The river regulation project of the Pasi Bridge in Bangladesh is located on the Ganges River in Pubuna, Bangladesh, and is an integral part of the Pasi Bridge and the river regulation project. The project started in September 2000 and was fully completed in April 2004, with an output value of $35 million. The project can be successfully completed, and the contract management and technical management during the construction period play a vital role. Introduce several typical cases for discussion by peers in the industry.
I. Introduction of the Project
The river regulation project of Passy is a sub-project of the project of Passy Bridge. The main content of the project is the river regulation and protection on both sides of the bridge. The renovation protection length is about 600 meters/side, and its plane layout is about 200 meters upstream and 400 meters downstream of the center line of the beam. In addition, there are two protection construction tasks, DAMUKDIA and SARA, and several projects, such as subgrade filling of approach bridge.
The total contract price of the Pasi Bridge Project is US$ 6.5438+US$ 26.9 million, of which the total cost of the river regulation project is US$ 33.64 million (including 60% foreign exchange). Contract period 1095 days, and maintenance period is 365 days. The engineer issued the commencement order on August 7, 2000, and the construction period is calculated from the date of signing, and the completion date of the project is August 6, 2003.
The main contents of the river regulation project are: dredging and filling 3.02 million cubic meters; Geotextiles and geotextiles are laid in rows of 243,000 square meters; Slope protection and apron riprap 5 1.05 million cubic meters; Paving of precast concrete blocks17500m3; 700,000 cubic meters of earthwork on land; There are also work contents such as planting grass and trees.
This project is funded by the Japan Overseas Economic Cooperation Fund (OECF). The project consultation is a joint venture between Parsons Linkhoff International Consulting Company of the United States and Wally International Consulting Co., Ltd. of New Zealand. The project owner is the Highway Administration Bureau of the Ministry of Communications of Bangladesh.
Second, joint management.
Contract is the basis for all parties to carry out their work. Generally speaking, the first step taken by the contractor and the owner is to make the work outside the original contract a part of the contract. That is, the responsibilities and obligations of both parties to the contract on this task are clearly defined through the change order. Contract management is an important part of project management. Unclear contract scope will lead to unclear rights and obligations, which may lead to the extra work in the project management process not being paid properly.
In the implementation of this project, we strictly manage the contract. In addition to the regular contract terms, we should also remember them. For those who have a large impact on the project construction, we should be familiar with the contract and find the basis from it, so that the construction and payment will develop in a favorable direction for us and lay a solid foundation for the smooth implementation of the project.
1. Change of elevation at the bottom of apron in the west bank
The elevation of apron bottom in the west bank is marked differently in different bidding drawings, one is-15m, and the other is-10m. This problem was not clarified in the bidding process. After winning the bid, we further studied the contract and found that besides the construction drawings, there are many descriptions in the contract, and the terms are also contradictory. For this reason, we argued with our consultants for two years and even made up our minds to make major plan adjustments. Finally, in a reasonable and favorable situation, the consultant changed it to-10 meter, which did not affect the design function, but greatly facilitated the construction and increased the number. Otherwise, we will not only invest more money to buy special equipment for deep-water dredging, but also it will be difficult to ensure the completion of the construction tasks there in the dry season.
2. Cancel the use of underwater cofferdam in the construction of underwater fill in the West Bank of Jordan River.
In the technical specification, the specific construction method is stipulated in the regulation of underwater fill in the west bank, but an attribute is added in the language description, which is extracted as follows: "The contractor must adopt underwater cofferdam construction to ensure the filling material forms the designed geometric size, and the cofferdam size will be decided by the contractor himself, but the contractor will be responsible for the cofferdam and the slope stability after cofferdam filling." .
Considering the heavy workload of the West Bank, it is impossible to complete the construction task of the West Bank in the dry season if the underwater cofferdam construction method is adopted. For this reason, the project department had an in-depth discussion with the consultants. For the benefit of the project, they agreed that we should directly carry out underwater reclamation without using underwater enclosures. In order to verify that underwater direct hydraulic fill can form the designed geometric size, before construction, we conducted underwater hydraulic fill test together, and obtained a feasible construction method, which was approved by them. After the flood season, we put into construction according to this method. According to the joint survey data, we successfully obtained the design section by this method, but at the same time, we observed the phenomenon of large-scale landslide on the slope.
Later, the consultation asked us to repair the landslide area with underwater cofferdam, on the grounds that underwater cofferdam would be beneficial to the stability of the slope, so we had an in-depth discussion. At this time, the basis to support our view is that the function of underwater cofferdam is to obtain the design section, not to increase the safety factor of slope stability. Since the design section can be obtained without cofferdam, there is no need to adopt underwater cofferdam construction. At the same time, it is pointed out that our view on landslide is that the safety factor of design slope ratio is too small. After many discussions, both sides finally made concessions, that is, they made some modifications to the design, and we also made a first-class cofferdam, with little investment, in order to increase the safety factor of slope stability and ensure that the protection construction can be completed before the flood season.
The cancellation of this work has bought us time to successfully complete the construction in the West Bank and saved a lot of construction costs.
3.SARA's additional maintenance works
Due to the imperfect design and other factors, the entire SARA construction was forced to be carried out across the year. Specifically, from February 2002 to June 2002, the construction tasks between 0400 and O930 were completed first, and from February 2002 to March 2003, the construction tasks between 0000 and O400 were completed.
After the first phase of protection construction was completed in June, 2002, as the flood season of Padma River approached, the completed first phase of the project would be forced to face the flood season, which led the owner to occupy this part of the completed project in advance. Therefore, according to the FDIC terms, we put forward the requirement of delivery by installments, but the consultation emphasized that there was no agreement on delivery by installments in the special terms and conditions of the contract, so we did not issue a certificate of delivery by installments.
In June 2003, 5438+ 10, after two flood seasons, problems occurred between 0680 and 0750, and some stone concrete blocks collapsed and were damaged. The engineer's representative sent us a letter asking us to make repairs, but avoided talking about who should be responsible, saying only that the problem would be solved according to the terms of the contract in the future. We have carefully studied the scope of the engineer's representative's rights, and think that he has no right to give instructions on this maintenance work, and this work is beyond the scope of the original contract, so it should be made a part of the contract first. To this end, we sent a letter to the engineer himself requesting a change order, but due to the inefficiency of Bangladesh and other reasons, the change order was not issued. But the engineer gave a reply, so we can at least take this reply as an instruction, and we have perfect information from the perspective of the contract. Otherwise, the work can be carried out only by a letter from the engineer's representative, which will easily lead to disputes on contract views and payment in the future.
4. Determine the unit price. SARA design change project
Because there is no construction drawing in the bidding stage, we tracked the design process in time during the construction drawing design, and put forward relevant suggestions for the design from the perspective of ensuring the design function, safety and convenience for construction. When these suggestions are adopted, it also brings opportunities for design changes, that is, two price numbers are added to the original contract price number, namely, the excavation and reuse of old stones after excavation, and the specifications of concrete block prefabrication and paving have also changed.
In the process of negotiating and determining the unit price with the owner, the project department carefully studied the terms of the contract, actively strived to make use of the provisions in the contract and adopted the current market price as the basis for determining these unit prices. After one and a half years of negotiations, it finally succeeded and brought remarkable benefits to the project. If we don't carefully study the special terms and conditions of the contract and use the existing similar price number of the tender as a reference according to the general terms and conditions of the contract, we will lose a good opportunity to create benefits.
Third, technical management and design changes.
Technical management, contract management and business management are inseparable. To do a good job in project construction, we must have sufficient technical preparations, such as the formulation and optimization of construction plans. During the implementation of this project, many technical problems were encountered in the process of formulating the scheme. Although design changes are difficult in the implementation of foreign projects, when we encounter these technical problems, we still try our best to solve them through design changes.
1. Single stone weight optimization
This project needs 865,438+00,000 tons of stone, and the stone with a weight of 65,438+000 kg/block is 50% of the total. According to our investigation on the way of stone procurement, there is no stone in Bangladesh, and all the stone needs to be imported from neighboring countries in Bangladesh, so we finally chose India. The national conditions of India and Bangladesh are that all the stones are manually loaded and unloaded, and the transport vehicles are ordinary trucks. According to the inquiry, the purchase price of 100kg/ block of stone is very high, and the supplier is not interested in providing large stones, but only willing to provide stones below 100kg/ block. In view of this situation, we collected the hydrological data of the river extensively, and then checked the stone specifications in the original construction drawing according to the design principles. Through inspection, we found that the safety factor of the original design stone specifications was too large, so we submitted the calculation results to the consultant and made suggestions to the consultant from the perspective of the actual situation and project implementation in Bangladesh. As a result, the stone optimization was successful. On the one hand, this change in stone specifications reduces a lot of engineering costs, on the other hand, it also avoids the situation that large stones are difficult to purchase and the project cannot be carried out.
2. Modification of the elevation of the design apron bottom in the West Bank of Jordan River.
The west bank protection project is one of the main projects of this project, which is located on the west side of the main river. The total length of the construction section is more than 600 meters, and the project cost is about 654.38+007,500 USD. According to the original bidding drawings, the elevation of apron bottom for underwater earthwork excavation is-15m, and the slope ratio is 1: 3.5. During the preparation of the construction scheme, it was found that the maximum excavation depth of 3800 Desheng dredger could only reach-12m, and the design bottom elevation could not be excavated at all. This means that according to this design, the current equipment can not carry out the protection construction in the West Bank at all. When comparing the schemes, it is found that the investment cost of new special equipment for deepwater dredging is too high. If the 3800 dredger is deepened, some technical problems will appear. At the same time, from the perspective of slope stability and hydrological conditions, even if the above scheme can be implemented smoothly, the construction period we are facing is very tight. Therefore, only when we are confident enough in technology to ensure that the earthwork construction is completed within the specified time and the success rate reaches 100%, can the construction task be completed on schedule. This is done to improve the safety factor of slope stability, improve the productivity of underwater earthwork equipment, shorten the earthwork construction time as much as possible, and leave time for the next working procedure. According to the understanding of the existing deepwater dredging equipment in the world, we decided to take the road of design change. It took more than 65,438+0 years to make design changes. During this period, we organically combined contract management, business management and technical management. After a long discussion, the elevation of the apron bottom in the west bank was finally raised from-15m to-10m on 24th October, 2002. It not only eliminated a major obstacle affecting the construction, but also achieved the expected goal of not rebuilding dredgers and purchasing deep-water dredging equipment, reduced the project investment, improved the slope stability conditions, reduced the risk of slope collapse during the construction process, reduced the construction difficulty, and ensured that we could fully complete the west bank protection project in the dry season.
3. Modify the slope ratio on the east and west banks.
The time span of this work is from June 5438+0, 2006 to June 2003. The slopes on the east and west sides of the original tender drawings were 1: 35, and the tender stipulated that the contractor was fully responsible for the slope stability.
During the construction of the 200 1 test section, due to the landslide of the permanent slope and the temporary slope during the construction, our construction progress was delayed. Not only that, we also invested about 80 thousand dollars to deal with the landslide of permanent slope. In the following year and a half, we have been urging the owners to pay for this part of the project. After numerous talks, the owner and consultant said that the expenses during the experimental period, that is, the above expenses, should be paid to us. In view of this situation, on the one hand, we revised the method of slope excavation (revised the technical specification), changed the original method of slope repair by dredger into step-by-step excavation to form slope, and also adopted measures such as quick excavation and quick running, piling and hanging reamer, rather than exceeding. However, in the subsequent construction, landslides still occurred many times. During the construction of this project, there were 20 landslides, including the east bank 10.
In view of the above situation, we took various measures to urge the consultation and the owner to modify the east and west bank slopes from the original 1: 35 to 1: 5, which greatly improved the slope stability conditions, prevented and reduced the landslides in the future construction, and brought remarkable benefits, which not only ensured the timely completion of the project, but also reduced the cost loss after the landslide during the construction period.
4. The design orientation of Damukdiya and Sarah
In the bidding stage, these two tasks are tentative projects, and there is no construction drawing when bidding. According to the bill of quantities, the construction contents here are mainly underwater riprap and concrete blocks on the water. The work content is the same as that of the east-west guide embankment. After winning the bid, the owner decided to carry out these two tasks. During the construction period, the construction drawing was designed. Because it is directly related to the construction, we actively track the design progress in the design process, and actively help to consult and draw drawings, understand the designer's intentions in time, and feedback our views on the design to them. During the design process, many of our suggestions were adopted. In this way, we saved the process of "throwing the ship" in SARA's construction. In the construction of DAMUKDIA, the diversion dike on soft foundation was avoided, and the risk was eliminated, which laid the foundation for the successful completion of the protection project and ensured the construction period.
5. Technology application
According to the technical specifications of this project, we equipped the dredger with the first set of GPS global positioning system of our bureau at that time.
The dredging length of the dredger in this project is 300 ~ 500m, and the dredging depth is 23m. According to the contract, in order to stabilize the slope, it is necessary to excavate in layers, and the excavation thickness of each layer is 2m. Due to the above influence, the dredger needs to move frequently and locate in a new excavation position, which is often affected by many factors such as night/fog, resulting in extended non-working hours. In addition, the construction lofting is also affected by night/weather. After equipped with GPS, the construction of dredger is no longer affected by night and weather, and the attendance rate is guaranteed. In addition, the visual operation of dredger construction is realized, and the excavation accuracy is improved. What's more worth mentioning is that while using GPS to realize the above functions, we further study and extend the functions of this set of GPS to underwater topographic survey, and then master the computerization of data acquisition and processing through technical research, which greatly improves the work efficiency. The application of these achievements, especially when underwater topographic survey is often needed, greatly facilitates the construction and saves the time for the dredger to wait for the constructors to read the drawings before arranging the construction. It can be said that the use of this achievement has laid a solid foundation for the smooth implementation of this project, otherwise, we will face the situation of insufficient construction period due to the influence of river flood.
6. Integrate theory with practice
In Sarah protection construction, we encountered the problem of local slope failure caused by seepage hydrodynamic pressure. In order to solve this problem, the project held a technical seminar, and finally determined the soil replacement scheme using the open-pit method to achieve:
(1) Extend the seepage diameter and reduce the hydrodynamic pressure.
(2) The horizontal seepage flow water pressure is converted into uplift pressure by using the cogging.
(3) Using undisturbed soil outside the gullet to increase the shear strength.
(4) Using the soil at the tooth opening position to increase the sliding resistance.
After adopting this method, the effect is very obvious, which not only prevents the leakage from affecting the construction, but also ensures the stability of the slope, laying a solid foundation for the smooth construction.
7. Changes in measurement methods
The addendum to the tender for this project stipulates that the measurement of stone materials shall be based on the thickness and plane size of stone materials marked in the drawings, that is to say, the settlement will be based on the design quantity. However, in order to confirm whether the construction meets the design requirements, the technical specification stipulates that the thickness of riprap is determined by the two measurement results before and after riprap. In addition, the technical specification stipulates that the thickness marked on the drawings is the minimum required thickness, and no thickness less than this thickness is allowed after actual construction.
Considering that the stones will settle in different degrees during and after riprap construction, if the construction is carried out according to the above requirements, a certain amount of "over-throwing" must be used to meet the design requirements, but we can't get the due payment for the "over-throwing" stones, and the underwater geological conditions are also very different. From the results of post-construction measurement and engineering quantity, the settlement of individual parts is more than 3m, and the overall settlement is 1 ~ 60.
In view of the above provisions, before the construction, we put forward the problem of "settlement" and suggested setting up "settlement observation pole". Although there were different opinions during the negotiation, under our active promotion, the settling pole of 1 was finally set, but the height of the settling pole was too high (17m) and it was destroyed during the riprap, so the scheme was rejected through negotiation. On this basis, alternative schemes such as "measuring riprap with scale" and "measuring stone in yard" are put forward to achieve the purpose of measuring during riprap construction and before riprap. After a long discussion, these plans were unanimously accepted.
The provisions of the original tender have brought great risks to the contractor. We think that the tender preparers neglected the settlement problem, which led to the unreasonable provisions of the technical specifications, divorced from reality and not operable. In order to avoid risks in the construction process and safeguard the interests of the contractor, we actively promote the negotiation to change the measurement method, make the measurement work transparent, change the underwater into the underwater, change the difficult into the easy, and avoid the occurrence of "over-investment", thus greatly reducing the project risk and cost.
The construction contract is a legal document that both parties must follow to carry out their work. Due to different understandings, disputes are very easy to arise in contract management, and the understanding and interpretation of contracts are also different. Therefore, it is very important to understand and grasp the contract correctly in the construction process. Contract disputes encountered during the implementation of this project are all major issues that affect the smooth implementation of the project. However, the project department used the understanding of the contract, supplemented by appropriate business work, removed the obstacles of the project construction and successfully completed the construction task.
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