Measures to control basic project construction cost?

Jinhai Plaza Project is located at the northeast corner of the intersection of Ji Hua 5th Road and Fenjiangnan Road in Chancheng District, Foshan City, with a total construction area of 60595m2, including underground construction area of15,595m2, aboveground construction area of 45000m2, total building height of 99.95m, 26 floors above ground and 3 floors underground, with a total cost of 230 million. This project is located in a first-class office building with novel shape and Lingnan characteristics. When completed, it will become one of the landmark buildings in the bustling area of Foshan. This project is a reinforced concrete frame structure. Raft foundation, engineering piles are bored piles with diameters of φ 800, φ 1000, φ 1200 and φ 1600 respectively.

2 characteristics of construction cost management

As the main part of foundation engineering, the cost management of building foundation engineering has the following characteristics: (1) Most of the building foundation engineering is concealed engineering, and the sub-projects such as engineering piles, earthwork excavation and earthwork backfilling cannot be directly applied to the cost calculation of building engineering drawings, which increases the difficulty of building foundation cost management. (2) There are many kinds of engineering projects involved in foundation engineering, and the business scope is wide. In the process of management, project cost personnel should be familiar with this business. (3) There are many methods that can be used in the construction of building foundation engineering, and the construction equipment and technology have developed rapidly [1], but the budget quota and cost standard can't meet the development needs.

3 cost control measures in the construction stage

3. 1 Cost control before construction

In the process of foundation construction, the influence of prior control on the project cost accounts for more than 75%. Therefore, it is of great significance to control the cost before construction [2]. Prior control mainly includes the following aspects: (1) determining the unit price of building materials. In engineering construction, building materials are the main aspects that affect the engineering cost. In the process of construction, we should budget the prices of electricity, water, sand, cement and other materials, strictly control the prices of basic materials, ensure the rationality of material unit price and the reliability of material sources, and avoid the situation of disorderly pricing and high valuation [3]. (2) Accurate measurement of the project. The calculation of fixed engineering quantity has great influence on the project cost. When calculating the engineering quantity, we should carry out the measurement in strict accordance with the relevant specification process, analyze the geometric properties of the engineering structure, make full use of the standard atlas, and calculate according to tables and procedures, so as to reduce the calculation differences and ensure the accuracy of the engineering calculation. (3) Reasonable usage quota. In the construction of engineering projects, the quota is the main basis for determining the project cost according to the consumption of materials and labor. In order to ensure the accuracy of expenses, we must scientifically apply the items and materials in the quota subhead according to the requirements of relevant documents and regulations.

3.2 Construction cost control

In the process of basic engineering construction, the supervisor and the owner are the main responsible personnel for the cost. Because the foundation project is a concealed project, when the project changes, it will have a great impact on the project's income. Therefore, it is necessary to control the construction technology. In order to control the project cost reasonably, it is necessary to analyze the possible changes in construction, and then find the best way to control the project cost [4]. For some inevitable engineering changes, according to the relevant clauses in the bidding documents and construction contracts, reasonably explain the changes, measure and measure the concealed works, and file the data well. This paper mainly analyzes the construction difficulties and cost control of sub-projects such as bored pile, underground continuous wall and basement bottom pull.

3.2. 1 Construction cost control of cast-in-place pile

Punched cast-in-place pile is used in pile foundation construction. The diameters of pile foundation are φ 800, φ 1000, φ 1200 and φ 1600 respectively. The bearing stratum is moderately weathered rock, and the rock penetration depth is not less than 5~23m. The rock penetration depths of uplift piles are 1m and 1.5m respectively, and the main construction techniques are: burying liners, punching, slag removal, lowering reinforcing cage and hole cleaning. During construction, in order to control the project cost and reduce the construction cost, the specific positions of sedimentation tank and mud tank should be selected reasonably first, which will not affect the normal traffic of punching machine and crane, reduce the construction efficiency and improve the construction cost. According to the specified requirements, the sand content of the wall protection mud should be controlled within 4%, the mud viscosity should be kept at 18~22S, and the colloid rate should be above 99%. In the process of construction, the relevant indexes of the wall protection mud should be tested irregularly to avoid the unqualified mud quality and increase the construction cost. When drilling, the construction speed should be controlled within the range of machine-team footage 1m, and the construction should be carried out in strict accordance with the requirements of table 1. In order to avoid the phenomenon of hole collapse caused by too fast construction speed, affect the construction progress and increase the construction cost. Therefore, the hole wall should be made as firm as possible to avoid hole collapse in the normal drilling process in the future. When pouring concrete after hole cleaning, be careful not to interrupt the pouring process, and the pouring should be successful once, so as not to affect the pouring quality and increase the construction cost.

3.2.2 Cost Control of Diaphragm Wall Construction in Basement

In the basement construction of this project, the side wall of the basement is set on one side of the continuous wall with a thickness of 800 mm As the continuous wall has been poured, the template for installing the side wall can only be installed on one side, and the pouring height is 3~4m, which is relatively high. How to improve the stability and rigidity of the side wall formwork and prevent the formwork from falling off or exploding to affect the quality of the side wall is a difficult point in construction and also the focus of cost control [5]. During construction, nine plastic-coated plywood is used as the template of lining wall, and installation is carried out according to the construction sequence of first vertical stare blankly and then horizontal stare blankly. Control the distance of installing steel pipe support at 300mm, fix the horizontal steel pipe with iron wire on the vertical wooden Fang, and then fix the vertical steel pipe and the horizontal steel pipe with right-angle fasteners. In order to ensure the size and rigidity of the formwork system, the wallboard is supported by steel tube diagonal braces. According to the above measures, the construction quality is guaranteed, and there is no phenomenon of mold explosion and mold escape after construction.

3.2.3 Mass concrete construction cost control

The basement floor of this project is 2.0m thick, and the core tube floor is 4.0m thick. In the construction of mass concrete, specific construction technology should be formulated and strictly controlled from the aspects of construction organization and construction technology to ensure the smooth development of mass concrete construction. Carefully consider the selection of concrete materials, the design of concrete mixture ratio, the test of concrete temperature, the maintenance of concrete and other aspects, control the concrete layer by layer, centrally mix the concrete, and transport the concrete with a mixer. Before pouring concrete, the setting-out personnel of the construction team should make a control sign of concrete elevation on the steel bar. When there is wall reinforcement, put a sign on the wall reinforcement; When there is no wall reinforcement, a Ф12 reinforcement can be welded on the floor epithelial reinforcement for lofting. In order to avoid cold cracks in mass concrete pouring, the construction team is required to assign special personnel to look after the concrete flowing in low-lying areas, plant flags when necessary, and cover it in time before initial setting. In the process of construction, the personnel of relevant departments are required to coordinate with each other and cooperate with each other, so as to ensure that the concrete is poured at one time, and no concrete cracks appear after construction, which ensures the construction quality, saves the repair cost and reduces the construction cost.

3.3 Cost management measures after completion

(1) In the final accounts of completion, ministry of materials and equipment and the Construction Department should actively cooperate with the Budget Department to make final accounts, summarize relevant information and hand it over to the Budget Department, which will analyze and compare the actual material loss and labor costs. (2) Improve the claim awareness. Strengthening claim management is also the main way to improve economic benefits. By collecting meteorological data, memos, meeting minutes, construction diaries, engineering audio-visual materials and other materials, we can make full use of the opportunity of changing drawings and increasing workload to win claims and increase profit space [6].

4 conclusion

Building foundation engineering not only has great influence on the construction quality of the project, but also has great influence on the project investment. According to the actual situation of construction project cost management, this paper puts forward the cost management in three stages: engineering investigation, design and construction. Take the whole method, whole process and multi-level management methods to do a good job in cost management and improve the economic benefits of project construction.

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