To investigate the applicability of stress release for
pilot heading in soft rock tunnel, the mechanical model of stress release for
soft rock tunnel excavation by pilot heading method is established based on the
classical elasticplastic theory. The elasticplastic solution of tunnel excavation considering the stress release
of pilot tunnel is derived by a twostage method. The
stress release ratio of surrounding rock is defined to reflect the effect of
stress release, and the influences of pilot tunnel radius on stress release
effect under different insitu stresses, elastic
modulus and strengths of surrounding rock are studied. Results show that the
ground pressure applied on the support can be reduced by the excavation of a
pilot tunnel, especially in high geostress environment or weak rock, the stress
release effect is much more obvious by pilot heading method. However, the pilot
tunnel radius is not as larger as possible. The field tests show that for a
threelane large crosssection
soft rock tunnel, the large section of the pilot tunnel is unfavorable to the
stability of the surrounding rock. Stress release measure should be carried out
under the premise of ensuring the stability of surrounding rock in tunnel
construction. Thus, the primary support should be installed as soon as possible
to realize the safe and rapid construction.
XIA Caichu
,
JIN Tianyao
,
XU Chen
,
HAN Changling
. Mechanical Mechanism and Applicability of Stress
Release for Pilot Heading in Soft Rock Tunnel[J]. Tunnel Construction, 2020
, 40(S2)
: 1
-9
.
DOI: 10.3973/j.issn.2096-4498.2020.S2.001
