谭乃根, 杨仁树, 谭卓英. 鄂尔多斯高原台地边缘地带地应力随钻测量与分布特征[J]. 工程科学学报, 2024, 46(4): 581-588. DOI: 10.13374/j.issn2095-9389.2023.06.07.001
引用本文: 谭乃根, 杨仁树, 谭卓英. 鄂尔多斯高原台地边缘地带地应力随钻测量与分布特征[J]. 工程科学学报, 2024, 46(4): 581-588. DOI: 10.13374/j.issn2095-9389.2023.06.07.001
TAN Naigen, YANG Renshu, TAN Zhuoying. In-situ stress measurement while drilling and stress characteristics at the margin of Ordos Plateau[J]. Chinese Journal of Engineering, 2024, 46(4): 581-588. DOI: 10.13374/j.issn2095-9389.2023.06.07.001
Citation: TAN Naigen, YANG Renshu, TAN Zhuoying. In-situ stress measurement while drilling and stress characteristics at the margin of Ordos Plateau[J]. Chinese Journal of Engineering, 2024, 46(4): 581-588. DOI: 10.13374/j.issn2095-9389.2023.06.07.001

鄂尔多斯高原台地边缘地带地应力随钻测量与分布特征

In-situ stress measurement while drilling and stress characteristics at the margin of Ordos Plateau

  • 摘要: 传统水压致裂法和新的热胀致裂法等测量地应力均属于先成孔后测量,容易发生钻孔后变形、自然开裂和应力释放,很难从根本上保证裂纹是试验时发生还是钻孔后已自然发生,难以保证测量结果的准确性. 为了克服常规水压致裂法地应力测量过程中钻孔完整性和致裂过程真实性难以确定的问题,采用地应力光声随钻测试系统对鄂尔多斯高原西南边缘地带典型区域地应力进行了水压致裂法测试,揭示了高原台地边缘地区的应力特点,获得了地应力随深度的变化规律,并与华北平原典型区域地应力测试统计结果进行了比较. 研究表明,鄂尔多斯高原西南边缘台地地带的地应力处于中国大陆浅层地壳地应力统计结果的低段区间,高原边缘地带的地应力随深度呈线性增长,最小水平主应力随深度的增长速度高于最大水平主应力的增长速度;最大最小水平主应力低于华北平原区;受区域构造及高原台地地形等影响,鄂尔多斯台地边缘的地应力方向相较于华北平原区,向东发生了偏转;最大最小水平主应力与垂直应力之比所反映的侧压系数低于华北平原区,但两个水平最大最小主应力的差异性高于华北平原区. 这说明,尽管高原边缘地带地应力总体水平低于华北平原区,但较大的水平应力差异性容易使地下空间发生剪切破坏,将不利于地下工程的稳定性. 由此可见,在台地边缘区域进行地下工程设计和建设时,应重点关注井巷工程的方向布置和低水平应力高应力差值带来的负面影响.

     

    Abstract: The traditional hydraulic fracturing and new thermal-expansion cracking methods employed for measuring in-situ stress require a subsequent lagging test after borehole drilling. This post-drilling often leads to deformation, cracking, and stress release. Additionally, determining whether a crack occurs during the test or naturally after drilling is challenging, posing difficulties in ensuring testing accuracy. To address these challenges for determining the borehole wall integrity of the test point and authenticity of the fracture process in the in-situ stress analysis using conventional hydraulic fracturing methods, we used an optical sonic measurement while drilling system to conduct hydrofracturing measurements of rock in-situ stress in the southwest margin of the Ordos Plateau. The stress characteristics at the margin of the plateau platform were revealed, and the variation law for estimating in-situ stress with depth was obtained. The statistical results were then compared with those obtained for the in-situ stress in a typical area of the North China Plain. The results show that the in-situ stress obtained for the southwest platform margin of the Ordos Plateau is lower than the statistical results of the crustal stress obtained for the shallow crust of mainland China. The in-situ stresses increase linearly with depth, and the growth rate of the minimum horizontal principal stress is higher than that of the maximum horizontal principal stress. The maximum and minimum horizontal principal stresses are lower than those observed in the North China Plain. Due to the influence of the regional structure and plateau platform of the Ordos, the direction of geostress is deflected to the east compared with the North China Plain. The lateral pressure coefficients reflected by the ratio of the maximum and minimum horizontal principal stress to vertical stress are lower than those in the North China Plain. However, the difference between the maximum and minimum horizontal principal stresses is higher than that in the North China Plain. This indicates that although the overall level of in-situ stress in the plateau edge zone is lower than that in the North China Plain, the larger difference between the maximum and minimum horizontal principal stresses is conducive to causing shear failure in underground space structures, which is unfavorable for the stability of underground engineering. This shows that when designing underground projects in the plateau platform area, more attention should be paid to the direction arrangement of the shaft and roadway engineering, as well as the negative effects of low horizontal stress and high-stress difference.

     

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