Concrete cracks often appear in construction period and operation period of the canal lining. For analyzing the cause of these cracks, the factors which will cause cracks are classified based on the data collected. Also sensitivity analysis on these factors is carried out with 3D contact nonlinear finite element method. The result shows that, the factors which resulting in concrete cracks are temperature variation, humidity, uneven settlement of foundation, expansion deformation of foundation soil, external loads etc.; Joint-cutting should be done as soon as possible, expansive property of the foundation soil and construction quality of canal lining should be strictly controlled.

Pile foundations are typically comprised in concealed construction work. In recent years, some major categories of concrete piles subject to typical damages have caused a lot of engineering disasters and accidents. These accidents have been caused by collapse of civil structures resulting in great casualties and economic loss. Therefore, damage detection and real-time health monitoring on foundation piles is an urgent research requirement. In this research, a piezoceramic based passive sensing approach is proposed to detect typical damages types of concrete piles, including partial mud intrusion, secondary concrete pouring interface, circumferential crack, and full mud intrusion. In this passive sensing approach, induced stress waves are generated by the impact hammer on the top surface of a pile and one smart aggregate embedded on the bottom of each pile is used as a sensor to receive the propagating wave signals. These sensors are embedded before pouring concrete. Structural defects affect the natural frequency of the pile. The power spectrum of piles with different types of damage were compared by plotting the sensor signals in frequency domain. The natural frequency decreases with the increase in defect severity. The experimental results demonstrate that the proposed approach can detect all four typical damage types in concrete piles.

In order to understand the contact condition of longitudinal joint of gravity dam and its influence on dam body stress, taking a concrete gravity dam section as the research object, the numerical simulations with 3D nonlinear FEM is carried out through the simulating of the construction period, the grouting process and the operation period. It shows that the opening of the longitudinal joint varies with many kinds of factors, such as the year temperature, water cooling, water load on the upstream surface, the construction process and so on. Under the present condition, secondary grouting to the longitudinal joint may not be carried temporarily. The computation results are basically in agreement with the prototype monitoring data.

The expansion effect of the MgO concrete must meet the requirement of the design for the temperature control. In this paper, its influence to the construction stress is studied using 3D FEM method. Results show that the expansion of MgO at later age is good for compensating the shrinkage induced by temperature drop and the expansion of MgO can improve the stress status in the constrained zones but may worsen the stress status in other zones. This provides the reference for popularizing dam construction technology with MgO concrete.

In order to study and analyze the internal heat transfer process of DC arc plasma torch, a two-dimensional axisymmetric model of DC arc plasma torch was established based on magnetohydrodynamics and heat transfer theory. The finite element analysis software COMSOL was used to simulate the temperature field under different conditions. The results show that when the terminal current is constant, the DC plasma arc voltage and the average temperature of the torch outlet increase with the increase of nitrogen standard flow rate, and the maximum temperature in the plasma torch decreases with the increase of nitrogen standard flow rate. When the standard flow rate of nitrogen is constant, the arc voltage decreases with the increase of arc current, and the average temperature of plasma torch exit and the maximum temperature in the torch increase with the increase of arc current. The analysis of simulation data provides theoretical guidance for the temperature control of experimental DC plasma torch.