Failure mechanism of large-diameter shield tunnels and its effects on ground surface settlements

A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.

Breakability analysis of the elastic rock beam based on the winkler model

Based on the Winkler model, a mechanic model was established with formulas derived concerned with the deformations before and after a roof breakage at places in front of and at the back of the working face. In accordance with the theory for rock beam breakage, the beam breaking position in front of the working face is specified. In addition, the formulas were developed for the velocity of the subsidence at observatory point A in front of the working face when the coal wall serves as the coordinate center and the advance distance at time t as the dynamic coordinate. In the application of the above-mentioned achievements to the practice of Xieqiao Mine and the mines of the Eastern Panji Company of Huainan Mining（Group） Co. Ltd., the results concerned with the velocity with which the roof stratum tends to subside before and after breakage as derived from the mechanic model are well compatible to the results based on in-situ observations and measurements.

Rapid assessment of regional superficial landslide under heavy rainfall

In order to establish a rapid method for regional slope stability analysis under rainfall,matric suction and seepage force were taken into account after obtaining explicit solution of infiltration depth.Moreover,simplified analysis model under 3D condition was put forward based on identification and division of slope units,as well as modification of sliding direction of each column.The result shows that explicit solution of infiltration depth is of good precision;for the given model,safety factors without taking seepage force into account are 1.82-2.94 times higher;the stagnation point of slope angle is located approximately in the range of(45°,50°);the safety factor changes insignificantly when wetting front is deeper than 2 m;when matric suction changes in the specified range,the maximum variations of safety factor are less than 0.5,which proves that matric suction plays an insignificant role in maintaining slope stability compared to the slope angle and infiltration depth.Incorporated with geographic information system,a practical application of regional slope stability assessment verifies the applicability of the proposed method.

模块化精轧技术在不锈钢高线中的应用

采用数值分析、有限元分析、实验室试验等方法研究了高速线材精轧变形宽展影响因素及宽展模型、模块化精轧机耦合刚度及刚度模型、高速轧制时咬钢速降控制策略。针对某不锈钢高速线材生产线精轧机组长期存在的稳定性差、收放料型不准确导致的产品尺寸精度波动大的问题进行升级改造,通过高适应性孔型系统、高刚度模块化高速轧机、高速轧制速降控制技术实现了模块化精轧技术在不锈钢高线中的应用。针对爬坡段易划伤问题,将滑动摩擦式爬坡导槽优化为滚动摩擦式三辊导槽,并将精轧前侧活套调整为立活套。改造后生产结果表明,模块精轧机运行稳定,锥箱振动值小于2.8 mm/s,精轧机组出口料型尺寸精度较改造前提高20%以上,最终产品尺寸精度及表面质量均得到了明显改善。

A reduced-order-model-based multiple-in multiple-out gust alleviation control law design method in transonic flow

Gust alleviation is very important to a large flexible aircraft.A nonlinear low-order aerodynamic state space model is required to model the nonlinear aeroelastic responses due to gust.Based on the proper orthogonal decomposition method,a reduced order modeling of gust loads was proposed.And then the open-loop and closed-loop reduced order state space model for the transonic aeroelastic system was developed.The static output feed back control scheme was used to design a simple multiple-in multiple-out(MIMO)gust alleviation control law.The control law was demonstrated with the Goland+wing model with four control surfaces.The simulation results of different discrete gusts show the capability and good performance of the designed MIMO controller in transonic gust alleviation.

The influence of rainfall on PR radar measurement of ocean surface wind speed and its calibration

Rain can significantly degrade the wind vector retrieval from Precipitation Radar （PR） by three mechanisms, namely, two-way rain attenuation, rain volume-backscattering, and ocean surface roughening from the rain splash effect. Here we first derive the radar equation for PR in rainy conditions. Then we use the rain attenuation model for Ku band, volume backscatter model for spherical raindrops and PR-TMI （TRMM Microwave Imager, TMI） matchup datasets from June to August in 2010 to solve the radar equation, and quantitatively analyze the influence of rainfall on PR radar measurement of ocean surface wind speed. Our results show that the significant effect of rain on radar signal is dominated by two-way rain attenuation and rain splash effect, and the effect of rain volume-backscattering is relatively the weakest, which can even be neglected in rain-weak conditions. Moreover, both the two-way rain attenuation and rain splash effect increase with the increasing of integration rain rate and in- cident angle. Last, we combine volume-backscattering effect and splash effect into a simple phenomenological model for rain calibration and select three typhoon cases from June to August in 2012 to verify the accuracy of this model. Before calibration, the mean difference and mean square error （MSE） between PR-observed σ0 and wind-induced σσ are about 2.95 dB and 3.10 dB respectively. However, after calibration, the mean difference and MSE are reduced to 0.64 dB and 1.61 dB respectively. The model yields an accurate calibration for PR near-nadir normalized radar cross section （NRCS） in rainy conditions.