scholarly journals Analytically Determining Bond Shear Strength of Fully Grouted Rock Bolt Based on Pullout Test Results

2020 ◽  
Author(s):  
Mousa Hazrati Aghchai ◽  
Parviz Maarefvand ◽  
Hossien Salari Rad
Keyword(s):  
Shear Strength ◽  
Analytical Method ◽  
Pullout Test ◽  
Rock Bolt ◽  
Displacement Curve ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Interface Shear ◽  
Bond Shear Strength ◽  
Load Displacement

Usually, in a fully grouted rock bolt pullout test the load-displacement curve of the rock bolt head is recorded. This paper presents an analytical method to use this curve for determining the bond (bolt-grout and grout-rock interface) shear strength parameters. For this purpose, the fully grouted rock bolt interaction with grout and surrounding rock in the pullout test is investigated and the load-displacement curve of the bolt head (beginning of the bonded section) is obtained analytically. For modeling the bolt-grout interface behavior a distribution of the shear stress along the fully grouted rock bolt by consideration of bolt shank failure is used. In this regard, different stages including complete bonding, partial decoupling, decoupling with the residual shear strength and complete decoupling are considered. With increasing the applied load, two possible cases involving the rock bolt complete pullout and bolt shank yielding are taken into account. Based on the presented analytical method, the obtained bolt head load-displacement curve can be compared with the one recorded in the pullout test. With this, the relevance of selected shear strength parameters compared to real parameters can be assessed. A flowchart for determining the bolt bond shear strength parameters is presented using the trial and error method (coded in Matlab). The proposed solution is used to determine two experimental pullout shear strength parameters. The results show good agreement between predicted and calculated load-displacement curves.

scholarly journals Study on the Strength Performance of Recycled Aggregate Concrete with Different Ages under Direct Shearing

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2312
Author(s):  
Xin Liang ◽  
Fang Yan ◽  
Yuliang Chen ◽  
Huiqin Wu ◽  
Peihuan Ye ◽  
...  
Keyword(s):  
Shear Strength ◽  
Shear Force ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Displacement Curve ◽  
Direct Shear ◽  
Replacement Ratio ◽  
Aggregate Concrete ◽  
Concrete Failure ◽  
Load Displacement

In order to study the mechanical properties of recycled aggregate concrete (RAC) at different ages, 264 standard cubes were designed to test its direct shear strength and cube compressive strength while considering the parameters of age and recycled aggregate replacement ratio. The failure pattern and load–displacement curve of specimens at direct shearing were obtained; the direct shear strength and residual shear strength were extracted from the load–displacement curves. Experimental results indicate that the influence of the replacement ratio for the front and side cracks of RAC is insignificant, with the former being straight and the latter relatively convoluted. At the age of three days, the damaged interface between aggregate and mortar is almost completely responsible for concrete failure; in addition to the damage of coarse aggregates, aggregate failure is also an important factor in concrete failure at other ages. The load–displacement curve of RAC at direct shearing can be divided into elasticity, elastoplasticity, plasticity, and stabilization stages. The brittleness of concrete decreases with its age, which is reflected in the gradual shortening of the elastoplastic stage. At 28 days of age, the peak direct shear force increases with the replacement ratio, while the trend is opposite at ages of 3 days, 7 days, and 14 days, respectively. The residual strength of RAC decreases inversely to the replacement ratio, with the rate of decline growing over time. A two-parameter RAC direct shear strength calculation formula was established based on the analysis of age and replacement rate to peak shear force of RAC. The relationship between cube compressive strength and direct shear strength of recycled concrete at various ages was investigated.

Reliability Method to Estimate Shear Strength Parameters

2011 ◽  
Vol 52-54 ◽  
pp. 1752-1756
Author(s):  
Li Hong Chen ◽  
Yu Fei Zhao
Keyword(s):  
Shear Strength ◽  
Linear Regression ◽  
Moment Method ◽  
Limit State ◽  
Safety Evaluation ◽  
Regression Method ◽  
Linear Regression Method ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Reliability Method

The design and safety evaluation of a geotechnical project is influenced by the shear strength parameters of geo-material. Moment method and linear regression method are the mainly used methods to estimate the shear strength parameters. But moment method is always over estimate the variation of strength parameters due to the smaller sample size, meanwhile the conventional linear regression method cannot obtain the standard deviation. Base on the reliability theory, a new method employing Solver add-in of spreadsheet was developed to calculate the shear strength parameters. The method was simplified by the principle that the shortest distance form origin point to the limit state surface in the normalization space was the reliability index. Four hundred and four samples of direct shear tests of rock mass from many large hydraulic projects in China were analyzed by four statistic methods including the new proposed one. Comparing results of different methods indicated that the new reliability statistic method had good performance than the traditional ways.

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