No abstract

Physical property inversion techniques are the methods to reveal the internal structures of Earth’s lithosphere. In this study, we introduce an Occam-type inversion algorithm into a spherical coordinate system, and invert the magnetization based on the three-component magnetic anomalies. The synthetic model tests show that the inversion effects of the vertical components are relatively stable, while the anti-noise ability is strong. We apply the algorithm to a set of vertical component anomalies derived from the satellite magnetic field model and obtain Dabie orogen 3D magnetization distribution. Multiple magnetic sources are identified within the orogen and adjacent areas, and the related tectonic evolution processes are analyzed. The significant magnetization characteristics of the orogen can be associated with mantle upwelling caused by the Early Cretaceous lithospheric delamination, along with the partial melting of the mafic–ultramafic lower crust that had not participated in the delamination. The magnetic sources near the Mozitan–Xiaotian fault, and those located in the western Dabie area, are also restricted by Mesozoic and Jurassic–Cretaceous deep melt activities, respectively. The study provides evidence for the suture line position of the plate subduction in the deep lithosphere. Furthermore, the results display certain indications of mineralization activities in the middle–lower Yangtze Valley metallogenic belt.

Rockburst is one of the common geological hazards. It is of great significance to study the evaluation indexes and classification criteria of the bursting liability of hard rocks, which is important for the prediction and prevention of rockbursts in hard rocks. In this study, the evaluation of the rockburst tendency was conducted using two indoor non-energy indexes, namely the brittleness indicator (B2) and the strength decrease rate (SDR). The measuring methods of B and SDR as well as the classification criteria were analyzed. Firstly, the most rational calculation formulas for B and SDR were selected based on previous studies. The B2 equaled to the ratio between the difference and sum of uniaxial compressive strength and Brazilian tensile strength of rocks. The SDR was the average stress decrease rate of the post-peak stage in uniaxial compression tests and equaled the uniaxial compressive strength dividing the duration time of post-peak rock failure in uniaxial compression tests. Secondly, the uniaxial compression tests of different rock types were designed and carried out, and the change trend of B and SDR with the increase of loading rate in uniaxial compression tests were studied in detail. The results showed that after the loading rate was greater than 5 mm/min or 100 kN/min, the B value was affected, limited by the loading rate, while the SDR value was more affected by the strain rate. The displacement control, with a loading rate of 0.1–0.7 mm/min, was recommended for the measurement of B and SDR. The classification criteria of B2 and SDR were proposed, and four grades of rockburst tendency were defined for SDR and B2 according to the test results.

This paper describes an investigation into the performance and pull-out capacity of a bladder-type inflatable anchor. The inflatable anchor is a type of support member used in foundation pit support engineering. Based on improvements and innovations, the multi-bladder-type inflatable anchor consists of two or more hydraulically inflated rubber membranes that are embedded in unconsolidated earth and then inflated to provide pull-out capacity. The primary objective of this study was to investigate the impact of inflation pressure, embedment depth, number of bladders, bladder length, and rubber film thickness on the pull-out capacity and displacement of the inflatable anchor. The tests were carried out in a cylindrical steel test chamber filled with medium coarse sand. The pull-out behavior of the bladder-type inflatable anchor and the five variables was investigated, and the benchmark values for all tests are determined by similarity ratio. Compared with the single bladder inflatable anchor, under the same conditions, the ultimate pull-out capacity of the two bladder-type inflatable anchor is 1.2 times higher, with ultimate displacement only 37.5% of the former, the ultimate pull-out capacity of the three bladder-type inflatable anchor is 1.7 times higher, with ultimate displacement only 32.3% of the former. The two bladder-type inflatable anchor is superior to the single bladder inflatable anchor and the multi-bladder-type has higher ultimate pull-out capacity and greater stiffness. The inflation pressure and the rubber film thickness have a significant influence on the bearing capacity. The number of bladders effectively controls the ultimate displacement.