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The paper introduced different testing methods and testing theories for broken rock zone of surrounding rock of roadway, discussed and analyzed advantages and disadvantages and scope of application of the different testing methods. By comparison, it got conclusion as follows: technology of the acoustic method is advanced and testing method is simple, but it is difficult to be applied in soft rock; the multi-point displacement measurement and the multi-point stress measurement can be applied for real-time monitoring of surrounding rock displacement or stress, but the accuracy of measurement is limited; the seismic wave method has high testing precision, but its equipment is expensive and complicated to install; the geologic radar method without drilling is a non-destructive testing method, but testing cost is high; the resistivity method has a high requirement in the precision of instrument and arrangement of electrodes; image resolution of the method of borehole camera is limited by harsh environmental conditions within the borehole and the pixel of camera. Therefore, each testing method has its limitations, nature of the surrounding rock should be considered in actual application to select appropriate method for accurate determination of broken rock zone of the roadway.

Background: Impaired ventilatory efficiency during exercise is a predictor of mortality in chronic obstructive pulmonary disease. However, little is known about the clinical features and associated factors of impaired ventilatory efficiency in China., Methods: We conducted a cross-sectional community-based study in China and collected demographic and clinical information, cardiopulmonary exercise testing, spirometry, and CT data. Impaired ventilatory efficiency was defined by a nadir ventilatory equivalent for CO 2 production above the upper limit of normal. Multivariable linear and logistic regression models were used to explore the clinical features and associated factors of impaired ventilatory efficiency., Results: The final analyses included 941 subjects, 702 (74.6%) of whom had normal ventilatory efficiency and 239 (25.4%) had impaired ventilatory efficiency. Participants with impaired ventilatory efficiency had more chronic respiratory symptoms, poorer lung function and exercise capacity, and more severe emphysema (natural logarithm transformation of the low-attenuation area of the lung with attenuation values below -950 Hounsfield units, logLAA -950 : 0.19±0.65 vs -0.28±0.63, p<0.001) and air trapping (logLAA -856 : 1.03±0.65 vs 0.68±0.70, p<0.001) than those with normal ventilatory efficiency. Older age (60-69 years, OR 3.10 (95% CI 1.33 to 7.21), p=0.009 and 70-80 years, OR 6.48 (95% CI 2.56 to 16.43), p<0.001 vs 40-49 years) and smoking (former, OR 3.19 (95% CI 1.29 to 7.86), p=0.012; current, OR 4.27 (95% CI 1.78 to 10.24), p=0.001 vs never) were identified as high risk factors of impaired ventilatory efficiency., Conclusions: Impaired ventilatory efficiency was associated with poorer respiratory characteristics. Longitudinal studies are warranted to explore the progression of individuals with impaired ventilatory efficiency., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)