Gioi thieu ve kiem dinh do on dinh cau truc cong trinh xay dung
Kiem dinh do on dinh cau truc la mot phan mem quan trong va khong the thieu trong quy trinh bao tri, su dung va danh gia tinh trang ky thuat cua cac cong trinh xay dung hien dai. Khi noi toi kiem dinh do on dinh cau truc, chung ta dang nhac den viec danh gia toan dien nang luc tang chiu tai, tinh dong bo va kha nang chiu duong cuoi cung cua he khung, cot, dia diem hoac tat ca cac bo phan lien quan den ket cau nha co.
Trong thuc te ky thuat, mot cong trinh co the duoc xu ly tot ve mat my quan, nhung neu he thong ket cau chua cam chuyen tac nghiep hay bi suy giam chat luong theo thoi gian thi nguy co phat sinh vuong lac lon se rat cao. Vi vay, viec xac nhan tinh on dinh khong chi la mot yeu cau phap ly ma con la yeu to song con doi voi moi cong trinh. Chung toi - dam bao don vi chuyen mon tu van cho ban - muon gioi thieu sau day noidung chi tiet nhat ve quyen nang nay.
Cơ so phap ly va cac tieu chuan ky thuat ap dung
Tai Viet Nam, hoat dong kiem dinh cong trinh xay dung, dac biet la kiem dinh do on dinh cau truc, dugc quy dinh rang ro trong he thong van ban phap luat. Viec thuc hien khong the lam theo cach "tam qua" hay kinh nghiem chu quan. Toi can phai danh gia tren co so cac van ban phap luat va tieu chuan viet nam (TCVN) va tieu chuan quoc te (ISO/EN).
Van ban phap luat chinh:
- Ngha dinh 06/2022/NĐ-CP: Ve quan ly cong trinh xay dung, quy dinh cac truong hop bat buoc phai tien hanh kiem dinh cong trinh.
- Lenh 217/2013/QD-TTg: Danh gia dieu kien an toan ky thuat cong trinh xay dung.
- Thong tu 06/2016/TT-BXD: Quy dinh chi tiet ve ho so, thue tin ky thuat cong trinh xay dung.
Ve mat ky thuat, cac tieu chuan duoc ap dung rong rai nhat de danh gia do on dinh cau truc gom:
- TCVN 9383:2012: Cong trinh xay dung - Nang luc chiu tai cua dat nen - Phuong phap danh gia nang luc chiu tai cua nen dat.
- TCVN 5574:2012: Ket cau be tong va be tong cot the - Thiet ke.
- QCVN 03:2009/BXD: Qui chuan ky thuat Quoc Gia ve Cong trinh xay dung - Luan hoa an toan.
- TCVN 4453:2012: Cong trinh xay dung - Cong tac san xuat va nhan bien giao be tong va be tong cot the.
- TCVN 6211:2018: Nen dat - Phan loai.
Vi du, khi danh gia mot cong trinh da xay dung gan 20 nam, chung toi se dap dung cac lua chon cong them (ACI 318 hoac Eurocode) de tim hieu xem do loi sai so sanh giua thiet ke goc va thuc te la bao nhieu. Nhung khong chi lay so lieu, cac tieu chuan nay con quy dinh phuong phap thu nghiem, ty le mau, va phap phap danh gia.
Cac phuong phap kiem dinh va cong nghe do dac hien dai
De danh gia chinh xac do on dinh cau truc, cac ky su kiem dinh khong the chi dung mat thuong hay cai bang de do. Chung toi phai ket hop nhieu phuong phap khac nhau, tu co ban den phuc tap, de co nhin tuc ton the.
1. Kiem tra ngoai quan (Visual Inspection)
Dau vao la giai doan tuyet doi can thiet. Ban can lay may anh, may quay video de ghi lai tat ca cac vi tri co dau hieu nhu cat be tong, bot sat, vet ran, hay do luan. Cac he thong do luan khong deu co the dan den mat on dinh. Tuy nhien, phuong phap nay chi mang tinh chat tham khao, khong the thay the cho cac phep do ky thuat.
2. Thu nghiem khong phai pha (Non-Destructive Testing - NDT)
Day la phuong phap khong lam hu hai ket cau. Chung toi su dung cac cong cu nhu:
- May sieu am (Ultrasonic Pulse Velocity): Do toc do lan truyen cua song sieu am trong be tong de danh gia chat luong be tong, do om va vi tri co khoang rong.
- May do do om be tong (Rebound Hammer): Hay con goi la may Rebound, do do om be tong tu do va co lien he voi do om thuc te.
- Radar Xuyen Dat (GPR): De tim vi tri cot the trong be tong, do do bao be, va xac dinh he thong cot the co bi ruot ra khong.
3. Thu nghiem phu troi (Destructive Testing)
Trong mot so truong hop bat buoc, de co so lieu chinh xac nhat, chung toi phai lay mau (core drilling). Mau be tong duoc lay ra va mang den phong thu nghiem de kiem tra do om, phan tich thanh phan hoa hoc. Neu do om thap hon thiet ke toi thieu 10-15%, cong trinh co the bi danh gia la khong on dinh.
4. Kiem dinh tai troi (Load Testing)
Day la phuong phap danh gia sur dung cuc ky quan trong. Chung toi se dat tai troi vao dia diem (thuong la sac be tong hoac sac nuoc) va do moi dich chuyen (deformation) cua dầm, san. Neu do dich chuyen nho hon cho phep (thuong la L/250 hoac L/300) va khong co dau hieu rut vit, thi cong trinh co the duoc coi la on dinh. Phuong phap nay thuong duoc ap dung cho cac cong trinh co quy mo lon hoac thay doi muc dich su dung.
Quy trinh thuc hien kiem dinh do on dinh chi tiet tu A-Z
Hoat dong kiem dinh do on dinh cau truc la mot quy trinh khoa hoc, co chuan. Chung toi - dam bao don vi chuyen mon - luon tuan thu quy trinh sau de bao dam tinh chinh xac va bao mat:
- Thu thap ho so thiet ke va bao cao thi cong: De biet duoc ban dau cong trinh duoc thiet ke nhu the nao, chat luong vat lieu la gi, va co bat ky su thay doi nao truoc do khong.
- Khao sat thuc te va danh gia tam bao quat: Ky su ky thuat den site de quan sat, danh gia muct do huu hai, hien trang va lap bang danh sach cac van de can quan tam.
- Lap phuong an kiem dinh: Dua tren ket qua khao sat, chung toi se xac dinh cac vi tri can lay mau, vi tri can do, va cac phep do can thuc hien. Phuong an nay phai duoc phe duyet boi chu dau tu.
- Tiep nhan du lieu va phan tich: Sau khi thu du lieu, cac so lieu duoc nhap vao cac phan mem phan tich ket cau (nhu SAP2000, ETABS, Robot Structural Analysis) de mo phong lai cong trinh. Qua trinh nay goi la "phan tich phan tu huu han" (FEA).
- So sanh voi tieu chuan va danh gia: Ket qua mo phong duoc so sanh voi cac gioi han cho phep theo TCVN. Neu cac uoc luong (stress, strain, displacement) vuot qua gioi han, chung toi se ket luan cong trinh khong on dinh.
- Lap bao cao kiem dinh: Bao cao se bao gom ket luan ve do on dinh, cac van de phat hien, va de xuat giai phap tu van ky thuat de sua chua hoac tang cuong.
Khach hang can lu y: Khong phai cong trinh nao cung can kiem dinh het. Tuy nhien, neu cong trinh gap cac vuong lac nhieu nham, mat co so ho so, hoac co nguoi nghi ngla an toan, thi viec kiem dinh la bat buoc.
Phan tich nguyen nhan mat on dinh va giai phap khac phuc
Sau khi thuc hien kiem dinh, neuh cong trinh bi danh gia la khong on dinh, chung toi se can tim hieu nguyen nhan goc. Co rat nhieu yeu to dan den mat on dinh cau truc, tu co ban den phuc tap.
1. Suy giam chat luong vat lieu
Be tong va sat la hai thanh phan chinh. Be tong co the bi tan bao do phan ung phan hoa hoc (alkali-silica reaction), hoac do tac dong cua moi truong (axit, muoi). Sat co the bi gion, oxi hoa (rust) do nuoc xam uap vao. Neu sat bi gion, tiet dien cham chap bi giam, do do nang luc chiu luc cua cot, dam bi giam theo.
2. Luong luan khong deu (Differential Settlement)
Day la mot trong nhng nguyen nhan pho bien nhat. Neu nen dat ben duoi cong trinh bi luan khong deu, cac cot se bi uong, be tong bi cat, va cac lien ket giua san va cot bi bong ra. Van de nay thuong gap tai cac khu vuc co nen mat, hoac cong trinh xay dung tren dat nen yen, khong dat yeu cau nen dat.
3. Tang tai troi vo luong
Chu dau tu thay doi muc dich su dung (vi du: tu nha o thanh van phong, tu van phong thanh kho hang) ma khong kiem dinh lai cau truc. Moi loai cong trinh co muc do chiu tai khac nhau. Viec tang them phuong tram, may mac, hoac thay doi he thong thong thoang co the lam tang tai troi vuot qua kha nang chiu cua ket cau.
4. Sai sot trong thi cong
Co nhieu cong trinh thi cong khong dung theo thiet ke. Vit the, be tong khong dat do om, he thong neo bot the khong du do dai. Day la nhung "tuy hiem" bi dong trong cong trinh.
De khac phuc, chung toi co the de xuat cac giai phap sau:
- Tang cuong ket cau: Bang cach tang tie dien be tong, them cot the, hoac lang them thep.
- Xu ly nen dat: Su dung phuong phap dot nan, hoac them coc nho de chia co loi tai.
- Theu cau truc: Trong truong hop mat on dinh rat nghiem trong, viec thu hui mot phan hoac toan bo cong trinh la can thiet.
Bang so sanh cac muc do hu hai va tinh trang ket cau
De ban de hieu hon ve ket qua kiem dinh, chung toi xin ghich bang danh gia tinh trang ket cau theo tieu chuan ky thuat. Bang nay giup ban hinh dung ra muc do mat on dinh la nhe hay nang.
| Tieu chi danh gia | Muc do 1: On dinh | Muc do 2: Mat on dinh nhe | Muc do 3: Mat on dinh nang | Muc do 4: Mat on dinh nghiem trong |
|---|---|---|---|---|
| Hinh thai be tong | Khong co vet ran, mat be tong nguyen van. | Cosomet ran nhe (d < 0.3mm), mat be tong co the bop, khong co be tung. | Ran lenen > 0.3mm, be tung be tong, cot sat co the bi lo ra. | Be tung re, cot sat bi gion, cat sat, be tong be ro. |
| Do om be tong | Dat yeu cau thiet ke (Tu 80% - 100%). | Giam 10-20% so voi thiet ke. | Giam 20-30% so voi thiet ke. | Giam > 30% so voi thiet ke. |
| Do luan | Nhom luan trong gioi han cho phep. | Luan khong deu nho, khong anh huong den an toan. | Luan khong deu trung binh, co hieu ung uong. | Luan khong deu lon, gay ra cat be tong, uong cot. |
| Kha nang chiu troi | Da dam bao 100% kha nang chiu troi. | Chua dam bao 100%, co the ap dung voi tieu tran. | Chua dam bao, can tang cuong. | Chua dam bao, nguy co sump hap cao. |
| Ke xuat ky thuat | Su dung binh thuong. | Bao tri, chep, chong thau, khong can tang cuong. | Can tang cuong cau truc (thep, be tong). | Can thu hui hoac thay moi ket cau. |
Trong thuc te, viec danh gia khong chi dua tren mot tieu chi ma phai ket hop tat ca. Vi du, mot cong trinh co the co do om be tong tot (muc 1) nhung co the co do luan khong deu (muc 3). Khi do, chung toi se danh gia muc do thap nhat de xuat giai phap.
Vai tro cua don vi kiem dinh uy tin nhieu Kiem Dinh Xay Dung Mien Nam
Trong thoi dai xa hoi phat trien, viec xay dung va su dung cong trinh khong chi can co nhanh ma con can co an toan. Mot cong trinh co the co the mat tien ngan nganh, nhung neu mat an toan thi chi phi cho viec sua chua, hoac tang vong nhac se rat lon, co the manh hon ca chi phi xay dung ban dau.
Voi kinh nghiem nhieu nam hoat dong trong nganh, Kiem Dinh Xay Dung Mien Nam luon cam ket cung cap cho ban nhom dich vu kiem dinh chat luong cao nhat. Chung toi khong chi la mot don vi thuc hien ky thuat ma con la nguoi ban tin can tin cay cua ban. Moi bao cao kiem dinh duoc lap ra boi cac ky su co chuyen mon cao, co giay phep ky thuat va duoc cong nhan boi Bo Xay Dung.
Khi ban chon Kiem Dinh Xay Dung Mien Nam lam don vi kiem dinh, ban se duoc huong:
- Doi ngu ky su chuyen nghiep: Da co kinh nghiem thuc chien tren nhieu loai cong trinh tu nha o, nha may, den cac cong trinh cong cong.
- Hien vien ky thuat hien dai: Su dung cac may do chuan quoc te de co so lieu chinh xac.
- Tu van ky thuat toan dien: Khong chi danh gia, chung toi con de xuat cac giai phap ky thuat phuc hoi, tang cuong chi phi hieu qua.
- Tien do nhanh, chi phi hop ly: Tu van cac giai phap kiem dinh phap ly, de ban tiet kiem chi phi ma van dam bao an toan.
Loi ich cuoi cung khong chi la mot ban bao cao, ma la su binh an cho moi nguoi khi su dung cong trinh, va su an tam cho chu dau tu khi dau tu vao cong trinh do.
Tre hien, viec kiem dinh do on dinh cau truc khong con la chon loc ma da la mot yeu cau bat buoc doi voi cac cong trinh co yeu cau cao ve an toan. Vi vay, ban can quan tam den viec nay ngay tu dau, de tranh cac vuong lac khong mong muon. Hy vong bai viet nay da giup ban hieu ro hon ve kiem dinh do on dinh cau truc. Neu co bat ky cau hoi nao ve ky thuat hoac muon tu van chi tiet, ban co the lien he voi chung toi de duoc ho tro tot nhat.
