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The adverse effects of the frequent reservoir earthquakes (REs) and the severe degradation of the hydrofluctuation belt (HFB) on the long-term stability of bedding bank slope since the Three Gorges Reservoir Area (TGRA) impoundment were considered fully in this paper. Under such complex conditions, the dynamic response pattern and instability mechanism of typical bank slopes were investigated systematically by using a method of combining field survey, laboratory shaking table (ST) model test, and Universal Distinct Element Code (UDEC) numerical exploration. The research shows that the degradation forms of the HFB of typical bank slopes in the key field survey of the TGRA can be arranged into four types: erosion (denudation), corrosion (suffosion), avalanche (collapse), and slip (flow). The dynamic response of slope shows obvious characteristics of "surface effect" and "elevation effect," and the cumulative displacement (CD), damping ratio (DR) and natural frequency (NF) of slopes show a trend of gradually increasing, and increasing and decreasing, respectively. Meanwhile, the "S–type" cubic function and "Steep rise type" exponential function can be used to characterize the cumulative damage degree (CDG) of slope at the excitation stages of microseisms—small seisms and strong seisms, respectively. Subsequently, the dynamic evolvement process for cumulative damage and unstable failure of slope considering the impact of degradation of rock mass in the HFB was obtained, and there are good agreement between the model test and numerical exploration results. Furthermore, fully considering the influence of slope height (SH), slope angle (SA), thickness of bedding plane (TBP), dip angle of bedding plane (DABP), dynamic load amplitude (DLA), dynamic load frequency (DLF), height of water level of the HFB (HWHB), degradation range of the HFB (DRHB), and degradation shape of the HFB (DSHB), the CD of slope subjected to continuous excitation of multiple seismic loads increases in the form of exponential function, the dynamic stability coefficient (DSC) of slope decreases slowly first and then drops sharply, and the response degree of slope deformation and sliding velocity is obviously different. Especially, the sensitivity level of every preceding factor to the dynamic stability of slope based on the orthogonal analysis method (OAM) is in the order of DLA > DRHB > SA > SH > DLF > HWHB > DSHB > DABP > TBP. [ABSTRACT FROM AUTHOR]

Groundwater flow velocity, including its magnitude and direction, is a crucial aquifer characteristic that plays a significant role in developing and protecting groundwater resources. Current groundwater measurement technologies yield low flow velocity accuracy and are expensive. This study proposes a new method for in situ measurement of groundwater velocity based on groundwater flow–induced cooling. It utilizes the cooling capability of flowing groundwater on a closed circulation of heated fluid to establish a functional relationship between the temperature difference of heated fluid and groundwater velocity. A series of experiments were conducted in a sandbox to verify this approach. The result shows that the new method can measure the groundwater velocity's magnitude and direction. Within the designed flow rate range (0−1.055 mm/s), the correlation coefficient between the calculated values obtained by the new method and the actual values exceeds 0.97, with only a 0.017 root mean square error and a 0.040 mean absolute error. Further, the method finds a significant sine function relationship between the temperature difference of heated fluid and the direction of groundwater flow, with the correlation coefficient exceeding 0.97. Accurately detecting groundwater flow velocity, including its magnitude and direction, plays a significant role in developing and protecting groundwater resources. However, traditional methods for measuring groundwater flow velocity, such as isotope tracing and borehole dilution tests, have a problem: measurement accuracy is not high, measuring equipment is expensive, and there is a long measurement time. Thus, we propose a fast and accurate method for measuring groundwater velocity. The new method utilizes the cooling capability of flowing groundwater on a closed circulation of heated fluid. A theoretical analysis of the method yields a mathematical relationship between the temperature difference of heated fluid and groundwater velocity. Based on the theoretical analysis, we designed and tested a series of experiments in a sandbox. The result shows that the new method can simultaneously measure the groundwater velocity's magnitude and direction and has the advantages of high accuracy and strong robustness, which provides a theoretical reference for in situ measurement of groundwater velocity. [ABSTRACT FROM AUTHOR]

The deformation of long–short supporting piles in soil–rock combined strata, which involves the cooperative working effect, is not easy to be analyzed by the theoretical method, and the deformation mechanism is not precise. Therefore, the deformation and mechanical characteristics of long–short supporting piles are investigated in this work by numerical simulation and field monitoring. The results show that for deep excavation in soil–rock combined strata, the lateral deflection curve converges rapidly below the excavation face, and the maximum point is located near the soil–rock interface. The bending moment of long and short piles increase simultaneously at each excavation stage, showing a remarkable cooperative working mechanism. The ratio number of long piles has a more significant impact on the internal force of the pile beneath the weathering line. Parameter analysis indicates the soil thickness and the rock deformation modulus have a considerable influence on the stability of deep excavation and the internal force of the supporting structure. For a given soil thickness, the embedded depth of long piles should be increased with increased softness and weathering of the underlying rock mass. Meanwhile, for deep excavation with thin overlying soil and hard rock mass, as described in this paper, the design of long–short supporting piles tends to be safe. The diameter of supporting piles and the number of short piles can be optimized to meet a reliable and economical design requirement, provided that the performance of the supporting structures can meet the design requirement in practice. [ABSTRACT FROM AUTHOR]

Batch interface tracking and contamination control are the key technologies for the operation and management of multiproduct pipelines. Existing studies only focused on sequence arrangement or segment stoppage to control the generated contamination, and few considered this problem comprehensively and systematically. This study fully considers the contamination control process and develops a scheduling model for straight pipelines to minimize the cost of contamination loss caused by segment stoppage. The objective of this model is to minimize the restart cost of idle segments and the penalty cost due to improper interface placement during segment stoppage. Three types of constraints for contamination control are proposed, namely operation control, flow rate control, and stoppage control. Three real-world multiproduct pipelines are used as examples to validate the proposed method. Compared with the actual operation schemes, the method helps to reduce the number of stoppage operations by 20%–50%, and decrease the probability that the interface is improperly located by 40%–67%. Therefore, this work can reduce the cost of contamination treatment and bring greater benefits to pipeline operators. [ABSTRACT FROM AUTHOR]

In the framework of generalized plasticity theory, this paper presents a new elastoplastic model to characterize complicated softening/hardening and dilation/contraction behaviors of sand–gravel composites in triaxial tests. The model has six parameters that are determined by the conventional triaxial test directly, which is of great practical interest to engineers. The dilatancy equation that is able to describe the dilatancy of sand–gravel composites during the whole shearing process is incorporated into the model. The advantage of the proposed model in predicting the dilatancy behavior of sand–gravel composites is demonstrated by comparing it with three widely used dilatancy equations. A set of drained triaxial compression tests were launched to examine the performance of the proposed model. In addition, the applicability of the model is also confirmed by sand–gravel composites tests covering a wider range of confining pressure in previous literature. The generality of the model on other granular materials including rockfill, Ottawa sand, calcareous sand, cement-sand–gravel material, and glass beads mixtures is also verified by comparing the experimental results with the corresponding fitting results. Furthermore, the proposed model is programmed into the nonlinear finite element program GEODYNA and applied to the numerical simulation of high concrete-faced sand–gravel dams. Summarizing the fitting and numerical results comprehensively, the constitutive model proposed in this study is capable of characterizing the mechanical behaviors of granular materials and can provide a powerful tool for geotechnical engineering. [ABSTRACT FROM AUTHOR]

Rockfill strength parameters are important indicators of the stability of a rockfill dam slope. Therefore, a rational representation of the distribution characteristics of these parameters is extremely important to accurately assess the stability of the dynamic response and reliability of the three-dimensional (3D) slope of a rockfill dam. A joint distribution model of the rockfill strength parameters is constructed in this study using the copula function. In addition, a dynamic reliability analysis method for slope stability is proposed using a number-theoretical method and the generalized probability density evolution method (GPDEM). First, the method is validated by comparing the results for a numerical example with those obtained by Monte Carlo simulation (MCS). Second, the traditional and proposed joint distribution models are comparatively analyzed in terms of the dynamic response and reliability. Finally, the effect of the type of copula function on the dynamic reliability of the slope is investigated. The results show that the copula theory, the number-theoretical method, and the GPDEM provide an effective approach to analyze the dynamic response and reliability of slope stability. The randomness of rockfill strength parameters is sensitive to the safety factor of the slope stability of rockfill dams. The reliability analysis method can reasonably characterize the influence of strength parameter uncertainty on dam slope stability, which makes up for the deficiency of using a single safety measurement standard in the deterministic analysis method. The copula function can reasonably characterize the nonnormal distribution characteristics of rockfill strength parameters, improve the calculation accuracy of the slope stability reliability of rockfill dams, and provide an important scientific basis for the accurate safety assessment of dam slope stability. The type of copula function has an important impact on the dynamic reliability results for slope stability. Thus, it is extremely important to build a joint distribution model of rockfill strength parameters based on a rational selection of the optimal copula function. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) composite frames are the ideal main support structure in civil and aerospace engineering applications because of their excellent material and structural properties for high stiffness ratio, high strength ratio, large span, and so forth. This paper investigated strong singularity optimum problems of FRP composite frames under fundamental frequency constraints. An area/moment of inertia-density strategy, the adapted polynomial material interpolation (APLMP) strategy, was adopted. The APLMP strategy changes the physical relationship of a tube's bending stiffness and cross-sectional area to relax the local vibration frequency constraint. The specific manufacturing constraints for laminated composite were considered in the mathematical model with fixed fiber winding angles and sequence according to certain guidelines to reduce the heavy calculation burden. The artificial densities of the APLMP strategy, which are a function of the areas of the composite frame, were defined as the size and topology optimization variables. Extensive large-scale two-dimensional and three-dimensional numerical examples demonstrated the validity of the APLMP interpolation strategy for topology design optimization of FRP frames. It was proved that the APLMP strategy can solve the challenge of the strongly singular optimum for structure topology design optimization of composite frames with frequency constraints. [ABSTRACT FROM AUTHOR]

The dilatancy equation plays an important role in establishing the elastoplastic model for sand–gravel composites. However, the equation is not comprehensive in its considerations. In this paper, experimental investigations of the dilatancy behaviors of saturated sand–gravel composites are carried out through a series of drained triaxial compression tests. The influence of density as well as confining pressure on the dilatancy characteristics of sand–gravel composites is analyzed, and a nonlinear relationship between the stress ratio η and the dilatancy d is suggested. A new and practical dilatancy equation that can accurately model the stress–dilatancy relationship of sand–gravel composites during the whole process of shearing is established. The equation is applicable whether the material is strain softening or strain hardening. The improved accuracy of the proposed equation in describing the stress–dilatancy relationship of sand–gravel composites is highlighted through comparison to the predictions of five widely used dilatancy equations. In addition, the generality of the proposed dilatancy equation is verified through analyzing the stress–dilatancy relations of six rockfill and gravelly materials found in published literature. [ABSTRACT FROM AUTHOR]

This paper focus on parameter identification of the main cables of cable suspension structures. Based on the dynamic stiffness theory, an inverse analysis characteristic function (IAC function) for identifying the main cable parameters (such as cable tension, moment of inertia, cable length, and mass per unit length) is established. This function allows for the consideration of cable flexural rigidity, sag, inclination, and additional lumped masses sustained by the suspender. The effects of the cable tension and moment of inertia on the IAC function are investigated via a numerical method. On this basis, a method for identifying the two parameters based on the peak-ridges of the IAC function is proposed. The method comprehensively utilizes measured multimode frequencies. It is unnecessary to determine the fundamental frequency and frequency order. A 20-m real cable test with suspended lumped masses is conducted to verify the correctness of the proposed methods. With the increase in the weight of suspended lumped masses, the advantages of the proposed method are more obvious. For operational cable tension less than 50% of the cable breaking tension, the cable moment of inertia is less affected by suspended lumped masses. [ABSTRACT FROM AUTHOR]

The evaluation of slope stability reliability under the condition of incomplete probability information is one of the most popular issues in geotechnical engineering. The key difficulty in the issue lies in how to effectively establish a joint probability distribution model that conforms to the distribution characteristics of shear strength parameters under the condition of incomplete probability information. In this paper, based on the incomplete probability information of the nonlinear strength parameters of rockfill, the joint distribution model of the nonlinear strength parameters will be established using the Copula function. Combined with a radial basis function network (RBFN), an intelligent response surface method for reliability analysis of rockfill dam slope stability systems will be proposed. Its feasibility and validity will be demonstrated through an example. The influences of the Copula function type and sample number on the reliability of the stability system of rockfill dam slope will be systematically studied based on the constructed intelligent response surface. The results indicate that the Copula function could reasonably describe the correlated, nonnormal distribution characteristics of the nonlinear strength parameters and effectively construct their joint distribution model. The Copula function could provide reliable, statistically significant parameter samples for reliability analysis of the stability system of rockfill dam slopes. The traditional independent normal distribution ignores the correlated, nonnormal distribution characteristics of the nonlinear strength parameters of the rockfill, which result in the smaller failure probability and overestimation on the reliability of the stability system of the dam slope. The Copula function type and the number of samples have a significant impact on the reliability of the stability system of a rockfill dam slope. Therefore, it is recommended that as much test data as possible is obtained for statistical analysis, and the optimal marginal distribution function and Copula function are selected to improve the accuracy of the failure probability analysis of the rockfill dam slope stability system, which is of great engineering significance in the safety evaluation of a dam. [ABSTRACT FROM AUTHOR]

An analytical method will be proposed to investigate the bearing mechanism of piles in an anisotropic discontinuous rock mass. Based on the characteristic line method, the discontinuous part of the rock is considered as the boundary condition of the plastified zone, and Riemann's invariant governing equation will be applied at the boundary conditions to link these boundaries. It was found that four different failure mechanisms exist that depend on the inclination angle of weakness planes (χ): (1) conditioned by the planes of weakness in the intermediate zone (MC), (2) conditioned by the planes of weakness close to Boundary 2 in the active zone (M2), (3) conditioned by the planes of weakness close to Boundary 1 in the passive zone (M1), and (4) not conditioned by the planes of weakness (MI). Each pile failure mechanism contains four failure modes under different pile embedment and geostatic loads: (1) deep pile with minor overburden (DL), (2) deep pile and large overburden (DH), (3) semideep pile and small overburden (SL), and (4) semideep pile and large overburden (SH). Therefore, 16 pile failure modes exist and are distinguished by χ and the embedment ratios (n). The friction angles of the weakness planes (φ) have significant effects on the pile failure mechanisms. Under the failure mechanism of MC, M2, and M1, the peak of the percentage of pile bearing capacity in anisotropic discontinuous rock over that in isotropic continuous rock (NβP,DL/NβP,MI) increased with φ. [ABSTRACT FROM AUTHOR]

Involvement in the operation of a multiobjective and multistakeholder hydropower system requires balancing conflicting objectives and coordinating economic gains to achieve a win–win situation through joint operation. This study developed integrated models of multiobjective joint optimization and synergistic revenue allocation of multistakeholders to resolve conflicts. The multiobjective operation model coupled with the technique for order preference by similarity to ideal solution method determines a noninferior solution for compromising social (water delivery and flood control), and economic (energy production) objectives with the incorporation of the decision makers' preference. Thereafter, a novel synergistic revenue allocation method based on the total differential equation (SRA-TD) is proposed. This method is used to systematically decompose the contribution of each stakeholder (reservoir) in the synergistic revenue through cooperation, thereby satisfying the principles of efficiency, rationality, and equity. The integrated models are applied to a hypothetical multistakeholder cascade hydropower system. Results are as follows: (1) The compromise solution selected from the multiobjective optimization operation results increases the firm water supply but reduces the energy production revenue without increasing flood storage compared with the benchmark solution (status quo). (2) The SRA-TD method decomposes the synergistic revenue contribution of each reservoir during each period and verifies its physical generation mechanism, thereby satisfying the basic principles of synergistic revenue allocation. (3) Last, the SRA-TD method comprehensively considers the dynamic effects of inflow conditions, reservoir characteristics, and topological structures of a reservoir system. The proposed method provides a viable alternative for promoting joint optimal operations in a multiobjective and multistakeholder cascade reservoir system. [ABSTRACT FROM AUTHOR]

Wetting deformation of the rockfill material, which is generated by particle sliding, breakage, and rearrangement, plays a vital role in earth-rockfill dam deformation that determines the safety of the dam. However, the previous wetting deformation particle breakage test was performed under the conventional stress path, which could not reflect the influence of stress path. This paper investigates the particle breakage of the basalt rockfill used in the Gushui dam during wetting deformation tests under the equal stress ratio path and drained triaxial shearing tests under the complex stress path. The results indicate that stress path, stress level, stress intensity, and particle breakage determine the wetting deformation under the equal stress ratio path. Under a low confining pressure (1,000 kPa), rockfill particle sliding and roll over are loosely constrained, and negligible particle breakage occurs during wetting deformation, which is mostly generated by particle sliding and rearrangement. Under a high confining pressure (2,000 kPa), rockfill particle sliding and roll over are more constrained. Thus, the contact force significantly increases and significant particle breakage occurs during wetting deformation. In addition, the relationship between the relative particle breakage index and plastic work under the equal stress ratio path and the following wetting deformation period can be simulated with a hyperbolic formulation, which cannot reasonably simulate the particle breakage under the transitional stress path after wetting deformation. The wetting deformation function under the equal stress ratio path was developed to incorporate the influence of the particle breakage and stress path. [ABSTRACT FROM AUTHOR]

The debonding between the steel tube and the confined concrete core of concrete-filled steel tubes (CFSTs) can weaken the confinement effect of the steel tube on the concrete core and may induce a decrease in the load-carrying capacity and in the ductility. The debonding detection technique for CFSTs is still a challenging problem resulting from the inaccessibility and invisibility of the interface. In this paper, by embedding piezoelectric lead zirconate titanate (PZT) based functional smart aggregates (SAs) in concrete core as actuators and pasting PZT patches on the predetermined locations of the outer surfaces of the specimen as sensors, a novel active interface condition monitoring approach for rectangular CFST members is proposed and is experimentally validated with a scale rectangular CFST specimen with artificial debonding defects. Analysis of the wavelet packet energy spectrum (WPES) of the measurements of PZT patches is carried out, and a damage index, called the weighted variation of WPES (WVWPES) is defined to detect the artificial debonding regions. The results show that the proposed WVWPES index is sensitive to the debonding defect. Finally, the proposed approach is applied to evaluate the interface condition of a large rectangular CFST column of a super high-rise building. [ABSTRACT FROM AUTHOR]

Particle breakage modifies the structure of rockfill material and influences its constitutive character, which is the key factor in earth-rockfill dam deformation control. However, the particle breakage laws for rockfill material under real stress paths during dam construction and impounding remain unclear. This paper investigates the particle breakage of basalt rockfill, which was used in the Gushui concrete-face rockfill dam, during drained triaxial compression under equal stress ratio paths (construction stress paths) and transitional stress paths (impounding stress paths). The results indicate that the type of stress path significantly influences rockfill particle breakage. Under the equal stress ratio path, particle breakage increases with shear strain and the growth rate decreases with the stress ratio. The relationship between the relative particle breakage index and the plastic work can be simulated using a hyperbolic formulation. Under the transitional stress path, particle breakage also increases with shear strain and the growth rate is influenced by the transitional confining pressure, the transitional stress path, and the equal stress ratio experienced before the transition. However, the relative particle breakage index cannot be reasonably simulated using the plastic work. [ABSTRACT FROM AUTHOR]

The "curse of dimensionality" is the main problem in flood control in multireservoir systems. This paper proposes a novel method of alleviating the "curse of dimensionality" by reducing the number of reservoirs for flood control joint operation. First, a criteria system for identifying effective reservoirs is established. Then an intelligent reasoning method is proposed to identify effective reservoirs according to dynamic information on the flood control situation. Finally, a multireservoir real-time flood control hybrid operation (MRFCHO) model is established dynamically and adaptively, in which the effective reservoirs are operated jointly and the noneffective reservoirs are operated separately. The proposed method is applied to a multireservoir system consisting of 14 reservoirs in the Huaihe River basin in China. The results show that the proposed method can identify effective reservoirs accurately in different flood control situations. The number of reservoirs for joint operation is lower than 50% of the total number of reservoirs under the premise of ensuring similar flood control effects, which reduces the dimensionality of the model and the complexity of decision making. [ABSTRACT FROM AUTHOR]