Punch Penetration Test Research Articles

A new approach on punch penetration test for prediction of boreability of jointed rock mass at northern section of Kerman water conveyance tunnel

A new approach on punch penetration test for prediction of boreability of jointed rock mass at northern section of Kerman water conveyance tunnel

Comparison of strength-based rock brittleness indices with the brittleness index measured via Yagiz’s approaches

Rock brittleness is one of the most significant properties of rock having a major impact not only on the failure process of intact rock but also on the response of rock mass to rock excavation. In fact, the brittleness is a combination of rock properties including not only the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) but also density and porosity of rocks. Due to that, the brittleness should be examined very carefully for any excavation projects, i.e., mechanized excavation, drilling and blasting. The aim of this paper is to compare the strength-based brittleness indices with both the rock brittleness index (BIo), directly obtained via punch penetration test (PPT) and also estimated via Yagiz’s approach (BI1) as a function of strengths and density of rocks. For the aim, database including more than 45 tunnel cases are used to compute common rock brittleness indices (BI2, BI3, BI4), different combination of UCS and BTS. Further, these indices are compared with both BIo and BI1 as well as each other. It is found that the BIo and BI1 have a significant relations (ranging of determination coefficients (r2) from 0.69 to 0.88 with strength-based brittleness indices commonly used in practice. Also, based on findings, several rock brittleness classifications are also revised herein.

A new rock brittleness index on the basis of punch penetration test data

Brittleness is one of the most important properties of rock which has a major impact not only on the failure process of intact rock but also on the response of rock mass to tunneling and mining projects. Due to the lack of a universally accepted definition of rock brittleness, a wide range of methods, including direct and indirect methods, have been developed for its measurement. Measuring rock brittleness by direct methods requires special equipment which may lead to financial inconveniences and is usually unavailable in most of rock mechanic laboratories. Accordingly, this study aimed to develop a new strength-based index for predicting rock brittleness based on the obtained base form. To this end, an innovative algorithm was developed in Matlab environment. The utilized algorithm finds the optimal index based on the open access dataset including the results of punch penetration test (PPT), uniaxial compressive and Brazilian tensile strength. Validation of proposed index was checked by the coefficient of determination (R2), the root mean square error (RMSE), and also the variance for account (VAF). The results indicated that among the different brittleness indices, the suggested equation is the most accurate one, since it has the optimal R2, RMSE and VAF as 0.912, 3.47 and 89.8%, respectively. It could finally be concluded that, using the proposed brittleness index, rock brittleness can be reliably predicted with a high level of accuracy.

Numerical Modeling of a Punch Penetration Test Using the Discrete Element Method

Abstract Understanding the brittleness of rock has a crucial importance in rock engineering applications such as the mechanical excavation of rock. In this study, numerical modeling of a punch penetration test is performed using the Discrete Element Method (DEM). The Peak Strength Index (PSI) as a function of the brittleness index was calculated using the axial load and a penetration graph obtained from numerical models. In the first step, the numerical model was verified by experimental results. The results obtained from the numerical modeling showed a good agreement with those obtained from the experimental tests. The propagation path was also simulated using Voronoi meshing. The fracture was created under the indenter in the first step, and then radial fractures were propagated. The effects of confining pressure and strength parameters on the PSI were subsequently investigated. The numerical results showed that the PSI increases with enhancing the confining pressure and the strength parameter of the rock, including cohesion and the friction angle. A new relationship between the strength parameters and PSI was also introduced based on two variable regressions of the numerical results.

Numerical modeling of the tool-rock penetration process using FEM coupled with SPH technique

The numerical simulation of penetration into rock is an important tool to gain insights into rock drilling mechanisms, since it can be exploited as an alternative to the expensive field testing. This research aims to present an innovative computer simulation of rock penetration process on the basis of the finite element method (FEM) coupled with smoothed particle hydrodynamics (SPH). An advanced material model, namely the Karagozian and Case Concrete (KCC) model, was employed for this purpose. The Punch Penetration test (PPT) was carried out on a medium strength sandstone for validating the numerical method. The comparison of the numerical and experimental results obtained concluded that the FEM coupled with SPH method in conjunction with the fully calibrated KCC material model is a reliable method for the study of rock penetration due to its ability to deal with large deformations and its realistic constitutive modeling. The modeling approach was finally applied to estimate the required force to penetrate an offshore reservoir rock block under the in-situ confining pressure with a double conical tool up to 5 mm depth. The effective stresses in sedimentary basins of Agosta and Dosso Campus at a depth of 3000 m below the seabed are considered as the confining pressures of this study.

Development of a new rock drillability index for oil and gas reservoir rocks using punch penetration test

Punch penetration test has shown a good relationship with the rate of penetration (ROP) of tunnel boring machine (TBM) into hard rock. In addition, various indices have been determined from the analysis of the force-penetration curve of the penetration test to present rock drillability, boreability, and brittleness. Therefore, in the present paper, punch penetration test will be used to determine rock drillability index (RDI). In this research, 9 samples were taken from the same formation in two wells drilled at southwestern Iran. Considering the limitations in taking more samples, and also to enhance reliability of the results, each of the samples was divided into smaller specimens, so as to conduct multiple tests at each sampling point. Evaluation of the force-penetration curves of samples indicated that most samples of well 1 have little changes of forces early in the test, but they increase as the test proceeds. Because the samples from the Well 1 were taken from shallow depths, The change in the slope of the curve determined on the basis of the samples taken from Well 1 can be explained by the pores existing in these samples. Different indices were extracted from the analysis of the force-penetration curve of each specimen, including first peak slope index (BI1), maximum peak slope index (BI2), area under the curve (BI3), and RDI. Initial examination of relationships between each of indices and the measured ROP follow an either exponential or power-law model. Evaluation of these models between each of these indices and actual ROP indicated that, an exponential curve gives the best fit to the obtained values. A comparison between estimated ROPs from the fitted relationships against measured values showed that the estimated ROP using the proposed index is highly accurate and reliable and can present a good measure of the reservoir rock drillability.

Performance Assessment of Hard Rock TBM and Rock Boreability Using Punch Penetration Test

Rock indentation tests are often called punch penetration tests and are known to be related to penetration rates of drilling equipment and hard rock tunnel boring machines (TBMs). Various indices determined from analysis of the force-penetration plot generated from indentation tests have been used to represent the drillability, boreability, and brittleness of rocks. However, no standard for the punch penetration test procedure or method for calculating the related indices has been suggested or adopted in the rock mechanics community. This paper introduces new indices based on the punch test to predict the performance of hard rock TBMs. A series of punch tests was performed on rock specimens representing six rock formations in Korea with different dimensions, i.e., the core specimens had different lengths and diameters. Of the indices obtained from the punch tests, the peak load index and mean load index showed good correlations with the cutting forces measured in full-scale linear cutting machine tests on the same rock types. The indices also showed good linear correlations with the ratio of uniaxial strength to Brazilian tensile strength, which indicates the brittleness of rock. The scale effect of using core specimens was investigated, and a preferred dimension for the punch test specimens is proposed. This paper also discusses the results of the punch test and full-scale rock cutting tests using LCM. The results of this study confirm that the proposed indices from the punch tests can be used to provide a reliable prediction of the cutting forces that act on a disc cutter. The estimated cutting forces can then be used for optimization of cutter-head design and performance prediction of hard rock TBMs.

Study of Formability of Sandwich Shells with Metal Foam Cores Based on Punch Penetration Test

The objective of this work is the study of the mechanical behaviour of a sandwich structure, composed by two out layers in aluminium sheets, separated by a core in metal foam also in aluminium, by penetration of a spherical punch. Considering a structure composed by these two different materials, each one presents a different mechanical behaviour separately [1, 2].The set up used in the present experimental work is composed by a punch, with a radius r, which imposes a displacement/force to a specimen fixed in its boundary.In these tests, specimens with four different length were considered; 25 mm, 50 mm, 75 mm and 150 mm. The values of force/displacement of the punch were registered.

Estimation of design parameters of TBM using punch penetration and Cerchar abrasiveness test

TBM의 사양을 설계하고 굴진성능을 예측할 때 실대형 선형절삭시험을 통하여 설계변수를 획득하는 것이 매우 효과적인 방법인 것으로 알려져 있다. 하지만 선형절삭시험을 위해서는 대형 시편을 획득하고 큰 하중용량의 시험을 수행하는 과정에서 상당한 비용과 노력이 소모된다는 단점이 있다. 따라서 선형절삭시험을 대체하는 경험적 예측 모델, 즉 CSM모델과 NTNU모델을 사용하여 몇 가지 지수를 산정하고 이로부터 설계변수를 추정하는 경우가 많다. 본 연구에서는 압입시험 및 세르샤 마모시험을 이용하여 TBM의 사양(추력, 토크)과 굴착에 따라 소요되는 디스크 커터의 개수를 추정하는 방법에 대하여 고찰하였다. 압입시험과 세르샤 마모시험은 TBM의 설계 변수를 추정하기 위한 유용한 시험법이나 그 활용법이 연구 되고 있지 못한 실정이다. 이 연구에서는 압입시험과 세르샤 마모시험결과를 간단한 형태의 지수형태로 도출하고 이를 선형절삭시험 및 실제 굴진자료와 비교하여 상관관계를 도출하고 이로 부터 디스크 커터의 작용력 및 수명을 예측하였다. 또한 이 일련의 계산 과정을 프로그램화 하였으며, 터널의 연장 정보, TBM의 기계정보, 구간별 암석의 물성을 입력변수로 하여 구간별 굴진율과 TBM 사양 및 운영조건, 디스크 커터의 소모개수를 예측할 수 있었다. Linear cutting test is known to be very effective to determine machine parameters (i.e. thrust force and torque) and to estimate penetration rate of TBM and other operation conditions. Although the linear cutting test has significant advantages, the test is expensive and time-consuming because it requires large size specimen and high load capacity of the testing machine. Therefore, a few empirical prediction models (e.g. CSM, NTNU and QTBM) alternatively adopt laboratory index tests to estimate design parameters of TBM. This study discusses the estimation method of TBM machine parameters and disc cutter consumption using punch penetration test and Cerchar abrasion test of which the researches are rare. The cutter forces and cutter consumption can be estimated by the empirical models derived from the relationship between laboratory test result with field data and linear cutting test data. In addition, the estimation process was programmed through which the design parameters of TBM (e.g. thrust, torque, penetration rate, and cutter consumption) are automatically estimated using laboratory test results.

TBM의 굴진성능 예측을 위한 압입시험에 대한 연구

This paper discusses the methods of estimating the punch penetration indices and data analysis punch penetration test to estimate the TBM normal force and penetration rate. In punch penetration test is known as a useful test to estimate penetration rates and normal force of TBMs directly with several slope indices indicated drill-ability and brittleness of rocks. However, the standard methods and indices for punch penetration test are not suggested yet. The main purpose of punch penetration test which is prediction of normal force of TBM disc cutter when cutters excavate rock mass. In this study, the punch penetration tests were performed for 6 representative Korean rock types and variety length and diameter of rock core specimens. Among slope indices were obtained from punch penetration test, PLI and MLI which is suggested in this study show high correlation with cutter force measured by full-scale cutting test. The results show that the predicted normal force of a single disc cutter and the experimental error was 10%. Based on these results, it is concluded that punch penetration test is reliable laboratory test for estimating thrust and penetration rates of TBM.

AN INVESTIGATION OF DIE WALL FRICTION DURING THE COMPACTION OF POWDERS.

Abstract Crystalline aspirin, hexamine, sucrose, and sodium chloride, and simple granulations of hexamine and of sucrose, have been compressed and the die reaction determined using a “moving-die” technique. The shear strength of the ejected compacts has been measured under zero load conditions, and when compressed to theoretical density, using a punch penetration test. Calculated values of die reaction based on friction theory have been compared with experimental measurements. Correlation between the two is best for aspirin and hexamine crystals when the compact approaches theoretical density and shear strength values for compacts of zero porosity are used in the calculations; for sodium chloride, correlation is best when shear strength values under zero load conditions are used.

A comparison of tablet lubricant efficiencies for a sucrose granulation using an instrumented tablet machine

Abstract Thirteen materials have been assessed as lubricants when added to a sucrose granulation and compressed on an instrumented tablet machine. Values of ejection force, force lost to die wall, and punch force ratio for each lubricated sample were compared, and the order of efficiency as lubricants was compared with the shear of lubricant powder compacts. The most efficient lubricants are those materials of lowest melting point, and not those with the smallest shear strength value as measured in a punch penetration test.

The compaction of some solid lubricant materials.

AbstractSamples of −100 mesh powders of stearic acid, palmitic acid, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, zinc stearate, zinc oleate, boric acid and a synthetic wax, were compacted and the die reaction determined using a “moving-die” technique. The shear strength of the compacts measured in a punch penetration test, with the exception of boric acid and zinc stearate, was independent of the compaction pressure above 500 kg/cm2. Solid discs of stearic acid and palmitic acid possessed the same shear strength as the powder compacts; discs of synthetic wax and zinc stearate gave higher values than the corresponding powder compacts. Values of shear strength calculated from measurements of die reaction were higher than values obtained in the shear strength test, but show good agreement with the results calculated by other workers from sliding friction experiments. Shear strength values for compacts of boric acid and discs of synthetic wax, talc crystal, and graphite, indicate that these materials are unlikely to be such good lubricants as stearic acid or its salts.

AN APPARATUS FOR THE INVESTIGATION OF DIE WALL FRICTION DURING COMPACTION.

Abstract A “moving-die” apparatus is described for use in the investigation of die wall friction during the compaction of powders. The powder can be compressed at constant rates varying from 344–860 kg/sec; the die can be moved at a constant rate at values of 0.1–0.25 cm/sec. The apparatus can also be used to apply the force necessary to cause shear in a punch penetration test for the measurement of shear strength of the ejected compacts. Preliminary experiments with 20–30 mesh crystalline sucrose indicate that values of die reaction, Fd, and ejection force, Fe, increase with increased applied pressure. For a given compaction pressure, Fe and Fd decreased as the rate of application of the compacting force increased. For the range of rates available Fd was independent of the rate of movement of the die. The shear strength of ejected compacts prepared at a constant pressure increased with increase in the rate at which the shear force was applied.

Assessment of brittleness using rock strength and density with punch penetration test

Brittleness fracturing of rock is one of the most popular research areas in rock engineering, since some rocks show brittle fractures under loads. Direct standard testing method for measuring rock brittleness have not available yet. Therefore, rock brittleness is indirectly obtained as a function of rock strength. The aim of this study is not only to introduce direct method to measure rock brittleness as an index via punch penetration test, but also to investigate the relationship between intact rock properties (uniaxial compressive strength, Brazilian tensile strength, and density of rock) and the brittleness measured from the test. To obtain these objectives, rock cores were gathered from 48 tunnel projects throughout the world. Followings the sampling, the samples were prepared and relevant rock tests were carried out to establishment of dataset at the Earth Mechanics Institute of Colorado School of Mines in the USA. Consequently, using generated dataset, new brittleness index (BI m ) and rock brittleness classification was introduced base on type, strength and density of rock together with result of punch penetration test. Further, the rock brittleness index was predicted as a function of the uniaxial compressive strength, Brazilian tensile strength and density of rock with correlation coefficient of 0.94.