The preparation of standardized soft rock specimens to perform unconfined compressive strength (UCS) tests is typically difficult, expensive and time-consuming. Needle penetration test (NPT) was originally developed in Japan as an alternative for the indirect estimation of UCS of soft rocks. The needle penetrometer is a simple, portable and non-destructive testing device that measures applied load and penetration depth for the rock to calculate the needle penetration index (NPI). A complimentary, portable and widely used destructive test is the point load test (PLT), which measures regular and irregular specimens by the application of a concentrated load using two coaxial conical platens that yield the point load strength index ( I S(50) ). We investigated and compared the NPT and PLT in terms of measuring changes induced by water saturation and obtaining UCS and the static Young’s modulus ( E st ) for dry and saturated soft sedimentary rocks. The results point to significant correlation functions from which to infer UCS and E st in terms of NPI and I S(50) in dry and saturated soft rocks. Furthermore, both NPT and PLT are suitable tests for evaluating changes in strength and deformability induced by water saturation. We also found a good correlation between the NPI and I s(50) .

中文翻译：

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通过针刺和点载荷试验评估干燥和饱和条件下软沉积岩的强度和变形性：比较研究

准备用于无侧限抗压强度 (UCS) 测试的标准化软岩试样通常很困难、昂贵且耗时。针刺试验 (NPT) 最初是在日本开发的，作为间接估计软岩 UCS 的替代方法。针入度计是一种简单、便携且无损的测试设备，可测量岩石的施加载荷和穿透深度，以计算针入度指数 (NPI)。点载荷试验 (PLT) 是一种补充性、便携且广泛使用的破坏性试验，它通过使用两个同轴锥形压板施加集中载荷来测量规则和不规则试样，从而产生点载荷强度指数 (IS(50))。我们研究和比较了 NPT 和 PLT 在测量含水饱和度引起的变化和获得 UCS 和干燥和饱和软沉积岩的静态杨氏模量 (E st ) 方面。结果指向显着的相关函数，从这些函数可以推断干燥和饱和软岩中 NPI 和 IS(50) 的 UCS 和 Est。此外，NPT 和 PLT 都是评估含水饱和度引起的强度和变形能力变化的合适测试。我们还发现 NPI 与 I s(50) 之间存在良好的相关性。NPT 和 PLT 都是评估含水饱和度引起的强度和变形能力变化的合适测试。我们还发现 NPI 与 I s(50) 之间存在良好的相关性。NPT 和 PLT 都是评估含水饱和度引起的强度和变形能力变化的合适测试。我们还发现 NPI 与 I s(50) 之间存在良好的相关性。