EFFECTS OF UPSTREAM SLOPE OF CLAY CORE AND HEIGHT OF THE ROCK FILL DAMS AGAINST HYDRAULIC FRACTURING

2016 ◽  
Vol 78 (8-5) ◽  
Author(s):  
Didiek Djarwadi ◽  
Kabul Basah Suryolelono ◽  
Bambang Suhendro ◽  
Hari Christady Hardiyatmo
Keyword(s):  
Hydraulic Fracturing ◽  
Water Pressure ◽  
Steep Slope ◽  
Upstream Face ◽  
Statistical Research ◽  
Element Analysis ◽  
Rock Fill ◽  
Clay Core ◽  
Base Width ◽  
Made In

Hydraulic fracturing in rock fill dams may occur in case where the upstream face of the clay core experiencing tension cracks due to the arching effects and water pressure from the reservoir. One of the causes of arching effects was the steep slope of the upstream clay core. A statistical research on the dam experiencing with hydraulic fracturing indicated that rock fill dams with un-compacted rock fill embankment zone with narrow and steep slope of core, where the ratio between height against base width of core > 2 were considered much more likely for hydraulic fracturing to occur, while if the ratio was between 1 to 2 were considered likely to occur. This paper investigates the height limitation of the rock fill dams on the ratio of the height against the base width of core of 2.00 and 2.50, which represent the conditions of more likely and much more likely hydraulic fracturing to occur. The clay cores were obtained from five (5) major dams in Indonesia; Batubulan, Batutegi, Pelaparado, Sermo and Wonorejo dams, where their heights vary from 37 m to 125 m. The variation of the clay core embankment materials was made in six (6) various fine contents, and compacted at their optimum moisture contents. Analysis was made on the modeled rock fill dam using finite element analysis with coupling of the stress, the deformation and the seepage analyses. The hydraulic fracturing may occur in case the vertical effective stresses in the upstream face of clay core were less than the water pressure from the reservoir. The results indicated that the maximum dam height with no hydraulic fracturing was governed by the percentage of fines in the clay core and the ratio of the height to the base width of the clay core. The clay core that consists of more fine contents, and smaller ratio of height against the base width of the clay core of the dam has greater resistance against hydraulic fracturing.  

scholarly journals Effect of Clay Core Configuration of the Rock Fill Dams Against Hydraulic Fracturing

2017 ◽  
Vol 171 ◽  
pp. 492-501
Author(s):  
Didiek Djarwadi ◽  
Kabul Basah Suryolelono ◽  
Bambang Suhendro ◽  
Hari Christady Hardiyatmo
Keyword(s):  
Hydraulic Fracturing ◽  
Rock Fill ◽  
Clay Core

A case study of hydraulic fracturing using finite element methods

1999 ◽  
Vol 36 (5) ◽  
pp. 861-875 ◽  
Author(s):  
Axel KL Ng ◽  
John C Small
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Water Pressure ◽  
Numerical Procedure ◽  
Tensile Fracture ◽  
Rock Fill ◽  
The Core ◽  
Element Method

Hydraulic fracturing can occur in the clay core of an earth and rock-fill dam if the vertical effective stress in the core is reduced to levels that are small enough to allow a tensile fracture to occur. This situation may arise if the total stress in the core is reduced by the "arching effect" where the core settles relative to the rock-fill shoulders of the dam. Water pressure increases in the core which occur on first impounding of water will reduce effective stresses further, and if they reach low enough values, a fracture will occur. The design of earth dams to resist hydraulic fracture is therefore of great importance (especially those dams with thin vertical or near-vertical central cores), as there have been several dam failures in the past that have been attributed to hydraulic fracture. This paper presents a method of predicting hydraulic fracture in the core of earth and rock-fill dams by using a numerical procedure based on the finite element method. The finite element procedure makes use of special joint elements that allow fluid flow and fracture to be modeled and is an advance over previous methods in that it allows the complete history of pore-pressure development in the core of a dam to be simulated. A study of the behaviour of the Hyttejuvet Dam, which was thought to have failed due to hydraulic fracturing, is also carried out, and the results of the analysis suggest that the failure of the dam was probably due to hydraulic fracturing that occurred during first filling of the reservoir. The fractures predicted occur at about the location that the actual fracture was thought to have been located. Key words: hydraulic fracture, earth and rock-fill dams, finite element method.

scholarly journals Selection of Soils as Clay Core Embankment Materials for Rock Fill Dams to Resist Hydraulic Fracturing

2014 ◽  
Vol 95 ◽  
pp. 489-497 ◽  
Author(s):  
Didiek Djarwadi ◽  
Kabul Basah Suryolelono ◽  
Bambang Suhendro ◽  
Hary Christady Hardiyatmo
Keyword(s):  
Hydraulic Fracturing ◽  
Rock Fill ◽  
Clay Core ◽  
Selection Of

scholarly journals Stress-path on the Hydraulic Fracturing Test of the Clay Core of Rock Fill Dams in the Laboratory

2015 ◽  
Vol 125 ◽  
pp. 351-357
Author(s):  
Didiek Djarwadi ◽  
Kabul B. Suryolelono ◽  
Bambang Suhendro ◽  
Hary C. Hardiyatmo
Keyword(s):  
Hydraulic Fracturing ◽  
Stress Path ◽  
Rock Fill ◽  
Clay Core

scholarly journals Investigation on the resistant of tropical residual soils as clay core of rock fill dams against hydraulic fracturing

2016 ◽  
Vol 2 (49) ◽  
pp. 1718-1722
Author(s):  
D. Djarwadi ◽  
K. B. Suryolelono ◽  
B. Suhendro ◽  
H. C. Hardiyatmo
Keyword(s):  
Hydraulic Fracturing ◽  
Residual Soils ◽  
Rock Fill ◽  
Clay Core

scholarly journals Viscoelastic analysis of Calving Glaciers

1980 ◽  
Vol 1 ◽  
pp. 37-41 ◽  
Author(s):  
D. V. Reddy ◽  
W. Bobby ◽  
M. Arockiasamy ◽  
R. T. Dempster
Keyword(s):  
Finite Element ◽  
Sea Water ◽  
Water Pressure ◽  
Computer Code ◽  
Ice Shelf ◽  
Element Analysis ◽  
Ice Shelves ◽  
Shear Moduli ◽  
Relaxation Functions ◽  
Spring Force

Calving of floating ice shelves is studied by a viscoelastic finite-element analysis. The fan-shaped breaking-up of glaciers due to forces that cause bending on creeping ice is assumed to be axisymmetric. Bending may be due to geometry of the bcdrock, action of tides and waves, and imbalance (at the ice front) between the stress in the ice and the sea-water pressure.The bulk and shear moduli of the ice are represented by relaxation functions of the Prony series, which is a discrete relaxation spectrum composed of a constant and a summation of exponential terms. These properties are also functions of temperature, that varies over the thickness of the ice shelf. The temperature distribution across the thickness of the ice is obtained from calculations based on a linear dependence of thermal conductivity on the temperature. Numerical results are presented for various calving mechanisms. A computer code, VISIC1, is developed by modifying a finite-element viscoelastic code, VISICE, for floating ice islands. The buoyancy of the water is taken into account by a Winkler spring model, with the spring force determined from displaced volume. Locations of crack initiation obtained from the analysis are used to predict the iceberg size immediately after calving.

Design for Desired Mode Shapes: Preliminary Results

1998 ◽  
Author(s):  
Elizabeth K. Lai ◽  
G. K. Ananthasuresh
Keyword(s):  
Finite Element ◽  
Feasibility Study ◽  
Mode Shape ◽  
Longitudinal Axis ◽  
Mode Shapes ◽  
Future Research ◽  
Structural Members ◽  
Element Analysis ◽  
Cross Sectional ◽  
Made In

Abstract This paper is concerned with the shape optimization of structures to attain prescribed normal mode shapes. Optimizing structural members in order to have desired mode shapes, besides the desired natural frequencies, is of interest in some applications at both macro and micro scales. After reviewing the relevant past work on the “inverse mode shape” problem, a feasibility study using the lumped spring-mass models and finite element models of an axially vibrating bar is presented. Based on the observations made in the feasibility study with bars, a meaningful optimization problem is formulated and solved. Using finite element analysis and numerical optimization, a method for designing beam-like structures for prescribed mode shapes is developed. The method is demonstrated with an example of designing the cross-sectional area profile of a beam along its longitudinal axis to get a desired fundamental mode shape. The nonuniqueness of the solution is noted and avenues for future research are identified.

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