The Planar Elastic-plastic Analysis Of Reasonable Clear Interval And The Construction Method For Small Interval Tunnel Of The Six-Qian Expressway

With the fast development of economy the quantity and increase of investment in highway in our country and being based upon even development of economy, highway ranges from plain region to a mountainous area, where more and more highway tunnel are constructed. As a result of special geological and topographical limitations, interval of tunnels cannot satisfy with general technical codes. When we cannot solve the problems above with separate double tunnels, multiple-arch tunnels and small interval tunnel appear. Judging from the current situation, the construction of multiple-arch tunnels is a few quality problems of multiple-arch tunnels. craze, occur at large. At the same time, small interval tunnel is widely used for montanic highway, which solves the connection as well, as overcomes the problems of multiple-arch tunnels. But the key technology in design and construction of small interval tunnel hasn't been resolved. Such as determinant condition and reinforce method of bosom rock columniation, reasonable construction method and long-term safety assessment. So it's quite necessary and meaningful to strengthen the study of small interval tunnel.According to the practical tunnel project, the Six-Qian expressway, this paper discusses the stress characteristic of surrounding rock of small interval tunnel, analyzes the reasonable construction method under the condition of practical project, studies the interval optimization under the reasonable construction method, by way of theoretic and the planar elastic-plastic analysis . Through establishing the tunnel construction numerical model, this paper makes the numerical simulation for the stress characteristic of small interval excavation methods under three excavation methods. Base on the conclusion of that we draw general compare on the stress characteristic,the strain characteristic,the displacement characteristic of surrounding rock and the stress characteristic of support structure, the reasonable construction method of small interval tunnel, under the conditions of Grade V region and tunnel depth on some extent. Combined with the analysis conclusion of the reasonable construction method, this paper makes the numerical simulation for the stress characteristic of small interval excavation methods under different clear intervals, and gives the reasonable clear interval under the conditions of Grade III,IV,IV region and tunnel depth on some extent.