| Tunnels and underground projects often encounter water-rich and weak surrounding rocks with loose structure,softening in contact with water,low strength,and poor self-stability,which can easily induce major geological disasters such as water inrush and collapse due to ground stress and engineering disturbance.In order to ensure construction safety,grouting is often used to reinforce the water-rich and weak surrounding rock.Splitting grouting can form a mortar vein network in the surrounding rock.It has the dual functions of skeleton support and soil compaction.The reinforcement effect is significant.Therefore,it is widely used in the reinforcement of water-rich and weak surrounding rocks.The grouting reinforcement effect has obvious characteristics of timeliness.Split-type grouting and solids continue to deform under the long-term action of ground stress,and their strength continues to decrease,which in turn affects the long-term operation safety of the tunnel.Previous studies have mostly focused on the effect of splitting grouting on the reinforcement of water-rich and weak surrounding rocks,while less attention has been paid to the long-term mechanical behavior of grouting and solidification and the long-term stability of the surrounding rock in the reinforcement area.In this paper,laboratory experiments,numerical simulations and theoretical analysis are used to carry out a series of researches on the rheological characteristics and long-term strength of split grouting reinforcement in water-rich and weak surrounding rocks.The influence law of mechanical properties,the deformation and failure mode of the solid body under long-term stress are investigated,and the long-term strength of the solid body and influencing factors are obtained.The related results can provide theoretical basis for the long-term performance prediction of the water-rich and weak surrounding rock reinforcement area and the safety evaluation of tunnel operation.The main research contents and conclusions are as follows:(1)The spatial distribution and morphological change characteristics of the grout veins in split grouting and solids are studied.Through the indoor grouting simulation test,the splitting veins were obtained.The spatial distribution and surface morphology characteristics of the veins were analyzed,and characteristic parameters such as the number of veins,inclination,thickness and surface roughness were extracted as the influence adding solid mechanics.Research on key performance indicators.(2)The influence of different factors(number of veins,inclination angle,thickness and surface roughness)on the triaxial compressive strength of the reinforced solid body and its mechanism are studied.Triaxial compression tests were carried out on the reinforced solids containing different types of pulp veins.The analysis found that the inclination angle of the pulp veins has the most obvious influence on the mechanical properties of the reinforced solids.(3)Based on the triaxial rheological test,the rheological characteristics and long-term strength of the split solids were studied,the rheological curves of the solids were obtained,and the rheological characteristics and influencing factors of the solids were analyzed.Studies have shown that the change of the inclination angle of the plasma vein will have a greater impact on the rheological characteristics of the reinforcement.When the plasma vein is parallel to the maximum principal stress,the reinforcement is suitable for the Burgers model.For other types of grouting and solids,the rheological characteristics accord with the improved Nishihara model.(4)The influence of the pulse veins on the long-term strength of the solid is studied.The transitional creep method is used to obtain the long-term strength range of the added solids.After the grouting and the solids undergo rheological deformation,the strength decreases significantly,and the long-term strength is about 76.5%to 89.5%of the instantaneous strength.At the same time,the pulp veins can effectively improve the long-term strength of the solids.When the inclined angle of the pulp veins is 90°,the strength of the solids loses the least and the long-term strength is the highest.(5)Based on the discrete element software PFC3D,the influence of complex factors such as the uneven distribution of plasma veins and the included angle of symmetric plasma veins on the rheological characteristics and long-term strength of the solid is studied,and the rheological characteristics of the numerical model are analyzed and the long-term strength is obtained..Studies have shown that the higher the uniformity of the plasma vein distribution,the greater the angle between the symmetric vein veins and the higher the long-term strength of the solids.ction of maximum principal stress,and the higher its long-term strength. |
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