Outlet Slope Research Articles

Real Time Monitoring Using Robotic Total Station on the Outlet Slope of the Cisumdawu Tunnel, West Java

Slope failure is still possible even though the slope has been designed and reinforcement has been carried out, as an example the slope of the Cisumdawu Tunnel Outlet which collapsed in October 2021. Therefore, monitoring technology is needed to anticipate slope collapse. In this study, the repaired slopes of the Cisumdawu Tunnel Outlet was monitored using a Robotic Total Station (RTS) to measure surface displacement in real time. Monitoring using RTS was carried out for approximately 40 days. The purpose of this study is to determine value and characteristic of slope displacement using an empirical approach from previous researchers. The displacement starts April 23rd at night until it reaches stability on April 24th 2022. The most significant displacement occurred in the prism target 08 which is located in the foot of slope and between the twin tunnels. It has 8 mm longitudinal displacement, the transverse displacement is 0.8 mm and the height has dropped by 13 mm. Almost the rest of the prism is in a stable state. From this study, the slope movement class is found to be regressive and categorized as velocity < 15 mm/day which is no failure expected within 48 hours. From this study, it was concluded that during the monitoring period using the RTS the outlet slope of the Cisumdawu tunnel was safe

Stability Evaluation of Diversion Tunnel Portal Slopes at Lau Simeme Dam Site, Indonesia, using Limit Equilibrium Method

Construction of the Lau Simeme Dam used a tunnel as a diversion channel. Slopes at the diversion tunnel portals were prone to failure due to the tunnel excavation and earthquake. Earthquake load was not considered in the designs of the inlet and outlet portal slopes. This research evaluated stability of the tunnel portal slopes under static and earthquake loads using limit equilibrium methods of the Bishop Simplified and Morgenstern-Price. Input material properties for the slope stability analyses were obtained from evaluations of soil and rock cores, including determination of lithology type and rock mass quality based on Geology Strength Index (GSI), and laboratory testing. Evaluations of soil and rock cores indicated that the inlet portal slope consisted of residual soil, good quality tuff breccia, and good quality sandstone. The outlet portal slope consisted of residual soil, poor quality sandstone, poor quality tuff breccia, fair quality sandstone, fair quality tuff breccia, and good quality tuff breccia. The earthquake load coefficient determined by the seismic analyses based on the peak ground acceleration map for 10% probability exceedance in 50 year was 0.125 g. The slope stability analyses showed that the designed inlet and outlet portal slopes were stable under static and earthquake loads. The Bishop Simplified and Morgenstern-Price resulted in relatively similar Fs values. The Fs values of the inlet and outlet portal slopes decreased with the earthquake load application. Although Fs values of the outlet slope under static and earthquake loads met the requirements specified by SNI 8460:2017, the rock mass conditions, particularly the poor rock masses of layers 2 and 3, required special attention. Application of slope reinforcement methods, such as shotcrete, is suggested to further increase the slope stability.

Numerical Analyses of Tunnel Outlet Slope at Leuwikeris Dam, West Java, Indonesia

The excavated slope of the diversion tunnel outlet at the Leuwikeris Dam was designed based on core test data and the Circular Failure Chart (CFC) method. Stability of the excavated slope under static and seismic loads has not been verified using a different method. The objective of this research was to evaluate performance of the excavated slope under static and seismic loads using the finite element method (FEM). Stability analyses of the natural slope were also carried out to assess the improved stability of the slope after excavation. Geological mapping, examinations of drill cores and borehole logs, and laboratory tests were conducted to characterise the soils and rocks comprising the tunnel outlet slope. The rock masses were characterised using the Geological Strength Index (GSI) for the input parameters of the Generalised Hoek-Brown criterion. The slope stability analyses under static and seismic loads were performed using the finite element-based computer package RS2. The results show that the diversion tunnel construction site consists of residual soil and very poor to fair quality andesite breccia rock and tuff breccia with thin claystone intercalation. The groundwater table was located approximately 40 m below the ground surface. In general, the seismic load reduced stability of the slopes. The critical strength reduction factor (SRF) values of the natural portal slope, which had 40º inclination, were 3.6 and 1.45 under static and seimic loads, respectively. Meanwhile, the SRF values of the excavated slope, which had seven benches and 55 to 74º inclinations, were 3.83 and 1.78 under static and seismic loads, respectively. The natural and excavated slopes were considered stable under static and seismic loads and met the stability criteria specified by the National Standardization Agency (2017). The slope design increased the slope FS values by 6% and 20% under static and seismic loads, respectively.

Deformation and simulation analysis of slope at outlet of flood discharge tunnel

The monitoring data of slope deformation are collected, the dynamic change and development trend of displacement are analyzed, and the deformation laws of different elevation parts are counted. Three-dimensional numerical model of the outlet slope of spillway tunnel is established by finite element method, and excavation simulation analysis is carried out. The results show that after the slope excavation is completed, the plastic zone gradually increases, mainly in compression-shear failure, and tensile-shear failure exists on faults, slope surfaces and local rock mass. The field measured deformation data show that the horizontal cumulative displacement and vertical cumulative displacement increase slowly, both exceeding 200 mm, and the horizontal displacement is larger than the vertical displacement. The monthly dynamic changes of horizontal displacement and vertical displacement are basically fluctuating within 5 mm. Through the combination of deformation measurement and simulation, the displacement variation law of slope and the distribution characteristics of plastic zone are analyzed, which can provide guidance for on-site slope stability prediction and safety construction.

Slope stability analysis of the drainage tunnel portal in Tanju Dam, Dompu District, West Nusa Tenggara

This paper presents design results of the tunnel portal slopes at the Tanju Dam, Dompu, West Nusa Tenggara. The objective of this research was to analyse the stability of the tunnel portal slopes using circular failure chart (CFC) method, limit equilibrium method (LEM), and finite element method (FEM). Input parameters were obtained from drill core evaluations and laboratory tests. By considering the rock mass rating (RMR) values of rock masses, which are categorized as class II, at the two slopes, adjustments for the cohesion and inner friction angle values are made. The inlet slope (IL) have cohesion values of 350 kPa and 40º inner friction angle and the outlet slope (OL) have cohesion values of 400 kPa and 45º inner friction angle. The CFC method shows that the IL and OL have safety factor (FS) values of 3.5 and 3.44, respectively. The LEM shows that the IL and OL have the FS values of 3.69 and 3.65, respectively. Meanwhile, the FEM shows that the IL and OL have FS values of 4.78 and 4.79, respectively. The stability analysis results indicate that designed slopes are stable.

Deformation and Reinforcement Monitoring Analysis of Tail Water Outlet Slope in a Hydropower Station

The slope stability situation surrounding the dam site area is very important to each correlative department during constructing hydroelectric power station. So it is important to enforce the high slope rock deformation monitoring, and to process and analyze the measuring data timely. Surface displacement of different height of slope were tracked and monitored based on the field investigation of a hydroelectric power station in Jinsha river. Deformation and the static stability of high slope were analyzed by utilizing rock deformation monitoring data. Taking the left-bank tailrace outlet slope of underground power station for example, we analyzed the slope stability by numerical simulation to obtain the characteristics of deformation and failure of slope. The time and space deformation distribution regularity of rock mass were summarized, the deformation, stress and failure of the studied slope were simulated. The results intuitively show the displacement distribution characteristics and slope plastic failure.

Valley Deformation and Slope Seismic Analysis near Tail Water Outlet of a Hydropower Station

The safety and stability problems of high rock slope, such as weaken massif, fully developed geological conformations, widely unloaded or flabby rock layer, and squirming or sliding rock, are often encountered in engineering practice. So it is important to enforce the high slope rock deformation monitoring, and to process and analyze the measuring data timely. The high slope of the left-bank tailrace outlet of Wudongde hydropower station in Jinsha river is given as an example to analyze valley deformation, and to evaluate the seismic stability of high slope by utilizing rock deformation monitoring data. The field data of rock deformation of the left-bank tailrace outlet slope were collected by monitoring system, along with the field data of valley deformation. Based on monitoring data of the left-bank tailrace outlet slope deformation and valley width reduction of Wudongde hydropower station, the time and space deformation distribution regularity of rock mass were summarized. Analysis results and monitoring records reveal the general law of valley deformation, and demonstrate that excavating and other perturbations can quicken the creep deformation of rock mass, and the damage will not happen under action of earthquake.

Numerical Modeling of Hydraulic Performance of Piano Keys Overflows with Different Geometry

Abstract. In this study, the properties of hydraulic flow were done on the piano keys overflow in the various geometric models by three-dimensional mathematical model of 3D Flow. The Hydraulic properties regarded in this study are the flow rate flood coefficient . In this study, the flow was considered kind of permanent, perturbation flow and incompressible fluid. The perturbation model used in this study is . Determination of free level profile was done by the use of VOF. The boundary model conditions include input level, output level, wall and free surface flow. The results show that the mathematical model accurately is capable of modeling this type of overflow. The results also show that the the piano keys overflow has higher discharge flood coefficient in compare to corresponding staggered overflow. Investigating the ratio of input key width to the output key width show that the range of 1.25 to 1.5 has the highest rate flood coefficient. The rate of flood coefficient in overflow of piano keys is more than the overflow of rectangle staged overflow with slope cycle. Also, overally the rate of flood coefficient in the model with the only outlet slope is more than the model with inlet slope and a model combined with outlet and inlet slope. Among the various models, the rectangle staged overflow with inlet slope keys has little engative effect on the rate of flood coefficient. The results of the study indicate that using the basis makes the rate of flood coefficient increased. Using a shield wall makes the rate of flood coefficient increased. The comparison of the findings showed that the rates of flood coefficient in PKRFH model was firstly more than the rates of flood coefficient in PKRFF (crests) but by increasing Ht/p the rates of flood coefficient gets gradually closer in the two models.

Sediment production and yield from an alluvial gully in northern Queensland, Australia

ABSTRACTSediment production, transport and yield were quantified over various timescales in response to rainfall and runoff within an alluvial gully (7 · 8 ha), which erodes into dispersible sodic soils of a small floodplain catchment (33 ha) along the Mitchell River, northern Australia. Historical air photographs and recent global positioning system (GPS) surveys and LiDAR data documented linear increases in gully area and volume, indicating that sediment supply has been relatively consistent over the historic period. Daily time lapse photography of scarp retreat rates and internal erosion processes also demonstrated that erosion from rainfall and runoff consistently supplied fine washload (&lt; 63 µm) sediment in addition to coarse lags of sand bed material. Empirical measurements of suspended sediment concentrations (10 000 to &gt;100 000 mg/L) and sediment yields (89 to 363 t/ha/yr) were high for both Australian and world data. Total sediment yield estimated from empirical washload and theoretical bed material load was dominated by fine washload (&lt; 63 µm). A lack of hysteresis in suspended sediment rating curves, scarp retreat and sediment yield correlated to rainfall input, and an equilibrium channel outlet slope supported the hypothesis that partially or fully transport‐limited conditions predominated along the alluvial gully outlet channel. This is in contrast to sediment supply‐limited conditions on uneroded floodplains above gully head scarps. While empirical data presented here can support future modelling efforts to predict suspended sediment concentration and yield under the transport limiting situations, additional field data will also be needed to better quantify sediment erosion and transport rates and processes in alluvial gullies at a variety of spatial and temporal scales. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Effect Analysis of Geometric Parameters on Stainless Steel Stamping Multistage Pump by Experimental Test and Numerical Calculation

In order to improve the efficiency of stainless steel stamping multistage pump, quadratic regression orthogonal test, hydraulic design, and computational fluid dynamics (CFD) are used to analyze the effect of pump geometric parameters. Sixteen impellers are designed based on the quadratic regression orthogonal test, which have three factors including impeller outlet slope, impeller blade outlet stagger angle, and impeller blade outlet width. Through quadratic regression equation, the function relationship between efficiency values and three factors is established. The optimal combination of geometric parameters is found through the analysis of the regression equation. To further study the influence of blade thickness on the performance of multistage pump, numerical simulations of multistage pump with different blade thicknesses are carried out. The influence law of blade thickness on pump performance is built from the external characteristics and internal flow field. In conclusion, with the increase of blade thickness, the best efficiency point of the pump shifts to the small flow rate direction, and the vortex regions inside the pump at rated flow gradually increase, which is the main reason that pump efficiency decreases along with the increase of the blade thickness at rated flow.

Design of diverter berms for soil erosion control and biorestoration along pipeline rights-of-way

Abstract Diverter berms are used to control soil erosion along restored pipeline corridors between the time the pipe is installed and the establishment of a vegetation cover. Current practice, based on standard design procedures, is often inadequate in areas of steep slopes and erosive rainfall because the resulting berm channels are too steeply graded and too widely spaced, and insufficient attention is given to their outlets. The Universal Soil Loss Equation provides a more flexible procedure for determining the spacing required to achieve a specified erosion target for given conditions of rainfall, soils and slopes. Where the required spacings are not feasible because they are too close, spacings should be based on ensuring that flow velocity does not exceed 80% of the maximum non-eroding velocity, and additional supporting erosion-control measures should be provided. Channels should be graded at 0.4% and the grade should never exceed 2%. The choice of type of outlet should be determined by the erodibility of the soil, the steepness of the slope, vegetation cover and whether the outlet slope is on undisturbed or made-up ground. Broad-based berms should be used as an alternative to narrow-based ones where there is a risk of damage from vehicles.