摘要
以沪渝高速公路湖北段平缓反倾红砂岩为研究对象,在平缓反倾红砂岩高陡边坡中岩体易软化崩解。自然冲侵蚀形成的高陡山体卸荷变形可达几十毫米至近百毫米,卸荷变形破裂方向与构造节理重叠,使节理裂隙变宽,贯通性提高,为高陡坡体提供了顺坡向陡直破裂面。加之公路切坡卸荷变形和坡体软化变形,岩体软化后的变形模量下降约80%,卸荷变形和软化变形各有数毫米的变形量,与自然坡体卸荷重叠,使坡体变形进一步加大,使红砂岩坡体潜在不稳定性增大。同时地下水作用使卸荷裂隙充填一定高度的静水压力,还使岩体产生软化,岩块软化系数一般在0.3~0.7,导致岩体强度显著下降,30～40 m高的静水压力可使边坡的稳定性系数从开挖前的5.56降至1.96,开挖后从2.77降至1.07,这两方面的作用可使切坡后较稳定的反倾坡体变化到极限平衡状态,甚至失稳状态。因此,施工中要特别注意切坡后的即时加固,并采取措施防止卸荷裂隙中地下水聚积,减少地下水对坡体的软化。
The deformation and stability of gentle anti-dip red sandstone slope in Hubei section of Shanghai-Chongqing Expressway is investigated.The high-steep slope in gentle anti-dip red sandstone is easy to soften and collapse.The unloading deformation of high-steep slope resulted from natural erosion can be dozens of millimetres to nearly 100 millimetres.The direction of unloading deformation overlaps with structural joints,which widen the joint fissure and increase the connectivity and finally provide a steep downslope failure surface for the high-steep slope.The unloading and softening deformations of highway cutting slope further increase the slope deformation and decrease slope stability;and the deformation modulus can decrease by 80%.Groundwater flows into unloading fissures and causes a certain height of hydrostatic pressure.Rock mass strength is significantly decreased by the softening effect of groundwater and the softening coefficient of rock block generally is about 0.3-0.7.Under 30-40 m hydrostatic pressure,the stability coefficient of slope decreases from 5.56 to 1.96 before excavation and from 2.77 to 1.07 after excavation.All of these adverse effects decrease the stability of anti-dip slope and even cause failure.It is concluded that reinforcements should be installed immediately after the slope cutting and measures should be taken to prevent the accumulation of groundwater in the unloading fissures,so as to reduce softening of slope.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2012年第3期805-811,共7页
Rock and Soil Mechanics
基金
国家自然科学基金资助项目(No.40802077)
云南省交通运输厅科技项目(2011(D)11-b)
关键词
红砂岩
平缓反倾岩层
高陡切坡
软化
卸荷变形
稳定性
red sandstone
gentle anti-dip bedded rock
high-steep cutting slope
softening
unloading deformation
stability
