摘要
软岩深基础端阻力值计算问题一直工程界较为关注的问题,目前我国规范一般采用单轴抗压强度frc乘以折减系数(远小于1)计算软岩端阻力值,但其远小于载荷试验值。大量工程实践表明,规范考虑的折减系数偏小,实际工程甚至存在端阻力测试值大于其单轴抗压强度frc值。旁压试验曲线与载荷试验曲线出现的直线段和弯曲段类似,用其试验参数确定的软岩端阻力值与实际值较为相符。主要探讨根据软岩各类试验强度参数计算其深基础端阻力的方法,单轴抗压强度、三轴试验参数和标准贯入度击数等参数计算的软岩端阻力值,但仅可作为工程勘察建议参考的初设值,在积累足够地区经验后,可用于二级或荷载不大的一级建筑物软岩端阻力设计值;载荷试验值是端阻力设计计算最为可靠的依据,通过对比试验后,旁压试验参数用于计算软岩端阻力设计值也较为可靠。
Typical soft rock has special engineering properties and it is widely distributed in China.How to estimate tip-resistance design values of deep foundation embedded in typical soft rock is a challenging issue in geotechnical engineering.Specification methods by test parameters are discussed;and tip-resistance design values of deep foundation based on Chinese codes,are obtained by multiplying a coefficient less than 1 with frc as the uniaxial compression strength of typical soft rock.Coefficients are of more disparity in different codes.Moreover,design valves in specification underestimate the bearing capacity of soft rock for neglecting effect of some field factors such as confining pressure and rock structure,et al..Parameters obtained by various test methods,field testing in chief bonding or indoor experiment to determine tip-resistance value are also presented.Advantages and disadvantages of each method are also discussed in different aspects.In the simulative conditions,results from plate load test and pressuremeter test agree well with bearing behavior of pile-tip soft rock in deep foundation to some extent.Tip-resistance value computed by dynamic triaxial test′s parameters value is more approximate to plate loading test value than that computed by uniaxial compression strength in some cases.Linear relationship using Nt,he standard penetration test valuet,o determine tip-resistance value has no enough theoretical foundation.Tip-resistance value computed by frc,c and ？ or N for typical soft rocki,s merely referred to as initial design value suggesting by survey department.Conclusively,determination of tip-resistance design value should be dependent mainly on field testing and verified by indoor experiment at the same time.Comparing and analyzing tip-resistance values of typical soft rock in areas,Changsha,Nanjing,Guangzhou,Nanning,show that values in the four regions are different and greater than experimental values and suggested values in Chinese codes,although they are belonging to the same soil categor
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2007年第A01期2913-2920,共8页
Chinese Journal of Rock Mechanics and Engineering
关键词
岩石力学
典型软岩
端阻力
试验参数
计算方法
rock mechanics
typical soft rock
tip-resistance
test parameters
calculation methods
