In situ experimental study on TBM excavation with high-pressure water-jet-assisted rock breaking

China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM.

流化床结晶软化高硬度地下水及其晶体生长动力学

采用流化床结晶软化的方法对北京市城区某地下水进行软化处理,研究考察了软化药剂投加量、诱晶颗粒粒径、诱晶颗粒填料高度、入水流速、碳酸钙过饱和度等参数对水质硬度去除的影响。研究发现,当药剂投加量为220 mg·L^(-1)时,出水钙硬度去除率可达90%以上,总硬度去除率达到60%,出水总硬度可达300 mg·L^(-1)左右。使用石英砂颗粒作为诱晶材料,粒径为0.21~0.43 mm。当诱晶材料填料高度为40 cm,入水流速控制在40~70 m·h-1时,均可得到较好的出水水质。优化反应参数,可控制处理后的出水总硬度在300 mg·L^(-1)左右,即去除235 mg·L^(-1)的暂时硬度,煮沸的水不再浑浊,无水垢生成,并且出水pH可控制在8.5以下。此外,探究了多相流化过程中诱晶颗粒的线性增长速率以及床层增长速率与过饱和度、颗粒粒径、入水流速的关系,通过计算得到晶体线性增长速率相关表达式。