Deep valley high fill slope comprehensive treatment system
By adopting a multi-level governance system on the high-fill slopes of deep-cut valleys, including collaborative governance of ditch top-ditch feet, stepped layered compaction, dual-channel intelligent flood discharge and ecological slope protection, the problems of poor slope stability, poor drainage and insufficient ecological restoration in traditional governance technologies are solved, and more efficient comprehensive governance results are achieved.
Patent Information
- Application Number
- CN202510287536.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-12
- Publication Date
- 2025-05-30
AI Technical Summary
Traditional deep-cut valley high-fill slope management technology has problems such as poor slope stability, poor foundation settlement control, insufficient drainage efficiency, easy blockage of flood drainage ditches and insufficient ecological restoration capabilities.
The groove top-ditch foot collaborative governance subsystem, step-type layered compaction subsystem, dual-channel intelligent collaborative flood discharge subsystem and ecological slope protection subsystem are adopted. Through collaborative governance and multi-level design, slope stability is improved, foundation settlement is controlled, drainage and ecological restoration is optimized.
It significantly improves the comprehensive management efficiency of high-fill slopes in deep trench valleys, improves slope stability and foundation settlement control, optimizes drainage and flood control capabilities, and significantly enhances the ecological restoration and protection functions of the slopes.
Smart Images
Figure CN120061368A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical fields of geological disaster prevention and control, water conservancy projects and ecological restoration, and specifically relates to a comprehensive treatment system for a high-fill slope in a deeply incised gully. Background Art
[0002] A high-fill slope in a deeply incised gully refers to a gully slope located in a steep terrain with complex geological structures and a filling height exceeding 15m. Such high-fill slopes have characteristics such as poor self-stabilization ability, large mountain flood flow, and high filling requirements. Traditional treatment technologies mostly adopt single measures, such as layered compaction, local anti-seepage, passive support, etc., and have the following defects in aspects such as slope stability control, foundation settlement control, drainage efficiency, and ecological restoration: Slope stability control: The compaction degree of the filling edge area of the slope is insufficient, and no geogrid is set in the filling body or the extension length of the set geogrid is insufficient, which easily leads to insufficient anti-sliding ability of the slope and instability.
[0003] Foundation settlement control: Traditional compaction processes do not distinguish the bearing capacity differences between the core area and the surface area of the filling body, which easily leads to an excessive settlement difference.
[0004] Insufficient drainage efficiency: Traditional schemes rely on a single surface flood discharge channel and do not set up a dual-channel collaborative structure of underground drainage and surface diversion. In the case of heavy rain, it is easy to cause overtopping damage due to insufficient drainage capacity or infiltration into the filling body, resulting in slope sliding.
[0005] Drainage failure of the filling body: No gravel drainage cushion layer and drain holes are set at the step interface, and the drainage in the filling body is not smooth. In the case of heavy rain, it is easy to cause local sliding of the slope.
[0006] Blockage of the flood drainage ditch: Only a simple intercepting ditch is set at the top of the traditional ditch, lacking a structure for intercepting falling stones and branches, which is easy to block the flood drainage ditch.
[0007] Defects in ecological restoration: Traditional slope surface protection uses shotcrete or stone revetment, resulting in insufficient ecological restoration ability of the slope. Summary of the Invention
[0008] The main purpose of the present invention is to solve the problems existing in the above-mentioned prior art and provide a comprehensive treatment system for a high-fill slope in a deeply incised gully.
[0009] The specific solution of the present invention is as follows: A comprehensive treatment system for high-filled slopes in deep-cut valleys includes a top-bottom collaborative treatment subsystem, a stepped layered compaction subsystem, a dual-channel intelligent collaborative flood discharge subsystem, and an ecological slope protection subsystem; the top-bottom collaborative treatment subsystem includes a top-of-gully water collection apron device and a bottom-of-gully retaining wall energy dissipation device, which are used to intercept upstream floods, falling rocks and branches, and reduce the erosion at the bottom of the gully; the stepped layered compaction subsystem includes a layered filling drainage system, a stepped rolling system, and a geogrid extension system, which are used to improve the compaction degree of the filling body and control differential settlement; the dual-channel intelligent collaborative flood discharge subsystem includes a surface flood discharge channel, an underground flood discharge channel, and an intelligent monitoring system, which dynamically switches the flood discharge mode by real-time monitoring of the peak flood flow; the ecological slope protection subsystem includes a vegetated concrete skeleton and deep-rooted vegetation, which realizes the ecological restoration and protection functions of the slope.
[0010] Further, the top-of-gully water collection apron device includes a water collection pool, an apron, vertical poles, and a grid fence; the water collection pool is arranged at the junction of the filling body and the upper mountain body of the gully, and is made of C35 reinforced concrete structure with a reinforcement ratio ≥ 2.0%, the inner wall is coated with a ≥ 3mm polyurethane waterproof layer, the length × width × height ≥ 8m × 5m × 3m, the thickness of the pool wall ≥ 400mm, the bottom surface of the water collection pool is connected to the underground flood discharge channel, and the side surface of the water collection pool is connected to the surface flood discharge channel; the apron is made of C40 cast-in-place concrete, the width ≥ 5m, the thickness ≥ 1m, and the slope ratio is 1:5 - 1:6; the vertical poles and the grid fence are arranged at the junction of the water collection pool and the apron, the vertical poles are made of galvanized steel pipes with a diameter ≥ 100mm and a spacing ≤ 2m, and the grid fence is made of galvanized steel wires with a mesh size ≤ 60mm × 60mm.
[0011] Further, the bottom-of-gully retaining wall energy dissipation device includes a retaining wall and an energy dissipation pool; the retaining wall is arranged at the junction of the filling body and the lower mountain body of the gully, and is made of C25 reinforced concrete structure with a reinforcement ratio ≥ 2.0%, the wall height is 6 - 10m, the top width ≥ 1.2m, the bottom width ≥ 3m, and it is embedded in the two side mountain bodies ≥ 1m; the energy dissipation pool is arranged under the retaining wall, the length ≥ 8m, the depth ≥ 1.5m, the bottom of the pool is paved with 30cm thick C35 concrete, and the inner wall is coated with 3mm polyurethane waterproof layer. The bottoms of the underground flood discharge channel and the surface flood discharge channel are both connected to the energy dissipation pool.
[0012] Further, the layered filling drainage system includes a crushed stone drainage cushion and cushion drainage holes; the crushed stone drainage cushion is arranged at each step surface, with a thickness ≥ 0.5m and a transverse slope ≥ 3%, and the cushion drainage holes are arranged in the crushed stone drainage cushion, using 150mm diameter HDPE pipes with a length ≥ 3m, a horizontal spacing of 3m, and a galvanized iron wire mesh is set at the pipe end, wrapped with geotextile.
[0013] Furthermore, the stepped rolling system includes a core compaction area, a transition compaction area, and a surface compaction area. The core compaction area is ≥8m away from the slope surface, with a layered compaction thickness of 1.5m, and is rolled with a 32t roller to a compaction degree of ≥97%. The transition compaction area is 3 - 8m away from the slope surface, with a layered compaction thickness of 1m, and is rolled with a 20t padfoot roller to a compaction degree of ≥95%. The surface compaction area is 0 - 3m away from the slope surface, with a layered compaction thickness of 0.5m, and is rolled with a 10t sheepsfoot roller to a compaction degree of ≥93%.
[0014] Furthermore, the geogrid extension system is to fully lay a bidirectional geogrid along the stepped rolling surface and extend it to the core compaction area by ≥15m.
[0015] Furthermore, the surface flood discharge channel is placed at the junction of the filling body and the mountain body, and a C25 reinforced concrete water channel is used, with a longitudinal slope of ≥2%. The underground flood discharge channel is arranged at the bottom of the existing ditch, and a corrugated pipe or box culvert is used, with a longitudinal slope of ≥5%.
[0016] Furthermore, the intelligent monitoring system includes an electromagnetic valve set at the entrance of the underground flood discharge channel and a pressure type water level gauge set in the catch basin. The electromagnetic valve is signal - connected to the pressure type water level gauge. The electromagnetic valve dynamically switches the flood discharge mode according to the monitoring data of the pressure type water level gauge. When the peak flood flow ≥ the design flow of the surface flood discharge channel, the dual - channel flood discharge is enabled.
[0017] Furthermore, the vegetative concrete skeleton is set on the filling slopes at all levels, and the grass seed mix ratio is Cynodon dactylon: Amorpha fruticosa: Medicago sativa = 4:3:3.
[0018] Furthermore, the deep - root vegetation is set on the stepped surfaces of the filling slopes at all levels, and a mixture of willows and reeds is used. The plant spacing of willows is 2m, the plant spacing of reeds is 0.3m, and the root depth is ≥1.5m.
[0019] The present invention has the following advantages compared with the prior art: 1. The comprehensive treatment efficiency is significantly improved: Aiming at the characteristics of the high - filled slope in the deeply - cut gully and the defects of traditional treatment technologies, the coordinated control of slope stability and foundation settlement, the coordinated control of surface flood discharge and underground flood discharge, and the coordinated control of soil and water conservation and ecological restoration are integrated into one, constructing a systematic comprehensive treatment idea, and the treatment efficiency is significantly improved.
[0020] 2. The control of slope stability and foundation settlement is significantly improved: Through the stepped layered compaction system, the compaction degree of the surface area and the transition area is improved. Combining the coordinated force of the geogrid extension system in different compaction areas, it effectively solves the problems of slope slip caused by insufficient process compaction degree in the surface area and transition area of the filled slope and the settlement risk caused by the difference in bearing capacity.
[0021] 3. Optimization of drainage efficiency and flood control capacity: The dual-channel intelligent coordinated flood discharge system realizes the linkage between surface and underground drainage, and the flood discharge capacity is significantly improved. The flood discharge channel can be dynamically switched under heavy rain conditions to avoid the overflow risk of the traditional single drainage channel. 4. Coordinated enhancement of ecological restoration and slope protection: The slope protection is achieved by combining slope vegetation concrete with deep-rooted vegetation on the steps. The vegetation coverage rate is increased to more than 90%, which is several times more ecologically beneficial than traditional concrete slope protection and has anti-erosion capabilities. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 It is a schematic plan view of the comprehensive management system for deep-cut gully high-fill slopes of the present invention; Figure 2 It is a cross-sectional schematic diagram of the comprehensive management system for deep-cut gully high-fill slopes of the present invention; Figure 3 It is a schematic diagram of the stepped layered compaction system of the present invention; Figure 4 It is a schematic diagram of the dual-channel intelligent coordinated flood discharge system of the present invention; In the figure: 1. Water collection tank; 2. Tank guard; 3. Poles and grid fences; 4. Fill boundary line; 5. Retaining wall; 6. Energy dissipation pool; 7. Stepped sloping fill surface; 8. Gravel drainage cushion layer; 9. Cushion drainage holes; 10. Rolling partition; 11. Geogrid; 12. Core compaction area; 13. Transition compaction area; 14. Surface compaction area; 15. Stepped rolling surface; 16. Underground flood discharge channel; 17. Surface flood discharge channel; 18. Solenoid valve; 19. Pressure water level gauge; 20. Galvanized wire mesh; 21. Vegetation concrete skeleton; 22. Deep-rooted vegetation. DETAILED DESCRIPTION
[0023] See also Figures 1-4 The present embodiment is a comprehensive management system for high fill slopes in deep valleys, including a ditch top-ditch foot collaborative management subsystem, a stepped layered compaction subsystem, a dual-channel intelligent collaborative flood discharge subsystem and an ecological slope protection subsystem; the ditch top-ditch foot collaborative management subsystem includes a ditch top water collection and protection device and a ditch foot retaining wall force dissipation device, which are used to intercept upstream floods, fallen rocks and branches and reduce ditch foot scour; the stepped layered compaction subsystem includes a layered filling drainage system, a stepped rolling system, and a geogrid extension system, which are used to improve the compaction degree of the fill body and control differential settlement; the dual-channel intelligent collaborative flood discharge subsystem includes a surface flood discharge channel 17, an underground flood discharge channel 16, and an intelligent monitoring system, which dynamically switches the flood discharge mode by real-time monitoring of the peak flow; the ecological slope protection subsystem includes a vegetated concrete skeleton and deep-rooted vegetation to achieve slope ecological restoration and protection functions.
[0024] Furthermore, the ditch-top water-collecting apron device consists of a catch basin 1, an apron 2, vertical poles and a grille fence 3. The catch basin 1 is located at the ditch-top part of the filling boundary line 4, with its long side perpendicular to the direction of the gully water flow. The dimensions are length × width × height = 8 m × 5 m × 3 m, the thickness of the pool wall is 400 mm, the pool body is made of C35 reinforced concrete with a reinforcement ratio ≥ 2.0%, and the inner wall is coated with a 3-mm polyurethane waterproof layer. The long side of the catch basin 1 is connected to the underground flood discharge channel 16, and the short side is connected to the surface flood discharge channel 17. The apron 2 is located upstream of the catch basin 1, with an apron width of 5.0 m, a thickness of 1.0 m, and a slope ratio of 1:5, and is made of C40 cast-in-place concrete. Vertical poles and a grille fence 3 are arranged at the connection part between the catch basin 1 and the apron 2. The vertical poles are made of galvanized steel pipes with a diameter of 100 mm, a height of 5 m, a spacing of 2 m, and a buried depth of 1.5 m; the grille fence is made of galvanized steel wires with a diameter of 5 mm and a mesh size of 60 mm × 60 mm.
[0025] Furthermore, the ditch-foot retaining wall energy dissipation device consists of a retaining wall 5 and an energy dissipation pool 6. The retaining wall 5 is located at the ditch-foot part of the filling boundary line 4, arranged perpendicular to the gully axis, with a wall height of 6.0 m, a top width of 1.2 m, a bottom width of 3.0 m, a foundation buried depth of 1.5 m, and the wall body is made of C25 reinforced concrete with a reinforcement ratio of 2.0%. The energy dissipation pool 6 is arranged adjacent to the lower side of the retaining wall 5, with a length of 8.0 m and a depth of 1.5 m. The bottom of the pool is paved with 30-cm-thick C35 concrete, and the inner wall is coated with a 3-mm polyurethane waterproof layer. The long side of the energy dissipation pool 6 is connected to the underground flood discharge channel 16, and the short side is connected to the surface flood discharge channel 17.
[0026] Furthermore, the stepped layered compaction subsystem consists of a stepped slope filling surface 7, a crushed stone drainage cushion layer 8, cushion layer drain holes 9, a rolling zone 10, and a geogrid 11. The slope ratio of the stepped slope filling surface 7 is 1:1.5, the step height is 8.0 m, and the step width is 2.0 m. A 0.5 m thick crushed stone drainage cushion layer 8 is laid on the step surface of the stepped slope filling surface 7, with a longitudinal slope of 3%. Cushion layer drain holes 9 are arranged at the outlet of the crushed stone drainage cushion layer 8. The cushion layer drain holes 9 adopt HDPE pipes with a diameter of 150 mm, a length of not less than 3.0 m, a horizontal spacing of 3.0 m, are wrapped with geotextile, and galvanized wire meshes are arranged at the pipe ends. The rolling zone 10 is divided into a core compaction area 12, a transition compaction area 13, and a surface compaction area 14. The rolling direction is from the core compaction area 12 to the surface compaction area 14. The horizontal distance from the core compaction area to the stepped slope filling and backfilling surface 7 is 8.0 m, the layered compaction thickness is 1.5 m, and a 32 t roller is used for rolling, with a compaction degree of not less than 97%. The horizontal distance from the transition compaction area to the stepped slope filling and backfilling surface 7 is 3.0 - 8.0 m, the layered compaction thickness is 1.0 m, and a 20 t convex block roller is used for rolling, with a compaction degree of not less than 95%. The horizontal distance from the surface compaction area 14 to the stepped slope filling and backfilling surface 7 is 0 - 3.0 m, the layered compaction thickness is 0.5 m, and a 10 t sheep's foot roller is used for rolling, with a compaction degree of not less than 93%. After the single-layer rolling is completed, the geogrid 11 is laid along the stepped rolling surface 15. The geogrid adopts a biaxial geogrid, with a tensile strength of not less than 100 kN / m. It is fully laid on the surface compaction area 14 and the transition compaction area 13 and enters the core compaction area 12 by not less than 15.0 m, and is anchored with U-shaped nails at a spacing of 0.5 m × 0.5 m.
[0027] Furthermore, the dual-channel intelligent collaborative flood discharge subsystem consists of an underground flood discharge channel 16, a surface flood discharge channel 17, an electromagnetic valve 18, an electric pressure type water level gauge 19, and a galvanized wire mesh 20. The underground flood discharge channel 16 is arranged along the terrain of the existing valley, with a longitudinal slope ratio of not less than 5%. A corrugated pipe with a diameter of 0.5 m or a reinforced concrete box culvert with a wall thickness of 300 mm is adopted. The entrance is connected to the long side of the water collection pool 1, and an electromagnetic valve 18 is installed at the pipe orifice. A galvanized wire mesh 20 is arranged inside the valve, with a mesh size of 3 mm × 3 mm. The surface flood discharge channel 18 is arranged at the junction of the filling boundary line 4 and the mountain body, with a longitudinal slope ratio of 2%. C25 reinforced concrete is adopted, with a reinforcement ratio of 1.5%. The cross-section is trapezoidal, with a bottom width of 2.0 m, a net depth of 1.0 m, a slope ratio of 1:1.0 on the mountain side, and a composite geomembrane is laid at the bottom of the ditch. A pressure type water level gauge 19 is installed on the side wall of the water collection pool 1. When the peak flood flow measured by the pressure type water level gauge 19 is less than the design flow of the surface flood discharge channel 17, the electromagnetic valve 18 is closed, and single-channel flood discharge is adopted; when the measured peak flood flow is greater than the design flow of the surface flood discharge channel 17, the electromagnetic valve 18 is opened, and dual-channel collaborative flood discharge is adopted.
[0028] Furthermore, the ecological slope protection system consists of a vegetative concrete skeleton 21 and deep-rooted vegetation 22. The vegetative concrete skeleton 21 is arranged on the slope surface of the stepped slope filling surface 7. The skeleton is built with M10 mortar rubble masonry, with a spacing of 3.0 m × 3.0 m. 15 cm thick vegetative concrete is sprayed inside the skeleton, and the grass seed mix ratio is Cynodon dactylon: Amorpha fruticosa: Medicago sativa = 4:3:3. The deep-rooted vegetation 22 is arranged on the steps of the stepped slope filling surface 7, and a mixture of willows and reeds is used. The plant spacing of the willows is 2 m, the plant spacing of the reeds is 0.3 m, and the root depth is 1.5 m.
[0029] The working principle of the present invention is as follows: The gutter top water-collecting apron 2 device is used to intercept floods, falling rocks and branches from the upper reaches of the gully. The gutter foot retaining wall 5 energy dissipation device is used to prevent water flow scouring. At the same time, the energy dissipation pool 6 also serves as the outlet of the underground and surface flood discharge channels 17, playing a role in hydraulic energy dissipation. The stepped layered compaction is used to improve the compaction degree of the surface area and transition area of the filling body, enhance the stability of the slope and control the differential settlement of the foundation. The dual-channel intelligent collaborative flood discharge system is used for gully flood discharge. When the peak flood flow is less than the design flow of the surface flood discharge channel 17, the single surface flood discharge channel 17 is adopted; when the peak flood flow is greater than the design flow of the surface flood discharge channel 17, the dual-channel flood discharge is enabled to ensure the drainage efficiency. The ecological restoration adopts the combined slope protection of the slope vegetative concrete and the stepped deep-rooted vegetation 22 to ensure the ecological restoration and soil and water conservation functions of the slope.
Claims
1. A comprehensive management system for deep-cut gully high-fill slopes, characterized by: It includes a ditch top-ditch foot collaborative management subsystem, a stepped layered compaction subsystem, a dual-channel intelligent collaborative flood discharge subsystem and an ecological slope protection subsystem; the ditch top-ditch foot collaborative management subsystem includes a ditch top water collection and protection device, a ditch foot retaining wall force dissipation device, which are used to intercept upstream floods, fallen rocks and branches, and reduce ditch foot scour; the stepped layered compaction subsystem includes a layered filling drainage system, a stepped rolling system, and a geogrid extension system, which are used to improve the compaction degree of the fill body and control differential settlement; the dual-channel intelligent collaborative flood discharge subsystem includes a surface flood discharge channel, an underground flood discharge channel, and an intelligent monitoring system, which dynamically switches the flood discharge mode by real-time monitoring of the peak flow; the ecological slope protection subsystem includes a vegetated concrete skeleton and deep-rooted vegetation to achieve slope ecological restoration and protection functions.
2. A deep-cut gully high-fill slope comprehensive management system according to claim 1, characterized in that: The ditch top water collection and protection tank device includes a water collection tank, a protection tank, poles and grille fences; the water collection tank is arranged at the junction of the fill body and the upper mountain of the valley, the bottom of the water collection tank is connected to the underground flood discharge channel, and the side of the water collection tank is connected to the surface flood discharge channel; the protection tank adopts C40 cast-in-place concrete, with a width of ≥5m, a thickness of ≥1m, and a slope ratio of 1:5~1:6; the poles and grille fences are arranged at the connection between the water collection tank and the protection tank.
3. A deep-cut gully high-fill slope comprehensive management system according to claim 1, characterized in that: The energy dissipation device of the ditch foot retaining wall includes a retaining wall and an energy dissipation pool; the retaining wall is arranged at the junction of the fill body and the mountain at the lower side of the valley; the energy dissipation pool is arranged at the lower side of the retaining wall, with a length ≥8m and a depth ≥1.5m. The bottom of the pool is paved with 30cm thick C35 concrete, and the inner wall is coated with a 3mm polyurethane waterproof layer. The bottoms of the underground flood discharge channel and the surface flood discharge channel are both connected to the energy dissipation pool.
4. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The layered filling drainage system includes a crushed stone drainage cushion layer and cushion layer drainage holes; the crushed stone drainage cushion layer is arranged on the step surfaces of each level, with a thickness of ≥0.5m and a transverse slope of ≥3%. The cushion layer drainage holes are arranged in the crushed stone drainage cushion layer, and galvanized wire mesh is arranged at the pipe end, which is wrapped with geotextile.
5. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The stepped compaction system includes a core compaction zone, a transition compaction zone, and a surface compaction zone; the core compaction zone is ≥8m away from the slope surface, has a layered compaction thickness of 1.5m, and is compacted by a 32t roller to a compaction degree of ≥97%; the transition compaction zone is 3~8m away from the slope surface, has a layered compaction thickness of 1m, and is compacted by a 20t convex roller to a compaction degree of ≥95%; the surface compaction zone is 0~3m away from the slope surface, has a layered compaction thickness of 0.5m, and is compacted by a 10t sheep-foot roller to a compaction degree of ≥93%.
6. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The geogrid extension system is to fully lay bidirectional geogrids along the stepped rolling surface and extend to the core compaction area ≥15m.
7. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The surface flood discharge channel is located at the junction of the fill and the mountain, using C25 reinforced concrete ditch with a longitudinal slope of ≥2%; the underground flood discharge channel is set at the bottom of the existing ditch, using corrugated pipes or box culverts, with a longitudinal slope of ≥5%.
8. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The intelligent monitoring system includes an electromagnetic valve arranged at the entrance of the underground flood discharge channel and a pressure water level gauge arranged in the water collection tank. The electromagnetic valve is connected to the pressure water level gauge signal. The electromagnetic valve dynamically switches the flood discharge mode according to the monitoring data of the pressure water level gauge. When the peak flow rate is ≥ the design flow rate of the surface flood discharge channel, the dual-channel flood discharge is enabled.
9. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The vegetation concrete skeleton is arranged on the filling slope surfaces at various levels, and the grass seed mix ratio is Bermuda grass: Amorpha fruticosa: Alfalfa = 4:3:
3.
10. The deep-cut gully high-fill slope comprehensive management system according to claim 1 is characterized by: The deep-rooted vegetation is arranged on the step surfaces of various levels of fill slopes, and is a mixture of willows and reeds, with a willow spacing of 2m, a reed spacing of 0.3m, and a root system depth of ≥1.5m.