Seismoacoustic Investigations of Buried Karst in the Dam Foundations in the Daugava Basin

The instability of dams will bring immeasurable personal and property losses to the downstream, so it has always been a trendy topic worthy of investigation. Currently, the rigid body limit equilibrium method is the most commonly used method for the dynamic stability analysis of dams. However, under the action of earthquakes, the instability of the integral dam-foundation system threatens the safety of the dams and is of great concern. In this paper, a stability analysis method that can reflect the complex geological structural forms of dam foundations is proposed in this paper. The advantages are that this method deals with the difficulty in assuming sliding surfaces and the lack of quantitative criteria for the dynamic instability analysis of dams with complex geological structural forms of dam foundations. In addition, through the method, the sliding channels that may appear in the dam foundations can be automatically searched under random earthquake action, and the safety factors of the dynamic instability of dams be quantitatively obtained. Taking a high RCC gravity dam under construction in China as an example, the proposed method is applied to the three-dimensional finite element model of the dam-foundation system of this dam, and then the dynamic stability calculation is carried out. Through this method, the formation process of the dam foundation’s plastic zone and the failure of sliding channels with different strength reduction coefficients are studied on and analyzed detailedly, and the quantitative acquisition of the safety factors is realized. The results show that the method is reasonable and feasible, and helps provide a new idea and method for the dynamic stability analysis of dams.

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Hydromechanical analysis of flow behavior in concrete gravity dam foundations

Canadian Geotechnical Journal ◽

10.1139/t05-095 ◽

2006 ◽

Vol 43 (3) ◽

pp. 244-259 ◽

Cited By ~ 16

Author(s):

Evandro Gimenes ◽

Gabriel Fernández

Keyword(s):

Flow Behavior ◽

Distinct Element ◽

Jointed Rock ◽

Design Guidelines ◽

Engineering Practice ◽

Rock Foundation ◽

Gravity Dams ◽

Concrete Gravity Dams ◽

Rock Interface ◽

Dam Foundations

A key requirement in the evaluation of sliding stability of new and existing concrete gravity dams is the prediction of the distribution of pore pressure and shear strength in foundation joints and discontinuities. This paper presents a methodology for evaluating the hydromechanical behavior of concrete gravity dams founded on jointed rock. The methodology consisted of creating a database of observed dam behavior throughout typical cycles of reservoir filling and simulating this behavior with a distinct element method (DEM) numerical model. Once the model is validated, variations of key parameters including lithology, in situ stress, joint geometry, and joint characteristics can be incorporated in the analysis. A site-specific simulation of a typical reservoir cycle was carried out for Albigna Dam, Switzerland, founded on granitic rock, to assess the nature of the flow regime in the rock foundations and to evaluate the potential for sliding surfaces other than the damrock interface to develop. The factor of safety against sliding of various rock wedges of differing geometry present within the dam foundations was also evaluated using the DEM model and conventional analytical procedures. Estimates of crack propagation patterns and corresponding uplift pressures and factors of safety against sliding along the damrock interface obtained with the DEM were also compared with those from simplified procedures currently used in engineering practice. It was found that in a jointed rock, foundation uplift estimates after crack development obtained from present design guidelines can be too conservative and result in factors of safety that are too low and do not correspond to the observed behavior.Key words: hydromechanical, jointed rock, flow, dam design.

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Internal erosion and piping of embankment dams and in dam foundations

Geotechnical Engineering of Dams ◽

10.1201/b17800-10 ◽

2014 ◽

pp. 409-526

Keyword(s):

Internal Erosion ◽

Embankment Dams ◽

Dam Foundations

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A More Realistic Study on the Mechanical Properties of CFRC Composite Grouting Material under a Long-Term Water Immersion Process

Advances in Materials Science and Engineering ◽

10.1155/2019/2736481 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11

Author(s):

Yao Xiao ◽

Huafeng Deng ◽

Jianlin Li ◽

Eleyas Assefa

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Carbon Fiber ◽

Water Immersion ◽

Fiber Content ◽

Grouting Material ◽

Bonding Properties ◽

Grouting Materials ◽

Dam Foundations

The long-term effect of water immersion on the mechanical properties of CFRC composite grouting materials was studied by using five different carbon fiber contents (0, 0.25%, 0.50%, 0.75%, and 1.00%). The direct shear and long-term immersion tests were performed based on the specified and optimum values of carbon fiber content, respectively. The results showed the following: (1) the application of carbon fiber significantly improved the shear resistance of CRFC composite grouting material by using “reinforcing” and “anchoring” actions. The shear strength of the specimen was increasing by 5.66%∼43.41% when the carbon fiber content increased from 0.25% to 1.00%. After a comprehensive analysis, the optimum carbon fiber content was found to be 0.75%. (2) The degradation in the compressive and tensile strength of CRFC composite specimens exhibited a consistent trend (i.e., a steep gradient was gradually followed by a gentle slope) under a long-term water immersion process. About 90% of the total degradation in the compressive and tensile strength has occurred in 90 immersion days (i.e., 16.05% and 18.45%, respectively). In comparison, the degradation in the tensile strength (20.05%) was slightly higher than the compressive strength (18.16%). (3) Under the long-term water immersion process: the properties of the specimens were gradually deteriorating, the carbon fibers were gradually reaching a fatigue stage, and the bonding properties of carbon fiber was decreasing, which resulted in a reduction in the compressive and tensile strength. The uniaxial compression failure mode changed from brittle to ductile, and the development of local failure was very noticeable. Based on the findings of this paper, groundwater has a significant impact on the mechanical properties of grouted rock mass such as dam foundations and abutments. Therefore, the degradation in the grouting materials has to be considered in practical cases.

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