Long-term and cyclic plate loading tests in weak rocks

The rheological behaviour under long-term loading or cyclic loadings is quite important in the problems relating to concrete dam foundations, especially in weak rock masses. In situ measurements to evaluate the rheologic characteristics present considerable problems. Testing technique, set up by ISMES, and shown in Fig.1 , is characterized by the following features: extensive loading areas (Φ=1 m), to affect a large rock volume also in depth. Load application by means of flat jacks, to obtain a uniform pressure distribution. Displacement recording at various depths, along the loading axis, by means of brehole extensometers, so as to detect possible dishomogenei-ties in the rock, and especially a loosened superficial layer. Oleopneumatic system to keep a constant load for a long time. Automatic data recording system. fig. 1 Scheme of long-term plate loading test. A diagram depicts the experimental setup for a long-term plate loading test designed to study the rheological behavior of weak rock masses under sustained or cyclic loads. The setup includes a large circular loading plate (1-meter diameter) placed on the rock surface to apply uniform pressure using flat jacks. Displacement measurements are recorded at various depths along the loading axis using borehole extensometers. The system features an oleopneumatic mechanism to maintain constant load over time and an automatic data recording system for continuous monitoring. The diagram shows the loading plate embedded in the rock surface, with arrows indicating the direction of applied pressure. Extensometers are positioned vertically beneath the plate to measure displacements at different depths, capturing potential heterogeneities in the rock, including a loosened superficial layer. https://www.w3.org/1999/xlink" xlink:href=" https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003762874/b5f61898-fce6-484a-924e-da88a4d886be/content/pg151_Image_1.tif "/>