Ocean Stress Project

应力方向和大小的确定 海洋地壳，以限制驱动力的模型 板是未来十年的主要目标， 大洋钻探计划。 虽然观察到的压力引起的 利用超声波电视井眼扫描的井眼漏失 提供了最大方向的指示， 这些ODP钻孔中的最小主水平应力， 对应力大小的直接测量或估计 进行了 应用于陆地选址的最新理论发展 可以延伸到大洋地壳上的钻孔， 对原地应力大小的限制 根据是否存在漏失和其他井眼 故障现象，并从约束所施加的摩擦 地壳的强度。 该项目将通过重新计算来估计原地应力的大小， 分析现有的钻孔电视数据。 将形成突破口 当周向应力 浓度和径向应力在井壁超过 岩石的强度。 可以对应力施加约束 如果发生崩落，如果岩石的强度 知道的 将对热效应和孔隙进行校正 压力效应。 实验室测量将由 岩石的抗拉强度和无侧限抗压强度 观察到拉伸裂纹或断裂的深度 得到了

Determination of the direction and magnitude of stresses within the oceanic crust to constrain models for the forces driving the plates is a principal objective of the next ten years of the Ocean Drilling Program. Although observations of stress-induced wellbore breakouts with ultrasonic televiewer wellbore scanning have provided indications of the directions of the maximum and minimum principal horizontal stresses in these ODP boreholes, no direct measurements or estimates of stress magnitudes have been made. Recent theoretical developments applied to sites on land can be extended to holes drilled in the oceanic crust to allow constraints to be placed on the magnitudes of in situ stresses based on the presence or absence of breakouts and other wellbore failure phenomena, and from constraints imposed by the frictional strength of the crust. This project will estimate magnitudes of in situ stress by re- analyzing existing borehole televiewer data. Breakouts will form when the difference between the circumferential stress concentration and the radial stress at the borehole wall exceeds the strength the rock. Constraints can be placed on the stress magnitudes if breakouts occur and if the strength of the rock is known. Corrections will be made for thermal effects and pore pressure effects. Laboratory measurements will be made of the tensile and unconfined compressive strength for rock from the depth at which observations of tensile cracks or breakouts are obtained.