Study on the Influence of Probability Distribution Characteristics of Shot-concrete Strength on the Structural Reliability of Highway Tunnels
The probability distribution characteristics of shot-concrete strength are fundamental issues in the study of tunnel structural reliability,but there has been a lack of sufficient data support,and its impact on tunnel struc-tural reliability has not received sufficient attention.Firstly,core testing was conducted on shot-concrete of two typ-ical tunnels.The relevant literature data was collected for statistical analysis to obtain the probability distribution characteristics;Secondly,the limit state equation was derived.Under the conditions of Ⅲ～Ⅴ grade surrounding rock and its support,the decrease law of reliability indices caused by the uncertainty of sprayed concrete was calcu-lated.The results show that the strength of sprayed concrete in highway tunnels exhibits strong uncertainty,with the maximum variation coefficient of 0.381,and its probability distribution basically follows a normal distribution.The lower the level of surrounding rock,the greater the decrease of reliability indicators caused by the uncertainty of shot-concrete,specifically manifested as 6％decrease of Level Ⅲ surrounding rock,43％decrease of Level Ⅳ sur-rounding rock,and 67％decrease of Level Ⅴ surrounding rock.The reliability index of tunnel structure is positively correlated with the average strength of shot-concrete and negatively correlated with the standard deviation of shot-concrete strength.Therefore,when the tunnel structures are designed,design redundancy should be appropriately increased based on the uncertainty of sprayed concrete;Effective measures must be taken to reduce the uncertainty of shot-concrete during tunnel construction.
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