A novel method for automatically monitoring the preload degradation of linear guideway type (LGT) recirculating linear ball bearings of an X-Y table is proposed. Both simulations and experiments revealed that the reduction in the natural frequency corresponding to the yawing mode of the worktable was extremely sensitive to and varied linearly with the degradation of the LGT linear bearing preload. By attaching three accelerometers to the worktable of a machine tool and then exciting the worktable with a pulse from the servo motor of a feed drive, this study identified the natural frequencies of the worktable and their corresponding mode shapes by using operational modal analysis (OMA). Among all the natural frequencies obtained by OMA, the natural frequency corresponding to the specific yawing mode of the worktable was extracted using the modal assurance criteria, and the change in the extracted frequency was tracked; thus, the degradation of LGT linear bearing preload could be monitored automatically without exciting the worktable manually. In this study, the performance of this method was assessed experimentally, and this paper presents the method in detail.

Abstract. In order to study the characteristics of the lateral bearing capacity for the case-in-place pile socked in rock, a single pile lateral load test is conducted in site, in which, some instrument were installed in pile shaft, and the deflections in the pile top and the steel bar stresses were taken under the various loadings, and propose a number of recommendations to improve the horizontal bearing capacity of the single pile.

Based on the dynamic monitoring of the moisture content of highway slope subgrade and the corresponding shear strength test, the safety analysis model of slope subgrade was established. Based on the model, the influence of different water content on the subgrade in the test section was analyzed. The results showed that under different moisture content conditions, the safety factor of slope subgrade is obviously different. The moisture content of slope subgrade is dynamically changed after the subgrade filling. The slope safety factor decrease with increase of the moisture content of subgrade, and the slope safety factor is the highest under the condition of the best moisture content.

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