高拱坝坝肩稳定分析中拉裂面的作用机理研究

在拱坝坝肩稳定分析的刚体极限平衡法里,一般认为滑移体拉裂面完全脱开,不考虑其上的岩体抗力,对高拱坝而言,这种做法可能使稳定分析过于保守。基于三维有限元分析的多重网格分析方法,可以将三维有限元分析成果投影到任一滑面网格上,进而求得其上的应力分布及合力,以及滑面和滑块的安全系数。利用此方法对溪洛渡高拱坝工程的坝肩关键滑块的分析研究表明,直至超载3倍时,虽有部分区域受拉,拉裂面就合力来说仍处于受压状态,故拉裂面提供的抗力在较大荷载变幅内是可资利用的。计算表明计入拉裂面岩体抗拉力后,块体稳定安全度有显著的提高。

Mechanical properties and stress corrosion cracking behaviour of AZ31 magnesium alloy laser weldments

An AZ31 HP magnesium alloy was laser beam welded in autogenous mode with AZ61 filler using Nd-YAG laser system.Microstructural examination revealed that the laser beam weld metals obtained with or without filler material had an average grain size of about 12 μm.The microhardness and the tensile strength of the weldments were similar to those of the parent alloy.However,the stress corrosion cracking （SCC） behaviour of both the weldments assessed by slow strain rate tensile （SSRT） tests in ASTM D1384 solution was found to be slightly inferior to that of the parent alloy.It was observed that the stress corrosion cracks originated in the weld metal and propagated through the weld metal-HAZ regions in the autogenous weldment.On the other hand,in the weldment obtained with AZ61 filler material,the crack initiation and propagation was in the HAZ region.The localized damage of the magnesium hydroxide/oxide film formed on the surface of the specimens due to the exposure to the corrosive environment during the SSRT tests was found to be responsible for the SCC.

牵引式滑坡后缘破裂面形成机制试验研究

由于河谷下切或者坡脚开挖,常会造成自然斜坡牵引式滑动,形成多级后缘拉裂面。后缘面的形成机制对牵引式滑坡的稳定性分析有重要影响,因此开展试验测试和理论分析。开发能够同时模拟地下水对滑带软化作用和滑坡渐近破坏过程的试验装置,由若干渗透盒构成分段式滑面,可以模拟各种几何形态的滑动面,通过对不同渗透盒注水,可模拟滑带分阶段饱和软化,从而实现对各种滑坡破坏模式的模拟。设计4种试验方案,模拟圆弧型、折线型和直线型滑动面,以及三段线和两段线坡面线。分三阶段设计滑坡工况,测试滑体后缘面破裂倾角。试验表明,后缘面倾角试验值受滑体厚度和失稳滑段位置影响明显。假定牵引式滑坡的后缘面可能形成机制为整体滑动式、滑动拉裂式和滑动剪切变形式,计算后缘面倾角。比较表明,滑动拉裂机制计算值与试验值最接近,在试验值上下浮动,相对误差小于10%。据此认为牵引式滑坡的后缘面形成机制为:底滑面失稳下滑,在失稳滑面末端对应的滑体部位出现了拉破坏区,拉应力由最小主应力控制,拉破坏面方向与最大主应力方向基本一致。

Surface borehole synthesis tension deformation fracture time-space rule

In order to release the tension and shear effect of the superjacent rock strata movement during excavation in coal mine,protect the surface borehole case from fracturing fast and make a good use of the surface borehole during goaf methane drawing,a common synthesis tension deformation fracture model was set up based on the synthesis tension effect of the rock strata,and the deformation rule of the surface borehole case with time and space was researched.The results suggest that,to reduce the deformation the surface borehole should be built between the boundary of the stope and the knee of subsidence curve.At the same time,a 3DEC simulation model and an engineering example were carried out to examine the rules of theoretical model.The result suggests that the model and the rules accord to the test and have good building and protection engineering application values to the surface borehole.

Study on the propagation of interface crack of young concrete lining and rock under blasting load

In the construction of water conservancy and hydropower project,young concrete lining structure is often affected by blasting load. Young concrete has a lot of micro-fractures with random distribution,which are easier to propagate and connect under blasting load. This paper focuses on the calculation on dynamic stress intensity factors of bond interface crack of concrete-rock according to concrete age. Result shows that different incidence angles of stress wave lead to different crack propagation mechanisms. Under the normal incidence of impact load,the bonding interface crack propagation of the concrete lining is mainly caused by reflection tensile stress,which forms from the free surface. With horizontal incidence of stress wave,the bond interface crack propagation of concrete lining is affected by concrete age. With the increase of concrete age,the elasticity modulus margin between concrete and rock decreases gradually,and the crack propagation form changes from shear failure to tensile damage.