Research and Statistical Analysis on Impact Resistance of Steel Fiber Expanded Polystyrene Concrete and Expanded Polystyrene Concrete

Steel fiber foamed concrete (SFFC) combines the impact resistance of steel fiber concrete (SFC) and the energy absorption characteristics of foamed concrete (FC), and it has brought attention to the impact field. Using the mechanical properties of SFFC expanded polystyrene concrete, we prepared (EPSC) specimens with 10%, 20%, 30%, 40%, 50% by volume of expanded polystyrene (Veps), and steel fiber expanded polystyrene concrete (SFEPSC) specimens by adding 1% steel fiber (SF) based on the EPSC in this study. The relationship between compressive strength, the Veps and apparent density was revealed. The relationship between the first crack and the ultimate failure impact of SFEPSC specimens was obtained by a drop-weight test. The impact resistance of SFEPSC and EPSC and the variation law of Veps were studied by mathematical statistics. The log-normal and the two-parameter Weibull distributions were used to fit the probability distribution of impact resistance of the SFEPSC and EPSC specimens. Finally, both types of specimens’ destruction modes and mechanisms were analyzed. The mechanism of the EPS particles and the SFs dissipating impact load energy was analyzed from the energy point of view

Real-Time Safety Evaluation for Slope during Construction Using Numerical Forecast and Sensor Monitoring Platform

Geology uncertainties and real-time construction modification induce an increase of construction risk for large-scale slope in hydraulic engineering. However, the real-time evaluation of slope safety during construction is still an unsettled issue for mapping large-scale slope hazards. In this study, the real-time safety evaluation method is proposed coupling a construction progress with numerical analysis of slope safety. New revealed geological information, excavation progress adjustment, and the support structures modification are updating into the slope safety information model-by-model restructuring. A dynamic connection mapping method between the slope restructuring model and the computable numerical model is illustrated. The numerical model can be generated rapidly and automatically in database. A real-time slope safety evaluation system is developed and its establishing method, prominent features, and application results are briefly introduced in this paper. In our system, the interpretation of potential slope risk is conducted coupling dynamic numerical forecast and monitoring data feedback. The real case study results in a comprehensive real-time safety evaluation application for large slope that illustrates the change of environmental factor and construction state over time

The Duration Effect of Pulse-Type Near-Field Earthquakes on Nonlinear Dynamic Analysis and Damage Evaluation of Hydraulic Tunnels

Current research trends in significant hydraulic engineering projects focus on investigating the seismological properties of intensity and frequency content of pulse-type near-field earthquakes on the structural response. Conversely, the duration impact is not expressly addressed in the seismic design code for underground buildings. Currently, various duration indicators of as-recorded strong ground motions mainly consider the effective duration of the initial acceleration component record. In contrast, the duration indicators for the effective velocity duration (EVD) of the original velocity time-history component record have rarely been addressed. Specifically, there is a gap between the effective velocity duration and the structural response. To illustrate the impact on the structural response, an EVD of pulse-type NFGM duration was used. This EVD can be calculated for seismic excitations with set threshold values that enable a quantitative examination of the duration effects. A fluid-hydraulic tunnel-rock interaction system was built and used to estimate the seismic response characteristics induced by different duration NFGMs. The investigation’s findings highlight that the inelastic dynamic response and damage degree are strongly affected by the EVD. Additionally, the fixed threshold value of 5–95% showed an excellent correlation coefficient with the structural response. The significant duration was also found to be the most suitable alternative indicator to replace the EVD index. In addition, the reduced time-history methodology of near-fault earthquake records is presented and validated, with this method being used to improve the efficiency of the dynamic time-history analysis of hydraulic arched tunnels

The Duration Effect of Pulse-Type Near-Field Earthquakes on Nonlinear Dynamic Analysis and Damage Evaluation of Hydraulic Tunnels

Current research trends in significant hydraulic engineering projects focus on investigating the seismological properties of intensity and frequency content of pulse-type near-field earthquakes on the structural response. Conversely, the duration impact is not expressly addressed in the seismic design code for underground buildings. Currently, various duration indicators of as-recorded strong ground motions mainly consider the effective duration of the initial acceleration component record. In contrast, the duration indicators for the effective velocity duration (EVD) of the original velocity time-history component record have rarely been addressed. Specifically, there is a gap between the effective velocity duration and the structural response. To illustrate the impact on the structural response, an EVD of pulse-type NFGM duration was used. This EVD can be calculated for seismic excitations with set threshold values that enable a quantitative examination of the duration effects. A fluid-hydraulic tunnel-rock interaction system was built and used to estimate the seismic response characteristics induced by different duration NFGMs. The investigation’s findings highlight that the inelastic dynamic response and damage degree are strongly affected by the EVD. Additionally, the fixed threshold value of 5–95% showed an excellent correlation coefficient with the structural response. The significant duration was also found to be the most suitable alternative indicator to replace the EVD index. In addition, the reduced time-history methodology of near-fault earthquake records is presented and validated, with this method being used to improve the efficiency of the dynamic time-history analysis of hydraulic arched tunnels

Investigation on large-scale 3D seepage characteristics of a pumped-storage power station: a case study in Zhejiang Province, China

Pumped-storage power stations (PSPSs) have higher requirements for anti-seepage compared with regular power stations. As a result, investigating the seepage distributions of PSPSs is particularly important. However, existing researches remain limited in assessing engineering needs such as ensuring the efficiency of a power station. Taking the Qingyuan PSPS as a typical case, this study aims to investigate the large-scale seepage field distribution while exploring the efficiency of the anti-seepage system. Considering the geological characteristics and structural location, a 3D finite element model is established. Based on the continuous medium model while combined with seepage control measures, the change in leakage while the anti-seepage system failed is further assessed. It is concluded that the operation status of anti-seepage measures will have a certain impact on the leakage volumes of each part. Using a comprehensive assessment, anti-seepage measures can effectively prevent seepage. When failure occurs on anti-seepage curtains, the leakage volume at the corresponding position will show an obvious growth. In summary, the findings of this study highlight the significance of avoiding excessive leakage caused by anti-seepage structure failure, the effective operation of anti-seepage measures must be ensured. The abovementioned results can provide scientific support for the seepage optimization design of PSPSs. HIGHLIGHTS The refined finite element model is established.; Based on the continuous medium model.; The distribution of the large-scale seepage field is analysed.; The leakage volume and external water pressure under different deployment schemes of seepage control measures are assessed.; A parameter sensitivity analysis of the curtain failure rate is carried out.

Analysis of the influence of corrugated steel thickness on the damage characteristics and explosion resistance of corrugated steel-concrete composite structure

A three-dimensional refined numerical simulation model of corrugated steel-concrete slab composite structure under contact explosion load was established by using FEM-SPH coupling method to explore the anti-explosion performance of corrugated steel reinforced concrete slabs with different thicknesses. The influence of corrugated steel thickness on the dynamic damage evolution characteristics, anti-explosion performance and shock wave propagation mechanism of composite structure was investigated. The results show that the maximum error between the simulation results and the experimental results of the crater diameter of the concrete slab and the mid-span displacement of the corrugated steel in the corrugated steel-concrete slab composite structure is 1.6 % and 2.3 %, respectively, which verifies the effectiveness of the simulation method. The mid-span displacement, peak stress and acceleration at the center point of corrugated steel in corrugated steel-concrete composite structure decrease with the increase of corrugated steel thickness, while the energy absorption value increases with the increase of corrugated steel thickness. The mid-span displacement of 12 mm thick corrugated steel is 83.4 % lower than that of 3 mm thick corrugated steel. The failure mode of the composite structure under the same explosive equivalent is mainly manifested as the crater and penetration failure of the concrete slab, and the damage range gradually decreases with the increase of the thickness of the corrugated steel. The failure volume of concrete slab in the composite structure decreases with the increase of corrugated steel thickness, while the energy absorption value of the composite structure increases with the increase of corrugated steel thickness. The research results can provide a theoretical basis for the application of corrugated steel-concrete slab composite structure in the field of structural anti-explosion protection