【摘要】 为了研究软岩地基桥桩的荷载传递性状、破坏机理,并获取在该地质条件下更为可靠的桩基计算参数,对秦巴山区软岩地基3根钻孔灌注试桩进行竖向静载试验。结果表明:秦巴山区软岩地基桥桩试桩荷载沉降曲线呈陡降型,实测竖向极限承载力为20 500kN,桩的破坏方式为桩身材料强度破坏;淤泥质亚黏土地层中的碎石起到一定的骨架作用,增强了此地层桩极限侧阻力,发挥极限侧阻力所需的桩土(岩)相对位移为4～8mm;强风化砾岩表现为加工软化型,发挥极限侧阻力所需的桩土(岩)相对位移为3～8mm;中风化砂砾岩表现为明显的加工硬化型,所需的桩岩相对位移大,且桩极限侧阻力的特征点不明显;淤泥质亚黏土地层桩侧阻力占总荷载的60%～70%,随着桩顶荷载的逐步加大,该地层桩侧阻力所占比例不断下降,而嵌岩段桩侧阻力所占比例逐渐上升,达到55%～65%,嵌岩段桩侧阻力沿桩深的分布曲线表现出非线性的特征;试桩为端承摩擦桩,桩端阻力约占桩顶荷载的20%左右,且未充分发挥,在上部结构允许的沉降范围内,适当增加桩端的沉降有利于端阻力的发挥;桩侧阻力先于端阻力发挥,建议单桩承载力设计时分别采用不同的端阻力和侧阻力安全系数。更多还原

【Abstract】 In order to study the load transfer behavior and failure mechanism of bridge piles in soft rock foundation and obtain the reliable calculation parameters of piles under the special geological situation,the vertical static load test with three bored piles was done in Qinling-Dabashan Mountains.The results showed that the curves of loads and settlements for test piles descended steeply,the measured vertical ultimate bearing capacity was 20 500 kN,and the failure mode of pile was material strength failure;the gravel in muddy mild clay was positive to ultimate side friction force of pile,the relative displacements between pile and soil(rock) for bearing side friction force were 4-8 mm;strong weathering conglomerate processed was soft,the relative displacements were 3-8 mm;middle weathering glutenite processed was obviously hard,the relative displacements were large,and the feature point of pile ultimate side friction force was not obvious;pile side friction forces in muddy mild clay were 60%-70% of total loads,and the proportion decreased continuously when pile top load increased gradually;the proportion of pile side friction forces in rock-socketed increased continuously and reached to 55%-65%,the relationships between side friction forces and depths were nonlinear;test piles were tip-support friction piles,pile tip resistances were about 20% of pile top load and were not adequately born,and increasing the settlement of pile tip appropriately within the allowable range of upper structure was favorable to bear the tip resistance;pile side friction force was born before tip resistance,so it was suggested that various safety coefficients of side friction force and tip resistance were used to design the bearing capacity of single pile.更多还原