Roller Compacted Concrete Arch Research Articles

Cracking analysis of induced joints in roller compacted concrete arch dam

Induced joint is seen as a kind of crack prevention measure for roller compacted concrete arch dam. Whether induced joints can crack firstly when the temperature drops of dam body to release temperature stress and control disordered cracks mainly depends on the equivalent strength, structural form and arrangement of joints. In this paper, the non-penetrating RCC induced joints are used to simulate the bilateralism interval induced joints in practical engineering. The functional relation between the equivalent strength of rectangular induced joints and elliptical induced joints with the change of weakening degree is established through the axial tension test. At the same time, the temperature stress of a certain RCC double curvature arch dam is simulated, and the cracking of induced joints and its effect on the stress of the dam are analyzed. The results show that under the temperature control measures of pouring temperature control and water cooling in the whole dam, the bilateralism interval induced joints with equivalent strength less than 1.409 MPa are set in the high tension stress zone of the dam body, which can effectively release the temperature stress and ensure the safety of the dam body under the temperature load.

Analysis of anomalies measured by the osmometer in a roller compacted concrete arch dam

The water permeability of the RCC dam layer and joint surface is high, which often becomes the main channel of dam body seepage, and its safety monitoring is important. Based on the monitoring data of the osmometer of a roller compacted concrete (RCC) arch dam, this paper analyzes the abnormal seepage pressure of the dam body, and introduces the relevant inspection and treatment scheme, which can provide a reference for the construction and operation of other RCC dams.

A Comparative Study of the Cracking Effect of Induced Joints of Various Spatial Formations

The use of induced joints is a common cracking control measure used in the design of roller compacted concrete arch dams. Currently, in some projects in which radial twisted joints were used, during the construction period, some cracks appeared around the induced joints while the joints themselves failed to open. From the fracture mechanics point of view, this problem is related to the variations in the spatial formation of the induced joint planes. In this study, we formulated numerical examples involving square plate and cylindrical arch dam with joints of various planar spatial formations and used the virtual crack-closure technique and the Richard brittle fracture criterion to obtain the equivalent stress intensity factor of the joint plane, and we studied the joint plane stress intensity factor based on the variations in the joint plane formation angle. Based on the reciprocal of the normalized stress intensity factor, we obtained the equivalent strength correction coefficient for induced joints of varying plane angles, referred to in this study as the joint plane formation factor ψα, in order to reflect the influence of varying joint plane formations on the induced joint cracking. Our study results show that as the joint plane angle continuously increases, it is more difficult for the induced joints to open, which implies a gradual increase in the equivalent strength of the joint plane. Therefore, in the actual design of rolled concrete arch dams, the straight transverse joint layout should be used for induced joints. If the use of the radial twisted joint layout is necessary, the joint plane angle should not exceed 10°.

Early-warning model of deformation safety for roller compacted concrete arch dam considering time-varying characteristics

During its long process of serving time, roller compacted concrete (RCC) arch dam effected by the comprehensive combination of many factors shows a typical time-varying characteristic on its structure and material properties, which is objectively reflected in the prototype monitoring data. On the basis of the analysis on influence variables of dam deformation and the working mechanism of the RCC arch dam, in this paper, time-varying early-warning model for the RCC arch dam is established by introducing time-varying factors into hydrostatic pressure components and expanding temperature components, then the modeling method of time-varying early-warning model above is proposed combined with the partial least squares algorithm and genetic algorithm.

Dam Safety Evaluation Based on Multiple Linear Regression and Numerical Simulation

The Shimenzi roller-compacted concrete arch dam was built in a soft-rock region with faults and intercalations. The abutments are divided into several potential sliding wedges by major faults and intercalations. In this study, the safety of the dam was analyzed on the basis of measurements of the displacements, strains, and stresses in the concrete. A hydrostatic, temperature, time-displacement model was used to quantify the contributions of water level variations, temperature in the concrete, and time effects, to the dam’s upstream–downstream displacements. A multiple linear regression was used to train and test the relationships among the hydrostatic conditions (temperature, time, and displacements) and to evaluate the dam deformation characteristics and stability. Numerical models of dam stresses were then established and calibrated, which allow quantitative evaluation of dam safety by using statistical methods. The results indicated that (1) the dam is currently in an elastic deformation state; (2) the contribution of temperature to dam displacement differs with elevation; and (3) the state of stress is below the limits of material strength.

A new method to quantify breach sizes for the flood risk management of concrete arch dams

When predicting dam‐break floods and the associated risk zones for the flood risk management of dams, the breach size must be determined by considering the complex structure of the dam body under the effects of different loads. To predict the breach size quantitatively, this article proposes the concept of an element group, comprising a group of elements through the dam body. The dam‐body safety status is simulated by using the three‐dimensional (3D) finite element model ANSYS and is quantified by the element reliability index β for various loads such as hydraulic and earthquake loads. A new structural reliability method for calculating the breach size was developed to quantitatively predict the failure likelihood of a dam. This new method is more intuitive and reasonable than the point safety factor k. It allows for a more accurate and quantitative prediction of the breach size of new or existing dams. An existing Roller Compacted Concrete arch dam was taken as an example to demonstrate the applicability of the new method.

THERMAL AND STRUCTURAL ANALYSIS OF RCC DOUBLE-CURVATURE ARCH DAM

This paper focuses on the development, verification and application of a three-dimensional finite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Karun III Arch dam located on Karun River, Iran, which was originally designed as a conventional concrete arch dam, has been taken for the purpose of verification of the finite element code. In this study, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. A numerical procedure to simulate the construction process of RCC arch dams is presented. It takes into account the more relevant features of the behavior of concrete such as hydration, ageing and creep. A viscoelastic model, including ageing effects and thermal dependent properties is adopted for the concrete. The different isothermal temperature influence on creep and elastic modulus is taken into account by the maturity concept. Crack index is used to assess the occurrence of crack and evaluate the level of safety of the dam. This study demonstrates that, high tensile stress concentration has been observed at the lower part and the abutment boundaries of the dam.

Seismic deformation and seismic resistance analysis of Shapai Roller Compacted Concrete Arch Dam based on field monitoring and dynamic finite element method

Shapai Roller Compacted Concrete (RCC) Arch Dam is the highest RCC arch dam of the 20th century in the world with a maximum height of 132 m, and it is the only concrete arch dam near the epicentre of Wenchuan earthquake on May 12th, 2008. The seismic damage to the dam and the resistance of the dam has drawn great attention. This paper analyzed the response and resistance of the dam to the seismic wave using numerical simulations with comparison to the monitored data. The field investigation after the earthquake and analysis of insitu data record showed that there was only little variation in the opening size at the dam and foundation interface, transverse joints and inducing joints before and after the earthquake. The overall stability of the dam abutment resistance body was quite good except a little relaxation was observed. The results of the dynamic finite element method (FEM) showed that the sizes of the openings obtained from the numerical modeling are comparable with the monitored values, and the change of the opening size is in millimeter range. This study revealed that Shapai arch dam exhibited high seismic resistance and overload capacity in the Wenchuan earthquake event. The comparison of the monitored and simulated results showed that the numerical method applied in this paper well simulated the seismic response of the dam. The method could be useful in the future application on the safety evaluation of RCC dams.

Study on Ultimate Anti-Seismic Capacity of High Arch Dam

AbstractA three-dimensional numerical simulation model for the failure process caused by an earthquake is established based on the Shapai high roller-compacted concrete arch dam in the Wenchuan, China earthquake region. Several comprehensive influencing factors, including nonlinear behavior of concrete, infinite foundation radiation damping, dam-reservoir dynamic interaction, and the contact nonlinearity of the transverse joints and the induced joints, are taken into account to study their effects on the seismic safety of high arch dams. In the paper, an analytical method is proposed to evaluate the ultimate anti-seismic capacity of high arch dams, and failure modes of the arch dam resulting from earthquakes with different levels are studied. The seismic limit state of the arch dam is determined according to distribution of the concrete’s failure zone, divergence of finite-element calculation, and mutation of the time-dependent displacement curves of key points on the dam. The revealed mechanism of dynami...

Coupled thermal and structural analysis of roller compacted concrete arch dam by three-dimensional finite element method

This paper focuses on the development, verification and application of a three-dimensional nite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Ostour Arch dam located on Ghezel-Ozan River, Iran, which was originally designed as conventional concrete arch dam, has been taken for the purpose of verication of the nite element code. In this project, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. The thermal analysis has been carried out taking into account the simulation of the sequence of construction, environmental temperature changes, and the wind speed. In addition, the variation of elastic modulus with time has been considered in this investigation using Concard\'s model. An attempt was made to compare the stresses developed in the dam body five years after the completion of the dam with those of end of the construction. It was seen that there is an increase in the tensile stresses after five years over stresses obtained immediately at the end of construction by 61.3%.