中国煤矿井下地应力数据库及地应力分布规律

收集了采用井下小孔径水压致裂地应力测量装置获得的煤矿地应力数据,以及其他采用应力解除法、水压致裂法等获得的煤矿地应力数据,共计1 357条。在此基础上建立了“中国煤矿井下地应力数据库”,绘制了中国煤矿矿区地应力分布图。分析了我国煤矿井下地应力分布特征和主要影响因素,取得以下研究成果:① 埋深是影响煤矿井下地应力的重要因素。垂直应力总体上随埋深增加不断增大,但数据存在一定的离散性。最大、最小水平主应力总体上也与埋深呈正相关关系,但数据离散性更大。② 在浅部煤矿,地应力类型主要为逆断型应力状态(σH>σh>σV);在千米深井,主要为正断型应力状态(σV>σH>σh);介于两者之间主要为走滑型应力状态(σH>σV>σh)。③ 水平应力与垂直应力的比值(包括最大、最小水平主应力与垂直应力的比值;平均水平主应力与垂直应力的比值;最大水平主应力与最小水平主应力之差与垂直应力的比值),埋深越小,这些比值离散性越大,分布范围越广。随着埋深增加,比值的离散性和范围越来越小,并逐渐趋于某一定值。④ 粉砂岩、细砂岩、泥质砂岩和泥岩4类岩性地应力数据统计结果表明,总体上,岩石强度越高,承受的水平应力越大。⑤ 弹性模量较大的岩石,水平应力较高;弹性模量较低的松软破碎岩层,水平应力较低。

Database and characteristics of underground in situ stress distribution in Chinese coal mines

A total 1357 items of in situ stress measurement data in Chinese underground coal mines were collected,which include the data obtained by hydraulic fracturing method with small borehole applied by Mining Branch,China Coal Research Institute,and those from overcoring and hydraulic fracturing methods by other companies and organizations.The in situ stress database of Chinese underground coal mines was established on the basis of those data,and the in situ stress map for Chinese underground coal mines was drawn.The in situ stress distribution features and its affecting factors were studied.The achievements are as follows:① the buried depth of measurement sites is an important factor affecting the in situ stresses in underground coal mines.In general,the vertical stress increases with depth,as some discreteness of stress data exists.The maximum and minimum horizontal principal stresses also increase with depth,however,the discreteness of stress data is obviously greater than that of vertical stresses,and the increasing rate of horizontal stresses with depth is smaller than that of vertical stresses.② The stress regime is mainly thrust type (σH>σh>σV) in shallow coal mine,and normal type (σV>σH>σh) in coal mine with depth more than 1 000 m,while it is mainly slip type(σH>σV>σh) with depth in between.③ The ratios of horizontal stresses to vertical stresses,including those of maximum,minimum and average horizontal principal stresses to vertical stresses,the difference between the maximum and minimum horizontal principal stresses to vertical stresses,distribute in a broad range with a greater discreteness when depth is shallow.As the depth increases,the discreteness of these ratios gradually decreases with a tendency to approach constant values.④ The stress statistical results of four strata with different lithology,that is siltstone,fine sandstone,mud sandstone and mudstone,point out that,in general,the larger the rock strength,the higher the horizontal stresses the rocks bear.⑤ The rocks with higher elastic modulus bear larger horizontal stresses.However,the soft and fractured rocks with lower elastic modulus bear less horizontal stresses.