Static and Dynamic Load Tests of Shaft and Base Grouted Concrete Piles

This paper examines shaft and base grouted concrete piles by conducting vertical static load tests (SLTs) and dynamic load tests. Three concrete piles with shaft and base grouting, with base grouting only, and without grouting techniques were selected, and compressive SLTs were conducted. Two piles with grouting were also assessed with dynamic load tests. Another two uplift SLTs were conducted to one shaft and base grouted pile and one pile without grouting. Traditional presentations were provided to check whether the bored piles reached the design requirement. Interpretations of test results were also provided to determine the ultimate pile capacity. Results from these 5 SLT programs indicated that double-tangent and DeBeer's methods are close to each other, and Chin's method overestimates the pile capacity. Comparison of the results from the SLTs and dynamic load tests shows that the results from Chin's method are close to dynamic results, and Mazurkiewicz's method overestimates for friction resistance. The results also demonstrate that base and shaft grouted pile and base grouted pile increase by 9.82% and 2.89% in compressive capacity, respectively, and compared to the uplift SLTs; there is a 15.7% increment in pile capacity after using base and shaft grouting technology.

Effects of Intake Port Optimization on Soot Emission from Diesel Engine

All future engine developments must consider the primary task of achieving the required emission levels. An important step towards the development of combustion engines is the optimization of the flow in the intake ports. The charging movement in the combustion chamber, which is generated by the intake flow, considerably influences the quality of the combustion engine. In this paper, steady CFD analysis were applied to different structures of double-tangent-port. The swirl ratio can be improved while flow coefficient remains unchanged if port eccentricity is 34.4 mm. By defining three characteristic parameters, the speed non-uniformity index, standard deviation and mixture concentration standard deviation and equivalent ratio range, quantitatively describing the combustion process in cylinder, and then compared with transient CFD three-dimensional contours, we can see that characteristic parameters can be more accurate and comprehensive in analyzing the influence of inlet structure of soot formation. Effects of different intake ports on fuel-air mixing in a turbocharged diesel direct injection engine during intake and compression strokes are analyzed. It turns out that the optimized double-tangent-port has the highest uniformity of velocity, in the meanwhile, air/fuel mixing is relatively uniform. On the other hand, mixed-port and double-helix-port can cause uneven flow field which is bad for combustion, even though the swirl ratio can increase largely. Finally, the simulation results show that soot emissions of the optimized double-tangent-port have significantly lower levels, at 2200 r/min under full load.

Nonlinear Stability Analysis on Vessels Subjected to External Pressure

To determine stability performance and the critical load of the short cylinder vessel which is made of steel, this paper carried out the finite element linear buckling analysis for 5 meters long steel pressure vessel and obtained buckling critical load. Then performed the nonlinear instability analysis by the arc-length method and obtained the load-displacement curves of the overall stability of the pressure vessel structure. The critical load can be got by twice the elastic slope method and double-tangent intersection method, and the loads are slightly higher than the result of the theoretical calculation, so the result of the theoretical calculation is safe and reliable. Finally, several measures keeping stability of short cylinder pressure vessel are proposed.

An Experimental Correlation of Quenching Temperature Under Top-Down Reflooding in a Vertical Tube

A quenching experiment under top-down reflooding in a vertical tube was performed by adopting the transient hot block quenching test technique. The temperature history on the inner wall of test tube was calculated by using a quasi-steady-state two-dimension numerical technique, and the intersection of double tangent lines was used to determine the location and the time of the quench front. Based on some theoretical models of quenching temperature, at the same time, the effect of flow parameters in the tube during quenching was taken into account, a semi-empirical correlation for quenching temperature under the low pressure and low mass flow rate is presented in this paper. It is as follows:Tq−TsTo−Ts=11.8362(Ts−Tf,inTo−Ts)−0.0714[(cρk)w]0.2938×G0.0251×(Ts−Tf,in)−0.3145 The parameter range of this correlation is as follows: system pressure: 0.31∼0.88MPa: mass flux: 17.7∼902.kg/m2s; inlet subcooling: 3∼77°C; initial hot-wall temperature: 450∼600 °C.