Method for selecting parameters for tunnel support based on engineering-oriented behavior discrimination of surrounding rock

A method for selecting parameters for tunnel support based on engineering-oriented behavior discrimination of surrounding rock, comprising:

• step 1, obtaining basic geological data of a running tunnel by conducting geological investigation, establishing a model of a relative location relationship between the running tunnel and a stratum, and determining a chamber environment classification of a surrounding rock of the running tunnel;
• step 2, determining rock integrity of the surrounding rock of the running tunnel based on the basic geological data;
• step 3, determining a groundwater development level of the surrounding rock of the running tunnel based on the basic geological data;
• step 4, determining, based on the basic geological data, whether there is a slip surface on the surrounding rock of the running tunnel;
• and
• step 5, selecting support parameters for a corresponding support measure based on behavior of the surrounding rock including the chamber environment classification, the rock integrity, the groundwater development level, and whether the slip surface exists;
• wherein the step 1 comprises:
• step 11, determining hardness of the surrounding rock at a location of a vault of the running tunnel based on saturated uniaxial compressive strength of the rock in the basic geological data, and dividing the vault of the running tunnel into a hard rock region, a secondly-hard rock region, a soft rock region, and other stratigraphic regions based on the hardness;
• step 12, determining first, second, and third safety thicknesses of an overlying rock above the vault of the running tunnel based on a division result of the vault;
• step 13, determining a first distance from the vault of the running tunnel to a top boundary of the hard rock region based on the basic geological data, and when the first distance is greater than or equal to the first safety thickness, determining the chamber environment classification of the running tunnel as a grade A;
• step 14, when the first distance is less than the first safety thickness, determining a second distance from the vault of the running tunnel to a top boundary of the secondly-hard rock region, and if the second distance is greater than or equal to the second safety thickness, determining the chamber environment classification of the running tunnel as a grade B;
• and
• step 15, when the second distance is less than the second safety thickness, determining a third distance from the vault of the running tunnel to a top boundary of the soft rock region, and if the third distance is greater than or equal to the third safety thickness, determining the chamber environment classification of the running tunnel as a grade C;
• wherein the step 2 comprises:
• step 21, determining a compression wave velocity u of a rock mass and a compression wave velocity u0 of a rock block for a surrounding rock environment of the vault of the running tunnel based on the basic geological data;
• step 22, calculating an integrity coefficient k of the running tunnel based on the compression wave velocity u of the rock mass and the compression wave velocity u0 of the rock block:
• k
• =
• (
• u
• u
• 0
• )
• 2
• ;
• and
• step 23, determining the rock integrity of the surrounding rock of the vault based on the integrity coefficient k and a preset rock integrity classification table;
• wherein the step 3 comprises:
• step 31, determining, based on the basic geological data, a distance h from a center of the running tunnel to a phreatic line and a thickness hi of each different stratum between a groundwater level and the center of the running tunnel;
• step 32, determining, based on the basic geological data, a permeability coefficient ki of each different stratum located below the groundwater level and above the center of the running tunnel;
• step 33, calculating a comprehensive permeability coefficient K according to a following formula:
• K
• =
• ∑
• i
• n
• h
• i
• ∑
• i
• n
• (
• h
• i
• /
• k
• i
• )
• step 34, calculating an equivalent circle radius rt of the running tunnel according to rt=√{square root over (A/π)}, wherein A represents area of the running tunnel;
• step 35, calculating a water inflow Q0 per linear meter in a section based on the basic geological data:
• Q
• 0
• =
• 2
• ⁢
• π
• ⁢
• Kh
• ?
• (
• 2
• ⁢
• h
• /
• r
• t
• )
• ;
• ?
• indicates text missing or illegible when filed
• and
• step 36, based on the water inflow Q0 and a preset groundwater development level classification table, classifying the groundwater development level of the surrounding rock of the running tunnel into developed and undeveloped;
• wherein the step 4 comprises:
• determining, based on the basic geological data, whether the running tunnel passes through a large stratigraphic structural plane;
• and when the running tunnel passes through the stratigraphic structural plane, determining that the slip surface exists;
• or when the running tunnel does not pass through the stratigraphic structural plane, determining that no slip surface exists;
• wherein the step 5 comprises:
• step 51, determining four behavior indicators of the surrounding rock of the running tunnel:
• the chamber environment classification, the rock integrity, the groundwater development level, and whether the slip surface exists;
• step 52, determining a preset table for selecting a structural support parameter;
• and
• step 53, searching for support parameters for all support measures based on the four behavior indicators of the surrounding rock of the running tunnel and the preset table for selecting the structural support parameter.