CN-121992794-A - Karst region working well foundation pit excavation method

CN121992794ACN 121992794 ACN121992794 ACN 121992794ACN-121992794-A

Abstract

The invention discloses a karst region working well foundation pit excavation method, which relates to the technical field of geotechnical engineering, and comprises the steps of carrying out three-dimensional geological scanning outside a foundation pit design contour line, constructing a three-dimensional geological-karst model, carrying out grouting reinforcement on karst caves and broken zones according to the model, carrying out building a building envelope based on pretreated stratum conditions, adjusting the building depth and construction process of the building envelope according to geological differences, excavating a foundation pit vertically in layers and in blocks on a plane, dynamically adjusting excavation parameters and support time by combining real-time geological logging and multi-source monitoring data, carrying out timely construction on a permanent main body structure after excavation to the design elevation, and orderly replacing temporary supports, and carrying out physical improvement on soft rock slag generated by shield excavation for a working well fertilizer tank and the peripheral surface of the foundation pit. The invention can realize safe, efficient and green construction of the working well foundation pit in karst areas.

Inventors

CUI MENGLIN
SONG PENGJIE
XU HAO
MI SHIPENG
LV YONGJUN
YUAN BOWEN
WANG YONGJUN
LIU JIEFENG

Assignees

中铁二十局集团南方工程有限公司

Dates

Publication Date: 20260508
Application Date: 20251229

Claims (10)

1. The karst region working well foundation pit excavation method is characterized by comprising the following steps of: carrying out three-dimensional geological scanning outside a foundation pit design contour line, constructing a three-dimensional geological-karst model, and carrying out grouting reinforcement on karst cave and broken belt according to the model; Constructing an enclosure structure based on the pretreated stratum conditions, wherein the embedding depth and the construction process of the enclosure structure are adjusted according to geological differences; Dividing the foundation pit into layers vertically and blocks on a plane for excavation, and dynamically adjusting excavation parameters and supporting time by combining real-time geological logging and multisource monitoring data; after excavation to the designed elevation, timely constructing a permanent main body structure, and orderly replacing temporary supports; and (3) physically improving soft rock dregs generated by shield tunneling, and using the soft rock dregs in backfill of a working well fertilizer groove and the peripheral earth surface of a foundation pit.
2. The method of excavating a pit in a karst region working well according to claim 1, wherein the steps of performing three-dimensional geological scanning outside a design contour of the pit, constructing a three-dimensional geological-karst model, and grouting reinforcement of karst cave and fracture zone according to the model include: The method comprises the steps of obtaining the spatial position, the size, the shape, the filler property and the hydrogeologic information of a karst cave by adopting a mode of combining dense latticed geological drilling with cross-hole geophysical prospecting, and establishing a digital three-dimensional model containing the information based on the spatial position, the size, the shape, the filler property and the hydrogeologic information.
3. The method of excavation of a pit for a karst region working well of claim 2, wherein the steps of performing three-dimensional geological scanning outside a design contour of the pit, constructing a three-dimensional geological-karst model, and grouting reinforcement of karst cave and fracture zone according to the model further comprise: Classifying karst cave to be treated according to the three-dimensional geological-karst model, and designing a sleeve valve pipe grouting scheme aiming at the karst cave of a large-scale cavity or filled loose objects, wherein the arrangement mode and the grouting depth of the grouting holes are determined according to the characteristics of the karst cave so as to form vertical plugs and horizontal cover plates.
4. The method of excavating a pit in a karst region of claim 3 wherein the steps of performing a three-dimensional geologic scan outside the design contour of the pit, constructing a three-dimensional geologic-karst model, and grouting reinforcement of karst cave and breaker according to the model further comprise: Firstly, grouting holes are formed along the peripheral outline of a foundation pit to form a closed waterproof curtain, then an internal karst cave is treated, the grouting is controlled by adopting the pressure from low to high, and the grouting amount and the pressure change are monitored in real time.
5. The method for excavating a pit of a karst region working well according to claim 1, wherein the step of constructing an enclosure based on the pretreated stratum conditions, and adjusting the embedding depth and the construction process of the enclosure according to geological differences comprises the steps of: Carrying out differential design on the enclosure structure based on a geological safety state partition map formed after pretreatment; in the interactive stratum of soft rock and reinforcement, the upper soil layer is adopted to drill the leading hole, the lower stratum and the reinforcement layer are adopted to form grooves or hole by adopting a combined construction method of short spiral drill bit or broken by a groove milling machine, and unforeseen bad geologic bodies are identified by observing the change of drilling parameters in construction.
6. The method of excavation of a karst region working well pit of claim 5, wherein the step of constructing an enclosure based on the pretreated formation conditions, and wherein the depth of consolidation and construction process of the enclosure are adjusted according to geological differences, further comprises: And when concrete is poured, adopting double guide pipes to synchronously pour, and recording and early warning analysis are carried out on the groove sections with abnormally increased pouring square quantity.
7. The method for excavating a pit of a karst region working well according to claim 1, wherein the steps of excavating the pit vertically in layers and in blocks on a plane, and dynamically adjusting excavation parameters and supporting opportunities by combining real-time geological logging and multi-source monitoring data comprise: When each layered and segmented excavation is carried out, geological record is carried out on the exposed pit wall and pit bottom, and the slag sample analysis result is compared and checked with the three-dimensional geological-karst model; and comprehensively judging risk sources according to the comparison verification and data comparison results, and dynamically adjusting the subsequent excavation sequence and excavation speed or adopting local reinforcement and plugging measures.
8. The method of excavating a pit of a karst region working well according to claim 1, wherein the step of applying a permanent main structure in time after excavating to a designed elevation and sequentially replacing temporary supports comprises: and (3) according to the principle that a vertical bearing member is formed firstly, then the horizontal temporary support is replaced, after the permanent structures such as the bottom plate, the side wall and the floor slab are poured and reach the design strength, the corresponding temporary support is removed from bottom to top in sequence, and stress checking and monitoring are carried out before each removal.
9. The method for excavating a working well pit in a karst region according to claim 1, wherein the step of physically modifying soft rock residue soil generated by shield tunneling for backfilling a working well fertilizer tank and the peripheral surface of the pit comprises the steps of: And (3) carrying out character analysis on the soft rock shield residue soil, and then improving the soft rock shield residue soil by combining the airing and dehydration with the mixing of coarse particle materials or lime powder so as to reduce the water content, improve the grading and stability of the soft rock shield residue soil and enable the soft rock shield residue soil to meet the engineering backfill soil requirement.
10. The method of excavating a pit in a karst region of claim 9 wherein the step of physically modifying soft rock residue from shield excavation for use in backfilling the pit manure pit and surrounding earth surface of the pit further comprises: And tamping the improved dregs in layers during backfilling, setting settlement observation points in the backfilling area for long-term monitoring, and carrying out necessary supplementary treatment according to the monitoring result.

Description

Karst region working well foundation pit excavation method Technical Field The invention relates to the technical field of geotechnical engineering, in particular to a method for excavating a working well foundation pit in a karst area. Background Along with the rapid promotion of urban rail transit construction, the scale of underground engineering is continuously enlarged, and the construction environment is increasingly complex. In karst development zones, underground engineering construction frequently encounters complicated geological conditions such as karst cave, broken zones, groundwater and the like, and these factors form great challenges for excavation of working well foundation pits in shield construction. The working well foundation pit is used as a core link of shield launching and receiving, and the excavation process of the working well foundation pit needs to comprehensively stage various factors such as geological investigation, building envelope design, excavation supporting and environmental protection, and the like, so that higher requirements are put forward on construction technology and management level. Conventional geological investigation methods are generally adopted in the current karst region working well foundation pit excavation, for example, geological drilling holes are arranged on the periphery of the foundation pit to obtain stratum information, grouting filling treatment is carried out on the found karst cave, and then building enclosure structures such as underground continuous walls or bored piles are constructed according to a standardized flow, and layered excavation is carried out by matching with an inner supporting system. During excavation, key parameters such as deformation of the enclosure structure, supporting axial force and the like are tracked through monitoring points, a permanent main body structure is constructed after the excavation is completed, and generated muck is transported to a designated spoil field for disposal. However, the traditional methods have obvious defects when applied to karst areas, such as difficulty in accurately capturing three-dimensional spatial distribution characteristics of karst caves by conventional geological investigation means such as single-point drilling, so that grouting reinforcement is in dead zones, unforeseen karst caves or broken zones are easily encountered in construction, water burst, collapse and other safety accidents are caused, the design and construction of the enclosure structure often adopt unified standards, the local differences of karst development cannot be optimized, the problems of difficult grooving, concrete leakage and the like are easily caused in complex areas such as soft rock and reinforcement interactive stratum, stability and water stopping performance of the enclosure structure are weakened, the excavation process lacks a dynamic adjustment mechanism based on real-time geological information and multi-source monitoring data, when actual geological conditions deviate from the early investigation result, excavation parameters and support opportunities cannot be corrected in time, engineering risks are increased, and a large amount of soft rock and slag generated by tunneling shields are treated as waste in outward transportation, so that engineering cost and transportation burden are increased, and resource waste and environmental pressure are caused. The technical bottlenecks severely restrict the safety, economy and environmental protection of the excavation of the working well foundation pit in the karst area. Disclosure of Invention The invention mainly aims to provide a method for excavating a working well foundation pit in a karst area, which aims to realize safe, efficient and green construction of the working well foundation pit in the karst area. In order to achieve the above purpose, the method for excavating the pit of the karst region working well provided by the invention comprises the following steps: carrying out three-dimensional geological scanning outside a foundation pit design contour line, constructing a three-dimensional geological-karst model, and carrying out grouting reinforcement on karst cave and broken belt according to the model; Constructing an enclosure structure based on the pretreated stratum conditions, wherein the embedding depth and the construction process of the enclosure structure are adjusted according to geological differences; Dividing the foundation pit into layers vertically and blocks on a plane for excavation, and dynamically adjusting excavation parameters and supporting time by combining real-time geological logging and multisource monitoring data; after excavation to the designed elevation, timely constructing a permanent main body structure, and orderly replacing temporary supports; and (3) physically improving soft rock dregs generated by shield tunneling, and using the soft rock dregs in backfill of a working well fertilizer groove and th