闫晓龙

摘要：含软弱夹层的钻孔孔壁稳定性是制约钻探的关键问题，其稳定性的制约因素众多。在分析圆孔弹塑性理论的基础上，建立软弱夹层三维钻孔模型，采用摩尔-库伦判别准则，研究不同地质钻孔孔径、软弱夹层倾角、厚度以及其弹性模量、内聚力和泊松比条件下，孔周的围岩稳定性系数变化规律。结果表明：（1）完整围岩（软弱夹层厚度0 m）明显高于含软弱夹层孔壁的稳定性系数;（2）孔壁的稳定性随孔径大小增加而降低，随软弱夹层倾角和厚度的增加而降低;（3）孔壁的稳定性随泊松比的增加而降低，随弹性模量和内聚力的增加，变化规律则相反，稳定性系数对泊松比、内聚力、弹性模量的灵敏性依次降低。

关键词：地质钻探;软弱夹层;孔壁;围岩稳定性

中图分类号：TD262

文献标识码：A文章编号：1001-5922（2022）06-0176-06

Analysis of different weak interlayers on the stability influence of geological drilling hole

YAN Xiaolong

（Shaanxi Railway Engineering Survey Co.， Ltd.， Xi'an 710014， China

）

Abstract：The stability of drilling holes wall with weak interlayers is the key issue to restrict geological drilling， and the stability is restricted by many factors. Based on the analysis of the elastic-plastic theory of circular hole， this paper establishes a three-dimensional borehole model of weak intercalation， and uses the Moore-Coulomb criterion to study the variation law of stability coefficient of surrounding rock under the conditions of different geological borehole diameter， dip angle and thickness of weak intercalation， as well as its elastic modulus， cohesion and Poisson's ratio. The research results show that （1） the stability coefficient of the intact surrounding rock （the thickness of weak interlayer is 0 m） is significantly higher than that of the hole wall with weak interlayer; （2） the stability of the hole wall decreases with the increase of the diameter of the hole， and decreases with the increase of the dip angle and thickness of the weak interlayer; （3） the stability of the hole wall decreases with the increase of Poissons ratio， and the change law is opposite with the increase of the elastic modulus and cohesion. The sensitivity of stability coefficient to Poissons ratio， cohesive force and elastic modulus decreased successively.

Key words：geological drilling; weak interlayer; hole wall; surrounding rock stability

在工程地质钻探过程中，钻孔的稳定性问题是岩土工程中关注的问题之一，直接关系到钻探精度和取芯质量。在天然状态下，自然岩土层的初始应力和孔隙压力的共同作用下，处于平衡状态;而钻孔取样对土层的卸荷作用，使得钻孔壁失去原有的支持，取而代之的是孔内泥浆静水原理，孔壁的应力发生重新分布。在围岩作用下，孔壁的应力短时间内无法达到平衡状态，当孔壁的岩土体的强度不足以抵抗集中的应力，将出现孔壁失穩现象，使得孔内岩土固体颗粒被扰动和悬浮移位，造成扩孔、卡孔、埋钻等危害，为孔内测试工作带来不利影响，甚至废孔，使得钻孔周期增长、钻探成本增加。……