考虑实测锤击数影响的动力触探杆长修正系数研究

Rod length correction coefficient of DPT considering the influence of themeasured number of hammer blow

现行规范中动力触探锤击数修正系数的确定需考虑实测锤击数影响,而业内对此少有研究。在一次人工做功击打时,动力触探落锤和探杆通过碰撞传递机械能,基于一维碰撞理论,若恢复系数不为0,则二者碰撞后速度不等,在重力和土阻力作用下会继续碰撞。推导了仅计算首次碰撞后探杆能量、计算首次碰撞后落锤与探杆能量之和及计算首次碰撞后有限次碰撞3种计算方案下的杆长修正系数计算方法。研究结果表明:在碰撞过程中和在一次人工做功击打的两次碰撞间是否考虑土体阻力作用,对杆长修正系数的计算都有影响。使用计算首次碰撞后落锤与探杆能量和的计算函数对现行规范中杆长修正系数拟合,得到重型和超重型决定系数分别为0.9935、0.9751。仅考虑两次碰撞间土体对探杆阻力的影响,使用计算首次碰撞后有限次碰撞的计算方法,当恢复系数≤0.3时,计算得到的杆长修正系数随锤击数增大而减小。

In the current code,the determination of the correction coefficient of dynamic penetration needs to consider the influence of the measured number of hammer blow,which is rarely studied in the industry.During a blow,the dynamic penetration drop hammer and the probe rod transfer the mechanical energy through collision.Based on the one-dimensional collision theory,if the coefficient of restitution is not zero,the two will continue to collide under the action of gravity and soil resistance.The calculation method for the rod length correction coefficient under three calculation schemes is derived:only calculating the energy of the probe rod after the first collision,calculating the energy of the drop hammer and probe rod after the first collision,and calculating the finite number of collisions after the first collision.The results show that whether the soil resistance is taken into account in the collision process or between the two collisions of a single blow has an influence on the calculation of the rod length correction factor.The calculation function for calculating the sum of the energy of the falling weight and the probe rod after the first collision is used to fit the rod length correction coefficient in the current code,and the determination coefficients of heavy and super heavy are 0.9935 and 0.9751 respectively.Using the calculation method calculating the finite number of collisions after the first collision,only the influence of resistance of soil to probe rod between two collisions is considered.The calculated rod length correction coefficient decreases with the increase of the number of blows,when the coefficient of restitution is no greater than 0.3.