<p>Reference(s):</p> <p>ASTM D4380 (2012)<br />Farnsworth et al. (2010)<br />PTI Committee DC35 (2014)</p> <p><strong>Method Summary</strong></p> <p>This method measures the bearing capacity of anchors which include tiebacks, rock bolts, and rock dowels. A hydraulic jack is attached to the exposed end of the bolt or cable and a tensile force is applied. Three different tests are conducted via the Pull Test. They are the performance, creep, and proof tests. The performance test is a cyclic loading procedure that tensions anchors beyond the design load. The creep test is similar to the performance test, but the test anchors are held beyond the design load for an extended period while the creep distance is recorded. The proof test a single load applied to the anchor at 120% to 150% of the design load. The testing quantity and failure criteria vary from agency to agency. Generally, an anchor would fail if there was a decrease in load capacity or excess displacement, both of which signal anchor slip. This method also applies to all rock bolt anchoring methods.</p> <p><strong>Accuracy and Precision</strong></p> <p>This is an accurate and precise test method because a fully installed anchor is loaded beyond the design load. Regarding the anchor system, increasing the number of samples improves the accuracy of results.&nbsp;</p> <p><strong>Adequacy of Coverage</strong></p> <p>Pull Tests must be conducted on a rock bolt system for each rock material and bolt orientation until an average loading capacity for the system is found with 95% confidence. Some agencies have more stringent regulations, requiring proof testing for every installed bolt.</p> <p><strong>Implementation Requirements</strong></p> <p>Extensive knowledge of the rock composition to be reinforced is required so tests are conducted for each rock material. A sufficient amount of time is also required to load each anchor to the required load according to the proof testing procedure. The test method is relatively inexpensive.</p> <p><strong>General Comments</strong></p> <p>This is the standard method to measure the bearing capacity, and ultimately the effectiveness of rock bolts or tiebacks to reinforce a rock slope. This is a destructive method, deforming the anchor and removing rock material.</p>