The self-stability height of the foundation pit sidewall is an important criterion for evaluating the safety degree and designing the supporting structure. The strength reduction elastic-plastic finite element numerical calculation method has been adopted in this paper. Based on comparative analysis of the stability characteristics for deep foundation pit in binary strata of upper soil and lower rock under multiple working conditions, the potential fracture surface of deep foundation pit and the evolution law of corresponding safety factor have been revealed under different Hs and H. A new idea that the vertical soil sidewall height (Hs) and the vertical rock sidewall height (Hr) are used as two independent evaluation indexes, respectively, for deep foundation pit stability in binary strata of upper soil and lower rock has been put forward. The distribution characteristics and variation law of Hs0 and Hr0 under different Hs and different H have been revealed, respectively. The spatial distribution map of the self-stabilizing height for deep foundation pit vertical sidewall in upper soil and lower rock binary stratum has been constructed, and the mathematical fitting equation between Hr0 and Hs has been obtained. Finally, combined with the implementation effect of the deep foundation pit project of Ningxia Road Station for Qingdao Metro Line 3, the rationality of the conclusions is verified. The research results provide theoretical basis for quickly determining the self-stability characteristics of foundation pit vertical sidewall.

<abstract> <p>The detection effect of the transient electromagnetic method is ambiguous in engineering applications due to the existence of interference sources, so explaining the influence of these fixed interference sources on is crucial. In this paper, the response characterisation of transient electromagnetic signals of fixed interference sources are thoroughly investigated. First, the secondary field generated by these interference sources is analyzed, and a typical fixed interference source is calculated. Then, a sensitivity analysis of the transient electromagnetic response curve is carried out. Finally, the mathematical superposition method for multiple field sources is proposed and verified. The results illustrate that the transient electromagnetic response curve of uniform full-space surrounding rock with a single fixed interference source has an apparent lifting phenomenon in the middle stage and presents an approximate horizontal change rule at the late stage. The transient electromagnetic response curves of multiple field sources separately illustrate the response characterisation of different field sources at different time stages. These research results can provide a valuable reference for the on-site interpretation of detection signals.</p> </abstract>

<abstract> <p>The transient electromagnetic inversion of detection signals mainly depends on fast inversion in the half-space state. However, the interpretation results have a certain degree of uncertainty and blindness, so the accuracy and applicability of the three-dimensional full-space inversion need to be investigated. Two different three-dimensional full-space inversions were carried out. First, the numerical characteristic parameters of the response signals were extracted. Then, the correlations between the numerical characteristic parameters and physical parameters of the water-bearing abnormal bodies were judged, and the judgment criterion of the iterative direction was proposed. Finally, the inversion methods of the iterative algorithm and the BP neural network were utilized based on the virtual example samples. The results illustrate that the proposed numerical characteristic parameters can accurately reflect the response curve of the full-space surrounding rock. The difference in the numerical characteristic parameters was used to determine the update direction and correction value. Both inversion methods have their advantages and disadvantages. A single inversion method cannot realize the three-dimensional inversion of the physical parameters of water-bearing abnormal bodies quickly, effectively and intelligently. Therefore, the benefits of different inversion methods need to be considered to comprehensively select a reasonable inversion method. The results can provide essential ideas for the subsequent interpretation of the three-dimensional spatial response signals of water-bearing abnormal bodies.</p> </abstract>

The vehicle-mounted transient electromagnetic method (VMTEM) has been proposed to detect tunnel internal defects in operational tunnels based on the ideal space state. However, the space environment of tunnel surrounding rock is different compared with conventional application fields, so the interpretation of detection data has certain inadaptability and unreliability. In this paper, three typical space states involved in the detection process of operational tunnels were analyzed. The diffusion law of the transient electromagnetic response signal under the condition of three typical space states was carried out, the proportional coefficient of different space states was determined, and the spatial transformation problem was also determined. Meanwhile, the results obtained by the numerical simulation calculation and numerical derivation calculation were verified by laboratory experiments. The results showed that the correction coefficient of full space to half space was 2.50, and that of three-quarters space to half space was 1.42. The detection process in operational tunnels involves the mutual transformation process of three typical space states. The critical distance that the spatial transformation does not affect is 300 m. In addition, the results of laboratory experiments verified the typical space proportional coefficient and spatial transformation phenomenon well. The results can provide essential ideas for the subsequent space correction of the detection environment in operational tunnels.

The multi-point random ground motion is artificially synthesized based on the triangular series method. Then the variation law and damping effect of vertical seismic response of large span isolated structures with different spans are studied respectively, under the action of both frequent earthquake and rare earthquake. The results show that in some areas of large span isolated structures, the vertical seismic responses are larger than those of non-isolated structures, under the multi-dimensional multi-point seismic input. The damping effects of large span isolated structures under rare earthquake are better than those under frequent earthquake. The area that is near the supports is prone to a large increase in response after isolation, so there should be strengthened during the engineering design.