Evaluation of Strength and Deformability of Soft Sedimentary Rocks in Dry and Saturated Conditions Through Needle Penetration and Point Load Tests: A Comparative Study

Abstract

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 (IS(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 (Est) for dry and saturated soft sedimentary rocks. The results point to significant correlation functions from which to infer UCS and Est in terms of NPI and IS(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 Is(50) .

Predicting the Uniaxial Compressive Strength of a Limestone Exposed to High Temperatures by Point Load and Leeb Rebound Hardness Testing

“…(2) UCS = × 10 × HLD , Bieniawski (1975) 23.0 -Different rock types Hassani et al (1980) 29.0 -Sedimentary rocks O' Rourke (1989) 30.0 -Sedimentary rocks Singh and Singh (1993) 23.4 0.64 Quartzite rock samples Tugrul and Zarif (1999) 15.3 0.96 Granitic rock samples Sulukcu and Ulusay (2001) 15.3 0.69 Different rock types Thuro et al (2001) 18.7 0.60 Different rock types Basu and Aydin (2006) 18.0 0.97 Granitic rock samples Diamantis et al (2009) 19.8 0.74 Serpentinite rock Galvan et al (2014) 13.5 0.87 Limestone Kohno and Maeda (2012) 16.4 0.85 Different rock samples Şahin et al (2020) 12.8 0.83 Different rock types Rabat et al (2020) 14.3 0.98 Siltstones buildings and infrastructures in Castellon and Valencia since the seventeenth century. It is a low-porosity Cretaceous rock from the 'Caliza de Benasal' formation, and mainly composed of calcite (75-85%) and dolomite (15-20%) with traces of quartz, illite, goethite and hematite (Ovejero et al 2005).…”

“…UCS tests require numerous samples, and these must be accurately extracted and transported to the laboratory to be prepared with the dimensions required by standards. Alternatively, UCS can be determined by means of other laboratory tests such as the point load test (PLT) (Galvan et al 2014;Şahin et al 2020), Schmidt hardness test (SH) (Aydin 2009;Sabatakakis et al 2008), Leeb rebound hardness test (LHT) (Corkum et al 2018;Meulenkamp and Alvarez Grima 1999;Verwaal and Mulder 1993;Yilmaz 2013) and the needle penetration test (NPT) (Rabat et al 2020) which provide quicker, cheaper and sufficiently reliable results.…”

“…Its advantages are that it requires neither special preparation of specimens nor heavy and expensive equipment, it can be used in the field or the laboratory, tests and the calculation of results can be quickly performed, and it is non-destructive (essential to estimate rock strength in protected natural structures or historical or heritage buildings). NPT is very sensitive to UCS changes and is particularly suitable for soft rocks (with UCS less than 20 MPa) (Rabat et al 2020).…”

“…SH was originally conceived to determine strength of concrete, and was quickly adopted for obtaining the surface hardness and indirect determination of UCS on rocks (Barton and Choubey 1977;Deere and Miller 1965;Kahraman et al 2005;O'Rourke 1989;Ylmaz and Sendr 2002). It exhibits similar advantages as PLT or NPT, although obtaining the results is easier as it is a non-destructive test (Rabat et al 2020). SH also presents some drawbacks as it is highly (1) UCS = × I s(50) , sensitive to the edge effect and requires a sample size greater than 1000 cm 3 to obtain reliable results (Viles et al 2011).…”

Analysis of Stress-Strain States in the Vicinity of Mining Excavations in a Rock Mass with Variable Mechanical Properties

“…A characteristic feature of rock mass, especially Carboniferous rock mass, is the high variability of both its rock layers and the properties of the rocks that make up the individual layers [1][2][3]. Designing galleries, and in particular the choice of their supports, requires knowledge of the mechanical properties of the rock mass [4][5][6][7][8], which are most often defined as average values for a given geological separation on the basis of tests performed with hydraulic testing machines in laboratory conditions [9][10][11] or with the use of penetrometers on site [12,13].…”