کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6433584 1636731 2015 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Heterogeneous in situ stress magnitudes due to the presence of weak natural discontinuities in granitic rocks
ترجمه فارسی عنوان
به علت وجود اختلافات طبیعی ضعیف در سنگ های گرانیتی، مقادیر تنش در ناحیه تناوبی وجود دارد
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی


- We observe severe variations in stress magnitudes from stress measurements.
- We relate stress variations to distribution of weak natural fractures and faults.
- Slip along weak fractures seems responsible for lowered stress magnitudes.

Two field examples of hydraulic fracturing stress measurements are reported, in which the determined stress magnitudes exhibit severe variations with depth. The stress measurements were conducted in vertical boreholes drilled in granites in two different locations in South Korea. Several isolated intervals of intact rocks in the boreholes were vertically fractured by injecting water. The magnitudes of the minimum horizontal principal compressive stress (Shmin) were determined from shut-in pressures. The magnitudes of the maximum horizontal principal compressive stress (SHmax) were estimated based on the Kirsch equation using tensile strengths determined from hollow cylinder tests and Brazilian tests, in which pressurization-rate effects on tensile strength were taken into account. The stress states in both locations are in reverse-faulting stress regimes. The magnitudes of SHmax are generally within a stress range defined by frictional limits of favorably oriented fractures having frictional coefficients of 0.6 and 1.0. However, SHmax magnitudes do not increase linearly with depth, but rather scatter quite severely. It is noted that near the depths where the measured stresses are relatively low, natural discontinuities with wide apertures containing weak filling material exist, whereas near the depths of high stress, such wide discontinuities are scarce. Wide aperture discontinuities are predominantly oriented such that their slip tendency is high under the given stress conditions, meaning that if excessive shear stress is exerted, the weak discontinuities would slip to release the excessive stress. Such local processes would restrict SHmax magnitudes within values that can only be sustained by the shear strengths of the discontinuities, leading to severe variations of SHmax with depth. This result suggests that stress magnitudes are controlled quite locally by the frictional property of natural discontinuities, and that the stress state in granitic rock might be inherently heterogeneous because of the heterogeneous distribution of natural discontinuities having various frictional properties.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tectonophysics - Volume 664, 28 November 2015, Pages 83-97
نویسندگان
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