1, the influence of some common problems in design documents on cost compilation
1. 1 Problems caused by lack of communication between professional working groups in design. For example, the bill of quantities of subgrade earthwork and pavement engineering often includes the corresponding quantities of interchange, service area, parking area and toll station, and the quantities of interchange, service area, parking area and toll station are designed separately.
The design of 1.2 uses other materials with higher strength to replace part of the embankment, but does not deduct the original earthwork; Using lime soil to treat subgrade requires an additional amount of work, but the earthwork of the original fill section is not deducted.
1.3 The number of grooves has been included in subgrade earthwork, but it has been redesigned in pavement engineering.
1.4 The excavation amount of side ditch, drainage ditch, intercepting ditch and special slope treatment has been included in the subgrade excavation, but the engineering amount has been redesigned in the design of these structures.
1.5 When calculating the user, debit and discard items in the subgrade earthwork bill of quantities, the coefficient of converting natural compactors into compactors is not adjusted, or the adjustment does not match the highway grade, resulting in incorrect calculation of users, debit and discard items; In this table, the amount of earthwork increased by road gene clearing topsoil, tamping before filling and widening filling has not been allocated and calculated, which makes the amount of earthwork omitted in the design stage, but it happens again in the implementation, which is very unfavorable to the control of earthwork in Wei Ping area.
1.6 Poor, wrong, heavy and leakage that often occur in bridge engineering. For example, the number of reinforcement and concrete in full-width or half-width bridge cast-in-place piles is less than half, the main girder reinforcement is more than half, the bridge deck pavement reinforcement is missing, the number of concrete in cylindrical piers is less than π, and the number of bridge summary tables is inconsistent with that in detailed design.
For all kinds of problems in the above-mentioned design documents, cost compilers often fail to find them in time because of tight time and heavy tasks, which makes the cost compilation of some projects poor, wrong, heavy and leaking, and affects the rationality of project cost compilation.
2. Various problems that are easy to occur in the compilation of project cost.
2. 1 Compilation of material unit price
(1) Basic information of materials-location, quality, output, transportation% inspection || conditions, transportation distance, whether it passes through toll stations, etc. Without sufficient investigation, or without on-the-spot investigation, the unit price of materials in other projects is copied, or compiled completely according to the unit price provided by the construction management unit, resulting in a big gap between the prices of local materials such as quicklime and gravel and the actual situation in the project implementation process.
(2) The unit price of expressway cement is generally high. Except for the lack of cement in Yan 'an and Yulin areas, other areas in our province are rich in cement with relatively stable quality. Local cement can meet the requirements of cement stabilized pavement base, masonry engineering and concrete below 40. However, when compiling the cost, all the cement used in bridge and tunnel structures are Qinling brand or other brands, which leads to a big difference between the procurement and transportation of cement and the actual situation of the project, which makes the unit price of cement high.
(3) The frequent changes in the market prices of various steel and fuel materials have brought great difficulties to the reasonable compilation of the budget unit price. Due to the lack of necessary analysis and prediction of current market changes by some cost compilers, the prices of some materials fluctuate, which brings great difficulties to the phased control of project cost.
2.2 the main problems existing in the extraction of quantities and quota use
(1) subgrade engineering
(1) subgrade earthwork often has problems. First, the selection of earth-moving machinery does not match the highway grade and terrain conditions, and some cost personnel have the idea of making the project cost as high as possible, so the mechanical power selected is generally small, which invisibly increases the earth-moving cost; Second, due to the low level of earthwork quota currently used, such as mechanical drilling and blasting quota, mechanical cooperation includes the first quota transportation distance of bulldozer transportation, which is inconsistent with the current situation that bulldozer transportation is basically not used in the stone construction site. For long-distance transportation, it is not necessary to adjust the pushing consumption of bulldozers to zero when the waste is transported by loaders and dump trucks, and the quota is directly applied, which is costly. Third, due to the lag of transportation quota level, the long-distance transportation of earthwork with a transportation distance of more than 3 kilometers still applies the engineering quota to calculate the transportation cost, which makes the unit price of the compiled project abnormally high and seriously deviates from the construction practice.
② Problems existing in high slope protection and biological protection. In recent years, the design of slope treatment and biological protection has been strengthened in expressway design, and new high slope protection projects-planting grass in anchor concrete frame and planting grass in anchor concrete frame, as well as new protection technologies-hydraulic spray seeding, exotic soil spray seeding and thick substrate spray seeding have emerged. Due to the lack of supplementary quota in each province, the unit prices compiled by different design units and different cost compilers are varied and confusing, which are basically higher than the unit prices of the corresponding expressway projects implemented in this province, and some even deviate seriously from the actual construction.
For example, in the construction drawing budget of an expressway in Qinling Mountain area of our province, except for another set of quota calculation of concrete frame, steel bar and support, the cost of drilling, manufacturing, installation and grouting of anchor cable is calculated according to the comprehensive price of anchor cable length 420 yuan/meter, which is much higher than the cost 280 yuan/meter ratio compiled with reference to other provinces' supplementary quotas at the time of review; The unit spraying prices of thick substrate 120 yuan/m2, 180 yuan/m2, 150 yuan/m2 are too different. It is understood that it is generally between 80 ~ 120 yuan/square meter.
(2) Pavement engineering
① At present, the modified asphalt concrete is mainly used in the middle and upper pavement design of expressways. The construction practice shows that it takes 5 ~ 10 seconds longer to mix a modified asphalt concrete in the H4000 mixing station than to mix ordinary asphalt, which also affects the paving and rolling progress of asphalt mixture and invisibly increases the machine-shift consumption of mixing, paving and rolling machinery. How should this be reflected in the cost? At present, there is no corresponding supplementary quota, so in the cost compilation, ordinary asphalt is only adjusted to modified asphalt on the basis of fine and medium-grained asphalt concrete quota (generally, the processing cost of modified asphalt is increased by 950- 1090 per ton on the basis of the unit price of ordinary asphalt), regardless of the increased cost of mechanical efficiency reduction. Then, how to compile the engineering cost of modified asphalt concrete in the future remains to be discussed.
(2) when the compaction thickness of stabilized soil foundation and subbase exceeds the specified thickness, and it is necessary to spread in layers, adjust the consumption of labor, tractors, graders and rollers. At present, the problem existing in the compilation is that the quota does not stipulate the thickness limit of layered paving, so some projects have adjusted the paving of 16 ~ 20cm and 30 ~ 40cm respectively according to the two-layer and three-layer paving, which is inconsistent with the minimum thickness of 15cm and the appropriate thickness of 16 ~ 20cm stipulated in the Technical Specification for Pavement Design and Construction.
(3) The selection of the production capacity of mixing equipment, the set quantity and the transportation distance of the mixture. Some projects have not been designed for construction organization, and the setting of mixing equipment is considered by the cost personnel in the preparation. Because the cost personnel did not carefully analyze the topography of the project, the division and construction period of pavement blocks, the production capacity and the number of mixing equipment used were quite different from the actual situation of the project, which led to inaccurate calculation of pavement engineering cost.
(4) Adjustment of mixture ratio of pavement base and subbase. Some projects did not adjust the mixture ratio according to the design, or made mistakes. For example, in some projects in our province, the cement, lime and fly ash comprehensive stabilized macadam with the ratio of 1.5: 3.5: 15: 80 is used as the pavement base, and some compilers directly add the cement amount to the quota when applying the lime-fly ash macadam quota to calculate the cost, without reducing the lime material amount, which invisibly increases the cost and makes the calculation of the base cost wrong.
(3) Bridge and culvert engineering
① Calculation of the cost of filling semi-rigid materials at the back of culvert abutment. In the design, the back of culvert abutment is treated and semi-rigid materials such as lime soil are filled. It is unreasonable to directly calculate the total cost of this part of the project by applying the quota of lime, soil and ash when compiling the budget. Because the amount of fill at culvert position is generally not deducted from subgrade earthwork, extra calculation of this cost will inevitably lead to repeated calculation of some engineering costs such as material cost and construction cost of earthwork.
② Adjustment of hole-forming quota of non-standard pile diameter bored pile. The budget quota roughly divides the sub-items of the hole-forming quota for bored piles, and the standard pile diameters are only 1.0m, 1.2m, 1.5m, 2.0m and so on. However, in reality, non-standard pile diameter design is very common. In order to further determine the project cost reasonably, most of the budget of this province reduces the quota according to a certain proportion coefficient, some are adjusted according to the ratio of pile diameter, and some are adjusted according to the ratio of pile diameter to cross-sectional area, which makes the project cost vary greatly.
(3) Due to the lack of understanding of the site construction of special bridge types, some necessary large-scale supporting facilities were omitted in the construction. For example, some cost personnel often miss the budgets of continuous rigid-frame bridges and T-shaped rigid-frame bridges. Corner portal frame at pier top, hanger at closure section, hanger or bracket at end section of cast-in-place side span, lifting frame necessary for hollow pier construction over 20m, temporary elevator for construction, etc.
(4) Tunnel engineering
(1) Class II surrounding rock excavation and lining quota. In the design, the number of rocks classified as Class II is often provided as soft stones, and the soil quota is not applied according to the quota when compiling the cost, which makes the cost more.
② Calculation and application of tunnel growth coefficient. According to the norm, when the tunnel length is greater than 1000m, that is, when the construction face is more than 500m away from the mouth of the cave, for every 500m increase (less than 500m is counted as 500m), the number of working days and mechanical machine-teams in the tunnel will increase by 5% according to the corresponding norm. However, the Ministry of Communications often puts forward opinions when reviewing the preliminary design budget, and only adjusts the growth coefficient of tunnel excavation quota, which is inconsistent with the quota regulations. In addition, the growth coefficient of some projects tunnels is calculated by weighted average, which also does not meet the quota.
(3) Compilation of pipe trench cost in tunnel. Because the quota of cast-in-place concrete lining in the tunnel budget estimate includes vault, side wall lining, concrete or mortar rubble backfill, tunnel inner pipe (water) ditch and cover plate, some cost personnel set a separate amount to calculate the plastering cost of concrete and cement mortar in the tunnel central ditch, which makes this part of the cost double-calculated.
④ Compilation of civil engineering cost of shaft ventilation in extra-long tunnel. Due to the lack of corresponding contents in the highway budget quota, some cost personnel adopt the way of inquiry when compiling this part of the project cost, and directly use the obtained project unit price; Some directly apply highway quota for cost calculation; Some adjust the corresponding coal quota and then prepare supplementary quota for cost calculation, which is different. Because there are few vertical shafts and inclined shafts in domestic expressway construction, it is unknown whether the calculation according to the above method conforms to the actual engineering construction. This is a question worth discussing.
⑤ The connection with the calculation of transportation and travel expenses. According to the provisions of the design document compilation method, the installation of lighting and ventilation facilities belongs to the civil design of tunnels, but often the design unit divides this part of the engineering design into traffic engineering when dividing the tasks, so in the new traffic engineering of tunnel engineering, some projects appear double counting or omission at the same time.
(5) Other engineering facilities and construction projects along the route.
① Cost calculation of connecting line, auxiliary road and branch line. In recent years, many connecting lines, auxiliary roads, feeder lines and local hitchhiking projects have appeared in the process of construction implementation, and the mileage has become longer and longer, which has expanded the scale of construction drawing design and greatly increased the cost, which has brought adverse effects on the current project cost control. Secondly, when compiling this part of the project cost, because this kind of project generally adopts the technical standards below the second level, according to the supplementary compilation method of Shaanxi Province, the project cost should be compiled separately according to the second and third types of projects, and then remitted to the building installation fee. However, for the convenience of calculation, cost personnel often use highway standards directly, which makes the cost more.
② Overview of traffic engineering and housing construction engineering. For traffic engineering and housing construction engineering, the construction and installation costs are compiled separately according to the quota and compilation method of the relevant ministries and commissions. When the construction and installation costs of the main project were remitted, some projects failed to deduct the remittance costs according to the Traffic Engineering Compilation Regulations of the Ministry of Communications, and the deduction coefficient of some projects was wrong. The installation fees of professional engineering buildings compiled by other ministries and commissions shall be reduced in line with the principle of maintaining the original cost level when remitted to the installation fees of highway main projects. However, the reduction and exemption formula stipulated by the Ministry of Communications does not consider the reduction and exemption factors of construction technology and equipment costs, which makes the reduction and exemption costs more than construction technology and equipment costs.
2.3 preparation of other expenses for engineering construction
(1) The calculation of compensation for land requisition and demolition is inaccurate. Inaccurate cost calculation mainly includes three aspects. First, the number of land acquisition and demolition is not accurately designed, or the number is greatly increased due to too many changes during the implementation period, which makes the cost difficult to control; Second, the classification of land and buildings to be demolished is inaccurate, which is quite different from the actual construction, making the cost calculation unreasonable; Third, influenced by the national strategy of protecting agriculture, countryside and farmers, it is difficult to determine the compensation standard for land acquisition and demolition in some areas, which makes the calculation of expenses too uncertain and brings great difficulties to the reasonable compilation of expenses.
(2) The calculation of research and test fees and survey and design fees is unreasonable. If these two expenses are not calculated according to the contract or agreement in the construction drawing design stage, the expenses involved far exceed the examination and approval expenses of the preliminary design estimate.
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