Li Shucai

Ultrasonic detection method of freeze-thaw damage thickness of concrete

The freeze-thaw damage thickness of concrete is very important to assess the damage of structures. Such research at present is relatively small. For quantitative analysis of freeze-thaw damage thickness of concrete structure, this paper conducted a quick freezing method, entraining concrete test beam is immerged with 3.5% NaCl salt solution to freeze test. Based on ultrasonic detection methods, non-metallic ultrasonic instrument was used to detect concrete test blocks after 300 freeze-thaw cycles using multi-level measurement methods. Four test blocks were tested, each test block was tested 3 times. The formula of derivation of stress wave in the structures. The test data was analyzed and the damage thickness of concrete was achieved. The results show that: The damage thickness of concrete test blocks after 300 times freeze-thaw cycles and this value is less than the protective layer of steels.

Theoretical and experimental research on the grout fronts diffusion considering filtration effect

Based on the seepage continuity equation, Darcy law, mass conservation equation, linear filtering law and pressure drop equation, the theoretical model of grout fronts diffusion was established. And through the model, the filtration mechanism of cement particles and the diffusion law of slurry fronts were analyzed. By applying the model test system developed independent, the dynamic variation law of the pressure of grout fronts is studied and compared with the theoretical value. The results show that, the permeability coefficient of the precipitated cement increases along the grout diffusion distance under the filtration effect. The change rate of frontal velocity is negatively correlated with the permeability coefficient of precipitated cement. At the specific diffusion distance, the frontal pressure drop p increases first and then decreases, while the frontal pressure p and the average unit pressure drop Δ P show the trend of decreasing first and then increasing. The deviation rate of frontal pressure value between theory and test is only from –10% to 26%, which reveal a high degree of coincidence. The conclusions can be used to guide the grouting design, which has certain application value to the practical engineering.

Risk Measurement and Control of Water Inrush into Qiyue Mountain Tunnel

Qiyue mountain tunnel lies in Hurongxi highway in Hubei Province, soluble rocks are karstified intensively. To predict and prevent water inrush into tunnel when it is constructed, risk measurement is necessary to guide comprehensive advance geology prediction and prevention measures. Fuzzy mathematics model is put forward to distinguish potentially dangerous parts along tunnel. 7 main controls of rock karstification are selected as risk rank indicators. Use the fuzzy mathematics model differentiated the tunnel into 4 ranks of dangerous parts according to risk index. It is applied in Qiyue mountain tunnel and practice approves that the measurement and measures are useful.