嵌岩桩极限侧阻力和极限端阻力的估算方法研究

Study on Estimation Method of Ultimate Lateral Resistance and Ultimate End Resistance of Rock-Socketed Pile

嵌岩桩极限侧阻力和极限端阻力的大小受岩体强度、完整程度、成桩工艺、嵌岩深度等因素的影响,本文根据岩体强度、完整程度,提出根据广义Hoek-Brown准则法和Mohr-Coulomb定理法两种方法来估算嵌岩桩的极限侧阻力和极限端阻力。通过岩石质量指标RQD与岩体完整性系数kv的关系、地质强度指标GSI与岩体质量指标[BQ]的关系,通过试算法指出估算嵌岩桩极限侧阻力,应按岩石的饱和单轴抗压强度小于30MPa和大于等于30MPa两种情况进行拟合估算,并推导出修正的极限侧阻力估算公式。通过试算法指出利用Mohr-Coulomb定理法估算嵌岩桩嵌岩段极限端阻力时,关键是σ'3的确定,本文根据岩石的饱和单轴抗压强度和岩体的完整性系数的关系,通过试算比较拟合得σ'3的估算公式。通过试算与相关标准、规程所给定的经验值、实验值及工程实例检验,证明利用广义Hoek-Brown强度准则估算嵌岩桩极限侧阻力存在的缺陷与不足,利用广义Hoek-Brown强度准则估算极限端阻力较利用Mohr-Coulomb定理更可靠、更实用,更符合工程实际。

The magnitude of ultimate lateral resistance and ultimate end resistance of rock-socketed piles are affected by rock mass strength,integrity,pile-forming technology and rock-socketed depth,two methods,the generalized Hoek-Brown criterion method and Mohr-Coulomb theorem method,are proposed to estimate the ultimate lateral resistance and ultimate end resistance of rock-socketed piles.Based on the relationship between Rock Quality Index RQD and rock integrity coefficient kv,and the relationship between geological strength index GSI and Rock Quality Index[BQ],the paper points out the estimation of ultimate lateral resistance of rocksocketed piles by trial calculation,the saturated uniaxial compressive strength of rock should be estimated according to the conditions of less than 30 MPa and more than or equal to 30MPa.It is pointed out that the key is to determine the ultimate end resistance of rock-socketed pile by using Mohr-Coulomb theorem.According to the relationship between the saturated uniaxial compressive strength of rock and the integrity coefficient of rock mass,the estimation formula obtained by trial calculation and comparison.Based on the test calculation and the experience value,experimental value and engineering example given by the relevant standards and regulations,it is proved that there are defects and deficiencies in the estimation of the ultimate lateral resistance of rock-socketed piles by using the generalized Hoek-Brown strength criterion,compared with Mohr-Coulomb theorem,the generalized Hoek-Brown strength criterion is more reliable and practical in estimating the ultimate resistance,which is more in line with the engineering practice.