System and method of monitoring vibration of a blasting model test for a jointed rock mass

A method for monitoring blasting vibration of a jointed rock mass, wherein the method comprises:

• step one, determination of relevant dimensions of a jointed rock mass model:
• enabling an existing tunnel of the jointed rock mass model to be a circular cavity commonly used in deep underground engineering;
• determining an excavation diameter and a tunneling depth of the existing tunnel according to a similar theory and a size of the jointed rock mass model;
• determining a diameter and a depth of each of blasting holes;
• fixing sheet mica with different angles in a mold according to test needs;
• and pouring a first layer of transparent rock-like material, wherein a pouring thickness is equal to a difference value among a thickness d of the mold, the tunneling depth and the depth of each of the blasting holes;
• step two, reservation of the blasting holes:
• presetting seamless steel pipes at a center of a surface of the first layer of transparent rock-like material to reserve the blasting holes, after the first layer of transparent rock-like material is stand and harden;
• wherein an inner diameter and a height of each of the seamless steel pipes that are preset have a same diameter and a same depth as the diameter and the depth of a corresponding one of the blasting holes, respectively;
• step three, pouring of a second layer of transparent rock-like material:
• enabling a pouring thickness of the second layer of transparent rock-like material to be 0.5 times the depth of each of the blasting holes;
• before the second layer of transparent rock-like material is completely hardened, rotating the seamless steel pipes configured to reserve the blasting holes, so as to prevent the seamless steel pipes from bonding to the second layer of transparent rock-like material and being difficult to be pulled away;
• step four, embedding of stress and strain sensors for the jointed rock mass:
• arranging strain measuring lines and stress measuring lines on a surface of the second layer of transparent rock-like material along an axis direction of the jointed rock mass model, after the second layer of transparent rock-like material is completely hardened;
• wherein the strain measuring lines are formed by a plurality of strain measuring points;
• enabling each of strain measuring points to adhere a fiber grating strain sensor;
• similarly, wherein the stress measuring lines are formed by a plurality of several stress measuring points, enabling each of the stress measuring points to adhere a PVDF piezoelectric pressure sensor;
• and enabling the stress measuring points and the strain measuring points to be arranged on two sides of a joint according to test requirements, so as to measure an impact of blasting load on the jointed rock mass;
• step five, roughening of layered surfaces:
• enabling a surface of a model material is raked by using an iron rake to obtain a rough surface with a thickness of about 5 mm, after the stress measuring points and the strain measuring points are embedded, thereby reducing layering caused by layered pouring, so that the model material after being undergone layered pouring are closely bonded with each other to improve integrity of a model test block;
• step six, pouring of a third layer of transparent rock-like material:
• enabling a pouring thickness of the third layer of transparent rock-like material to be 0.5 times the depth of each of the blasting holes;
• rotating the seamless steel pipes configured to reserve the blasting holes again, before the third layer of transparent rock-like material is completely hardened, so as to prevent the seamless steel pipes from bonding to the third layer of transparent rock-like material and being difficult to be pulled away;
• and after the third layer of transparent rock-like material is completely hardened, pulling away the seamless steel pipes that are preset;
• and finishing the reservation of the blasting holes at this moment;
• step seven, prefabrication of the existing tunnel:
• presetting the seamless steel pipes at a center of a surface of the third layer of transparent rock-like material, after the third layer of transparent rock-like material is completely hardened, so as to prefabricate the existing tunnel;
• enabling the seamless steel pipes that are preset to each have a same inner diameter and a same height as the excavation diameter and the depth of the existing tunnel, respectively;
• repeating the step three and step six to complete the prefabrication of the existing tunnel, and arrangement of the stress measuring points and the strain measuring points around the existing tunnel;
• wherein the stress measuring points and the strain measuring points are reasonably arranged according to the test requirements and joint positions;
• and
• step eight, implementation of blasting:
• applying three-way load and stabilizing pressure according to a test scheme;
• adding a high-strength transparent glass cover outside the jointed rock mass model, after the three-way load is applied;
• setting up high-speed camera equipment at a predetermined distance from an outer surface of the glass cover, so as to capture a dynamic crack-growth process in real time;
• applying the blasting load and performing model blasting, after setting up;
• and collecting relevant data to analyze influence of a joint inclination angle on propagation and attenuation laws of blasting stress waves in the jointed rock mass, and to analyze an impact of the blasting load on stability of the existing tunnel in the jointed rock mass.