Zitao Zhang

China Institute of Water Resources and Hydropower Research | IWHR

Particle morphology is a critical factor affecting the mechanical properties of granular materials such as natural gravel, blasted rock fragments and sands. However, traditional methods for characterizing particle shape are often limited in precision and cost-efficiency, particularly for large particles essential in applications like rockfill dams....

The effects of strain rate on the strength of concrete should be considered when analyzing the dynamic responses of concrete structures subjected to earthquakes or explosions. This paper shows that the effect of strain rate on strength characteristics can be attributed to an increase in cohesion. Notably, the effects of friction, hydrostatic pressu...

With the increasing tension in the international arena, the anti-explosion safety of important infrastructures has attracted increasing attention. For the study on underwater explosion, the centrifugal model tests are an important method to study the damage effects by underwater explosion as the shock wave and bubble oscillation of the underwater...

Offshore wind turbines are usually founded on monopiles. During the operation period, the structure is subjected to complex lateral loading from wind, wave and current. The soils surrounding those monopiles may deform with increasing the number of loading cycles, leading to tilting of the whole structure; hence, it is vital to carry out physical mo...

High rock-fill dams are planned or under construction in high seismic intensity area, challenging the seismic design of those dams. This study aims to examine the seismic behavior of rock-fill dams using DEM simulations. The focus is put on the permanent deviatoric strain field and the shear stress-strain loops in rock-fills which can hardly be mea...

This study aims to characterize the seismic responses of silt-interlayered stratified sandy tailings slopes. In order to achieve this, a series of model tests were carried out in an advanced centrifuge shaking table. The experimental results demonstrate that sandy tailings slopes interlayered with silts are more prone to flow failure compared with...

The purpose of this study is to use small-scale centrifuge tests and numerical simulations to explore the effect of bubble pulse on concrete gravity dams subjected to underwater explosions. To the best of the authors’ knowledge, there is still no systematic research focusing on this topic. In this study, five small-scale centrifuge tests previously...

This paper reports the innovative development of a flexible, multiple-layer, economical but robust, and automated high-speed shear wave (Vs) tomographic control and data acquisition system for process monitoring in the laboratory and the associated validation for monitoring the dynamic process of model pile installation. This tailor-made tomographi...

This study aims to examine the effects of layering on the seismic behavior of tailings dams. The focus is put on the spatial distribution of excess pore pressure and its variations with time during earthquake loading. In order to achieve this, dynamic centrifuge tests have been carried out for tailings dam models with thin silty layers sandwiched i...

Underground structures in liquefiable ground are prone to severe earthquake damage, and the seismic responses of such underground structures can be affected by nearby superstructures. Two centrifuge shaking table tests on a precast underground structure with and without a superstructure above it in mildly inclined liquefiable ground were designed a...

Gravity dams are important infrastructures, and their failure would affect the public security. Physical modeling was conducted in this paper to determine the dynamic responses and damages of gravity dams subjected to underwater explosions. Five tests under different impoundment levels, centrifugal accelerations, standoff distances, detonation dept...

Dam structures are prime targets during wars, and a tragedy is likely to happen in a populated area downstream of a dam exposed to explosions. However, experimental investigations of the failure of a concrete gravity dam subjected to underwater explosion (UNDEX) are extremely scarce. In this study, centrifuge tests and numerical simulations were pe...

Major water conservancy projects are important national infrastructures, whose damages caused by underwater explosions are noteworthy. Hence, centrifuge model tests and finite element simulations were used to study the effect of water storage level changes on the responses of dam. First, the similarity between the scaled model and the prototype in...

As a complex process, an underwater explosion is affected by different factors. Shock factors are variables used to characterize the severity of a shock based on scaling laws, which are conventionally used to designate the effect of an underwater explosion on a target. To reveal the mechanism involved in the dynamic response of an air-backed plate...

The strength of rock-like materials has obvious strain rate effect. Based on the characteristics of uniaxial dynamic strength, a simple strength criterion is proposed, which can uniformly predict the uniaxial strength from quasi-static to dynamic. Under the framework of the unified strength criterion, the triaxial dynamic strength criterion is stud...

Bubble oscillations generated by underwater explosions can cause considerable damage to nearby marine vehicles or hydraulic structures as the energy inside the bubble is comparable to that of a shock wave. Since both compressibility and gravity affect the bubble impulse, it is not easy to reproduce the pulse pressure by experiments in vacuum tanks...

A series of dynamic centrifuge model tests on clay tailings reservoir as well as the reservoir after expanding has been performed in a centrifuge shaker. The seismic behavior examined in this study includes the acceleration amplification, variations in the pore water pressure both in soft clay foundation and in clay tailing, deformation of the soft...

This paper aims to characterize the seismic behavior of concrete-faced rock-fill dams. A series of dynamic centrifuge tests were carried out. The experimental results demonstrate that the stress evolution in the face slab is related to the pattern of energy buildup and that the overall stress evolution pattern is highly affected by pre-shaking. For...

Similar to fully saturated sand, the partially saturated sand can also liquefy under certain conditions during earthquakes. This study aims to characterize the seismic behaviour of partially saturated sand. Centrifuge shaking table tests were performed using the IWHR horizontal-vertical centrifuge shaker. The experimental results indicate that the...

This study aims to examine the stress evolution in the face slab during shaking and its failure mode under earthquakes. To achieve this，a series of dynamic centrifuge tests were carried out. The experimental results indicate that compressional and tensional stress increments are developed in the outer and inner faces of the slabs，respectively. Mean...

In this study, an innovative experimental setup for model pile tests was developed to characterize friction fatigue in sand during cyclic jacking. In the experimental setup, a high-performance precision electric linear actuator was used to control jacking of the model piles. P-wave tomographic imaging was used to characterize the associated changes...

In this study, a series of dynamic centrifuge tests were carried out in the IWHR centrifuge horizontal-vertical shaker to examine the seismic behavior of concrete-faced rock-fill dams (CFRDs) with empty reservoir. The experimental results demonstrate the acceleration amplification behavior both in the rock-fill and along the face slab. The results...

Reinforcing the zone near the crest using geo-grid is one of the seismic engineering measures for earth core rockfill dams. However，there lacks experimental study on the seismic response of the reinforced dams. In order to assess the performance of geo-grid reinforcement，a series of centrifuge dynamic tests was performed using the IWHR （China Insti...

Geotechnical centrifuge modelling is one of the most efficient physical modelling methods. Recently, with the development in hydraulic pressure, electronic control and sensing and testing technologies, the technique of geotechnical centrifuge modelling has been greatly improved. Correspondingly, its applications have been widened. Based on the cent...

Safety and protection of hydraulic structure is significant in national defense. There is no effective index to evaluate the dynamic responses caused by underwater explosion. Generally， the shock wave generated by underwater explosion propagates spherically. This paper derives the total energy of structure subjected to spherical wave. A new impact...

Aging- or creep-related phenomena in sand have been widely studied, and the discrete element method (DEM) has been frequently used to model the associated soil behavior and then to explore the associated underlying mechanisms. However, several difficulties involved in modeling still remain unsolved. To resolve these difficulties, a new approach bas...

Understanding the soil responses during monotonic jacking can help improve the estimation of axial capacity in pile foundation design. To examine the soil responses in terms of strain and stress distributions, stress paths, the movement of particles and contact force mobilization during monotonic jacking, a three-dimensional simulation of a centrif...

Static and dynamic liquefaction may produce different levels of damages on the infrastructures and various numbers of casualties. Understanding the associated initiation mechanisms therefore is very important for geotechnical engineers to predict and manage the relevant hazards. In this study, a series of DEM simulations of undrained triaxial compr...

In this study, model pile tests were carried out in a custom-made pressurized chamber to explore the mechanisms of a driven pile setup in dry sand. A bender element system and tactile pressure sensors were used in parallel to monitor the stiffness and stress changes in the soil surrounding the pile during the test. The experimental results demonstr...