波流作用下单桩冲刷MICP防护试验研究

Experimental study on scour protection of MICP around monopile in waves and current action

波浪掀沙,潮流输沙,波流耦合作用下单桩基础可能出现显著的局部冲刷,严重威胁结构物稳定性,必须进行合理的冲刷防护设计。鉴于此,本文开展了大断面水槽试验,对比抛石、翼板等传统防护措施与MICP防护措施的实际效果,分析了不同处理措施下桩周冲深的发展过程及极限平衡冲深,得到以下结论:MICP处理可以延缓砂床的冲刷启动,其防护效果优于抛石、翼板等传统防护措施;MICP防护效果与处理次数、处理范围有明显相关性;浅层MICP固化海床承担了更大的渗透力,其超孔压衰减梯度随MICP处理次数的增加逐渐增大。MICP生成的碳酸钙结晶在海床中主要起到颗粒包裹、粒间桥接及孔隙填充三种作用,一定程度上提高了颗粒重度和砂土强度,从而增强了海床抗冲刷能力。

The local scour around monopile will be significantly aggravated under the combined action of waves and current,which threatens the stability of the structure seriously.It is necessary to establish a reasonable protection design.Therefore,a series of large-section flume tests were carried out to compare the effective of traditional protective measures(ripraps and wing panels)with Microbially Induced Calcite Precipitation(MICP)measure.Besides the scour development around the monopile and the ultimate equilibrium scour depth under different treatment measures were analyzed.The research found that MICP treatment can delay the development of scour around monopile,and its protecting effect is better than ripraps and wing panels.At the same time,the protecting effect of MICP is obviously related to the number of times and scope of MICP treatments.The shallow MICP cemented seabed bears greater permeability,and the super pore pressure gradient increases with the increase of MICP treatment times.The calcium carbonate crystals generated by MICP mainly play three roles in the seabed,i.e,particle wrapping,particle cementation and pore filling,which improve particle weight and sand strength to a certain extent,thus enhancing the anti-scouring ability of the seabed.