Stability Of Concrete Gravity Dams Research Articles

Stability assessment method of damaged concrete gravity dams subjected to penetration explosion

The structural stability of concrete gravity dams is of primary importance. In this context, a quantitative and effective stability assessment method for concrete gravity dams subjected to penetration explosion is proposed by employing a series of analytical, numerical, and experimental approaches. Firstly, field blast test is carried out to obtain the possible damage characteristic and mode of a dam model to internal explosion. A fully coupled Lagrangian-Eulerian method is adopted to establish numerical models in this paper, and the validity of this method is discussed by comparing results obtained from this method with those obtained from the blast test. Then, the empirical and theoretical formulas of the penetration-explosion parameters for concrete gravity dams are presented, and these parameters contain penetration depth, damage mode, and damage range, which are the premise of the stability analysis. Moreover, these formulas are verified by the numerical models. Subsequently, the stability analysis method for damaged concrete gravity dams to penetration explosion is put forward. In the process of the stability analysis, structural stresses of the dam with different damage modes are gained, and then anti-overturning and anti-sliding stability analysis are conducted. In addition, a stability index and classification criterion for concrete gravity dams subjected to penetration explosion are proposed, and damage levels are quickly defined in four categories based on the criterion. Finally, a stability assessment model is established on the basic of the former analysis, which can effectively predict the stability performances of damaged concrete gravity dams under various penetration explosion attacks.

Effects of Rock Foundation Roughness on the Sliding Stability of Concrete Gravity Dams Based on Topographic Surveys

AbstractThis paper investigates the effects of rock foundation roughness on the shear strength of dam–rock interfaces and dam sliding stability. For this purpose, bathymetric and light detection an...

Seepage Safety Assessment of Concrete Gravity Dam Based on Matter-Element Extension Model and FDA

As an important infrastructure project, the concrete gravity dam plays an extremely important role in hydropower generation, irrigation, flood control, and other aspects. Seepage is an important factor affecting the stability of concrete gravity dams. Seepage safety assessment is of great significance to the safe operation of the dams. However, the existing seepage safety assessment models are not dynamic, and the correlation among indicators is often neglected and the overall seepage safety of the concrete gravity dams has not been considered. To solve these problems, this research proposes a dynamic matter-element extension (D-MEE) model. First, the D-MEE model is established through adroit integration of the matter-element extension (MEE) model and functional data analysis (FDA). Second, a dynamic criteria importance through the intercriteria correlation (D-CRITIC) method that can effectively consider the correlation among indicators is proposed to determine the weights. Third, the influence of different dam blocks on the overall seepage safety status is considered by constructing a spatial weight matrix. Finally, the proposed method is applied to the concrete gravity dam X in southwest China. The results show that the proposed method is effective and superior to the existing evaluation methods of seepage safety.

Small Displacement Coupled Analysis of Concrete Gravity Dam Foundations: Static and Dynamic Conditions

The explicit formulation of a small displacement model for the coupled hydro-mechanical analysis of concrete gravity dam foundations based on joint finite elements is presented. The proposed coupled model requires a thorough pre-processing stage in order to ensure that the interaction between the various blocks which represent both the rock mass foundation and the dam is always edge to edge. The mechanical part of the model, though limited to small displacements, has the advantage of allowing an accurate representation of the stress distribution along the interfaces, such as rock mass joints. The hydraulic part and the mechanical part of the model are fully compatible. The coupled model is validated using a real case of a dam in operation, by comparison of the results with those obtained with a large displacement discrete model. It is shown that it is possible to assess the sliding stability of concrete gravity dams using small displacement models under both static and dynamic conditions.

Shear Strength of Partially Bonded Concrete–Rock Interfaces for Application in Dam Stability Analyses

The shear strength of the concrete–rock interface has a substantial influence on the sliding stability of concrete gravity dams founded on rock. While several studies have been done on concrete–roc ...

The Investigation of Effective Parameters on the Stability of Concrete Gravity Dams with Case Study on Folsom, Blue Stone, and Pine Flat Dams

In this research, the effective parameters in stability of concrete gravity dams in the form of case study on three important dams: Blue stone; Folsom; and Pine Flat, are investigated. Typically, cognition and understanding of effective parameters in stability and knowing the role of each them, in designing new dams, could be very helpful. Concrete gravity dams (which are surveyed in this research) have their strength and stability because of their weight. The shape of their section are triangle and commonly, The base of the triangle is greater than the dam is stable, the more stable dam is. Also, in this investigation we are going to study the horizontal displacement called sliding of dam’s bottom, in contact with foundation by ABAQUS software. The sliding displacement has no considerable change in each of the three nodes on heel and toe, and also in middle part of dam, and eventually is equal in each three and all parts of the dam’s bottom and foundation. With choosing three nodes on the dam’s bottom and similar nodes on the foundation, and with differentiating horizontal displacements of these nodes with each other, the relative displacements of dam are obtained. With using these displacements acquired from ABAQUS software in RS-DAM software, we show them as time series graph and relative displacement. Whenever this graph has a jump with the increase of earthquake PGAs (end of the graph moves away from the starting point of it), dams is considered as unstable.

Effects of Vertical Acceleration of Earthquakes on Structural Stability of Concrete Gravity Dams

Effects of Vertical Acceleration of Earthquakes on Structural Stability of Concrete Gravity Dams

Structural Stability of Concrete Gravity Dams Strengthened by Rockfill Buttressing: Hydrostatic Load

Rockfill buttressing is often considered to strengthen existing gravity dams that have inadequate stability to resist the estimated hydrostatic and seismic loads. Various simplified methods for static stability analyses of composite concrete–rockfill dams, which represent the rockfill as equivalent forces, are discussed. Numerical analyses of composite dams using nonlinear rockfill and interface constitutive models are then considered. Hydrostatic stability analyses of a 35m composite dam are carried out to compare the results obtained from simplified methods and numerical analyses. Parametric analyses are performed to investigate the effects of various modeling parameters such as the friction angle of the concrete–fill interface, the friction angle of the concrete–foundation interface, and the reservoir elevation during the fill placement. Numerical analyses results show that lowering the reservoir prior to construction of the rockfill does not have a significant effect on the stress response of the strengthened dam in the case analyzed. For design purpose, it is shown that the simplified minimum/maximum earth pressure method is always on the safe side irrespective of the concrete–rockfill friction angle.

Seismic stability of concrete gravity dams strengthened by rockfill buttressing

Rockfill buttressing resting on the downstream face of masonry or concrete gravity dam is often considered as a strengthening method to improve the stability of existing dam for hydrostatic and seismic loads. Simplified methods for seismic stability analysis of composite concrete-rockfill dams are discussed. Numerical analyses are performed using a nonlinear rockfill model and nonlinear dam-rockfill interface behavior to investigate the effects of backfill on dynamic response of composite dams. A typical 35 m concrete gravity dam, strengthened by rockfill buttressing is considered. The results of analyses confirm that backfill can improve the seismic stability of gravity dams by exerting pressure on the dam in opposition to hydrostatic loads. According to numerical analyses results, the backfill pressures vary during earthquake base excitations and the inertia forces of the backfill are the main source for those variations. It is also shown that significant passive (or active) pressure cannot develop in composite dams with a finite backfill width. A simplified model is also proposed for dynamic analysis of composite dam by replacing the backfill with by a series of vertical cantilever shear beams connected to each other and to the dam by flexible links.

Three-Degree-of-Freedom Rigid Model for Seismic Analysis of Cracked Concrete Gravity Dams

A rigid model with three-degrees-of-freedom is proposed for the purpose of seismic analysis of cracked concrete gravity dams. The model considers the geometry of the dam and all its possible modes of motion: sliding, rocking, rock-sliding, and drifting. The governing equations for all the modes are derived with the Mohr-Coulomb friction assumption at the crack, and corresponding conditions to initiate and maintain the modes are also given. For impact that follows rocking and drifting modes, postimpact velocities of the model are explicitly determined according to the momentum principle and the concept of restitution from classical point collision. Studies with the proposed model on rectangular blocks demonstrate two different types of rocking according to the slenderness. Applications to dams indicate that a large coefficient of friction does not necessarily prevent sliding, and rocking and drifting modes should not be neglected in estimating the stability of concrete gravity dams cracked at the base or a...

Seismic structural stability of concrete gravity dams considering transient uplift pressures in cracks

A theoretical model is developed for transient water pressure variations along a tensile seismic concrete crack with known crack wall motion history. Experimental tests are performed to validate the proposed model. Experimental and numerical results show that water can penetrate into new seismic cracks making them partially saturated over a length L sat . The magnitude of L sat and the total water uplift force acting on a crack wall are decreased by crack opening and increased by crack closing. The model is then implemented in a nonlinear discrete crack finite element program for seismic analysis of concrete dams. A 90 m high gravity dam subjected to two different ground accelerations is analysed. The magnitude of uplift force in the opening mode of the crack is small such that the downstream sliding safety factor (SSF) during crack opening is similar to the SSF assuming zero uplift force in the crack. Although the transient uplift force during crack closing reduces the upstream SSF, compared to a similar value assuming zero uplift force in the crack, its magnitude still remains larger than the minimum downstream SSF corresponding to the crack opening mode.

Stability of Concrete Gravity Dams with Drained and Finite Cracks

This paper presents an analytical solution that can be used as a simplified design aid when assessing the stability of concrete gravity dams with cracks at their base under usual load conditions. The solution is based on the strength of materials approach. It differs from the classical U.S. Bureau of Reclamation (USBR) gravity method of stress and stability analysis in three ways: (1) The cracks are finite rather than infinite in a direction normal to the dam cross section; (2) the effect of drainage on the stress distribution in the uncracked part of the dam base and at the crack tip is fully taken into account; and (3) the criterion for cracking at the rock concrete interface is based on the effective stress principle used in soil and rock mechanics. The effective stress principle allows the minimum allowable stress at the crack tip to be related to the rock-concrete interface mechanical properties and the crack drainage properties in a more rigorous manner.

Seismic stability of concrete gravity dams operating jointly with their bases

Seismic stability of concrete gravity dams operating jointly with their bases

Seismic stability of concrete gravity dams : Leger, P; Katsouli, M Earthq Engng Struct DynamV18, N6, Aug 1989, P889–902

Seismic stability of concrete gravity dams : Leger, P; Katsouli, M Earthq Engng Struct DynamV18, N6, Aug 1989, P889–902

Seismic stability of concrete gravity dams

AbstractLinear finite element analyses are commonly used to simulate the behaviour of gravity dam—foundation systems. However, the foundation is generally unable to develop any significant tensile stresses. Therefore any tension occurring in the vicinity of the dam—foundation interface is largely fictitious. Moreover, the traditional overturning and sliding stability criteria have little meaning in the context of the oscillatory response of dams during earthquakes.In this study, time domain analyses using non‐linear contact elements located at the dam—foundation interface have been used to determine the dynamic sliding and uplifting response of gravity dam monoliths considering various elastic foundation properties. The magnitudes of the relative interface displacements, of the percentage of base not in contact (PBNC) and of the compressive stresses at the heel or toe of the dam have been used to monitor the seismic stability.The numerical results have shown that the non‐linear behaviour of the dam—foundation interface reduces the seismic response of the system, indicating the possibility of more rational and economical designs. The PBNC was identified as the critical seismic stability response parameter for all analyses except for very flexible foundation conditions where the maximum values of relative interface displacements need to be considered.

Discussion of “Parsons on Stability of Concrete Gravity Dams”

Discussion of “Parsons on Stability of Concrete Gravity Dams”

Closure to “Henny on Stability of Concrete Gravity Dams”

Closure to “Henny on Stability of Concrete Gravity Dams”