Lecture #1: What Is Geological Engineering

GE ENG 5471: Rock Engineering

Homework Assignment 4: Point Load Test

A) Please read and familiarize yourself with the accompanying handout, ASTM D5731-07

B) For on and off campus students, please view the accompanying video demonstration at the following url: https://www.youtube.com/watch?v=Q79IdLC_LO4

Diametral tests were performed on core samples from 2 different boxes (rock types) and the data is shown below. There is also an Excel sheet with this data in the Assignment 4 folder.

C) For each of the tests:

1. Calculate the corrected point load strength IS(50). 2. Estimate the unconfined compressive strength of the rock. σc. 3. Justify your choice of calibration (to unconfined compressive strength) from at least one profession paper that you can find in the library or on-line. Please provide proper reference. 4. Calculate the central tendency and the variability of the point load strength index (for each box).

Ram area 14.426 cm2

Bonus question. Is there a significant difference between the diameters of the core in the two boxes? WHAT YOU NEED TO DO:

1. Read the ASTM standard. 2. Calculate the load the platen is placing on the sample using the pressure in the hydraulic system and the ram area. 3. Calculate the failure stress (and consequently strength) of the sample based on the load and the appropriate area formulation. 4. Transform the strength to the equivalent of a 50 mm diameter sample. 5. Calculate the average point load strength for the box, based on the ASTM standard. 6. Calculate an equivalent Unconfined compressive strength.

Deliverables:

1. 1-2 page memo explaining the procedure and significance of a point load test in regards to testing for the unconfined compressive strength of a rock. 2. Your completed Assignment 4 Excel Data Sheet. You need to fill in the red cells and answer what factor the corrected point load index must be multiplied by in order to get the uniaxial compressive strength. Please do this for both sets of data (Limestone and Sandstone) You also have the opportunity to answer the bonus question at the bottom of the data sheet and be sure to explain your answer.

You may submit these files as two separate PDFs or as a single PDF.

Due Date: September 19, 2017 (9/19/17) @ 4 p.m. CST to the TA’s email.