Brief description of the construction object

In connection with the development of an emergency situation in the area caused by the decompaction of the soils of the near-tunnel zone of the decommissioned sections of the tunnels (tracks I and II), research work was carried out. The purpose of the research and scientific work performed was to determine the causes and forecast negative phenomena in the "mass - flooded tunnels" system. The conducted geophysical studies indicate that the processes in the "tunnel-mass" system are far from stabilization. Based on the submitted reports, based on suggestions and recommendations, options for the production of work on filling tunnels and fixing the soil mass with their feasibility study aimed at ensuring the stabilization of the system and reliable operating conditions and development of urban infrastructure. The developed options for the production of works on filling the tunnels and fixing the soil massif were submitted for consideration. Rdeveloped a project for filling tunnels and fixing the soil mass in order to localize the sediment zone of the territory. The depth of the tunnels in the entire area of ​​work is from 64 to 88m. The length of the flooded sections is 535,5 m in the I track tunnel, and 474,0 m in the I track tunnel. The design of distillation tunnels is an outer lining of cast iron tubing 06,0 / 5,6 m and an inner reinforced concrete. a shell with metal insulation around the perimeter in the form of an 8 mm thick metal sheet anchored in concrete. The project provides:filling with technological solution with simultaneous drainage from the flooded tunnels of track I in the section from PK 180+33,4 to PK185+66,93 and track II in the section from PK 180+93,1 to PK 185+67,05; Withstabilization of the soil mass in the zone of maximum precipitation (section 320x30m from PK181+64 to PK 184+81,16) by constructing soil-cement columns using sleeve technology and fixing the soil using the jet grouting method "Jet Grouting". 

Brief description of the construction conditions

Geomorphologically, the construction site is confined to the Prinevskaya lowland. The hydrographic network of the region belongs to the Baltic Sea basin. The absolute marks of the earth's surface according to the height reference of wellheads range from 21,50 to 23,84 m. In the geological and lithological structure of the site within the depth of new and archival drilling of 142,0 m, the following take part: Technogenic deposits (t IV) - bulk soils. The exposed thickness of the deposits is from 0,5 to 6,2 m, their bottom is crossed at depths from 0,5 to 6,2 m, absolute marks are from 15,3 to 22,7 m. Biogenic deposits (b IV) - in the area under consideration are represented by peaty soils. The exposed thickness of the deposits is 0,6 m; the bottom is crossed at a depth of 3,6 m, the absolute mark of the bottom of the layer is 19,2 m. Lacustrine-glacial deposits (lg III). The exposed thickness of the deposits is from 23,1 to 34,6 m, their bottom is crossed at depths from 25,0 to 35,8 m, absolute marks are from -13,7 to -4,2 m. Glacial deposits of the Luga stadial (g III lz). The exposed thickness of the deposits is from 2,7 to 12,0 m, their bottom is crossed at depths from 36,0 to 43,0 m, absolute marks are from -19,3 to -13,7 m. Undivided lacustrine-glacial deposits (1d H-1Sch. The exposed thickness of the deposits is from 1,4 to 18,5 m, their base is crossed at depths from 39,7 to 59,8 m, absolute marks from -36,5 to - 17,7 m Deposits of the Moscow moraine (g II ms). The exposed thickness of the deposits is from 1,2 to 17,0 m, their bottom is crossed at depths from 43,0 to 65,0 m, absolute marks are from -41,6 to -21,2 m. Lacustrine-glacial and fluvi-glacial deposits (lg,f II dn-ms). The exposed thickness of the deposits is from 16,0 to 76,0 m, their bottom is crossed at depths from 59,0 to 121,0 m, absolute marks are from -98,4 to -37,2 m. The Upper Proterozoic Kotlin deposits (V kt2-2) are represented by greenish-gray silty clays of hard consistency. The exposed thickness of the deposits ranges from 1,9 to 32,0 m, they have been penetrated to a depth of 85,0 to 142,0 m, absolute marks are from -119,4 to -61,1 m.

Characteristics of the hydrogeological conditions of construction

In terms of hydrogeology, within the work area, a supra-morainic aquifer (groundwater horizon, waters of sandy lenses and interlayers, sporadically distributed in lacustrine-glacial sandy loams, loams) and an intermorainic aquifer represented by fine, medium sands containing pressure waters are distinguished within the work site. The above-morainic aquifer complex is developed everywhere, confined to the sands lacustrine-glacial deposits, as well as sandy and sandy loam layers in the thickness of technogenic deposits. The complex is represented by silty, fine and medium sands and gravel-pebble soils saturated with water. The lower aquiclude is the soils of the Luga moraine. The groundwater table at the time of drilling was recorded at depths of 1,7 to 3,0 m, at abs. marks from 18,5 to 22,3 m. The aquifer is fed by atmospheric precipitation and runoff of melt and rain water. The water-bearing complex is predominantly non-pressure. In some areas, where sands lie under soils with low filtration properties - loams and banded loams, a local pressure of groundwater can form (reaches 22,0 m). The intermorainic water-bearing complex is confined to the sands of lacustrine-glacial and fluvial-glacial deposits, it was revealed at depths of 41,8-74 ohm. The complex is represented by silty, fine, medium and gravel sands, boulder-pebble soils, water-saturated, pressure (pressure reaches up to 65,6 m). According to the results of chemical analysis of water samples of the above moraine aquifer complex in relation to concrete (grade W4) of normal permeability in accordance with SNiP 2.03.11-85, they are non-aggressive in terms of the content of caustic alkalis, the pH value and the content of sulfates, and are slightly aggressive in terms of the content of aggressive carbon dioxide. In accordance with GOST 9.602-2005, groundwater is highly corrosive in relation to lead and aluminum sheaths of cables. According to the results of chemical analysis of water samples of the intermorainic aquifer complex in relation to concrete (grade W4) of normal permeability in accordance with SNiP 2.03.11-85, they are non-aggressive in terms of the content of caustic alkalis, the pH value and the content of sulfates, and are slightly aggressive in terms of the content of aggressive carbon dioxide. In accordance with GOST 9.602-2005, intermarine aquifer water complex are characterized but in relation to lead and aluminum sheaths of cables have high corrosive activity. In accordance with GOST 9.602-2005, soils have an average corrosive aggressiveness to carbon and low-alloy steel. According to SNiP 2.03.11-85, table 4, in the normal and wet zone, soils are not aggressive in relation to concrete and reinforced concrete structures.

Design solutions

Before the start of work on filling the tunnels with a technological solution installation is being carried out. jumpers and gates in the decommissioned tunnels on the stage of the metro station on PK 180+12,45 and PK 180+10,45 of the upper and lower tunnels, respectively. The filling of the tunnel of the 1st track is carried out through vertical wells No. 52-52 (10 pieces), drilled by a rotary machine along the axis of the tunnel with a step of 180 m from PK 33,4 + 185 to PK 66,93 + 58 with a depth of 70 to 0426 m, with simultaneous fixing the walls of the well with casing pipes 325, 219 and 10704mm GOST 91-0250 and grouting the annulus. Prior to drilling of the tunnel lining, a section of soil above the tunnel shell is injected with cement mortar. Drilling along the tunnel lining is carried out by core drilling using hard-alloy bits 173 and XNUMX mm. The process solution is injected into the tunnel sequentially through each of the 0168mm wells with simultaneous removal of water displaced from the tunnel through adjacent wells. The filling of the tunnel of the II path is carried out in two ways: inalong the axis of the tunnel from PK180 + 93,1 to PK181 + 25,06, similarly to filling the tunnel of the 10st track, wells No. 53-55 (Zsht.) are drilled with a step of XNUMX m; Ot PK181+25,06 to PK185+67,05 existing wells No. 10-52. Drilling of wells to the inverted arch is carried out by the core method with crowns 0173mm, to the shelyga of the lining of the lower tunnel (II path) - by the rotary method with the well walls fixed with casing pipes 0168mm. Injection of a section of soil above the tunnel shell with cement mortar and drilling along the tunnel lining using a core method with core bits 0140 mm is carried out. The process solution is injected into the tunnel through wells 0168 and 108mm. Adjacent wells are designed to drain water displaced from the tunnel. To stabilize the soil mass, a two-component technology for fixing the pound mass by the Jet Grouting method and the creation of injected columns using collar technology are used. The soil mass is fixed in the zone of maximum settlement in a section measuring 320"30m (along the axis of the tunnel from PK 181+64,00 to PK184+81,16). Soil-cement piles 01 Dm with a depth of 25,0 m (2290 pieces) are staggered with a step of 2,0 m. Sleeve columns with a depth of 5 5-64m and 90m are constructed by a drilling rig in a rotary way in a checkerboard pattern with a distance between wells of 6 m in a row and 5 m between rows. The number of well rows is 2 on each side of the tunnel and one row above the tunnel. The injection of a hydrophilic solution based on a nanometric colloidal silica suspension is carried out at a depth of 50 to 90m. To control the quality of the work performed, it is planned to monitor the condition of the sealing structures, the array and the daylight surface. The calculation of the influence of the method of work on the surrounding array was made using the Plaxis 3D Foundation software package. The software package for geomechanical calculations "Plaxis" is designed to solve complex geomechanical problems using the finite element method in planar, axisymmetric and spatial formulations, using linearly elastic, elastic-plastic and viscous-creep models of deformable media. Modeling of stages of work is provided. The Plaxis software package for geomechanical calculations is certified by the State Standard of Russia, certificate No. ROSS NL.ME20.H019 80. At PK180+12,45 and FIK180+10,45 tunnels I and II, respectively, the installation of shutters ZT-D 1504A with a mechanical drive is provided. The frame of the shutter is a monolithic g.6. structure (concrete B25 W8 F50) 2,0 m long. The tunnel is filled with a technological solution MEYCO MP 367 FOAM (a two-component injection resin of urea silicate that does not contain solvents and is designed for fast filling of cavities, stabilization of soil massifs). The components are supplied ready to use and are pumped under pressure proportionally in a 1:1 volume ratio with a wet two-component injection pump equipped with a static mixer nozzle installed in the body of the packer. Injection of the bottom-hole zone of wells above the tunnel shell is carried out with a reinforcing mortar Rheocem 650 (high-grind Portland cement for injection into rock and soil) with W / C = 1,0 and W / C = 3,0 with Rheobuild 2000PF ultra-fine grinding Portland cement. Sleeve columns are injected with Meuso MP 320 hydrophilic solution based on manometric colloidal silica suspension. The solution has a low viscosity, does not contain solvents and is intended for injection into rock and strengthening sandy and silty soils. The gel time is controlled by changing the amount of Meuso MP 320 set accelerator added to the component. To fix the soil by the method of jet grouting, a cement mortar based on Portland cement M400 (W / C = 1: 1) is used with the use of a complex additive KDSC.