13.Phuong phap lua chon may xuc mot gau cho thi cong? Phan tich ro cac yeu to can quan tam khi lua chon may xuc mot gau? Nang suat may xuc mot gau, anh huong cua viec lua chon may den nang suat va chat luong thi cong?

. To chuc thi cong may dao mot gau

+ Chon loai may dao mot gau

Viec chon loai may dao mot gau cho thi cong la nhiem vu quan trong cua nguoi can bo phu trach to chuc thi cong. Nang suat co cao, hieu suat su dung co tot hay khong mot phan la do nguoi can bo ky thuat quan ly su dung may nam vung tinh nang ky thuat va dieu kien su dung may den muc do nao. Doi voi viec chon lua may dao mot gau, ta can quan tam den cac yeu to: khoi luong cong tac, dang cong tac, loai dat, dieu kien chuyen cho, thoi han thi cong. Tuy tung dieu kien cu the ma chung ta lua chon thiet bi cong tac lap tren may dao mot gau cho hop ly. Vi du:

- May dao gau thuan co ket cau bo cong tac chac chan, luc dao lon, dung co loi khi dao dat va do vao xe van tai de cho di xa. May dao gau thuan chi lam viec tot khi nen dat noi dung may kho rao. May dao gau thuan dao duoc nhung ho sau va rong, theo nhieu tang, moi tang co nhieu ranh dao.

- May dao gau day co can dai nen co the do dat tu ho dao di kha xa. No dung tu tren cao de dao nhung ho sau (toi 10 hoac 20 met) va dao dat o nhung noi co nuoc nhu vet bun v.v... So voi may dao gau thuan thi may dao gau day co nang suat thap hon (neu cung mot dung tich gau) vi kho huong cho gau do dung vao phuong tien van chuyen, thao tac de xuc day gau kho khan hon may dao gau thuan. Dung may dao gau day dao roi do thanh dong hoac do truc tiep vao noi can dap thi nang suat cao.

- May dao gau nguoc chi dao duoc nhung ho nong (may dao co dung tich gau 0,5m3 thi chieu sau dao toi da la 5,5 met). Dung may dao gau nguoc de dao muong mang nho, dao ranh dat duong ong, duong day cap dien v.v... Voi nhung cong viec nhu tren nguoi ta thuong chon may dao gau nguoc co dung tich gau q=0,15; 0,25, 0,35; hoac 0,50 m3. Cung co the dung may dao nhieu gau.

- Khi dao nhung ho sau va dat tuong doi mem, neu su dung may dao gau thuan thuong phai dao them nhung con duong len xuong cho ban than may dao va cac phuong tien van tai. Khoi luong dat dao cua cong viec nay cung kha lon, cho nen trong truong hop nay ta co the thi cong bang may dao gau day lai kinh te hon.

Trong cac truong hop thi cong sau day nen lua chon may dao banh xich:

- Khoi luong thi cong dat tap trung, khong can di chuyen may nhieu;

- Thi cong tren nen dat yeu (may on dinh hon khi lam viec va di chuyen);

- Khi thi cong dat da nham (banh lop se mon nhanh hon).

Nen lua chon may dao banh lop khi:

- Thi cong tren nen dat co kha nang chiu tai cao;

- Khoi luong thi cong khong tap trung;

- Thi cong trong thanh pho co yeu cau thuong xuyen di chuyen may.

Theo kinh nghiem viec chon may xuc con dua vao khoi luong dat thi cong. Khi khoi luong dat dao lon thi nen dung loai may dao co dung tich gau lon. (khi lua chon may co the tham khao cac bang chon trong tai lieu).

+ Cac so do thi cong may dao mot gau

Tuy theo dia hinh thi cong ma ta co cac so do dao thich ung.

Doi voi may dao gau thuan thuong co cac cach dao sau:

- Dao doc do ben: (hinh 3.7) khi duong truc di chuyen cua may dao song song voi duong di chuyen cua xe van tai. Cach dao nay bao dam xe dung lay dat va may dao lam viec khong phai ngung tre. Duong di chuyen cua may dao va o to co the tren cung do cao hoac may dao co the dung thap hon o to mot it.

- Dao doc do sau (hinh 3.8): cach dao nay doi voi nhung khu vuc truong doi doc theo huong chay cua xe van tai, hoac nhung khu vuc tuong doi doc theo huong chay cua xe van tai, hoac nhung khu vuc thanh tang, thanh bac. De giai quyet goc quay do cua may dao qua lon (toi 1700) thi ta co the mo rong khoang dao cho xe o to vao duoc de dang dong thoi giam thoi gian chu ky lam viec cua may dao.

- Dao ngang (hinh 3.9): cach dao nay thuong ap dung khi khai thac dat da nui, khai thac than lo thien. Ta thay hinh thuc dao nay cac phuong tien van chuyen thuong dung lay dat gan vuong goc voi truc di chuyen cua may dao. Trong truong hop khoang dao sau vuot qua chieu cao cua may dao thi ta phai chia thanh ranh (tang) dao.

Doi voi may dao gau nguoc

Dung may dao gau nguoc de dao nhung ho mong, ranh dao, muong dao v.v... Voi khoi luong dao dat khong lon, tinh chat cong viec khong phuc tap, loai dat khong ran lam, dung tich gau xuc thuong nho; ta dung may dao gau nguoc la tien loi va kinh te khi dao va do dat sang ben canh ho dao. Khi ay may dao dung dao doc voi ranh dao va do dat sang hai ben ranh dao hoac mot ben ranh dao (hinh 3.10).

Khi dao va van chuyen dat vao o to de cho di xa, ta co hai hinh thuc thi cong:

- Neu chieu rong ho dao khong lon (khong vuot qua ban kinh dao cho phep cua may xuc) ta se co hinh thuc dao ngang, nghia la huong di chuyen may dao song song voi ho dao.

- Neu chieu rong ho dao lon va thuan tien de o to vao lay dat ca hai phia thi ta co hinh thuc dao doi dinh, nghia la may xuc vua dao vua lui doc theo ho dao.

Doi voi may dao gau day

May dao gau day co ban kinh lam viec tuong doi lon nen no co the truc tiep dao roi do dat vao nen dap, hoac do dat thanh dong. No thich hop dung de nao vet bun, khai thong song, ngoi, muong ranh. Noi chung thi cong voi dat mem, uot thi may dao gau day co nang suat cao. Chieu sau dao khong nen vuot qua 50% chieu dai can.

Tuy theo dia hinh thi cong va dieu kien dat dai ma co cac so do lam viec cua may dao khac nhau.

Thi du, voi dieu kien o to khong the dung duoi ho dao de lay dat duoc, ta co so do thi cong nhu (hinh 3-11).

Tren so do nay, ta thay truc dao cua may xuc luon luon song song voi truc duong o to dung lay dat. Vi tri dung cua o to lam sao cho goc quay do cua may dao la nho nhat, de giam thoi gian chu ky lam viec cua may dao, dong thoi de dam bao an toan trong khi may dao quay do dat vao thung o to, thi nen cho thung o to huong vao phia quay can do cua may dao. Cac kich thuoc cua khoang dao se tuy thuoc vao tung loai may dao va o to.

Truong hop o to co the dung duoi ho dao de lay dat, khi do vi tri dung cua may xuc cao hon han o to thi ap dung so do dao con thoi (hinh 3-12).

Voi so do dao nay, goc quay do cua may dao la nho va may dao co kha nang lam viec lien tuc khong phai cho doi o to. Cach thi cong nhu kieu nay dam bao nang suat cao. Tuy nhien no co nhuoc diem la phai lam duong cho o to len xuong ho dao de dang.

d- Nhung bien phap nang cao nang suat may dao mot gau

- Cong thuc tinh nang suat dao mot gau:

(3.1)

trong do: N- nang suat cua may dao lam viec trong 1 gio

q- dung tich gau, m3; tck - thoi gian mot chu ki lam viec, s;

kd¬- he so day gau (la ty so giua the tich dat da thuc te xuc duoc day gau va the tich hinh hoc cua gau);

kx- he so toi xop cua dat;

ktg- he so su dung thoi gian; doi voi may dao thuong lay ktg= 0,20,25, cac he so kd¬ va kx co the lay theo bang duoi day:

- Cac bien phap nang cao nang suat may xuc mot gau

Hien nay o nuoc ta co rat nhieu loai may dao mot gau dang thi cong o nhieu cong truong vao cac cong viec khac nhau nhu: khai thac da, khai thac quang than, dao dat, v.v... Da co nhung don vi, ca nhan su dung may dao dat duoc nang suat cao, kinh nghiem nay chua duoc pho bien rong rai nen cung con nhieu noi nang suat lam viec cua may dao van thap (thuong hut chi tieu dinh muc). Nguyen nhan cua viec dat duoc nang suat cao phu thuoc rat nhieu yeu to, sau day la nhung yeu to anh huong den nang suat va bien phap nham nang cao nang suat cua no.

+ Nguoi cong nhan phai biet su dung thanh thao may, rut ngan chu ky lam viec bang cach ket hop cac thao tac mot cach toi da.

Thi du, trong khi cho may dao do dat da vao o to co the phoi hop them cac dong tac: keo tay gau ve phia may dao; nang gau len do cao can thiet de chuan bi do; dua tay gau ra phia ngoai truoc khi do; ha gau xuong vi tri can do; do dat, da khoi gau.

Khi quay may dao lai phia via dao co the phoi hop cac dong tac: keo tay gau lai phia buong lai; ha gau xuong de bat dau dao; do dat da ra khoi gau.

+ Chon phuong tien van chuyen tot, phu hop voi dung tich gau. Ty le giua dung tich gau may dao va dung tich thung xe o to la mot yeu to quan trong anh huong toi nang suat may.

Thi du, may dao CE-3 khi dung tich cua phuong tien van chuyen voi dung tich gau la 1:1 thi nang suat may dao chi dat 60% so voi may dao do vao phuong tien van chuyen co dung tich thung chua gap 8 lan dung tich gau dao. Thong thuong chon phuong tien van chuyen phuc vu may dao nen chon loai thung chua lon hon dung tich gau tu 4 den 5 lan.

+ Lap kich thuoc khoang dao hop ly (xem bang chieu cao dao hop ly cua mot so loai may dao), va cho dung cua cac phuong tien van chuyen chinh xac, sao cho goc quay trung binh cua may la nho nhat va hieu suat cua no lon nhat.

+ To chuc tot cac phuong tien van chuyen lam sao duoc lien tuc, khong de xay ra truong hop may dao phai cho o to.

+ Chuan bi cho dung lam viec duoc thuan loi, tranh go ghe va doc nghieng. Khi khai thac da, quang phai duoc lam toi, xop bang phuong phap no min.

+ Tuy theo moi loai dat, da ma thay the loai rang gau, kich thuoc gau cho hop ly. Thi du, voi dat mem, xop thi co the thay gau voi dung tich lon hon.