用于中小规格冲击钻及旋转勘探钻具，凿进软岩层、中硬岩层。
For small rotary rock drill bits and rotary prospecting bits to cut soft, medium-hard rock.
现场试验结果表明，PDC锚杆钻头是钻进中硬岩层的理想钻头。
The results of field tests proved that PDC anchor bit is ideal in mid hard rock drilling.
由于金属矿层状顶板分布较少，故硬岩层状顶板的支护研究也相对较少且处于起步阶段。
Owing to the less common distribution of layered roof in metal mines, the research of the support of hard rock layered roof is relatively less and still at the initial stage.
高抗压强度的硬地层，如硬石灰岩。燧岩。硬砂岩。石英岩。石英砂。玄武岩。花岗岩等极硬岩层。
Medium hard formation with high compressive strength. Such as limestone, taconite, blaize, quartzite, silica sand, basalt, granite ect.
主tpy - 30型钻机是一种液压浅孔物探普查钻孔机，该机主要适用于土层，沙土层和中硬岩层中的钻进。
TPY-30 drilling machine is a type of shallow-hole drilling machine for exploration, it is suitable for drilling in soil, sand soil and medium harden rock drilling.
张双楼煤矿主采煤层为7煤和9煤，两层煤之间赋存唯一一层厚硬岩层，即9煤层的直接顶也是7煤层的直接底。
The hard-and-thick strata ACTS both as the floor of coal seam No. 7 and as the roof of coal seam No. 9 in Zhangshuanglou coal Mine; and coal seam No. 9 is also hard.
针对上硬下软近水平双层岩基的破坏过程，考虑软弱下伏岩层对应力分布的扩散效应，提出双层岩基极限承载力的计算方法。
On the basis of analyzing the failure process and considering the influence of stress spreading, the method determining ultimate bearing capacity of double layer rock foundation is put forward.
这样的循环一次次重复，形成了一层层硬且易碎的岩层。
The cycle repeated over and over again, building up a series of crusty, crumbly layers.
在软硬相间的层状岩体中地应力分布很不均匀，应力大小与岩层硬度具有正相关性，硬岩中的水平应力大于软岩的水平应力。
The stress distribution is far from uniform in this stratified rock, the horizontal stress magnitude in hard rock layers is significantly higher the that in soft layers.
在软硬相间的层状岩体中地应力分布很不均匀，应力大小与岩层硬度具有正相关性，硬岩中的水平应力大于软岩的水平应力。
The stress distribution is far from uniform in this stratified rock, the horizontal stress magnitude in hard rock layers is significantly higher the that in soft layers.
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