The Stability Study Of Weak Rock Road Tunnel Under The Action Of Seepage

The problem of groundwater is the difficulty in the tunnel engineering,both of the stress field and the seepage field will be changed by the tunnel excavation,and the change of seepage field will be influential to the stress,displacement,pore water pressure and seepage flow.The grouting reinforcement is one of the most common methods to solve the problem of the groundwater seepage at present,but now people cannot find detailed description about that in the design specifications(JTG D70-2004)of the highway tunnel.The author uses the numerical simulation method of FLAC3 D to analysis the chang of stress and strain in tunnel excavation and support stages,aiming at different water depth and the different thickness of the grouting reinforced region.The main results are as follows:1?Fixed tunnel buried depth is 250 meters,the underground water level(the outside water pressure of lining structure)is higher,the displacement,vertical stress,horizontal stress,pore water pressure and seepage flow is bigger,and with the rise of the water level,the rate of arch bottom displacement increasing(the displacement rise 5.6% following waterhead rise 30 meters averagly)is quicker than the rate of arch top displacement increasing(the displacement rise 2.6% following waterhead rise 30 meters averagly).Indicating it is more influential in arch bottom displacement,when the groundwater level is changing.2?The monitoring node of the arch haunch take the biggest change of seepage flow,the spandrel and the vault take second place,the arch spring and the arch bottom are at the least.The seepage velocity is larger and larger with the rise of the underground water level.The seepage velocity increase gradually in the process of excavation,it become the peak value at the monitoring excavated section,however the seepage velocity decrese quickly after the monitoring excavated section,then decrese speed become slow,and become stable finally.3?The displacement,pore pressure and seepage flow decrese gradually with the incresement of the thickness of the grouting reinforcement ring,but the stress is increasing.The reason is that the seepage flow will diminish when the behind vertical stress of the lining structure increase as the thickness of the grouting reinforced region increase.It means that the effect is very obvious to diminish the pore pressure and the displacement of the tunnel lining structure by using the grouting reinforced region.However the thickness of the grouting reinforcement ring exceed 6 meters,the effect above becom weak.