Design and calculation method for initial support of tunnel initial support bearing all design loads

Abstract

The invention provides a design and calculation method for an initial support of a tunnel initial support bearing all design loads. The design and calculation method is characterized in that the initial support of the tunnel initial support bearing the all design loads is designed and calculated by adopting two methods, namely "two hinged arches + 2x2 chain poles + elastic resistance", and "two hinged arches + 10x2 chain poles"; the calculation of the method makes the "structure" completely correspond to the "loads", and makes the corresponding relationship between "measures" and "problems" established on site clearer, and the purpose is more explicit; the method adopts a force method to calculate, thus complete structural internal forces and a displacement function relationship can be obtained, and the change rule of the structural internal forces and displacement can be reflected explicitly; and besides, a familiar general theory is adopted, which can facilitate technical personnel on site to design and calculate the tunnel initial support, and provide a theoretical basis for the development of a construction plan.

Description

technical field [0001] The invention relates to the technical field of engineering calculation, and specifically designs a calculation method for the initial support design of a tunnel in which the initial support bears all the design loads, more specifically a structure for the initial support of a soft rock tunnel that bears all the design loads Mechanics force method design calculation method. Background technique [0002] Practice has proved that the surrounding rock is in a loose state after excavation of soft rock tunnels, so the basic condition for the application of the "New Austrian Method" principle - the elastic-plastic condition of the surrounding rock is not met. Therefore, under the current technical conditions, soft rock tunnels, especially shallow tunnels, should not be designed and constructed using the "New Austrian Method" principle, but should be designed and constructed using structural mechanics in accordance with the "load-structure" model. [0003] "...

AI Technical Summary

Problems solved by technology

Nowadays, the construction of soft rock tunnels mostly adopts the step method for excavation and support in sections. After the full-section support is formed, the two-part integral lining is followed by the first inverted arch, then the arch and the wall, that is to say, the end of the lining and the end of the support. There is a certain distance, which is about 45m according to the current relevant regulations. However, the load of the tunnel is related to the width and area of ​​the excavated section. , at this time, the entire load is borne by the initial support, while the designed initial support only bears a small part of the load. The actual load it bears is more than twice the design load, and the initial support must be damaged, resulting in a landslide. This logical error is always ;Secondly, there is often such a phenomenon in the field. When it is found that the initial support is seriously damaged, such as cracking, peeling, and serious deformation, measures should be taken to deal with the lining according to the original design parameters as soon as possible. Since the initial support has been damaged, it means that The bearing capacity has been lost. At this time, the load acting on the secondary lining is no longer 0.5~0.7, but the full load, so the result will inevitably lead to the destruction of the secondary lining.

It seems that this seemingly very safe regulation has great potential safety hazards.

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