山西沁水盆地现今地应力特征

Characteristics of current in-situ stress of Qinshui Basin

基于沁水盆地内多点地应力实测数据,运用数学计算与回归分析手段,采用有限元数值模拟法,建立地质模型,模拟15#煤层及顶、底板现今地应力分布特征。结合深层地应力资料,编制沁水盆地现今地应力方向、量值的平面分布和随埋深变化的剖面。研究结果表明:沁水盆地的地应力方向和量值分布在平面上具有一定规律性,最大水平主应力方向以NNE—NE为主,应力状态受构造形态、断裂及岩体性质的影响较大;地应力在盆地平面上呈环状分布,构造轴部(背斜轴部和向斜轴部)数值较高,翼部较低,最小水平主应力集中于12.00~31.00 MPa,最大水平主应力集中于26.00~42.50 MPa,垂向应力介于17.00~55.00 MPa;现今地应力特征受深度影响十分显著,埋深越大,各主应力值数值越大,应力系数主要表现为随着埋深的增大,系数值向某一数值逐渐靠拢;应力系数在平面上的展布也存在一定的规律,呈环状或中心对称,并与盆地构造形态及断裂因素有关。

Based on the several groups of in-situ stress data taken from Qinshui Basin and the methods of calculation and regression analysis, the geological model was established and the distribution characteristics of current in-situ stress of No.15 coalbed and its roof and floor in Qinshui Basin were simulated by finite element numerical simulation. Combining the deep in-situ stress data, the distributions of stress direction and magnitudes along surfaces and profiles were analyzed. The results show that there is a kind of regularity in distribution of stress direction and stress magnitudes, stress direction performs NNE NE trending, in-situ stress state is greatly influenced by the structural morphology, fault and rock mass properties; in-situ stress of Qinshui Basin distributes in a ring shape, high magnitude is shown in the core section of syncline and low magnitude in the basin edge; the magnitude of minimum horizontal principal stress is from 12.00 to 31.00 MPa, the magnitude of maximum horizontal principal stress is from 26.00 to 42.50 MPa, the magnitude of vertical stress is between 17.00 and 55.00 MPa; depth makes great influence on in-situ stress, stress magnitudes increase with the increase of depth, stress coefficients are close to a certain value with increasing depth; the planar distribution of stress coefficients presents a similar regularity with ring shape and central symmetry and is influenced by structural morphology and fault as well.