基于气井防砂砾石粒径构成特征的砾石堆积孔隙直径分析

根据气井防砂砾石的粒径构成特征及完井防砂砾石充填是多种粒径砾石混合而成的堆积碎散性特征,通过剖析高压充填条件下混合粒径砾石堆积的排列结构,建立砾石堆积孔隙直径结构理论模型,推导出计算砾石堆积孔隙直径尺寸的公式。同时,通过理论计算分析了砾石颗粒的粒径比对砾石堆积孔隙直径尺寸的定量影响规律,为水合物试采井防砂砾石粒径的选择提供了理论依据。

GiT-based structural geologic feature analysis of the southern segment of Longmenshan fault zone for earthquake evidence

The Longmenshan fault is a thrust fault which runs along the base of the Longmen Mountains in Siehuan province, southwestern China. The southern segment of the fault had two distinct responses to the Ms 8 Wenehuan and Ms 7 Lushan earthquakes. This study determines characteristics of the structural geology of the Longmenshan fault to evaluate how it influenced the two aforementioned earthquakes. This research was done within a Geo- information Technologies （GiT） environment based on multi-source remote sensing and crustal movement data extracted from the Global Positioning System （GPS）. The spatial distribution of the southern segment of the Longmenshan fault zone was comprehensively analyzed to study both earthquakes. The study revealed that the Wenehuan and Lushan earthquakes occurred on two relatively independent faults. In addition, there was a nearly constant-velocity crustal movement zone between the two epicenters that probably had a compressive stress with slow motion. Furthermore, the central fault and a mountain back fault gradually merged from north to south. The Lushan earthquake of the Wenchuan earthquake. was not an affershock The research showed that fault zones within 30-50 km of State Highway 318 are intensive and complex. In addition, crustal movement velocity decreased rapidly, with a strong multi-directional shear zone. Thus, activity in that zone was likely stronger than in the northern part over the medium to long term.

GIS-based spatial prediction of landslide using road factors and random forest for Sichuan-Tibet Highway

Accurate evaluation of landslide susceptibility is very important to ensure the safe operation of mountain highways.The Sichuan-Tibet Highway,which traverses the east of the Tibetan Plateau,frequently encounters natural hazards.Previous studies generally use statistical methods to analyze the hazards along the Sichuan-Tibet Highway.In this research,we present two road factors,namely aspect to road and road profile to increase the accuracy of landslide susceptibility mapping by considering the influence of landslide movement direction on road.First,the aspect to road,which represents the impact of different landslide movement directions on the highway,was extracted by combining road direction with mountain aspect.Then,the road profile,which reflects the subgrade structure between the road and surrounding mountains,was extracted according to the terrain data.Finally,the landslide susceptibility maps were produced based on the random forest(RF)method by using 473 landslides and 10 conditioning factors,including road factors(aspect to road,road profile)and primitive factors(slope,aspect,curvature,relief amplitude,peak ground acceleration,crustal movement velocity,faults,rainfall).The area under the receiver operating characteristic curve(AUC)and the Gini importance were used to evaluate the performance of proposed road factors.The AUC values on two groups that add road factors and only use primitive factors were 0.8517 and 0.8243,respectively.The Gini importance indicated that road profile(0.123)and aspect to road(0.116)have a significant contribution to landslides compared with the primitive factors.The results of multi-collinearity analysis and frequency ratio confirmed the suitability of the road factors for predicting hazards along the highway.