下贯能耗监测分析用于揭示水下DCM施工中土层变化的方法研究及验证

Research and verification of the method for monitoring and analyzing downflow energy consumption to reveal changes of soil layer in underwater DCM construction

DCM法加固水下软基,通常根据勘察孔的土层分层情况,针对不同深度的土层性质设置相应的工艺参数进行施工。由于勘察孔数量有限,地层分部通常不均匀,因此必然存在部分土层的施工工艺参数与实际的土层类型不匹配,导致施工参数冗余(浪费材料)或不足(成桩质量有风险)。通常施工中依据处理机电流判断土层变化,但电流不仅与土层类型有关,还与下贯速度有关,只通过电流划分土层容易导致误判。文章通过统计临近勘察孔的施工桩单位进尺的输出能耗,考虑下贯速度的影响,发现单位进尺的输出能耗突变处与勘察孔的土层界面高度相关,可有效指导土层划分,且相对于用电流更为稳定,对优化工艺参数有指导意义。对典型断面进行识别后,经统计发现对于该断面,识别后土层类型与勘察预期不一致的土层占总加固量的15.8%,占底部加固量的54.2%,说明对不同深度的土层类别进行划分是有必要的。

The DCM method for reinforcing underwater soft foundation is typically based on the layering of the soil identified through borehole investigation,and corresponding construction parameters are set for soil layers at different depths to account for their specific properties.Due to the limited number of boreholes and the uneven distribution of soil layers,there are inevitably instances where the construction parameters for certain soil layers do not match their actual soil type,resulting in redundant parameters(wasting materials)or insufficient parameters(creating risks in piling quality).During construction,the change in soil layers is judged based on the current of the processing machine.However,the current is related to the type of soil layer and also to the downflow speed.Relying solely on the current to divide soil layers can easily lead to misjudgment.By statistically analyzing the output energy consumption per unit length of construction piles near adjacent survey holes,and considering the impact of downflow speed,it was found that the sudden change in output energy consumption per unit length is highly related to the soil layer interface in the survey hole,which can effectively guide the division of soil layers,and is more stable than using current,and has guiding significance for optimizing process parameters.After identifying the typical section,it was statistically found that for this section,soil layers whose types were inconsistent with the survey expectation accounted for 15.8%of the total reinforcement amount,and 54.2%of the bottom reinforcement amount.It indicates that it is necessary to classify soil layers at different depths.