Strength and deformation behavior of ODP Leg 110 sediments

The shape and morphology of the northern Barbados Ridge complex is largely controlled by the sediment yield and failure behavior in response to high lateral loads imposed by convergence. Loads in excess of sediment yield strength result in nonrecoverable deformations within the wedge, and failure strength acts as an upper limit beyond which stresses are released through thrust faults. Relatively high loading rates lead to delayed consolidation and in-situ pore pressures greater than hydrostatic. The sediment yield and failure behavior is described for any stress path by a generalized constitutive model. A yield locus delineates the onset of plastic (non-recoverable) deformation, as defined from the isotropic and anisotropic consolidation responses of high-quality 38-mm triaxial specimens; a failure envelope was obtained by shearing the same specimens in both triaxial compression and extension. The yield locus is shown to be rotated into extension space and is centered about a K-line greater than unity, suggesting that the in-situ major principal stress has rotated into the horizontal plane, and that the sediment wedge is being subjected to extensional effective stress paths.巴巴多斯海脊北段复合体（northern Barbados Ridge complex）的形态与形貌，在很大程度上受沉积物屈服特性与破坏行为控制，而二者的响应机制源于板块汇聚作用施加的高侧向载荷。当载荷超过沉积物屈服强度时，沉积楔状体内部会产生不可恢复变形；破坏强度则是应力释放的上限阈值，超过该阈值后，应力将通过逆冲断层（thrust faults）得以消散。相对较高的加载速率会引发固结延迟，且原位孔隙压力高于静水压（hydrostatic）。针对任意应力路径下的沉积物屈服与破坏行为，均可通过广义本构模型（generalized constitutive model）进行描述。屈服轨迹（yield locus）界定了塑性（不可恢复）变形的起始点，该轨迹基于高质量38mm三轴试样（38-mm triaxial specimens）的各向同性与各向异性固结响应所定义；通过对同一批试样分别开展三轴压缩与三轴拉伸试验，得到了破坏包络线（failure envelope）。研究表明，该屈服轨迹已旋转至拉伸应力空间，且以大于1的K线为中心，这意味着原位最大主应力已旋转至水平面内，同时沉积物楔状体正承受拉伸有效应力路径。