拉力型粘性土层锚杆抗拔力现场试验

Field Test of Pull-out Resistance of the Tension Anchor in Cohesive Soils

深坪锚杆试验是一项采用多种方法以测试土层锚杆力学特性、长度及试验方法为主要目的的大型综合性试验,其中B型为一次注浆拉力型粘性土层锚杆,按不同长度分为4组共16根锚杆,试验结果表明:(1)本锚杆试验所采用的判稳标准,即最短持荷观测期15 min、蠕变率2.0 mm及计算周期的初始时刻不少于5 min,与国内标准中采用的7类判稳方法相比,具有试验时间短、准确度高等优点;(2)粘性土层中的拉力型锚杆,长度不超过18 m时,沿锚杆粘结应力大致均匀分布;(3)花岗岩残积土中,锚杆锚固段有效长度不少于18 m;(4)常规施工水平及一次注浆时,锚杆浆体与花岗岩残积土的粘结强度平均值为103.7 kPa。

Shenping anchor test is a large comprehensive test programme,in which several methods are used to test the mechanical properties,lengthes and test methods of anchor bolts.Type B anchor bolt is a one-pass grouting ten⁃sile anchor in cohesive soils.A total of 16 anchor bolts with different lengths are divided into 4 groups,and the test results show that:(1)the stability criterion proposed in this paper is that the shortest load observation period is 15 min,the creep rate is 2.0 mm,and the initial moment of the calculation period is not shorter than 5 min,proving the shorter test time and higher accuracy compared with the 7 types of judgment methods adopted in domestic stan⁃dards;(2)for the tensile anchors in the cohesive soil layers,when the length does not exceed 18 m,the bond stress is approximately evenly distributed along the anchor rod;(3)in the granite residual soil layer,the effective bond length is not less than 18 m;(4)under the precondition of conventional construction and one-pass grouting,the average bond strength between grout and granite residual soil layer is 103.7 kPa.