Bài học xử lý sự cố cát chảy hố móng sâu bằng cọc xi măng đất

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Ngôn ngữ: vie

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Thông tin xuất bản: Tạp chí Khoa học và Công nghệ Thủy lợi, 2020

Mô tả vật lý: tr.16

Bộ sưu tập: Báo, Tạp chí

ID: 299836

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Because of fast construction progress and lower cost than the diaphragm wall, soldier pile walls are commonly used in deep excavation. However, when designing and constructing soldier pile walls, tightness between the piles is not assured, the permeate flows the outside soil into the excavation, causing subsidence, cracking adjacent buildings, shifting the wall. This paper presents the results of troubleshooting analysis for an excavation project using the form of soldier pile wall, without waterproofing membrane, under soft ground conditions and high underwater level. Using soil cement columnms at the junction of bored piles to waterproof and reinforce the weak soil inside the foundation pit to avoid push-up. The displacement and internal force of the soldier pile wall was analyzed by using FRWS7.2 and Midas NX software to consider the effect of passive earth pressure by compression-springs theory. The results of the design and construction calculations show that the proposed solution handles infiltration and push up thoroughly, ensuring the safety of excavation construction and adjacent buildings. Thanks to those findings, the paper propose that foundation pits supported by soldier pile walls in urban areas have to consider waterproofing items from the design stage to ensure the safety of the excavation itself and adjacent buildings.Hình thức chống đỡ hố móng sâu được sử dụng khá phổ biến là tường cọc nhồi vì tiến độ thi công nhanh và chi phí thấp hơn tường ba rét. Tuy vậy, trong thiết kế và thi công tường cọc khoan nhồi không đảm bảo kín khít giữa các cọc sẽ bị dòng thấm cuốn trôi đất ngoài vào trong hố móng gây lún sụt, nứt công trình lân cận, làm chuyển vị tường hố móng. Bài báo giới thiệu kết quả phân tích xử lý sự cố cho một công trình hố móng sử dụng hình thức tường cọc khoan nhồi, nền đất yếu, mực nước ngầm cao, không có màng chống thấm. Giải pháp xử lý là khoan phụt tạo cọc xi măng đất tại phần tiếp giáp các cọc khoan nhồi để chống thấm và gia cố phần đất yếu phía trong hố móng để chống đẩy trồi. Trong bài toán phân tích chuyển vị và nội lực của tường móng có xét đến ảnh hưởng của áp lực đất bị động theo nguyên lý lò xo chịu nén không chịu kéo thông qua phần mềm FRWS7.2 và Midas NX. Kết quả tính toán thiết kế và thi công cho thấy, giải pháp đề xuất xử lý triệt để thấm và đẩy trồi, đảm bảo an toàn thi công hố móng và công trình lân cận. Kiến nghị các hố móng trong đô thị chống đỡ bằng tường cọc khoan nhồi phải đưa hạng mục chống thấm cho tường từ ngay giai đoạn thiết kế để đảm bảo an toàn cho bản thân hố móng và công trình lân cận.

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