Research On Explosion Resisting Capacity Site Tests Of Underground Cavern Reinforced By Grouted Rockbolts

As science and technology develop, hi-tech weapons can attack aims in high precision. The depth that weapons penetrate in land gets deeper and deeper. The explosion strength gets stronger and stronger. So the underground protective structures face tremendous threat. To improve the explosion resisting capacity of protective structures and surrounding rock when the land-penetrating weapons explode, this passage may supply some references to the safety problem of underground engineering projects through the research for the site explosion resisting capacity tests of underground cavern reinforced by grouted rockbolts; through the numerical analyse; and through theoretic research of rockbolts. Some conclusions are brought as follow:1. The explosion resisting capacity site tests of underground cavern reinforced by grouted rockbolts include: short and close rockbolts; long and close rockbolts; regular rockbolts; and grout sprayed. From the macroscopic destroyed appearances, the sprayed grout are cast and crazed. Some sheared crevices appear at the arch of carven. The positions at the top and arch are easily to be destroyed. Especially some grout at the ends of some rockbolts ruined more heavily for the long and short rockbolts type than for the short and short rockbolts type. It indicates that the destroyed situation for the long and short rockbolts is more serious.2. Comparing the displacements at the top of caverns and the relationships between the displacement peak values and the relative explosion distances, the ratio that the displacement peak values divided by the span decayed in negative index law. Every displacement wave has a simple regularity. It goes down to a bottom that is the maximal displacement, then it reboundes to a smaller displacement, at last the wave verges to placidity. For the time that the wave reaches maximal displacement, it is between 43 ms and 47 ms for regular rockbolts type, and it is about 39 ms or 40 ms for short and close rockbolts type or long and close rockbolts type. For the displacements at the top of caverns, the vertical displacement peak value for long and close rockbolts type is higher than for short and close rockbolts type. It suggests that the length of rockbolts may not support caverns to resisting explosion. The strain waves of every rockbolt are also brought out and analysed. The rockbolts are mainly subjected to compression. The strain value for long and close rockbolts type is higher than for short and close rockbolts. This passage also introduces rockbolts strain peak value enveloping line and the maximal strain does not appear at same position for every rockbolt. The strain of rebar has analogous regularity. The strain is not only tension but also compression. For analyse of acceleration at different positions, the regularities are different. The acceleration peak value decreases in negative index law.3. Making use of numerical analysing software, the vertical displacements at the top of three kinds of caverns in different protective conditions are analysed. And the strain situations of the caverns and rockblolts are also researched. The destroyed situations at top and arch of caverns are still severe. And also the short and close rockbolts have a better protective effect than the long and close rockbolts. The conclusions are same as the site tests. In addition, the influences of the rock elastic modulus to the displacement at the top of cavern are analysed. And the influences of explosion relative distance to the displacement at the top of cavern are analysed, too.4. Some researching jobs about rockbolts' effects are put forward. A viscoelastic model of rockbolt thinking of surrounding rock effects is analysed. The stress wave propagation situation is researched and stress wave's transmission and reflection situation at the position of prayed grout is brought out.