant slope is also the modified Helmhotlz equation. The same equation comes out when the slopes of the hydraulic conductivity plotted against depth and against the hydraulic potential in a semi-log graph are constants. The modified Helmholtz equation will be solved exactly considering a semi-infinite aquifer drained by a circular tunnel. A unique state function, which according to the case considered has different interpretations, is obtained in closed form as an infinite sum involving modified Bessel functions. The amount of water that flows into the tunnel contrarily to the state function may change from case to case and will be calculated exactly and in closed form for the different cited cases. The analytic solution has a wide range of application, is valid for different cases, and within every case needs being adapted to the particular problem to be solved. An illustrative application will show an adaptation of the solution to rock masses when the hydraulic conductivity plotted against the effective stress in a semi-log graph has a constant slope. This will allow estimating the relative precision of approximated formulae for the electricity and circuits class 6 pdf water inflow in fissured rock masses such as the Zhang and Franklin equation and the first order approximation.

The steady gravity flow that is generated by a circular tunnel disturbing the hydrostatic state of a semi-infinite, homogeneous and isotropic aquifer is solved exactly. Many aspects of the flow are found in closed analytical forms such as the water inflow, pressure, leakage and recharging infiltration, which give a complete view of the aquifer in the drained steady state. It is found that the maximum value of the recharging infiltration does not exceed the hydraulic conductivity allowing stating a criteria for recharge intervention to ensure the stability of the aquifer. In addition to the main results, two aspects of the water inflow are treated. These are the necessary modifications that are to be considered in the case of an inclined water table and in the case of a lined tunnel that develops a constant internal pressure. It is also found that under an inclined water table a tunnel may cease to drain on its complete circumferential edge and a limiting condition is stated. Furthermore, the Muskat–Goodman and other water inflow predictions are compared to the gas efficient cars 2012 exact gravity water inflow.

To predict site of probable mountain slope failure by evaluating three-dimensional influences of mountain slopes, infiltrated … [Show full abstract] water levels obtained by the model are applied to the multi-planar sliding surface method which was proposed elsewhere. The results show that sites of the most dangerous sliding mass almost appeared at the same gas key staking tool sites where failures occurred in the past time.

Another predicting method, moreover, is proposed in the present study by using a digital land form model which was also proposed to calculate F values. Infiltrated water levels at each cell are applied to the infinite slope stability analysis method. Potential failure areas are mapped and are classified into various dangerous degrees by the time when the safety factor becomes less than unity under the assumptions that the depth of the surface layer is 1.2m and rainfall, 20mm/hr, continues 50 hours. More hazardous cells are found to appear at the sites where mountain slope failures took place in the past time. Read more