Ultimate Bearing Capacity Of Strip Footings Considering Void Influence

Ultimate bearing capacity of shallow foundation,as one of three classical problems for soil mechanics,has achieved great development,both in terms of analytical formulas and experimental studies.Furthermore,many formulas are used to calculate bearing capacity.However,with a large number of industrial and civil buildings being constructed,underground voids have increasingly occurred in design and construction of civil engineering.When underground void occurs,it will become considerably more complex for determining ultimate bearing capacity of footing.Since footing stability is closely related to the safety of people's life and property,it is necessary to carry out a deep study on ultimate bearing capacity of footing with underground void.Combining proven and state-of-the-art studies at home and abroad,a more systematic study on ultimate bearing capacity of strip footing with underground void was carried out by using a novel numerical approach,namely,the method of Discontinuity Layout Optimization(DLO)in this paper.Since the DLO method uses lines connected between all joints within a global scope to search and determine the final slip lines,a more reasonable failure mode of footing and a value of ultimate bearing capacity close to real solution could be obtained and acquired,comparing with traditional methods of analytical calculation.Research means and calculation principles used here was elaborated,and the suitability of the DLO method for research on bearing capacity of strip footing with underground void also was testified.By simulating a large number of failure modes,a detailed exploration into the effect of the shape,size and buried depth of void and the strength parameters of ground soil on failure mode of footing was undertaken,and the three major failure modes of footing with void had proved again.In case a change occurs in variables set above,a mutual transformation could occur between those failure modes.In addition,by taking large number of numerical simulations,the value of ultimate bearing capacity of strip footing with void in different engineering conditions was obtained.With this basis,a detailed analysis on the extent of effect of each variable on the value of ultimate bearing capacity respectively was made.A point of view that the diameter of void is negatively correlated with bearing capacity while buried depth of void,eccentricity and strength of ground soil are positively correlated with the bearing capacity was raised.Based on numerical simulations,a calculation scheme for ultimate bearing capacity of strip footing with void was proposed,namely,multiplying each item of a general calculation formula for bearing capacity of shallow foundation without void by correction factor considering effect of void.This corrected factor is obtained through stepwise calculating by using principle of linear superposition.A datasheet has been formulated of correction factors under different engineering conditions,with its rationality being verified by comparing with calculation results from other literatures and results made by numerical simulation.