Abstract
The deformation of karst cave-surrounding rock and its roof thickness are the key indicators to evaluate the stability of karst cave foundation. According to engineering characteristics of pile foundation in karst area, Using mechanical analytical method, cave-surrounding rock elasticity theory and Griffith criterion to calculate the safe thickness of Karst cave roof. According to karst cave-surrounding rock unstable and failure conditions, such as groundwater, different pile diameter, different thickness of Karst cave roof.Through comparing and analyzing engineering cases, the results show that the mechanical analytical method to determine the safety thickness of Karst cave roof can not meet the engineering requirements, determine the safe thickness of Karst cave roof Should be based on stability of cave-surrounding rock.
Highlights
Karst landform is widespread in China. due attention has been paid to the influence of karst collapse on the foundation stability
The evaluation method of karst foundation stability can be classified into qualitative analysis and quantitative analysis
Qualitative analysis is the basis for quantitative analysis
Summary
Karst landform is widespread in China. due attention has been paid to the influence of karst collapse on the foundation stability. 2. Quantitative analysis on the stability of karst cave foundation roof Methods of calculating the safe thickness of the roof are as follows: 2.1.The mechanical analytic method. M; p for total load of the roof, kN/m; l for cave span, m; σ for the computed bending resistance of the rock mass and estimated as 1/8 of the allowable compressive strength, kPa; b for the width of the beam and slab and estimated as 1.0m; H for thickness of roof strata, m; Q for shearing force of the standoffs, Q=1/2pL; for computed shearing strength of the strata (in the case of limestone, estimated as 1/12 of the allowable compression strength), kPa. 2.2.1.Stress redistribution of circular caves elastic surrounding rock. The vertical and horizontal stresses of the karst cave (r=5R0) are calculated according to the following formulas(7):. When the the karst cave surrounding rocks at the position r=5R0 do not wreak damage under the redistribution of stress, the karst cave is stable and the expression of judging its stability in accordance with the Griffith Criterion is the following formulas (9):. Judge the stability with the first formula if σ1+σ3≥0 and with the second formula if σ1+σ3
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