In this paper, a testing methodology was developed in the laboratory to measure the tensile strength of large-scale incipient rock joints. In the test, an expansive grout was used to develop the tensile force. Each test comprises two phases: Phase i test and Phase ii test. The Phase i test identified sample failure time, while the Phase ii test measured the corresponding tensile force arising from the expansive grout. Ostensibly homogeneous rock samples without incipient joints were firstly tested to establish the methodology. Tensile strength of block samples containing incipient rock joints was then measured using the established testing scheme. The test results have been compared with those obtained from conventional Brazilian and uniaxial tension tests as suggested by ISRM. The proposed approach is capable of giving a measure of tensile strength of large-scale incipient rock joints, although somewhat smaller strength than that from the standard approaches was occasionally measured in the preliminary tests on ostensibly homogeneous samples. Effects of stress concentration, sample scale, loading rate and expansive tensile force on the testing results were discussed. Furthermore, this simple and practical testing scheme is proposed for the measurement of the in situ tensile strength of rock and incipient discontinuities in the field, which if successful will provide a more scientific guidance on the rock mass classification and engineering design. 相似文献
The method of bi-dimensional empirical mode decomposition (BEMD) and the combined methods of entropy weight–Technique for Order of Preference by Similarity to an Ideal Solution (TOPSIS) were used to decompose gravity–magnetic data and evaluate targets in the Luziyuan Pb–Zn–Fe polymetallic ore field and surrounding areas. Three meaningful bi-dimensional intrinsic mode function (BIMF) images were obtained by BEMD at different wavelengths, depicting different layers of geological architectures in the study area. The results are as follows. (1) The BIMF2 images depict the shallow local geological architecture and show positive gravity–magnetic anomalies of the skarn alteration and Pb–Zn–Fe mineralization distributed around concealed granites. (2) The BIMF3 images depict the medium-depth geological architecture, indicating that concealed granitic stocks, which are shallow extensions of a deeply concealed pluton, intruded along the NE-trending fault. (3) The BIMF4 images depict gravity–magnetic anomalies at greater depth, which likely reflect regional geological architectures, indicating the potential presence of a large, concealed intermediate-acid pluton in the negative anomaly zone. Three potential targets (A, B, and C) were delineated based on BEMD results of the original gravity–magnetic data. The entropy weight–TOPSIS evaluation results show that the ranking of the metallogenic potential of the delineated targets in the study area is B, A, and C, with relative proximity values of 0.4576, 0.3925, and 0.1499, respectively. The results of this study can be used to guide future exploration.
Given insufficient geological investigation and inadequate interpretation of geological settings, remedial works for localized cut slope collapses may induce large-scale failures and cause remarkable damage, as well as economical loss. A number of recent reports have addressed individual large-scale failures due to inappropriate cutting, but the systematic classification of failure patterns has received less attention. In this study, a re-profiling triggered landslide is described in detail. The deep slip surface is located by field measurements; then, the stability of the slope before and after cutting is assessed with the limit equilibrium method. Three types of slopes prone to deep-seated failures are introduced: the loose deposits type, the ancient landslide type, and the deep adverse discontinuities type. The mechanism of each failure pattern is illustrated with a case study. The stability analyses indicate that inappropriate slope profiling may greatly reduce the factor of safety (FS) of a slope. Recommendations are given for mitigating the deep-seated landslide induced by inappropriate cutting, and a case history of successful measures is presented. 相似文献
Piping flow networks have often been identified in hydrogeological field studies of gravelly soil slopes in the southern part of China. The present experimental studies have shown that under long-term groundwater seepage, piping flow networks gradually develop in the slope. Factors affecting the development of flow pipe seepage network included the grain size distribution, the degree of soil compaction, and soil depth. Piping seepage networks favorably form if the content of the gravel was high, the soil cohesion was low, the degree of the soil compaction was low, or the soil depth was shallow. Due to the enhanced permeability associated with the presence of flow pipe seepage network in gravelly soil slopes, groundwater can be effectively drained away. This can beneficially prevent the rise of groundwater level in the slope during raining seasons, hence reducing pore water pressure along the potential failure surface and increasing slope stability. Once the flow pipe seepage network was disturbed or damaged, the water level in the upper portion of the slope experienced a great rise, hence reducing the slope stability. Therefore, slope toe excavation and excessive loading at the slope crest should be avoided for slopes with well-developed flow pipe seepage network in order to preserve it. 相似文献