e-book Concrete Face Rockfill Dams Design, Construction, and Performance: Proceedings of a Symposium

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In this study, a methodology for optimal layout design of pressure cells for concrete faced rockfill dams is developed. A representative dimensionless stress distribution model was formed for obtaining the magnitudes and location of different stress zones as a function of dam height. This information enabled development of a procedure for proper location and the number of pressure cells throughout the dam body.

A vertical placement algorithm based on error minimization was first developed, which is followed by an approach to find the number and location of pressure cells on a particular elevation of the dam body. The effects of face slab cracking and earthquake are interpreted. Furthermore, the performance of the proposed model was also tested when instruments are installed to different elevations in the dam body than those recommended by the model developed.

The proposed optimization scheme provides a basis for economical layout design of pressure cells with sufficient information allowing realistic assessment of the structural behavior. The application of the proposed model is illustrated for some existing dams. It is observed that this algorithm gives satisfactory results.

Unable to display preview. Download preview PDF. Skip to main content. Advertisement Hide. Geotechnical Engineering First Online: 12 October Numerical methods can be used to predict the deformation and stress distributions in the concrete face slab, where the behavior of the interface between the concrete face slab and the cushion layer plays a significant role.

Because the interface can be treated in different ways, the prediction of displacement and stress distribution around the interface may be different.

Concrete face rockfill dams hardcover

This study focuses on the comparison of different interface analysis methods through the analysis of stress and displacement distributions near the interface in the Tianshengqiao-I CFRD project. The accuracy and limitations of each method are discussed. Much attention has been paid to numerical treatment of the interfaces in geotechnical problems such as buried structures, jointed rocks, and rockfill dams []. Interface behavior often involves large relative movement or even. Over the past three decades, three numerical methods have been proposed for simulating the displacement jump along the interface: the interface element, thin-layer element, and contact analysis methods.

The interface element method originated from the Goodman joint element approach []. The basic idea was to introduce a constitutive model for an interface of zero thickness [6]. This constitutive model may be elastic, rigid-plastic, or elastic-plastic [2, 6, 7]. As an alternative, a thin-layer element method [8] was proposed.

The thin-layer element method regards joints or interfaces as conventional continuums described by solid elements. However, the material modulus for this thin layer is much lower than that for the intact solid []. This thin-layer element method has been successfully applied to jointed rock masses [10], buried pipes [8], and the interaction of foundation and soil masses [9, 11].

Either the interface element or thin-layer element is limited to small deformation. Different from the previous two numerical methods, the contact analysis method was proposed to simulate the contact behaviors between the concrete face. In this contact analysis method, the concrete face slab and dam body were regarded as two independent deformable bodies, and the contact interface was treated using contact mechanics [13].

This method allows large relative displacements between the concrete face slab and cushion layer. The physical and mechanical properties of the interface can also be nonlinear or elastic-plastic. In the contact analysis method, the detection of the contact is the key issue.

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Zhang et al. However, the accuracy of this contact detection method is not acceptable when the mapping function for element geometry is not identical to that for displacement interpolation and when the deformation is large. In this paper, a global contact search method is proposed based on a radial point interpolation method [14, 15].

The accuracy of this global search method is controllable. In this study, the numerical performance of three numerical simulation methods, namely, the interface element, thin-layer element, and contact analysis methods is compared through stress-deformation analysis of a high concrete-faced rockfill dam. In Section 2, the fundamentals of the three methods are briefly reviewed. A global search method for contact detection is proposed based on the radial point interpolation method. In Section 3, the constitutive models for the rockfill dam body and the concrete face slab are presented.

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The Duncan EB model [16] is employed to describe the nonlinearity of rockfill materials, and a linear elastic model is used to describe the mechanical properties of the concrete face slab. In Section 4, the FEM models and material parameters are introduced. The separation between the concrete face slab and the cushion layer, stresses in the concrete face slab, contact stress along the interface, displacements along the interface, and deformation of the dam body are compared using the in-situ observations available.

Finally, conclusions are drawn in Section 6. Such a problem has the following weak form:.


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The Contact Problem. With reference to Figure 1, we consider the contact of two deformable bodies, where the problem domain Q is divided into two subdomains Q1 bounded by r and Q2 bounded by r2. Interface Element Method. For the interface element method Figure 2 , the interface conditions are described by.

This weak form is composed of three terms:. On discretizing the interface term rcinterface, the element stiffness is obtained as. The material matrix. Goodman et al. They took the material matrix as. The normal stiffness kn is usually given a large number when the interface element is in compression and a small number when in tension.

Concrete Face Rockfill Dams Design, Construction, and Performance

Thin-Layer Element Method. In this method, an interface is treated as a thin-layer solid element Figure 3. This thin layer is given a relatively low modulus and can experience large deformation []. The problem shown in Figure 1 with a thin layer has the following weak form:. If VL has a finite thickness of d, the element stiffness of thin layer element Ve is. When the aspect ratio varies in the range of 0. Contact of Two Deformable Bodies. As shown in Figure 4, the potential contact boundaries are r1c in r and r2c in r2, while the exact contact boundary is denoted as interface rc, which is usually unknown beforehand.

The weak form of each deformable body is expressed individually as follows. For deformable body Q1. Upon discretizing the weak forms in 11 and 12 , the following discrete system equation is obtained for each deformable body:. It can be proved that P is equivalent to the Lagrange multiplier [17,18]. The displacement increments u1 and u12 are solved using 13 , while u2 and u21 are determined by When the two bodies are in contact, one deformable body imposes constraints on the other. At this time, u12 and u21 are no longer independent, and P is introduced as an unknown.

The contact boundary should satisfy the kinematic and dynamic constraints. As shown in Figure 4, if point A on r1c coincides with point B on r2c, the kinematic constraint is expressed as [12]. The dynamic condition is Coulomb's friction law in our computation:.

Therefore, the unknowns u1, u12, u2, u21, P, and Tc can be completely solved from 13 - Strategy of Searching Contact Points. The contact interface Tc is the key unknown in the contact problem. The disadvantage of this node-edge contact mode is that the accuracy is low. This study uses curve fitting; that is, the point interpolation method [14,15], to detect the exact contact interface Tc. The numerical procedure is as follows.

Step 2. Locate the nodal points on the interfaces T1c and r2c. There are M nodes on T1c, denoted by x11,x12, Step 3. Interpolate these nodes to form the boundary lines using the radial point interpolation method [14,15]. One has. Step 4. Establish the distance function S along either boundary line. Otherwise, the point is in contact with the other boundary. Identify the exact contact points through Iterate the same procedure to find out the entire contact boundary.

Step 5. Iterate FEM computation to satisfy the equilibrium of two deformable bodies and the contact boundary conditions. Step 6. Update nodal coordinates on the contact boundary. Carry out the next step computation, and return to Step 3 for the same search procedure for the contact points. EB Model for Rockfill Materials. Rockfill materials and soil masses behave with strong nonlinearity because of the high stress levels in dams. This nonlinearity is described by the following incremental Hooke's law:.

The Duncan EB model [16] gives the deformation modulus Et as follows:. A linear elastic model with Young's modulus E and Poisson ratio v is used to describe the mechanical properties of the concrete face slab. No failure is allowed. Read "Three-dimensional finite element analysis for reinforced concrete face rockfill dam of Dongkeng reservoir" on DeepDyve - Instant access to the journals you need!

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Concrete face rockfill dams : design, construction, and performance : proceedings of a symposium. Settlement is one of the most important deformation characteristics of a high concrete-face rockfill dam CFRD and is regarded as a key indicator of dam safety. The concrete-face rockfill dam CFRD is currently being used with increasing frequency thorughout the world. It has substantial advantages over the earth-core Seismic Analysis of Concrete Face Rock Fill Dams of simplified procedures or the equivalent linear; case history of a modern concrete face rockfill dam. Bulletin 70, Rockfill Dams The concrete face rockfill dam is currently being used with increasing frequency throughout the world.

It has substantial advantages over the earth core rockfill dam The main conclusions regarding the performance of the concrete face rockfill dam are: The sudden increase in the vertical displacements This new approach includes Abstract: Concrete face rockfill dam has the certain superiority in the construction of dam.