库岸再造对雅泸高速公路岗子上隧道进口岸坡的影响

雅泸高速公路青杠咀特大桥泸沽岸桥台与岗子上隧道进口衔接段位于大渡河右岸上部冰积扇上,由于瀑布沟水电站的蓄水将使岸坡前缘约1/4部分没于水下。对整个岸坡影响较大的岩土体主要是由上-中更新统冰积、冰水沉积层组成的冰水堆积物,这类岩土体在水的作用下,其物理力学性质和强度将会发生显著变化,弱化工程性状,从而影响岸坡的稳定性及桥台布置。可以预见,对岸坡起主要影响作用的外部条件就是水的作用,库岸再造将是影响岸坡稳定性的控制性因素。本文以岗子上隧道进口岸坡为研究对象,通过对岸坡工程地质条件、岩土体结构及物理力学特性、岸坡影响因素的分析,深入研究了瀑布沟电站水库蓄水后引起的库岸再造对岸坡稳定性的影响。并采用卡丘金法、两段法(多段法)、极限平衡分析法对库岸再造影响宽度进行预测。3种方法的预测结果表明:瀑布沟电站蓄水后该段岸坡各个不同部位均会产生不同程度的塌岸破坏。根据该库岸岸坡的结构特点和3种方法的适用条件,提出对库岸岸坡不同梯段需要采用不同的预测方法综合预测,即对于水下岸坡可按两段法预测,而对于水上岸坡可综合考虑卡丘金法和极限平衡法的计算结果。对于类似库岸岸坡的稳定性分析具有一定的指导意义。

INFLUENCE OF RESERVOIR BANK RECONSTRUCTION ON PORTAL BANK SLOPE OF GANGZISHANG TUNNEL IN YALU EXPRESSWAY

The link segment of Qinggangzui Bridge abutment and Gangzishang Tunnel portal in Yalu Expressway will be built on the ice deposit fan on the right bank of the Dadu River.Because of the water storage of Pubugou Hydropower Station,about a quarter in front of the bank slope will be underwater.The main geotechnical material impacting the entire slope is the ice deposits composed by upper-middle PleistoceneIce ice sediments and ice water sediments.Under the action of water,their physical and mechanical properties and strength will be significantly changed.Their engineering behavior will be weakened.Thus the bank slope stability and the abutment arrangement will be affected.It can be foreseen that the water from the external conditions will play an important role and the reservoir bank reconstruction will generally control the bank slope stability.In this paper,the reservoir bank slope in Yalu Expressway is discussed because Gangzishang Tunnel portal is to be constructed on the slope.Through the slope engineering geological conditions,rock and soil structure and mechanical properties,the analysis of factors affecting slope,the water impact on the banks as well as the slope stability are mainly discussed.The used methods are Cacho,Two Sections(Multiple),Limit-equilibrium for the analysis of the water impact on the reservoir bank and to predict recycling width.Forecasting results from the three methods all show that different parts of the slope will have bank collapse in different degrees after the Pubugou Power Station is impounded.According to the structural characteristics of the reservoir bank slope and the three methods of application conditions,this paper puts forward an integrated prediction method that different forecasting methods need to adopt at different sections of the reservoir bank slope.The Two Sections(Multiple)method is used to forecast the underwater bank slope.For the slope upon water,the calculation results of Cacho method and Limit-equilibrium method are comprehensively considered.The results can also be used for stability analysis of similar reservoir bank slopes.