A loess tunnel hole top falling water hole treatment method
By using a cement-soil sealing method on the roof of the loess tunnel, incorporating fine sand and combining it with steel pipe grouting, the problem of tunnel collapse caused by sinkholes on the roof of the loess tunnel was solved, achieving a fast, low-cost, and environmentally friendly construction effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NO 6 ENG CO LTD OF CHINA RAILWAY NO 3 ENG GRP
- Filing Date
- 2023-09-22
- Publication Date
- 2026-06-26
AI Technical Summary
The problem of tunnel collapse caused by sinkholes in loess tunnels, and the fact that traditional construction methods affect the ecology and increase construction time and costs.
The cement-soil sealing method was adopted, with fine sand added to improve fluidity. Combined with steel pipe grouting and cement-soil compaction, the filling was ensured to be dense. A water-sealing layer was set up during the excavation process to prevent tunnel collapse.
This approach enables a rapid and cost-effective solution to the sinkhole problem without affecting the construction schedule or the environment, thus preventing tunnel collapse and reducing construction difficulty and environmental impact.
Smart Images
Figure CN117167024B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of tunnel construction technology, specifically relating to a method for treating sinkholes in the roof of loess tunnels. Background Technology
[0002] This project relies on the Lixi Expressway project, whose tunnels are all loess tunnels. Due to the geological conditions of the tunnels being Malan loess and Lishi loess, and the influence of rainwater over the years, large and small sinkholes have appeared in the shallow buried sections at the entrances and exits of each tunnel. Among them, the sinkholes at the exits of Guojiashan Tunnel and Kongjiashan Tunnel are located directly above the tunnels, about 50 meters from the tunnel entrances. After on-site investigation and discussion by all parties, it was decided to adopt the open-cut method, which would cause great damage to the surrounding ecology. Due to the steep terrain, the open-cut method would involve a huge amount of excavation with slopes on both sides, resulting in a long construction period and high construction costs. Using the conventional cut-and-cover method to pour concrete slabs would be difficult to transport, and the large weight of the concrete slabs might damage the stability of the loess itself. Cement and soil would also cause blockage and poor fluidity when filling the sinkholes. Summary of the Invention
[0003] To address the aforementioned problems, this invention provides a method for treating sinkholes in the roof of loess tunnels. Without affecting the tunnel's construction schedule or damaging the ecology, the sinkholes are treated by sealing and compacting with cement and soil.
[0004] To address the issue of poor fluidity of cement-soil, a certain amount of fine sand is added during the pouring of cement-soil into the sinkholes, allowing the cement-soil to fill the sinkholes densely. To address the problem that rainwater accumulation on the ground during tunnel excavation and initial support can cause sinkholes in other sections of the loess, leading to tunnel collapse, 10% cement-soil is constructed in the surface pit after the sinkholes are treated as a water-sealing layer cover to prevent tunnel collapse caused by water accumulation and vibration during excavation.
[0005] The present invention adopts the following technical solution:
[0006] A method for treating sinkholes in the roof of loess tunnels includes the following steps:
[0007] The first step is to locate the sinkhole based on the geological cross-section map of the tunnel, clear the loose soil around the sinkhole, and remove the original surface vegetation.
[0008] The second step is to excavate the loess at the top of the hole, mix the loess and cement in a certain proportion to obtain cement-soil mixture 1, sprinkle dry fine sand into the hole wall of the sinkhole, mix fine sand into cement-soil mixture 1, and quickly pour it into the sinkhole until the sinkhole is filled.
[0009] The third step is to compact the top surface of cement-soil one, mix cement-soil two, and construct two layers of cement-soil two on the original ground surface of the tunnel top to form a cement-soil slab on the surface.
[0010] The fourth step is to excavate the main tunnel and complete the initial support. During the initial support, steel pipes are buried at the junction of the sinkhole and the main tunnel. After the support is completed, grout is injected into the sinkhole through the steel pipes to ensure that there are no voids at that location.
[0011] The fifth step is to construct a cement-soil lining on the original ground surface after the secondary lining of the Luoshuidong section is completed, and leave a -10% cross slope to collect water on the slope to the lowest point, and drain the surface water from the top of the tunnel.
[0012] Furthermore, in the second step, the cement content in the cement-soil mixture is 4-6% by mass, the thickness of the fine sand sprinkled into the hole wall of the sinkhole is 0.5-1cm, and the mass content of the fine sand mixed in the cement-soil mixture is 4-6%.
[0013] Furthermore, in the third step, the cement content in the cement-soil mixture is 10-15%, and the thickness of both cement-soil mixture layers is 40-60cm.
[0014] Furthermore, in step five, the cement content in the cement-soil mixture is 10-15%, and the thickness is 40-60 cm.
[0015] The beneficial effects of this invention are as follows:
[0016] 1. This invention utilizes the compacting properties of cement-soil to ensure that it forms a cohesive whole after being poured into the sinkhole, preventing tunnel collapse and roof fall caused by vibration during excavation. Fine sand is added during the pouring process, utilizing its fluidity to ensure the cement-soil flows to the bottom of the sinkhole, guaranteeing filling quality. Two layers of 10% cement-soil are applied to the tunnel roof before and after the secondary lining construction to prevent tunnel collapse due to rainwater accumulation during excavation and initial support. The treatment is convenient, quick, reduces construction time, and lowers costs.
[0017] 2. Compared with traditional open-cut tunnel construction, this method avoids the environmental impact of converting the mined section of the tunnel to an open-cut section, which would increase the construction period and incur huge costs. It also solves the problem of pouring concrete on the tunnel roof required by conventional cut-and-cover methods. This method for treating sinkholes has a shorter construction period and lower construction difficulty requirements. It has the advantages of high efficiency, simplicity, environmental protection, and practicality. Attached Figure Description
[0018] Figure 1 This is a construction diagram of the present invention;
[0019] Among them: 1-Cement-soil one; 2-Fine sand; 3-Cement-soil two; 4-Cement-soil three; 5-Original ground surface; 6-Vegetation; 7-Initial support; 8-Secondary lining; 9-Drainage hole. Detailed Implementation
[0020] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.
[0021] Reference Figure 1 The present invention provides a technical solution: a method for treating a sinkhole 9 on the top of a loess tunnel. The sinkhole 9 is located above the tunnel's dark section. The location of the sinkhole is found according to the geological cross-section of the tunnel. First, the loose soil around the sinkhole is cleared, and then the original surface vegetation 6 is cleared.
[0022] The 4% cement-soil mixture 1 is made by mixing loess and cement. 0.5-1cm of pre-prepared dry fine sand 2 is sprinkled into the wall of the sinkhole 9. The 4% cement-soil mixture 1, mixed with 4-6% fine sand 2, is then quickly poured into the sinkhole 9 until it is completely filled.
[0023] The 10% cement-soil mixture 3 is first compacted using a small rammer. Then, two 50cm thick layers of 10% cement-soil mixture 3 are constructed on the original ground surface 5 at the top of the tunnel to form a cement-soil slab on the surface.
[0024] The aforementioned initial tunnel support 7 is a tunnel support structure. During the excavation of the main tunnel, the initial tunnel support 7 is completed. At the junction of the sinkhole 9 and the main tunnel, steel pipes are buried during the construction of the initial tunnel support 7. After the support is completed, grout is injected into the sinkhole 9 through the steel pipes to ensure that there are no voids at that location.
[0025] The 10% cement-soil mixture 4 is made of loess and cement. After the secondary lining 8 of the Luoshuidong 9 section tunnel is completed, the 10% cement-soil mixture 4 is constructed on the original ground surface 5, and a -10% cross slope is left to collect the water on the slope to the lowest point, and to drain the surface water from the top of the tunnel.
[0026] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for treating sinkholes in the roof of loess tunnels, characterized in that: Includes the following steps: The first step is to locate the sinkhole based on the geological cross-section map of the tunnel, clear the loose soil around the sinkhole, and remove the original surface vegetation. The second step is to excavate the loess at the top of the hole, mix the loess and cement in a certain proportion to obtain cement-soil mixture 1, sprinkle dry fine sand into the hole wall of the sinkhole, mix fine sand into cement-soil mixture 1, and quickly pour it into the sinkhole until the sinkhole is filled. The third step is to compact the top surface of cement-soil one, mix cement-soil two, and construct two layers of cement-soil two on the original ground surface of the tunnel top to form a cement-soil slab on the surface. The fourth step is to excavate the main tunnel and complete the initial support. During the initial support, steel pipes are buried at the junction of the sinkhole and the main tunnel. After the support is completed, grout is injected into the sinkhole through the steel pipes to ensure that there are no voids at that location. The fifth step is to construct a cement-soil lining on the original ground surface after the secondary lining of the Luoshuidong section is completed, and leave a -10% cross slope to collect water on the slope to the lowest point, and drain the surface water from the top of the tunnel.
2. The method for treating sinkholes in the roof of loess tunnels according to claim 1, characterized in that: In the second step, the cement content in the cement-soil mixture is 4-6% by mass, the thickness of the fine sand sprinkled into the hole wall of the sinkhole is 0.5-1cm, and the mass content of the fine sand mixed in the cement-soil mixture is 4-6%.
3. The method for treating sinkholes in the roof of loess tunnels according to claim 1, characterized in that: The cement content in the cement-soil mixture described in the third step is 10-15%, and the thickness of both layers of cement-soil mixture is 40-60cm.
4. The method for treating sinkholes in the roof of loess tunnels according to claim 1, characterized in that: In step five, the cement content in the cement-soil mixture is 10-15%, and the thickness is 40-60cm.